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RX-7 Performance Handbook Mystery Chapters

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All material on this page is copyright 2000-2012 Mike Ancas, Dale Black and Dennis Witt

ORIGINAL INTRODUCTION

As we travel through this new millennium, many people are searching for renewed meaning in their lives, and coming up empty. Science fiction writers depicted us living on the moon and exploring distant galaxies by the year 2000, but in reality, a large portion of our population still can’t figure out how to set the clock on their VCRs. But there is a lot we can be proud of. Even though we are not yet breaking bread with our Vulcan neighbors, from a scientific viewpoint our race has done rather well.

Many of the advances we take for granted today can be traced back to the engineers from the 1960’s. Their task was figuring out a way to blast our astronauts into space, and then bring them safely back to earth. As a result of this endeavor, current technology has progressed to the point where computer science is developing at the speed of light; the internet is changing the way many of us work and play, and physicists are struggling with mind-boggling issues such as the infinitely expanding universe.

So, what does all of this have to do with cars? Except for the fact that the internal combustion engine is still around, automobile technology has also evolved in terms of design, mechanics, and electronics. When the hop-up movement first took hold in the 1950’s, cars were relatively simple creatures. The introduction of affordable aftermarket parts made it possible for the average guy to improve the performance of his American made muscle car, and “working on the car” became a popular pastime.

In the 1960’s, Detroit began to take notice of the public’s increasing desire for performance and offered factory hopped-up versions of the more popular models: Corvette Sting Rays, Shelby Cobra Mustangs, Chevy Z28 Camaros, Plymouth Roadrunners, etc. Those who had a “need for speed” began flocking to the local drag strips for bragging rights as to which of the “Big Three” built the better car. The early 1970’s was a crucial time for the development of the rotary engine. Deemed the “engine of the future”, most auto companies (especially GM) had already lost millions of dollars in licensing fees trying to develop the engine for commercial use. Speculation on the rotary engine nearly put GM into a financial crisis before they finally abandoned the idea. But then 2 things happened that would change history. Not a natural disaster, such as a hurricane, flood, or earthquake which are usually attributed to such moments. But 2 man made artificial events, the first of which was the OPEC oil embargo and resulting energy crisis of 1973. This nearly killed Toyo Kogyo’s new importing company, Mazda, who set up shop in Seattle Washington. The rotary engine got poor gas mileage. Other Japanese auto companies were in the right place at the right time to capitalize on this crisis. Honda began importing it’s first car, the 600 coupe, into the US one your prior to this oil embargo. The us embraced Also VW Beetle. But then, another artificial event happened. The newly formed US EPA announced emission standards that would take effect in 1975. Panic was widespread in the auto industry since there would be no way piston engines at the time would be able to meet those standards. Rotary engines, due to their low emission of nitrogen oxide, were again looked to save the auto industry. And this time, the new company out of Seattle was in the right place at the right time. It seem funny to look back then and see how the piston engine was viewed as polluting, and the rotary as clean. With the development of the low emission piston engines in the 1990’s, the tables have turned. The economy had also shifted, and many families found it increasingly difficult to make ends meet. As we became more environmentally and economically conscious, the cars we designed reflected this shift in priorities. Emission controls choked the horsepower from even the high performance models. The outlandish was gradually replaced by the practical, speed and excitement gave way to sensibility and efficiency.

The 1980s, however, saw a different kind of movement take place. Companies like IBM and Macintosh were making computer technology available to the general public. As the demand for more efficient computers grew, technology began to advance exponentially. The auto industry had already been using computers and robotics for some time, and took advantage of these new technological breakthroughs to help design cars more quickly, and bring them to production in a more timely manner.

The motto of the 1990’s could easily have been: “Better and Faster“. Our lives consisted of cellular phones, FAX machines, Fed-Ex, e-mail, gigabites, and nanoseconds. We had put increasing emphasis on the value of our time and the efficiency of our machines. The result was an overall attitude of impatience. Some people even experienced anxiety waiting for the light to come on after they had thrown the switch.

This lack of tolerance for inefficiency, however, wasn’t all bad. Japanese auto companies had long adopted a doctrine of open-minded productivity, and were in position to embrace this “better and faster” philosophy. This was demonstrated in the progression of technology that took place over the past 20 years with the RX-7, one of the most significant sports car to emerge from Japan (or any other country) in the 20th Century. The import performance movement may have started in 1970 when Datsun introduced the 240Z. Until then there had not been an affordable and reliable high performance automobile available to the U.S. consumer. With the success of the Z-cars, Japanese auto manufacturers began to realize that the American market was willing to expand the definition of “sports car” to include a vehicle powered by something other than a V-8 engine. But the unsuspecting enthusiast could never have expected what would follow.

Mazda had been laying the ground work for what was to come when the Wankel Rotary Combustion Engine appeared in the popular R-100 and RX-2. With the US barely noticing the advancement of this revolutionary powerplant, it must have been a shock when the RX-7 was first imported into the U.S. as a 1979 model. Sure, it looked like a sports car, but what was up with that engine? It was barely larger than a differential. So right from the start, the first generation RX-7’s mission was to gain the respect of skeptical U.S. sports car enthusiasts. As time when on, Mazda continued to make slight improvements in the body style, frame and engine. But when the 6 port 13B was finally fitted into the 1984 GLE, the RX-7 hop-up movement really took off. Car enthusiasts began transplanting this new powerplant into the earlier cars that were somewhat horsepower challenged. At the same time, Mazda tuning innovators such as Dave Lemon (Mazdatrix) and Jim Mederer (Racing Beat) began finding ways to make RX-7’s go faster and handle better.

The import performance movement, which really began to gain momentum in the mid 1980’s, reached new heights in the late 1990’s. This was probably due to a readily accessible supply of aftermarket performance parts, the growth of motorsports in general, plus a wealth of information and support that became available on the internet. With names like Peter Farrell, Cameron Worth and Sylvan Trembly continually inventing ways to make more and more reliable horsepower from the 2 and 3-rotor Wankel, it didn’t take long before the 3G RX-7 began to establish itself as a true supercar. Now, with hundreds of RX-7 clubs in the U.S. and throughout the world, the RX-7’s popularity has reached new heights despite the fact that the car was no longer imported into the U.S. after 1998. It remains as one of the most beloved and enduring sports cars in history.

Form versus function

In the beginning, when it came to hopping up an RX-7, traditionally the first thing the car owner needed to resolve was this dichotomy. In the past, form was often diametrically opposed to function, and the car owner had to choose one over the other based on the intended use of the vehicle. Would the goal be good looks, or would it be performance? As the import movement of the 1990’s grew, it created competition among aftermarket parts manufacturers so that car owners were given more choices when it comes to selecting affordable performance parts that possess both function as well as form.

But the “form versus function” conflict exists on yet another level which can be exemplified when considering what kind of wheels and tires to buy for your RX-7. 19” wheels are not intended for racing, but 14” rims are no longer cool. They don’t fill up the fender wells, unless you lower the car to the point where you can’t drive it anywhere without ripping the exhaust system off. But as you increase rim diameter and decrease tire section height, you reduce the size of the air chamber, which decreases load capacity often resulting in diminished handling. So how do you choose?

First decide whether your goal is “form” or “function”. If you can’t make up your mind, buy two sets of rims, one for racing and one for show. But unfortunately the form versus function debate will persist even after you resolve the wheel and tire dilemma. The sad fact is that race cars don’t make good street cars. They are too stiff, don’t always idle well, get poor gas mileage, and have few creature comforts. On the other hand, great street cars don’t usually make good race cars. They are too heavy, have softer suspensions and stereo systems.

