Pettit Racing General Information
Information and Recommendations
The following suggestions are intended to keep your car out of the shop and on your favorite road,
- Before you Upgrade
- The Mazda RX7
- RX7 FD Recommendations
- "Lessons Learned"
- Rotary Engines
- Heat is Wasted Horsepower
It is fact, that mechanical things will function as designed for a period of time, then preventive maintenance must be done, if neglected one can expect less than optimum performance or worse, a failure may occur.
If you trust your life to a mechanical thing it should be mechanically sound (i.e., up to date on maintenance, clean fluids and filters, brakes and suspension operational and working properly, good tires etc) Obviously, if something is wrong it could be dangerous and continued use under these conditions will usually cause more damage and expense when repairs are done.
If your vehicle is not running properly, or maintenance is not up to date or, or your just not sure, please see our recommendations on this page, or on the FAQ resource
As well, before upgrades are done, everything above applies including both turbos must be working properly and producing the correct boost levels. Upgrading a poorly maintained vehicle with inconsistent or low boost will not produce the expected results and could even cause expensive engine damage.
Always install upgrades in logical stages and install only one upgrade at a time. This allows you to evaluate changes in vehicle dynamics from each modification and if any problems arise, you only have to go back one step to find the cause.
Mazda’s Legendary RX-7:
The only rotary powered twin turbo sports cars ever built. As delivered from the factory these great cars had astounding performance, 13.5 1/4 mile @ 107 mph. 0-60 under 5 sec. amazing suspension and brakes.
Standard features on all 3rd generation RX-7's include:
1.3 liter sequential twin turbo rotary engine
Air to air intercooler
Digital Electronic fuel injection w/ electronic boost control
5 sp dual cone synchronized transmission w/ overdrive
Race type coil over shock- absorbers
4 wheel independent double wishbone alloy front & rear suspension
Power 4 wheel disc three channel Anti-lock brake system
Torson type limited slip differential
Factory alarm system
Bose stereo w/ pwr antenna
Wind tunnel body design for minimizing wind noise
The cars prepared by Pettit Racing have even more favorable performance.
The TKT (turn key terror) edition cars produce from 320 hp - 370 hp depending on the upgrade level and boast power to weight ratios as low as 7.5 lbs / hp.
Banzai Edition RX7's host a 3 rotor twin turbo engine capable of producing 500 hp with performance #'s like 0-60 in 3.9 sec., top speed over 200 mph and a power to weight ratio under 6lbs / hp.
Unfortunately there were only about 30k RX'7 shipped to the us and now its thought maybe half are still around. Of these, only about 250 TKT edition RX-7's have been built, making them some of the most unique, sports cars ever produced.
It’s a fact that Pettit Racing builds fast reliable cars and knows how to win. In ‘98 Pettit Racing won the Team and Driver Championships in the U.S.R.R.C. GT2 Pro Series. Pettit Racing has also won five SCCA road racing championships, over fifty national races and set numerous track records in rotary powered cars.
The ageing RX'7 and daily driving:
Because these cars are continuously ageing, those of us who like to use our cars for daily drivers are frequently challenged with new problems, this is not so bad if all the known ones are handled, however; when most conversations about RX7's still mention apex seal failures and concerns about the vac/sequential control system working properly and the 72 hose connection, (I've actually never counted them myself )etc. etc. One has to wonder what everyone is still doing wrong. Since inception Pettit Racing has reliably corrected and improved all of the known issues for countless twin turbo RX7 owners. but as they get older new failures will continue to occur.
We have heard and seen many recommendations and remedies people have tried and countless types of induction, intercoolers and turbos. Many owners on the web and forums are said to have 450 and 500 hp daily drivers, but often these cars don't actually run.
Some real stuff you don't hear about are some of the new problems, that we are facing. For instance the multi speed dual fan system has complex wiring, four relays and three trigger sources, we are encountering problems with this system more often and it is a common cause of overheating and a precursor for engine failure, not to mention issues from flakey electronics installations, poor workmanship from the repair industry and plenty of bad advice from the web.