This leads us to the primary lesson of performance tuning: All performance improvements come at a price, and that price is the loss (on some level) of streetability. Everything that makes your car go faster and handle better forces you to make some sort of compromise. You may have to give up a comfortable ride in order to experience stiff and precise handling. You may have to give up a quiet ride in order to experience an increase in horsepower.

Sometimes even with the best intentions, many of us go too far trying to build a faster street car, and end up turning our daily drivers into a race-only vehicles. It must be a male hormone thing. But by exercising some margin of restraint, an RX-7 can be built to serve both purposes well. Learning from our mistakes and successes recounted in this book, you should be able to build awesome street car, capable of blowing the doors off of most other cars on the road. But to return to the fundamental dilemma, before undertaking any type of performance improvement project, a car owner really needs to make a decision as to whether or not the priority will be based on form or function. Once a decision is made, this book will provide some guidance to help you realize your goals. Most chapters cover form as well as function. Street racers will be able to take advantage of the latest good looking “go fast” and handling modifications, while pure racers will be able to access practical information to help their cars become more competitive.

This book assumes that anyone planning performance improvements to their car already has a workshop manual. This book is in no way intended to replace or supersede and information in an RX-7 workshop or owners manual. For that reason, it is devoid of the boring charts and schematics that often fill the pages of typical aftermarket performance handbooks. Exploded views of your car’s suspension or engine are already in a typical workshop manual. Don’t look for discussions about highly technical information, or in-depth demonstrations of any internal engine modification procedures. Attempting to do a bridge port on a rotary engine by your self is a waste of both your time and money. You could easily end up ruining an expensive engine. This type of work should be left to the experts, and there are many competent RX-7 specialists out there. In any event, 99.9% of the people who buy this book don’t have the equipment to do this type of job properly, and if you are the 0.1% of those who do, then you don’t really need it.

You will find that this book concentrates more on what average weekend mechanic can do to improve the performance of their car. Countless aftermarket parts are discussed, and many do-it-yourself projects are reviewed. The first step in any project, however, is setting priorities, such as “form” versus “function”. Chapter 1 will help you make some preliminary decisions and get you started on your way to a great experience in the realm of Mazda performance. The rest of the book won’t help anyone with their journey to achieve meaning in the new millennium, but it could be a fun diversion along the way.

Engine Management for the Third Generation RX-7 by Dale Black

When you consider that the effects of most upgrades are greater on the rotaries than on comparable-sized piston engines, then you can understand that engine management becomes more important. For example, throwing on an open intake and free-flowing exhaust might get you a few ponies on a 4-cylinder Honda, but it can get you twice as much on a 12A or four times more on a turbocharged 13B! So when exactly does engine management become critical? The closer you get to a rotary’s power threshold, as with forced induction, the more fragile they become. You might say that if you are pushing the stock fuel delivery system (including the stock preprogrammed fuel maps) to its limit, then it’s time to consider an ECU modification. As with most fuel injected rotaries, changing the ECU programming it about the only way to make fuel related power adjustments, short of using added injectors and separate controllers.

Before getting too involved, let’s go over fuel delivery, as it is crucial to understand it’s relation to optimum power from a programming standpoint. Many owners of fuel injected cars think the way to increase power is to get more fuel in the air/fuel mixture by either raising the fuel pressure, installing larger injectors, or by installing additional injectors. This is misleading since more fuel is not necessarily the goal. However, getting the right amount of fuel for the volume of air being brought in is the key. An air/fuel ratio gauge is a useful tool for tuning if you don’t have access to diagnostics equipment.

Fuel mixture control is separated into two modes: closed-loop and open-loop. During closed-loop engine operation (idle and low load – 2000 RPM and below), the ECU uses the oxygen sensor to trim the air/fuel ration to the chemically ideal value of 14.7:1) for best emissions performance, thus, any adjustments you make within this range get canceled out by the stock ECU. Open-loop fuel adjustments are not canceled out, and generally considered to affect medium to high load, which is considered 4000 RPM and above and of course, wide-open throttle (WOT). Since emission at these loads and speeds are essentially unregulated, engineers generally choose a very rich fuel curve to protect the engine against knock and thermal stress and to ensure that fuel pump and injector wear will not result in dangerously lean conditions over the life of the engine. In doing so, they compromise peak power and harm fuel efficiency. Stock vehicles generally respond to fuel subtractions in these open-loop ranges. For modified engines, the guidelines above also apply, however heavily modified engine may need fuel addition in the upper RPM range. Timing becomes a critical variable in power tuning and a device which can measure injector “duty” cycle is helpful as well (for example, if you find the stock injectors frequently hit 95% or above, then larger or additional injectors are probably needed.) Again, more on that later.

Fuel-injected rotaries can be a real brain teaser to set up just right. Regarding the old adage, “three strikes and you're out”, you might say that in tuning a rotary engine, it is very possible to be out after only one “strike”, meaning a detonation causing knock. That is why it is always best to start with either the stock programming or an extra rich air fuel mixture as a baseline to start. But regardless of how you go about tuning, you should be able to add and subtract fuel.

Aside from the aforementioned additional injectors/controllers, which will be discussed later, there are basically three ways to retune a third generation Mazda RX-7’s engine for optimal performance. The first is by using a reprogrammed stock ECU. Here, the main chip is swapped out with one that has been specifically programmed for you modifications. There are a number of performance companies with the right amount of know how to do this, often without even having the car on site. Among those are Pettit Racing, Mostly Mazda, XS Engineering,, and Rotary Performance of Texas. One downside to this type of engine management is that there programming is not changeable without removing the ECU and sending it out along with a list of modification changes.

The second way to go about tuning an engine by reprogramming is by using what’s called a “piggy back” system, which basically means that there is an external computer that plugs inline of the stock ECU. Here, it is possible to incorporate various program settings for different venues of performance. Plus, it becomes possible to change the programming with changes made to your car. Two good piggy-back systems currently available for the third gen are the Peter Farrell Supercars’ Programmable Management Computer (PFS PMC for short) and the Wolf 3d System. The PFS PMC is the same as EFI System’s PMS (Programmable Management System), but cannot be obtained directly.

Finally, if you’ve made modifications beyond that of popular bolt-ons, such as porting of the internal engine, throttle body, intake, and/or turbo manifold, then you should consider a complete ECU replacement. Often referred to as a “standalone” because it’s sole purpose is to control the engine’s functions and nothing else, it is a popular option among racers, especially those competing professionally and whose cars are not driven on the street. As you might guess, this is an extreme performance method of optimizing power and is not only highly illegal, but extremely difficult to program for street use anyway. It is not recommended you pursue this avenue unless your sole intention to trailer your car to competition events. I say this, not in fair warning by any means, but because it does not provide any compromise between high performance and street-ability. Examples of such systems are the Electromotive Tech II, Motec, DFI and the Haltech.

TROUBLESHOOTING THE THIRD GEN by Dale Black

Okay, quick reality check… no car ever manufactured is 100% bulletproof against all imperfections, and the third Gen RX-7 is no exception. However, if you consider the list of recalls and technical service bulletins (TSBs), you might think it was designed as a piece of junk right from the start. Then, take a look at the TSBs and the common complaints and see how they pertain to such petty things as a light bulb that sometimes stays on inside the glove box when it’s closed. Ah yes, the RX-7 has finally drawn a perfectionist ownership worthy of its exclusive price tag. Enter Felix Unger of the Odd Couple. Anytime a person pays a lot, (s)he expects a lot. Overall, the items covered in the TSBs are just that… petty, unimportant things that just don’t matter… to RACING! But the majority of the initial third gen buyers were drawn to it’s looks, not necessarily it’s world-class performance. Eventually, those same customers began to think, “Pay more, get less?”, in relation to Mazda’s ads of low weight and purposeful lack of amenities. These are the people that filed most of the complaints against the car, eventually giving it it a reputation as a finicky car. What they had failed to understand was that the third gen was purpose-built. Even long-term tests in such magazines as Motor Trend and Car & Driver noticed these “imperfections” but were willing to forgive the car because of it’s sheer exhilarating driving experience and looks. Very few other cars ever produced in automotive history share the capability this car had right off the showroom floor. These cars merely need stripped of their amenities to be capable of winning races the world over. So with all this in mind, we appeal to you, the second and third-hand owners who can appreciate the car for it’s true calling. But don’t worry, we didn’t forget the handful of original owners who knew what the car was all about. Now that you’ve followed the rest of this book and at the very least have laid down a plan of performance work, we now give you, the guide to tweaking your FD to perfection!

RECALLS

It’s important to know about recalls on ANY car, but you might consider it imperative to a performance car. There were exactly THREE recalls regarding the third gen., however, only one applied to later production models (see dates in following text). Remember, the Mazda dealer is required to place a sticker for each recall on the inside of the driver’s side door jam. However, if you are not the original owner, you may want to make certain the recalls have been done. Previous owner(s) may have had them done but may have removed the stickers in an attempt to make things look cleaner.

Recall #54407 - Coolant Leak This recall was announced to address a problem with various cooling system components failing after being prone to extreme temperature conditions. In a few rare cases, it was believed to be the cause of an engine fire (dried, concentrated antifreeze left over from a leak is combustible). Affected models include those produced prior to December 21, 1994. Parts replaced as a result of the service and the changes made are as follows:

PART NAME MATERIAL (Old ( New) DESIGN TEMP ((C) (Old ( New) Water Pump Seal NBR ( EPDM 125 ( 150 Water Level Sensor Polyacetal ( PPS 125 ( 200 Filler Cap * NBR ( EPDM 130 ( 150 Filler Neck Nylon ( Aluminum 130 ( 235 Upper Radiator Hose Polyester ( Nylon 130 ( 150 Throttle Body Coolant Hose Polyester ( Nylon 130 ( 175 Air Separator Tank Coolant Hose Polyester ( Nylon 130 ( 150 Thermostat Gasket NBR ( EPDM 125 ( 150 (Pressure also reduced from 1.3 Bar to .9 bar)

Recall #60504 - Fuel Leak Similar to the above recall, only pertaining to fuel lines. It affects RX-7s produced before September 1994 and includes those with a VIN of JM1FD33**R0303550 and earlier. The recall consists of replacing the fuel lines with those of a different material and adds a fan control relay to the ECU which runs the radiator fans for 10 minutes after shutting off the engine, provided a certain temperature was observed. The fuel lines, as in the coolant lines, were found to become brittle and develop cracks after being exposed to extreme heat (as in racing) and then cooling down from being parked. The replacement lines are resistant to higher temperatures. The easiest way to check if the recall was done on your car is to check the back of the ECU for a small, black square control module. The part numbers for the recall items are as follows: N3A1-18-SE0 Fan Control Module N3A1-13-S70 Fuel Hose Kit

Recall #65609 - Brake Line This recall covered all third Gen. RX-7s ever produced and was not regarded as critical as the first two. There is a brake vacuum hose which runs from the upper intake manifold (pass-side) to the line connecting the master cylinder. The original hose contains a check valve, which has been known to stick after time from the oil mist running through the intake. The replacement hose does NOT have the check valve. Other than that, the size, shape, and material is the same. To check yours, you simply need to squeeze the hose near the middle to feel for the check valve (kinda makes a bump as in a worm’s body) . If there is one, you will not be able to collapse the hose, however, if you can squeeze the hose diameter anywhere along it’s length, then you know the right part is in place. Not that it’s a difficult piece to remove if you so desire to be extra sure.

THE LITTLE THINGS

We call these the “little things” because they don’t affect performance, but considering some of the fixes, cost Mazda quite a bit. They may not seem little to them. Also, they are listed in order of importance (in our opinion), from least to most, not chronologically or by TSB (Technical Service Bulletin) number.

A Chip Off the Old Block

One of the earliest complaints with the third gen RX-7 was that of the paint chipping easily. This never resulted in an official TSB, however, was handled on a case-by-case basis. The problem was caused by a poor primer bond and many of the owners who complained received a new paint job at their dealer, courtesy of Mazda. But it wasn’t until numerous complaints stacked up that got Mazda’s attention. Several owners had even contacted legal representation when told (at first) by Mazda that it was a result of their driving habits. The poor primer was used up until late ’93 (94 models). It’s too late to get this problem rectified for free, however, you can tell if you have the defective primer (remedies by early ’94) by examining any paint chips you have, checking for a white primer. The corrected primer has a medium gray color and adheres the paint to the body rather well. Another common complaint with the early FDs was with the matte-black interior panels chipping and peeling. This resulted in TSB #05692, issued in December of ’92. It applies to those RX-7s produced through August 4, 1992, (up to VIN ending in 207441), although several customers with later models had complained. The revised parts listed below reflect a stronger adhesive between the panel and the coating:

Center Panel (houses the stereo and climate controls) FD01-55-210B
Meter Hood (Houses the gauges) FD01-55-420E
Switch Panel (Houses the shifter and ashtray – manual) FD01-64-471D
Switch Panel (Houses the shifter and ashtray – automatic) FD01-68-4LY
Arm Rest Trim/Lid (Driver’s side) FD01-68-4M0A
Front Assist Grip (Passenger’s side) FD01-69-44XA
For the ’94 models, Mazda redesigned the parts again, this time without the coating.

Worth The Trouble?

Enough people have complained about the “thud” the power windows make when lowered all the way down, that Mazda redesigned the rubber stopper. This TSB (#03193) was issued in June of ’93 and the resulting new part number is #FD0158565. I would just as soon live with it than risk damaging the door panel to get at it.

Shake, Rattle, Roll and Whistle

Technical Service Bulletin #01093, Category S deals with a noise from the rear hatch hinges, commonly referred to as the “rear-hatch-rattle”. This TSB was released in February of ’93 and applies to vehicles with a VIN ending in 210513 and before (produced through November 30, 1992). Mazda redesigned the hatch hinges to eliminate the rattling that occurred when driving over bumps and on rough roads. The modified part number is FD01-62-210C, while the original part number is FD01-62-210A. There are other ways to solve this problem as well. Some owners have experienced success by repositioning the latch, which can be easily accessed by removing one interior trim piece. However, a few report that the rattle returns after several months or so many miles. I have found a more permanent solution, which is to tightly wrap a thin strip of metal around the latch’s “loop” and secure it with tie-wraps. While it doesn’t look pretty, it’s worked for over a year so far after more-than-average hatch use (I frequently compete in autocrosses, drag races, and go to driving schools, thus requiring removal of all “excess baggage”, not to mention all the regular trips to the grocery store and weekend get-aways).