Cyber RX7 vs. Driver RX7:
All this info could lead one to believe there are two worlds of rx7 owners, the ones on the web and forum making the same mistakes over and over again and all the owners you don't hear from who actually put down miles on there cars, instead of sitting at the box.
New buyer summary:
To sum it up and if you like challenges it seems that the most reliable 13btt RX7 for daily use would be one that is least aged preferably garaged and well cared for with low miles, minimum mods and no aftermarket alarms or or major electronics . Then take care of all common and known problems keep some clean underwear for passengers and enjoy.
The Banzai Edition is the model "T" of RX7's a very simple setup with only 3 or 4 vac hoses, a fully programmable ecu w/self diagnosis and even a simplified cooling fan system with single speed dual fans. Since the 20b will produce aprox. 400 rwhp and nearly as much torque at a relatively low boost it is the most reliable setup. Unlike the 13b rx7 everything under the hood of a Banzai, is easy to access a car that any good tech can easily service or repair.
#1. Always keep up with routine maintenance schedules as outlined in the owner’s manual.
#2. Upgrade chassis and engine grounding points with our FREE KIT. Just call and ask for one.
Do it now!!!
#3. Replace cooling system plastic air separator (A.S.T.), well known for splitting in half with no warning causing massive coolant loss and overheating. Our very popular aluminum upgrade units are always in stock.
#4. Replace that dirty fuel filter!!! Countless premature engine failures are caused by a dirty fuel filters. Don’t let this happen to you. Poor fuel quality also contributes to engine failures
ALWAYS USE PREMIUM FUEL!!!
#5. Install a turbo boost gauge! This is the only way to be sure the turbos are working properly. We produce several Kits. All are easy to install, and come pre‑wired with detailed instructions.
#6.Use fuel lubricant. This has been proven to extend engine life at least 30%.
For more info Check out Protek-R
#7. Get a Fire Extinguisher!! A must have for any vehicle...that way you will never need it! Our auto fire extinguisher installs in minutes and it looks cool, too.
#8 Most RX7’s benefit from cooler operating temperatures our 185f fan switch is a direct replacement for the original 210f part and as they get older its common to see 225f before the fans kick. As we all know cooler running improves longevity for the engine as well as all under hood components.
#9 Whenever possible open the oven door (hood) this stops the baking process and improves longevity for all under hood components. We have many customers that have proven this works; their cars continue to perform flawlessly year after year.
We always use premium quality fuel and we always mix Protek-R with every tank. 93-octane minimum for boost up to 12 psi. For higher boost levels, we recommend mixing a couple gallons of race fuel with 1/3 - 1/2 tank of 93, this can help prevent detonation. Check out Protek-R
How should I care for my RX-7?
The following was posted to the RX-7 list by Jeff Witzer. It was titled "Lessons Learned"...
"In the struggle to solve problems with my car, I have learned a few things that I'd like to pass on. This is prompted by last weekend's fix of some engine performance problems that had taken much of the fun out of driving.
There are several people on the list with much more intimate knowledge of our cars, but this might be a good collection of advice for the novice who whats to take good care of their 3rd gen. I've got well over 80,000 miles on my car and it still drives hard and produces a solid 14.5 pounds of boost with no complaints. Cam Worth at Pettit has remarked several times that he can't believe how well it still runs. He asked me to pass these on...
Warm the car up before driving hard
Start the car and immediately poke the throttle to prompt the kick-down. (Pettit actually recommends turning it off for a couple of seconds immediately after it catches to allow freshly pumped oil to seep into the bearings while they're loose, then restarting.) A lot of wear occurs during that 30 seconds or so at 3,000 RPM. It does this to warm the cat to operating temp sooner, but at the expense of your bearings. Within a minute, start driving. Warm up the car under light load, not sitting idling in your garage. Wait until the temp gauge shows normal operating temp before going above 4,000 RPM or above 5 lbs boost (see boost gauge below).
Let the car cool down after driving
Allow at least two minutes of cool down at idle after normal highway driving or after short bursts of full throttle. Allow up to 5 minutes after extended use of high boost. This allows cooling oil and water to reach the hot bearings in the turbo. Neglecting this will cause the oil there to coke into solids, accelerating wear. Always allow at least 30 seconds of cool down after using boost. I use and recommend a turbo timer which lets the car run for a preset time after the key is turned off and removed. I've heard rumors of list members getting in trouble for leaving their car running while unattended, so YMMV.
Oil and Filter changes every 3,000 miles (max)
This should be obvious. General consensus (and my practice) dictates 20W50 and OEM filters (new crush ring each time). This is for summer driving (which is all we get in Tampa). Some recommend synthetics, which can be run in rotaries, but may leave deposits as oil is routinely burned. For non-racing applications, stick to dino juice. I also use Pettit's Protek-R fuel lubricant, but some on the list have argued against it's claims... again, YMMV.
Rotate tires every 6,000 miles
You wouldn't believe how much this extends tire life. Of course this only applies if you've got the same tire sizes all around. I also get my alignment checked at this interval, but normal driving probably doesn't demand this.
Spark plug and fuel filter changes every 15,000 miles
You wouldn't believe the crud that the fuel filter grabs. Remember, the 3rd gen uses Miata filters, but flows twice as much fuel. New plugs have been the fix to most of my hesitation problems. The manual says 30,000 miles but I haven't found anyone who has gotten that much out of stock plugs. For normal applications, stock plugs are best.
Replace oxygen sensor around 60,000 miles
This is what has been biting me over the past few months. Major 3000 RPM hesitation, stumbling over 5000 RPM, loss of power if held at constant RPM with light throttle, and loss of fuel economy. Thanks to Cam at Pettit for this cheap fix. I was convinced my fuel injectors had clogged or finally given out (major $$, major effort).
Use synthetics in the gearbox and differential
After the car is broken in, replace these fluids with synthetics to improve shift feel, quite gearbox whine, and reduce friction and wear.
Install a boost gauge
This will be the best diagnostic tool you'll have. It's best to determine if that loss of power can be blamed on a loss of boost (due to the common splitting, cracking, or loosening of vacuum lines) before going through the expense of tracing fuel and electrical problems.
Be wary of dealer service departments
Since most dealerships service few 3rd gens, they tend to botch most non-routine procedures. Oil changes, spark plugs, fuel filters, etc they seem to do fine, but recalls (especially the fuel line recall) seem to be impossible for them. There are caveats, of course. If you don't see a third gen in a bay or two in the garage, I'd worry. Find a specialist you can trust.
Take upgrades slowly
Upgrade your car one step at a time. This way, if one of the mods is faulty or the car isn't prepared for it, you'll know which mod is to blame. Usually it's best to follow this order: cat-back exhaust, intake system, intercooler, ECU, main cat replacement, pre-cat replacement. Make sure your ECU can handle the increase in boost that the following cat replacements will generate. Talk to specialists before removing cats to ensure your engine is ready.
Check tire pressure and wear every car wash (weekly)
The 3rd gen is quite touchy when it comes to tires. Don't overlook these. Detailing your car is another subject...
All other normal car checks apply
Follow normal procedures for everything else. Take note of new noises or changes in performance and handling seriously.
Good luck and have fun!"
The Rotary Engine - How does Dr Wankels invention work?
There are some terms specific to the rotary engine that may help you understand its operation, or that you may want to refer to when viewing the table below.
A rotor is a somewhat triangular shaped engine component. It is roughly equivalent to the piston of a conventional engine, except that it has a total of three combustion surfaces (located between each apex) to the piston's one (the top or face of the piston).
Each rotor has three apexes, which are the points of the triangular shape of the rotor.
The rotors drive the eccentric shaft, which is the equivalent of the crankshaft in a piston engine.
A rotary engine consists of a sandwich with several layers. The rotor housing is one such layer that is the same width as, and contains a rotor. The inner shape of a rotor housing, which the rotor's apexes follow, is called a peritrochoid curve. These housings contain the exhaust ports*.