Similar to the above, except with the hood. Described as a “squeaking” sounds rather than a rattle, TSB #05792, Category S, was issued in December ’92 to address this concern. It pertains to FDs produced through July 2, 1992 (or up to VIN ending 208750). The so-called “fix” was to place a washer (part number FDY1-56-788) under each rubber cushion, however, I did the same thing I did for the hatch and to much success as well. Again, my hood goes up/down more than the average RX-7’s and that says a lot. Mazda actually redesigned the hood for those vehicles produced after July 2, 1992, which indicates to me that the washer program didn’t work out. Finally, a little grease on the latch goes a long way, as it is the real source of the “squeak”. But the grease will need replenished every once in a while.

Some owners of early FDs experienced a squeaking sound when opening/closing the doors. The noise was caused by the door checkers. To correct the problem, Mazda modified the part. TSB #01094, Category S, was issued on February 11, 1994 and applied to those vehicles produced through VIN ending in 210664. The part number changed from FD01-58-270A to FD01-58-270B. Some third generation RX-7s may emit a whistling noise around the windshield when being driven at high speeds (now who would do that?). It is caused by air being pulled between the molding and the windshield, so Mazda designed a foam seal repair kit to eliminate it. Later FDs have the foam seal attached to the windshield molding at the factory. The TSB number is 04992, Category S, issued October 5, 1992. It applies to those FDs produced through May 31, 1992, or which have a VIN ending in 207061 or earlier. The Foam Seal Kit is part number B001-77-739.

Mazda released TSB # 00293, Category S, on February 5, 1993 to take care of wind noise from around the door windows. The noise was caused by air entering the cabin near the outside door handles (both sides) due to the windows not fitting flush with the guide channels. Mazda redesigned the parts as indicated below. This problem occurred in vehicles manufactured through April 30, 1992 (VIN ending in 205708 and earlier).
Front Glass Guide (R) New Part # FD01-58-601B Old Part # FD01-58-601A
Front Glass Guide (L) New Part # FD01-59-601B Old Part # FD01-59-601A

While we’re on the subject of squeaks, rattles and other noises, one complaint that didn’t result in an official TSB is that of a rattling, or “vibration” from under the car at certain RPMs. The problem is that the bolts which secure the heat shield to the main catalytic converter corrode, resulting in a loose fitment. It just so happens that the vibration caused at a certain RPM range causes the rattle to become more pronounced. New bolts with high-temp locktight and lock washers will solve the problem. If the catalytic converter itself is rusted, you may want to consider a smaller aftermarket replacement unit which doesn’t require a heat shield.

To Catch A Thief

Rather than fix a bug in the third generation RX-7’s alarm system, Mazda decided to just issue a sticker, to be placed in the owner’s manual. Technical Service Bulletin 00393, Category AD, was issued on March 3, 1993. It applies to VIN ending in 207440 or lower. Your local dealership is supposed to put a sticker on the lower right side of page 2-10. If any of the doors, hood, and/or hatch are opened prior to removing the key from the ignition switch, the theft deterrent system will not arm. Another sticker which applies to vehicles made after June 7, 1992 gets placed on page 2-11.

Bust a Cap

Some vehicles may have center caps that do not fit flush with the aluminum wheel. This is caused by contact between the cap and the axle flange. Mazda redesigned the center cap and instructed their dealers to replace them for any owner who desires, under warranty, of course. The resulting TSB# 00392, Category Q, issued on September 14, 1992 applies to FDs built prior to February 10, 1992 (or up to VIN ending in 201892). The original PN FD01-37-191A was replaced with FD01-37-191B.

Auto-Tranny ECU Woes

If the hold indicator light starts flashing on your automatic-shift FD while it’s running, you may be in for a new ECU! Take it to your dealer and have them test for torque reduction control fail code 57. This TSB# 01292, Category K, was issued July 15, 1992 and pertains to 1993 RX-7s built prior to May 11, 1992. The old ECU PN is N3A2-18-9E1 while the newer one adds a “B” at the end. Take a look at your to see which one you have if you’re not the original owner.

Four Holes in One

There are four tie-down holes located underneath the car, two behind the front wheels about 10 inches from the side of the car and two in front of the rear wheels about 4 inches from the side. These tie-down holes are used during transport. Tie-down hole plugs need to be installed on FDs produced after May 20, 1992. The plugs will prevent water from penetrating the body which will result in rust. These plugs should have been installed by your dealer. This pertains to TSB# 05092, Category S, issued October 19, 1992.

I’ve Got a Secret

If the anti-theft feature of the stock FD’s stereo is active when power is disconnected, such as for service, the display will flash “C-O-D-E”. The feature is supposed to function so that if the code is not entered correctly after three attempts, “E-R-R” will flash, indicating that the unit is unusable. However, “bugs” in the system may cause it to go directly to “E-R-R” any time the power is disconnected when the anti-theft feature is active. Mazda did some thinking ahead of time and programmed a “secret” code, or button sequence, which will unlock the stereo and return it to normal function. For the longest time, this “secret” code has been unpublished to protect owners against thieves from stealing the units without fear of the anti-theft feature. Well, even though this book is being published year after Mazda stopped importing the FDs, there will be no exception here. There are still enough of them out there being driven on a daily basis and we don’t want to jeopardize even one five-year-old stereo. Not to mention, the code may be similar to other Mazda stereos, even to this date. If you are experiencing this very problem, please visit your local Mazda dealer for service. Since it is a known problem, they should know about it and do it for free. I’m sure they’ve inadvertently activated the “E-R-R” on some of their customer’s cars.

THE NOT-SO-LITTLE THINGS

Unlike the “little things” these items DO affect performance. They may all be considered important and are therefor not mentioned in any particular order.

Engine Mounts

One of the first complaints that related to something more important than squeaks and rattles was that of a noise coming from the front suspension and/or steering. The sound, described by many as a “clunk”, occurred at low speeds or when the wheel was turned from lock to lock. There were three TSBs which Mazda released to address this problem. The first was TSB #00293 Category B, issued in February of ’93, and applies to vehicles produced through May 31, 1993, or VIN ending in 207061. Here, engine mounts were redesigned with greater clearance between the rubber mount and the mount housing. Although the part changed, the part number did not. If you’re curious as to whether or not your car had the mounts replaced, call your local dealer and give them your car’s VIN. They should be able to look any of these on their computer. The second TSB related to this “clunk” was # 00493 Category R, issued in May of ’93 and then revised in August that same year. This time, the rubber A-arm bushings got replaced (two per side) with revised part #FD0134480A. The last of the three TSBs was # 00293 Category N, issued in October ’93. Now the steering rack boots were redesigned for both the left and right sides. The modified part numbers are: FD0132125A = Left (Driver’s) Side FD0232125A = Right (Passenger’s) Side

Stick With The Best

To improve fuel injection performance, Mazda has tested and approved a highly effective fuel injector cleaner. The kit and cleaner is recommended for all Mazda fuel injection systems. Mazda’s cleaner uses a chemical reducing agent rather than the common solvent used in typical aftermarket cleaners. As a result, in tests against aftermarket competitors, Mazda’s cleaner outperformed all others and was the only one to restore the fuel injector’s flow rate to original factory specs. Mazda recommends cleaning the injectors every 15,000 miles. The items listed below pertain to TSB# --193, Category F and applies to ALL fuel injected models.

DESCRIPTION PART NUMBER REMARKS Fuel Injector Cleaner 0000-77-2019 Case of 12 cans
Toolkit 0000-77-2026 With instructions, required for Use with the cleaner
Service brochures 9999-95-043N-92 QTY: 1 pkg. Of 50

Emission Failure

RX-7 Fails State emission inspection. TSB# 00593, Category F, pertains to all RX-7s in respect to failing state emission inspections. The TSB was issued April 28, 1993 and states that some RX-7s with properly functioning emission control systems may still fail unless the following procedure is done prior to the test:

Engine should be warmed up, but not overheating All electrical loads, especially the A/C, should be turned off. For 5-speed models, the neutral range should be selected For automatic models, the neutral(N) or park(P) range should be selected. Before testing, bring engine operating temperature to normal by running the engine for three minutes at 2500-3000 RPM. Test the vehicle as soon as possible after the engine has been warmed up to normal operating temperature.

Engine Stalls During Warm-up Period

Some 1993 RX-7 vehicles may experience stalling during deceleration with the throttle released approaching a stop. This occurs during initial warm-up and sometimes after the car has reached operating temperature. Also, when idling with the A/C on, engine speed decreases as the A/C compressor engages or the idle may fluctuate. The ECU has been modified to countermeasure this phenomenon as per Technical Service Bulletin 03292, Category F, issued on December 23, 1992. It pertains to 5-speed models with VIN ending in 208703 or lower (produced through July 2, 1992) and automatic models with VIN ending in 210513 or lower (produced through September 30, 1992). The modified ECU is designed to 1) make air/fuel ratio adjustments to maintain stable idle at all temperatures and 2) turn off the A/C compressor when the clutch pedal is depressed or when the accelerator pedal is released. The following list was used as of 1997, so you may want to consult your dealer, or Mazda’s Customer Service if you suspect your car is suffering from this problem. Replace ECU under warranty with the following part: N3A1-18-881R ECU (Federal 5-speed) N3A2-18-881R ECU (Federal Automatic Transmission) N3A3-18-881R ECU (California 5-speed) N3A4-18-881R ECU (California Automatic Transmission)

Slipping Clutch

TSB# 00193, Category H, was issued on December 17, 1993 to address a common complaint with clutch slippage and/or premature wear, and was revised in 1994. It applies to those 1993 FDs with a VIN ending between P0200001 - P0299999 and 1994 FDs with VIN ending between R0300001 - R0300031. Here again, Mazda put blame on the customers, stating that those with the following habits may experience this problem; starting from a stop in second gear and/or hard acceleration. What were they thinking? Anyway, the facing material of the clutch disk was changed to decrease slippage and improve wear. The original clutch disc part number N315-16-460A was replaced with part number N315-16-460B, and then N315-16-460C. Mazda has used the revised clutch discs in RX-7s since October 8, 1993.

The Grind

If grinding occurs when shifting to fifth gear, a damaged fifth gear synchronizer ring is the cause in most cases. Although Mazda tried blaming the driver for this one, enough occurrences have been reported to provoke them to redesign the shift select spindle to increase the accuracy of the shift pattern. It’s also been said they raised the spring force from 6.7kg to 8.9kg on the shift select spindle. This is TSB #00194, Category J issued in January of ’94 and pertains to those FD’s with VIN ending in 210508 and earlier. The new part number for the shift select spindle is R503-17-550 and the synchronizer ring is part number W501-17-725B.

UNMENTIONABLES

The following items were not causes for known Technical Service Bulletins but are well known within the rotary community. They should be dealt with by the experienced owner with knowledge and/or discussed with other owners before taking corrective action. Paying a visit to the nearest rotary specialist shop or third Gen. RX-7 expert is highly recommended in many cases.

Risk of Fire in Fuel Rail

On the right side of the primary fuel rail is a brass cap - this is the pulsation damper. It's job is to smooth out the flow of fuel from the in-tank pump. In my hand is the plastic cap that normally covers the damper, and rolling around inside of that is the infamous screw that prevents the damper from leaking. This is the condition I found the parts in when I removed the intake. This is bad! Several owners have had engine fires as a result of this screw falling out and fuel leaking down onto the 1800 degree manifold - boom, Hindenburg. Well, maybe not quite that spectacular, but a serious fire nonetheless. Screw the little bolt back into place, clean off the surface of the damper around the bolt, and load it up with JB Weld so it can't back out again. DO NOT USE LOCKTITE. Gas can break down loctite, and then you have little chunkies floating around in your fuel system, clogging up injectors. It's a good idea to check this out whenever you have the upper intake manifold off, or if you smell gas under the hood!

Clogged Pre-Catalytic and/or Main Catalytic Converter

In many cases, the material within the pre-catalytic converter (pre-cat) breaks down from extreme heat and vibration, such as experienced during competition. This material, or debris, can either remain inside the pre-cat, thus clogging it, or it can flow into the main catalytic converter (main-cat) with the same result. In either case, the result is restricted exhaust flow and increased temperatures… ultimately which can result in the death of the engine! One sign this might be happening would be excessive engine temperatures, which can be observed either by the gauge or by noticing abnormally high amounts of heat under the hood near the pre-cat. Or, you may experience rough or fluctuating idle. Another sign is that of slow acceleration or extensive turbo lag. You could also experience a “bucking” during acceleration, or backfiring under deceleration. If caught early enough, a common remedy is to replace the pre-cat with a straight-through pipe, also known as a downpipe for the direction the exhaust flows. There are many brands and vendors available as well as options, so you may want to do some research before making a purchase. Some of the options included stainless steel piping instead of a mild steal, and ceramic coating to help keep the heat in the exhaust system instead of emanating to the engine compartment or floor of the car.

If caught later, and you suspect the main-cat to be clogged (same symptoms as described above) you could opt to replace it with either a high-flow model or a straight-through pipe, known as a mid-pipe (or center pipe) because it’s the middle (or center) pipe in the exhaust system. The same options are available for the latter that are available for the down-pipe. Just keep in mind that anytime you replace any catalytic converter with a straight-through pipe, you are likely to fail emission inspection, thus they are deemed “for off-road use only”. Not only that, but you are also likely to void any applicable engine warranty.

Wheel Hop Under Heavy Acceleration From A Standing Start

Early FDs were criticized for having excessive wheel hop during hard acceleration. It became such a big deal that Mazda started installing rear subframe connectors, which look like lengths of steel tubing connecting the subframe to the unibody. But wheel spin was still a problem for stock RX-7s because their twin-turbos made plenty of torque at the low end. Mazda then did away with the subframe connectors in favor or a redesigned rear subframe all together. Later RX-7s are said to have the best of both worlds, where the frame flexes just enough under hard acceleration to reduce wheel hop and minimize wheel spin.

Air Separator Tank Cracks or Explodes

In many known instances, the stock plastic Air Separator Tank (AST) cracks at the seams, thus seeping coolant. Even worse, it has been known to explode, dumping the coolant completely. The latter was only known to happen under extreme cases, such as at a track event. But in any case, if your third Gen. RX-7 is driven hard, you may want to consider replacing the plastic AST with an aftermarket aluminum version. These are available through certain RX-7 specialty shops such as Pettit Racing and Mostly Mazda (Now M2 Performance). There are individuals within the RX-7 community who make these at a fraction of the cost. They may not look at nice, but will perform just as well.