A side housing is another layer of a rotary engine sandwich that is much like the bread of a regular sandwich. Every rotary engine has exactly two of these as they are the layers that cap each end. These housings generally contain intake ports. The RENESIS engine also features side exhaust ports
The intermediate housing is found between two rotor housings. Because the rotary engines found in RX-7 & 8s have two rotors, they have only one intermediate housing. Intermediate housings also contain intake ports*. The RENESIS intermediate housing features a "siamesed" exhaust port for both rotors.
*Note: There are some rotary engines, called 'peripheral port' engines, that have their intake ports in the rotor housings and none in the side/intermediate housings.
How the Rotary Engine Works:
An intake event occurs when there is a chamber with an expanding volume open to the intake system. On a piston engine, this is when the intake valve is open and the piston is moving down. Intake on a rotary takes place when the intake ports are uncovered by the rotor, at which time the chamber open to the port will be increasing in volume.
A closed chamber decreasing in volume describes the compression cycle. A piston engine is in compression when the valves are closed and the piston is moving upward. Compression is achieved on a rotary as a result of the rotor moving in its housing such that the volume of its closed chamber is decreased.
The power or expansion cycle begins as the compressed intake charge is ignited by a spark. The gas expands as it is heated by the burning fuel. In a conventional engine, this force pushes the piston downward which works to turn the crankshaft. In a rotary engine, this force pushes rotor in a direction that expands the chamber which rotates the eccentric shaft.
The exhaust cycle clears the contents of the chamber preparing it for another full cycle. This is achieved in a conventional engine by opening the exhaust valve as momentum carries the piston upward. In a rotary, the leading apex of the combusting chamber uncovers the exhaust port in the rotor housing through which the spent charge is exhausted.
Other Comparisons to Piston Engines:
Rotary engine displacements seem small when compared to piston engines of similar power. In fact, both displacements are measured the same way. Displacement is the sum total of positive combustion chamber volume increases for one complete revolution of the main shaft (crank or eccentric). In a piston engine, this means the total amount of space swept by its pistons. In a rotary, it is easiest to think about the difference between the maximum and minimum volumes for a single chamber multiplied by the number of rotors (where each rotor has 3 chambers). Remember that the rotor actually revolves at one third the speed of the eccentric shaft, which is the reason only one chamber's displacement is used in the calculation. The difference in power is due to the fact that the rotary uses its full displacement to produce power for each revolution of the eccentric shaft while only half the displacement of the piston engine is producing power for each revolution of the crankshaft. Other differences also play a role; rotaries do not have the losses of reciprocating motion and there is no valve train to power.
Combustion Frequency and Power Stroke Duration:
When you consider the facts above, you will see that on a rotary, each rotor fires once per eccentric shaft revolution. In a piston engine, only half of the combustion chambers fire for a given revolution. This means that a 2-rotor engine fires as often as a 4-cylinder engine. However, the power stroke duration in a rotary is 50% longer, it being 3/4 of a main shaft revolution to the piston engine's 1/2. This makes a 2-rotor engine similar to a 6-cylinder.
Where does the turbo fit in?
Turbocharging is the exhaust-driven form of supercharging, wherein air is forced into the combustion chamber. When more air is available, more fuel may be burned, producing more power. This is known as "forced induction"
Mechanical supercharging involves a belt- (or sometimes gear-) driven air pump of usually one of the following types, Roots, Twin Screw or centrifugal.
The Roots type supercharger typically sits on top of a large V-8 engine and pumps air down into the intake manifold by the intermeshing of worm gears.
The Twin Screw supercharger spins 2 intermeshed "screws" which compress and pump air through a pipe to the intake manifold. It's placement options are more flexible so this type is more widely used. This is the type Pettit use for our RX8 supercharger.
The centrifugal supercharger spins a fan-like blade to pump air through a pipe to the intake manifold. It's placement options are more flexible so this type is more widely used.
The centrifugal supercharger may be driven by a belt (as described above), an electric motor (new technology), or by an exhaust driven turbine. This last form is turbocharging.