Catch Tank Clogs

Your FD is equipped with a device called a Catch Tank and is part of the fuel evaporative system. It is installed just under the throttle body and is inline with the charcoal canister and the intake manifold. Its purpose is to collect any charcoal “pellets” released from the canister and prohibit them from entering the intake. If your car is driven hard over time, such as in years of autocrossing, the charcoal canister’s contents may deteriorate at a rapid rate, thus depositing a greater amount of debris in the system. This will clog the catch tank, thus rendering it useless and causing fuel seepage from its lines.

One-way Check Valves Sticking

Aside from the one-way check valve mentioned in the brake recall, there are several others installed inline with different systems in the engine compartment, mainly the fuel system and the turbo control system. First, there is a valve between the aforementioned Catch Tank and the intake. If the catch Tank fails, it will release debris to this check valve, thus clogging it and resulting in the same consequences. If the valve doesn’t clog and will pass the debris through into the intake, it can find its way to any of the numerous check valves and solenoids that are part of the turbo control system. Heat is another common source of check valve failure, especially if your car is exposed to rapid heating and cooling conditions such as at competition events where after competing, you turn off the engine and raise the hood the let out the heat. Although this isn’t a good idea anyway (you should always let the engine idle for a while to keep the fluids flowing until normal operating temperature is observed). Constant heating and cooling of the checkvalves can warp the shell or the “guts” thus causing it to stick open or closed.

Solenoids Sticking

There are many solenoids that control many different things, of which there are six directly related to your turbo control system (see page F-10 of the Factory Service Manual). Unfortunately, they are susceptible to the same causes of failure as the checkvalves. If you are experiencing trouble with how your turbos operate and there are no obvious causes (such as splits in hoses or couplings and disconnected vacuum/pressure lines), then you may want to examine these solenoids for failure. The test procedure in the manual outlines tolerances as well. Very rarely do any solenoids fail all-together, however, if their operating tolerance is out of spec, then you may experience random turbo control problems, making it difficult to describe the problem to your local dealer or service shop.

On a final note, remember that any of the above TSBs were covered any existing factory warranty, and were only taken car of if the owner complained. Many of the items are not critical and the amount of time and money Mazda spent to correct them was minimal. You may wish to pursue some of the above items (and you still can), but you’ll have to pay for the parts and/or labor if your factory warranty is expired (there are only a handful of 1995s still under warranty at the time of this writing). The recalls, however, had to be taken care of and Mazda even had to pay on some hefty lawsuits as a result of defects prior to the respective recall campaign. It took Mazda a long time to recover from the losses they suffered by the FD, but the icon remains a legend to this day.

FULL BLOWN PERFORMANCE - Carburetion vs. fuel injection

Do you want crank you car’s performance level up a notch? Many experts today feel that the only way to go is with aftermarket programmable fuel injection, but there are also folks who feel that computers are for the office, not for racing. That real cars have a heart, and that heart is made of metal, not circuits. It’s the old argument: what’s better, carburetion or fuel injection? One common viewpoint is: “fuel injected cars start easier, idle consistently, and you can easily control the fuel mixture to optimize performance.” A counterpoint endorses a more classic view of the automobile: “carbs are what gives a car it’s personality. They’re a simpler concept reminiscent of simpler times. You feel more connected to the car because you get more hand’s on involvement”. You can hear discussions similar to this one in garages all over the country, and the participants often become passionate about their views. But before we start duking it out, we thought it it would be a good idea to take a long hard look at the pros and cons of both systems.

Obviously, you would have to be insane (or an SCCA member) to convert a 2G or 3G car to carburetion. That’s not to say that SCCA people (like us) aren’t a little be crazy, but at least there is a method to their madness. It’s the SCCA itself that seems insane sometimes. Why else would you be forced to rip out one of the most efficient fuel management systems ever developed for a street car, then replace it with a carburetor, just so you could go Road Racing with your 3G? But that’s exactly what you have to do if you want to compete in GT-3. Second generation owners face similar challenges. Even the “regional” road racing circuit, know as IT racing, restrict many fuel injected cars from competition. The SCCA Solo program, however, is more of an entry-level racing effort. Classes are structured so that you can maintain, or even modify, a fuel injected RX-7 and still compete successfully. The first generation cars are another story. Since their engines usually outlast every other component on the car (including the carburetor, body, tranny, etc). And up until 1984, they were all carburetor-equipped anyway, so, the only RX-7 that lends itself to a practical comparison between carburetion and fuel injection is the 1G. The act of choosing an aftermarket system itself provides a look into the future, as well as a hint as to what system is most desirable and efficient. In the early 1990’s there were more aftermarket carburetors to choose from than EFI systems, but as more people began to examine the benefits of each conversion, the tide turned. Probably the most popular conversion was replacing your stock unit with a high performance Delortto carb. There were actually a few Delorottos to choose from, offering the enthusiast options ranging from reliable street performance to pure racing. When Delorotto stopped producing side draft carbs, Mikuni and Weber offered an alternative. Distributed mainly by Racing Beat in the U.S., this “over the top” manifold and side draft set-up not only looked cool, but worked very well. Mikuni was the best choice if you planned on driving your RX-7 on the street. The Japanese-made carb idled much better than the Weber, and could match it’s performance on the race track as well. The jets were easily accessible by removing a small cap on the top of the carb, making tuning a simple task. The Weber, however, was more of a crude carb. It did not idle as well, and for that reason was recommended only for racing purposes. And even though the Weber carb is still listed in some RX-7 performance catalogs, it has been discontinued and is hard to find. Mikunis are even more scarce. So how many choices do carb fanatics have left: just one. But the good news is that this last choice may be the best. Holley, a long time U.S. manufacturer of quality carbs, still makes a unit that can be used to crank up the performance of your RX-7. And as this book was going to press, Holley has made a new commitment to the RX-7 community by working closely with Racing Beat to further develop their line of available carbs. Depending on how you want to use your car, there are several choices when it comes to an aftermarket carburetor. Holley offers a down-draft carb for both 12A and 13B, as well as for use on stock, street-ported, or even bridge-ported rotary engines. So even though there is only one brand left from which to choose, there are several options within that manufacturer depending on how you want to use your car.

It’s a sign of the times, and a testimony to what enthusiasts prefer, that there are now more EFI systems to choose from than aftermarket carbs. This shift occurred in the early 1990’s. Haltech used to be the only player in the mid-1980’s, followed by Electromotive in the late 1980’s, but now there are so many EFI brands on the market, it’s hard to keep track. The systems range from low cost (SDS- Simple Digital Systems under $1,000) to big buck (Motec, costing over $4,000 when all is said and done), and of course, everything in between. The rule of thumb remains consistent with what your father always told you when faced with making a decision such as this: “You get what you pay for”. The cheaper systems don’t seem to have the range adjustability that’s necessary to effectively smooth out “dead” spots in their EFI programming. You may be able to tune the systems for great low and high end torque, but for a few seconds during the transition, your RX-7 may feels like it’s pulling a trailer. The mid-priced systems are an excellent alternative to a Motec. One of our favorites is the Electromotive TEC-II, which Publisher friend Tim Suddard just used to power his Ro-Spit (rotary powered Triumph Spitfire). The TEC-II is very well suited for a rotary engine, and with enough of them out there in use on 12As and 13Bs, there are fuel maps to help give you a starting point when it comes time to fine tune your new system. Then there is the ease of tunability that should be considered when making your choice of aftermarket EFI systems. Most have a self contained programming pad that is included in the conversion kit, while others, like Haltech, require the use of a lap top computer to change parameters. We are not about to recommend a system. That should be based on your budget, and more importantly, what local resources you have at your disposal. For instance, is there is a DFI dealer near you that offers installation and technical support, then your choice should be a no brainer.

Lesson one when it comes to fuel injection systems is: even if you are planning to install the unit yourself, it won’t be long before you are on the doorstep of the EFI dealer, credit card in hand. If you have more than one dealer near you, then choose the one who has a chassis dyno in their shop. A dyno is essential for correctly tuning an new EFI system, and could be valuable when you perform other non-EFI related modifications. As a good customer, you may be able to buy future dyno time at a discount. Even if the local distributor’s price is $100 more than you can purchase the system for on the internet, we recommend spending the extra money to get it from the dealer, even if you install it yourself (see lesson 1). Try to develop a good relationship with the EFI dealer as it will come in handy later. It is true that once you get your new EFI system tuned properly you can basically forget about it. But if, over time, you add more bolt-on performance parts to your engine, your EFI system may need to be tweaked to reap more benefit from the improvements you made. The rule of thumb is: the EFI conversion should be planned as the last change you make to your powerplant. Spending countless hours tuning your system could all be in vain if, shortly afterwards, you buy a new header and/or exhaust system.

POINT: Traditional Power, by Mike Ancas

If after looking through the previous chapter, you have convinced yourself that converting to fuel injection is something you can’t live without, please read the next section written by Dennis Witt. You may want to postpone that decision until you know what you may be getting into. Most readers are familiar with the problems that can be encountered when dealing with hi-performance carburetion. This poor reputation, however, dates back to a time when carbs were generally unreliable and difficult to adjust properly. There is a new generation of carbs that are much more user friendly and can always be set up quicker and easier than installing an aftermarket EFI system. Holley, one of the leaders in intake technology, exemplifies this truism.

The carb we selected to do our conversion with was Racing Beat’s Holley 465 CFM 4-barrel that was specially modified to work on a rotary engine. Our project car was a 4-port engine from an RX-4. The first step is to remove the old manifold, as you will not be using it. The kit from Racing Beat comes with a new intake manifold, foam air filter assembly, linkage, and all the gaskets you will need. We also ordered the optional heat shield to help isolate the intake from the hot exhaust header. Remember, cooler air is denser air, which is more combustible and provides more horsepower. We had installed an aftermarket electric fuel pump and

Purolator fuel pressure regulator, which is highly recommended if you want to deliver a more consistent fuel flow to the carb. Removing the old manifold and carb turned out to be the most time consuming part of the project (took about an hour). Then the new manifold, carb and linkage were secured into place - done. Everything just bolts right on - it really is that easy. Our new carb required no adjustment other than setting the idle. At this point in the conversion, we knew we would be way ahead of the aftermarket EFI project as far as ease of installation and time commitment, since the carb project only took one afternoon to complete.

COUNTERPOINT: Electronic fuel injection, by Dennis Witt

Technology has a subtle way of changing our daily lives. The amazing advances in micro chip development has revolutionized the century old process of mixing a fuel and air mixture in the modern automobile engine. In a very short time span, the manner in which competitors have attempted to maximize horsepower and torque curves has been dramatically altered by the combination of computer power and fuel injection.

Historically, the fuel injected cars were a rarity, primarily due to the cost of the system and its mechanical complexity. Today what was once impossible is now feasible at a very reasonable cost in both time and money.

There are aftermarket systems available now which allow for the conversion of the old and outdated carburettored vehicles to take advantage of the powerful new electronically controlled fuel injection systems. Our comparison should validate the theory that a carburetor conversion “sucks” when compared to an electronic fuel delivery system that “injects”.

The heart of our fuel injected project is comprised of an intake manifold, 40mm throttle bodies, and a fuel rail kit, and linkage supplied by TWM. Injectors and technical advice were provided by RC Engineering, who has just about any size injector in stock and can tailor a “wet” system for any vehicle. The electronic brains of our conversion was handled by Haltech’s F7 control module. This is a throttle-position controlled injection system that computes air flow by monitoring throttle position and engine speed. Based on the resulting “air mass” computation and inlet air temperature, it adds fuel to the intake by electrically triggering a fixed-flow injector for a precise length of time (milliseconds). This is referred to as the injector’s pulse width. The more air that flows into the engine, the longer the pulse.

Now a bit of advice for anyone attempting an EFI conversion: start with a fuel injected RX-7 like an ‘84-85 GSL-SE or any 2G! We don’t recommend converting a 3G to aftermarket EFI, since there are ECUs available that can change parameters without the need for a new delivery system. But we were converting a car that was not initially designed for fuel injection, and that’s a difficult process. The main reason is because the standard 1979-85 RX-7’s carb only needs 3-4 pounds of pressure from the fuel pump, however it takes 30 to 40 pounds to run fuel injectors. If you start with a carburetored car, you will find that none of the existing fuel lines or hoses are capable of handling these higher pressures. So the first modification you face is how to get the fuel from the gas tank to the injectors without causing your fuel lines to burst. The solution requires the installation of a larger diameter stainless steel fuel line from the tank to the engine compartment (a difficult and dirty task).

That having been accomplished, if you haven’t taken a sledge hammer to the car in frustration yet and still want to move on, you will now need a get high pressure fuel pump to keep the hungry injectors happy. We chose a pump manufactured by N.O.S and distributed by RC Engineering, but you could go to a boneyard and find a used Bosch from a BMW 320i or a VW Golf. Next, AN fittings should be attached to the fuel pump and plumbed into our new stainless steel line. Not using the highest quality components could result in a rupture of raw gas spraying over both electrical and hot engine parts, resulting in a fuel fed fire rendering all of your hard work into a glob of melted metal and rubber.

We chose a 3/8” diameter steel line to handle the additional fuel flow, connected to a high pressure fuel filter to insure that no contaminants clog the expensive system. The stainless steel line conversion was one of the most difficult parts of the project.

Another frustration we faced was that the individual parts used to install an aftermarket EFI system come from different manufactures, hence the project is not an “insert part A in tab B” process. A significant amount of time was expended trying to figure out how the entire system would be tied together. One of the first things you must know is that different EFI systems use different injectors. there are essentially tow types of fuel injectors: “peak and hold” and “saturation”. We did another EFI project where we were given the wrong injectors for the system we selected, so be sure that the two are compatible.

You also need to be sure that you have selected the right size for your engine. Both RC Engineering and MSD have a formula that will help compute exactly what injector you need for your application. For this project, we used 34 lb/hour peak and hold injectors. Used injectors will also work (if you can find them), but we don’t recommend. It is likely that they are clogged, worn and will still need to be flow balanced by a company like Marren Motorsports, and that’s an extra expense.

Used injectors could throw off your parameters and result in decreased performance. You will also need to run an air filter, and we found that the ITG system fit well in the limited space between the throttle body and the RX-7’s inside fender well.

If your header is not fitted to contain an oxygen sensor, then a hole must be drilled so that a 22 mm nut can be welded in position. Your EFI system’s mapping is refined by monitoring the air to gas ratio throughout the operating range of the engine, and modifying the various parameters to optimize performance.

Of course you will also need a fuel pressure regulator to tame the 60+ psi worth of fuel that is headed toward the injectors. One is available from Essex Industries. At high pressure, sometimes not all of the fuel is needed, but you can tap into the fuel return line that’s already on your 1G RX-7 to direct this unused fuel back to the gas tank.