The Turbocharged Rotary Engine:
In the above diagram you can see a series of turbine blades being propelled by the force of the exhaust gasses rushing out of the engine. These blades are connected, via a shaft, to a compressor which forces air into the intake via an intercooler. The intercooler is an air-to-air heat exchanger designed to cool the air which has been heated during the compression process. Cool air is denser than hot air and dense air is the goal of turbocharging.
Notice that the behavior of the intake airflow arrow differs in the turbocharged engine diagram from the normally aspirated engine previously shown. The size of the intake (and exhaust) airflow arrows signifies flow in volume and speed. In the normally aspirated engine, this is dependent on the vacuum created by the change in volume of the combustion chamber. Near the end of the intake "stroke" of the rotary engine, the volume of the combustion chamber nearly stops expanding, dramatically slowing the draw of air. In the turbochanged engine, the force of the turbo continues to ram air into the still open intake port, pressurizing the chamber with air, unlike the slight vacuum in the normally aspirated combustion chamber. With more air to mix with, more fuel may be added, and more power produced.
Prior to the turbocharger is the wastegate, a vacuum or spring held trap door which leads to a shortcut around the turbine half of the turbo. When turbo boost reaches a preset level, this door is gradually opened to bleed off the exhaust pressure, avoiding overboost. The diagram shows this wastegate in an open position.
When less power is needed, the turbine naturally ceases pressurizing the air and the combustion chamber's vaccuum draws air in. Thus a turbocharged car can produce more power on demand without using more fuel under less demand.
How are the RX7 turbos configured?
The 3rd generation Mazda RX-7 has the world's first production twin sequential turbocharged engine. The key word here is sequential. In every other automotive twin turbo setup, the turbos provide boost simultaneously. Each of the turbochargers in this type of application is generally smaller than the one turbo used in a single turbo setup. A small turbo accelerates quicker, suffering less from "turbo lag" than its larger counterpart and, as a result, produces less power and torque but sooner and at lower rpm. Fitting twin turbochargers in sequence produces better results as the first turbocharger receives the full force of all the exhaust gasses (instead of sharing with the other small turbo) and gains speed much quicker, which enhances throttle response and increases low speed torque. At a predetermined speed, the second turbocharger is called upon to add more boost. With the twin turbos in full operation, exhaust gas flow resistance is greatly reduced, contributing to higher power output.
Assuring a smooth transition from single to twin-turbo operation as been an inherent problem with the implementation of a sequential turbo system. If the secondary turbo is not spinning at a high enough speed when it is brought in, the whole system "staggers", temporarily failing to produce enough torque for a smooth change-over.
Mazda's rotary engineers attacked this problem with a vengeance and perfected a solution to this technical challenge. In the primary boost stage, when only he primary turbocharger is operating, a portion of the exhaust gas is led to the secondary turbocharger, spinning it into a "pre-operation" mode. The boosted air from the secondary turbo is not required at this stage, so it circulates in an essentially closed intake chamber. Left in this condition, the turbo would eventually go into what is called "surge". This phenomenon is accompanied by a rapid temperature rise at the entry and exit of the compressor, which would harm the turbocharger if prolonged. In order to preclude this surging condition, a bypass valve is opened to form a loop in which the air circulates.
The secondary turbo maintains a pre-operation speed of around 100,000 rpm. However, this is still not high enough to effect a smooth transition to twin-turbo operation. The secondary turbocharger must accelerate faster. This is achieved by deliberately inducing surging by closing the bypass valve and letting the compressor spin within a closed chamber. This sends the secondary turbo's speed to as high as 140,000 rpm. When this speed is attained, the secondary turbocharger receives its full share of exhaust gas, and, at the same time, a control valve opens, allowing the secondary turbocharger to start supplying boosted air, adding to the primary turbocharger's. As previously stated, surging is harmful if prolonged, but in this transition state, it only lasts a few seconds, and therefore has not detrimental effect on the engine's durability and reliability.
The RX-7's 13B engine used twin Hitachi HT12 turbos with a 51 mm, 9 blade turbine and a 57 mm, 10 blade compressor. The turbine and compressor blades are a curved "high-flow" type that offers less resistance to air and gas flow. This results in faster turbine and compressor spin-up at high rpm.
The twin turbos are mounted on a cast iron exhaust manifold which has been named "Dynamic-Pressure" manifold by Mazda's rotary engineers. This manifold is elaborately shaped to minimize the distance between the exhaust ports and the turbochargers' entry paths, improving low speed boost by as much as 25 percent.
A special blueprinted, balanced, and contoured version of this same unit is used on our race cars. These units are capable of producing higher boost levels for extended periods. Check products page for more details.
Always remember to properly warm up and cool down your turbo and they will reward you with trouble-free operation.
Heat = Wasted Horsepower:
Thermal management technology has evolved to an art. Enthusiasts everywhere are realizing that potential horsepower and reliability gains are significant and are worth far more then their cost. Auto manufacturers go to great lengths to reduce heat radiation from exhaust and turbo systems on to the surrounding components. They use multi layer heat shields, reflective barriers and even ducting of air. All manufacturers agree that proper shielding of radiant heat is extremely important. Any vehicle can benefit from this technology, especially high performance and racecars.
RX7’s with single turbo setups, seem to gain the most from this technology, since most aftermarket single turbo kits are not supplied with adequate shielding, radiant heat blasts the lower intake, superheating the charge just as it enters the ports, this can raise the charge temperature in to the danger zone. Unfortunately, the air temp sensor is located upstream well before the radiant heat takes its toll, therefore RX-7 owners have no idea that this radiant heat is robbing horsepower and reliability.
Are you wasting horsepower? Pettit Racing is producing new Cool Power Thermal Management Systems designed to fit most RX7 single turbo kits, we are also working on a kit for the factory setup as well.
The new Pettit Racing Cool Power Kit uses the latest proprietary technology for thermal protection. These materials do not emit or expose the driver to harmful substances. The Thermal Barrier Panel or “TBP” is made from non-woven thermal insulation and is created specifically for use in areas where minimum space is available. The Thermal Barrier Wrap or “TBW” is made of woven thermal insulation, both types resists temperatures up to 2000 degrees F. Both materials contain no asbestos, are non flammable, will not corrode, and resist mildew and deterioration.
The Cool Power Kit for single turbo setup includes:
A custom Thermal Barrier Cover, fits around the turbo hot section, it is reinforced with inconel wire, assembled with stainless steel staples and has proven to be a very durable and long lasting part.
A stainless steel heat shield- fits between the lower intake and the turbo system, is layered with thermal barrier panel. The simple design retains an air space between lower intake and shield, further reducing heat transfer.
-20' foot roll of Thermal Barrier Wrap, “TBW” for the down pipe with enough material to wrap front section of the mid pipe.
-2 Thermal Barrier Panels, “TBP” are precut for the floorboard area just above the hottest section of the exhaust system and are designed to reduce heat transfer in to the passenger foot well and floorboard area. This can make a significant improvement in occupant comfort level.
-2' feet of hi temp metal tape, which is used to seal the panel edges.
-3 Stainless hose clamps to secure the wrap.
The Cool Power Kit for twin turbo setup includes:
-A 20-foot roll of Thermal Barrier Wrap, “TBW” for the down pipe with enough material to wrap front section of the mid pipe.
-2 Thermal Barrier Panels, “TBP” are precut for the floorboard area just above the hottest section of the exhaust system and are designed to reduce heat transfer in to the passenger foot well and floorboard area. This can make a significant improvement in occupant comfort level.
-1 Thermal Barrier Panel, precut for hot side of the cold air V-duct pannel
-2 feet of hi temp metal tape, which is used to seal the panel edges.
-3 Stainless hose clamps to secure the wrap
Not only does heat rob you of power, but uncontrolled heat can kill your rotary. Run cool, with Pettit Racing.
- All Natural Power (ANP)
- Rally Clutch
- Cromoly Flywheel
- Engine Essentials
- Silicone Hose Kits
- Differential Mounts