The moral of the story is that there are many things that can and will go wrong when you tackle a conversion like this. If you mentally prepare yourself to face these problems before you start, it could help preserve you sanity.

Time Commitment

The carburetion conversion is much more simple to undertake, period. With all components on hand, it can be done in one day. In summary, if you are starting with a carburetted car, you should make sure your fuel pump can deliver 2-5 psi of fuel pressure.

A trip to the local auto parts store can give you several to choose from for under $75. Switching fuel pumps can often be a dirty job, and some improvising may be necessary, but an average mechanic will have no trouble with any part of this carb conversion project.

Removal of the stock intake system and replacement with a TWM intake is a no-brainer. You will need to add some fuel hose in the engine compartment, and splice in an adjustable (1-5 psi) fuel pressure regulator (a fuel pressure gauge is also recommended). Then, some fiddling with the throttle and choke cables should complete your labor of love.

The EFI conversion, on the other hand, will take a tad longer. We recommend starting with a fuel injected car in the first place. That will save hours of labor converting a fuel delivery system that is used to providing fuel at 3-5 psi, to one that can handle 60 psi. If you don’t change the fuel hoses, the new 60 psi fuel pump will cause the weaker hoses to explode fuel into every nook and cranny of your nice little RX-7.

If you have never replaced all of the fuel hose in your car, you haven’t lived. There is a great sense of satisfaction that comes with completing the task, similar to the feeling you get when you have been beating your head against a wall, and then suddenly stop.

Installing the new intake manifold is no big deal, but there is more fiddling required than with the carb conversion. Much finesse is required when rerouting the throttle cable to the side of the engine as opposed to the top, where it was originally located (you’ll also need a longer cable).

Another problem we have seen with some EFI intake manifolds is they require more spring strength to keep the butterflies closed, and many stock throttle cables can’t withstand this tension. A day at the track can be ruined when your throttle cable gives way under the pressure (don’t ask us how we know this).

Fine tuning

Carburetion systems have been given a bad rap when it comes to fine tuning. Playing around with jetting can drive you a little crazy. But it is, at worst, a trial and error ordeal, something that any moron (even us) can endure. The shop that sells you the carbs should be able to give you a good starting point, and you can take it from there. Plan to spend anywhere from a few weeks to a few months to get the set-up that best fits your application.

On the other hand, the EFI systems are not easy to set up either. The problem is there are so many parameters, you don’t know where to start. Even when you get some initial guidelines, the amount of variables you need to manipulate can be mind-boggling.

It takes a great deal of experience (again, mostly through trial and error) to get the hang of it. And in the end, you will find that you are speaking a different language than your friends. When you tell them your car is running a little rich today because your water temperature and manifold pressure seem to effecting the duty cycle of your injectors (which is dependent on the MAP sensor and degree of dialed-in knock/retard), they will look at you as if you are retarded. If that happens, just scratch your head, declaring that you figured out that your closed loop high parameter needs to be 14.1 inches in order to obtain stociometric balance. That will shut them up.

The bottom line: Horsepower and Torque

Aftermarket performance carburetion on a rotary engine, if done correctly, can net 200+ hp and a 200+ lb/ft. of torque, depending on porting. Dyno tests show that much of that power isn’t achieved until after the tach goes above 5K. On the other hand, a fully sorted-out aftermarket EFI conversion will usually add about 5-10% to that number. So when it comes to raw power, the Haltech system will nearly always beat a Holley conversion. And although the best built carburetted RX-7s get good torque, there is more to be had with an EFI system. That’s because even a stock a fuel injection system can deliver better low end torque than a car sporting a performance carb. And when it comes to aftermarket EFI systems, your torque curve can be customized to deliver power wherever you need it. This is where EFI systems really stand out.

So the bottom line is that the EFI systems can deliver slightly more horsepower, and even a stock EFI system inherently will provide better low end torque than a carbed car. Add to that the adjustability of a system like the SDS, Haltech, Motec or Electromotive units, and the torque can be placed right where you need it most. But you must first consider what type of racing you want to do with your car before deciding which system to buy. The Solo II Street Prepared class is infested with aftermarket EFI cars, but to run an aftermarket EFI system in a Prepared classes will cost a 150+ lb. weight penalty. Most drivers feel that this is too much weight to spot the carburetored cars. That’s why the Holley carb conversion remains the hot set-up for the Prepared classes.

Tunability

Due to the multitude of parameters to consider, which in turn gives way to an infinite number of programming combinations, initially setting up an aftermarket EFI system is a long, tedious undertaking. There are initial “start-up” maps provided in the software, but most of the tuning needs to be done on a dyno with an air/fuel meter within view. On the other hand, a carb project is much simpler to set up. But that’s where the advantage ends. Once you get the knack of an EFI system, you can get it to do just about anything you want. For example, if you get to the track, and it is a hot humid day, no problem. Your programming adjusts for this scenario. You will be crossing the finish line ahead of the carbed cars whether you race in Texas or Alaska.

If you have ever seen the Pike’s Peak Hillclimb, you may have heard that most of the fastest vehicles have EFI computer systems on board that can adjust the air/fuel mixture dozens of times per second! They get to the top first because the atmospheric conditions at the starting line are vastly different than at the top. With an altitude change of over 7,000 feet , you could start out with a hot, sunny day and end up in the sleet and snow. And don’t forget what 15,000 feet does to the air pressure. If you have a hard time breathing at that altitude, it is a sure bet that your car does too. The computer in these aftermarket EFI systems can adjust for this variable, and carburetors can’t.

Reliability

With todays modern carburetors, reliability is not as much a problem as in the past. We had a Mikuni that ran great for years, but eventually the throttle bodies began to wear and very small vacuum leaks developed around the shafts. This is the same kind of problem that many British cars develop. But throttle bodies on the EFI engines can also wear, and often they are under more stress. This is because an EFI system can be more sensitive to the loss of vacuum that will occur if your throttle doesn’t completely close. For this reason, larger throttle return springs are often used, which tends to put more tension on the entire linkage assembly, thus increasing wear to the components. And injectors don’t last forever, either. They can clog, wear, and once the spray pattern and flow rate has been altered, you must have them cleaned. Professional cleaning will cost over $100 per set, and sometimes cleaning won’t help. Replacing an injector adds additional expensive. Remember to replace your fuel filter (also more expensive on an EFI car) every year or two. Your injectors will be grateful. Then there’s the higher pressure fuel pump, which works harder and is more expensive than the low psi unit on the carbed cars. If one of those wears out, the EFI pump will put a bigger dent in your wallet. Of course, these are about the only parts of an EFI system that wear.

So when it comes to reliability, maybe we should call it a draw. But if something goes wrong, it will typically cost more money to replace components in an EFI system.

Conclusions

Having witnessed both systems at work on the same car, the results were not surprising. 0-60 times were around 7 seconds for the Holley conversion, but after the EFI system was properly tuned (took 6 months), over a full second was shaved from that time, plus there was slightly improved gas mileage (as if anyone cares). The EFI system was also much better at start-up on cold days. Actually, the choice as to whether to go with a carburetor or an aftermarket EFI system is a simple one. You should base it on what you are planning to do with your car, and how high the credit limit is on your Mastercard. If you have some bucks, need low end torque, tunability and have plenty of time on your hands, then the choice is simple. Get yourself injected. If, however, you are in more of a hurry and only want to spend hundreds instead of thousands of dollars, then a Holley carb may be your best choice. Either way, you will have a killer RX-7 when you are finished with either conversion and experience full blown performance.

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