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P B Garrott's GTU / SC - DESCRIPTIONS

This is a two owner 1988 RX-7 GTU which was purchased in 1997 with 60,000 miles on the clock.

Upgrades were performed with SAFE power increases in mind since this is a daily (summer) driver. Mods in order: intake improvements, followed by fuel enhancements, supercharging and exhaust mods. Suspension, cooling, and electrical / gauge mods were done interspersed with the speed changes.

NOTE: Use caution when selecting a vendor for a supercharger kit. This supercharger project used a kit from Design Energy (Mariah Motorsports) which included a Paxton Auto supercharger and Nelson bracketry and ancillary pieces. This kit turned out to be seriously under-engineered and thus grossly over-priced. The SC pulley supplied is undersized and will overspin the Paxton supercharger - ultimately causing catastrophic failure. Paxton took 3 months to rebuild the SC after an extended arguement about warranty. Design Energy appears to be clueless about the kit's subcomponents and they don't stand behind the Nelson pieces - some of which are low quality. I had TWO mounting brackets fracture at the same place owing to bad castings. If one is knowledgable, it would be possible to fabricate a superior kit for less than HALF the cost of this one. I don't recommend dealing with Design Energy or Paxton. CAVEAT EMPTOR.

SUPERCHARGER: Paxton/Nelson SN-2000 from Design Energy Mariah Motorsports required approx. 20 hours for actual preparation and installation. Installation required re-routing engine wiring harness, careful shimming and alignment of serpentine pullies, upper radiator hose/neck replacement, removal of cold-start injector system and installation of remote boost dependent fuel pressure regulator. A conservative dyno pull yielded 212.2 RWHP which is more than a 60 hp increase. Design Energy is a small supplier that is erratic with its support and advice . . . but they are the only source if this kit.

REAR TOE ELIMINATORS (Racing Beat ): You're best off using a press to remove the old bushings. Ths is a larger job than one might expect and it takes several hours even if you have the right equipment. Makes the 7 much more predictable at the limit. Racing Beat is a solid and helpful supplier and they have now got a full online catalog (hurrah!). RB offers excellent advice.

ELECTRIC FAN: Flex-a-lite 150 from Summit Racing (Summit Racing )including thermostatic switch and mounting brackets. Brackets are massive but usable. The fan is adjustable for cut-in temperature. It can be mounted without removing the radiator but it's not recommended. Allow several hours. Keeps the 7 as cool as stock fan or cooler (in Ohio at least). Doesn't add power to the engine but DOES free up existing power to go to the wheels instead of the fan. Summit is mostly oriented toward American iron but their delivery is good and their pricing is okay.

OPTIMA BATTERY TO PASS. BIN: (Summit Racing) Recommend at least 2 ga. cable (0 ga. is ideal). Routed cable between the carpet and tunnel on the passenger side to a bukhead terminal and into original harness in engine compartment. Used a 200 amp. audio fuse at the battery for short protection. Recommend only sealed batteries due to hydrogen gas potential from charging battery. Can be tricky, took me over four hours as I tried to be very careful about power cable and sharp sheet metal. This mod lightens the front end and reduces polar moment. Enhances turn-in response.

COLD AIR BOX: Built from a series of hand-fit cardboard templates which were joined and transferred to sheet aluminum - then bent, drilled and riveted. The box is closed on five sides and the top seals to the hood with truck weatherstripping. See pic/dims. Fitting the template is the time consumer - took me over four hours. I've seen over 40 degree F. difference between box and engine bay. (Note: this was removed to make space for the oil pump for the SC oil cooler system.)

C's SHORT SHIFTER: (Mazdatrix) Buy replacement bushings and boots and do it all at once. 45 minute job. Nice short throw without excessive effort. I recommend filling the transmission with synthetic lubricant (Redline MT90) at this time - it makes a BIG difference in shifter smoothness. Mazdatrix has a broad RX-7 product line and a knowledgable staff (sometimes temperamental) - highly recommended.

BONEZ SUPERFLO: (Rotary Performance) This exhaust setup is run during "emissions season." See "header" for normal setup. This is a good way to replace both of the front cats and the rear cat with a presilencer and a high-temp free-flowing cat all in one (monolithic) unit. I recommend, however, buying just a high flo main cat (without the welded-on pre-cat eliminator) from Bonez / Rotary Performance in case you want to go with a header in the future. Direct bolt-on job. Quality product with definate power gain. RP is knowledgable and they have a wide 7 product line . . .though they tend to over state product capabilities. Recommended.

RACING BEAT HEADER PRESILENCER: (Racing Beat) [usually on the car - see above] This is an excellently constructed 2 into 1 header with heavy mild steel flanges designed for direct bolt-in fit - replacing the exhaust collector and all the cats. This exhaust front-end was purchased used and then ceramic coated at Performance Coatings of WA (fast service and good workmanship Performance Coatings ) and the resulting system is cooler underhood than the stock manifold. Installation is straight forward and takes an hour or so however it will require you to move your O2 sensor and EGT (if you elect to put the probe in the "collected" pipe) 8 inches farther away from the exhaust ports than on the stock setup. Result is negligible to the O2 but I found EGTs to read 200 degrees cooler there.

APEXi N1 CAT-BACK (RX-7 Store) This is an excellently constructed single-side exhaust utilizing very large tubing starting with ~ 2.5" at the cat-end to over ~3" at the rear muffler - which is stainless. The tip is over 4" - a bit ostentatious for my taste. The tubing is coated with a purple titanium application which seems to handle the heat and road debris without discoloring or corroding. This pipe uses stock hangers and is a straight swap. This is a loud setup when fed from a header without a catalytic converter. Even with the optional silencer bolted into the tip it is still loud (but a NICE loud - a deep grumbling type of sound). I painted the muffler and tip with flat black (color of the car) engine enamel to down play the look. Very stealthy now. The RX-7 Store (Columbus, OH) is a newer online supplier with a broad selection of 2nd and 3rd gen pieces. Excellent price on the N1 and prompt delivery. Recommended.

RACING BEAT STREET/STRIP CLUTCH & PP: Excellent quality clutch for spirited street driving with probably 25% more clamping force than stock with little increase in pedal pressure. If you are going to go with a light flywheel (light steel from RB is nice Racing Beat) do it now. This is a good job to bite the bullet on and have it done at a shop with a lift.

[I have an ACT heavy duty clutch and pressure plate on the bench but haven't installed it yet . . . the RB clutch just won't wear out even with the supercharger beating up on it. Stay tuned]

LIGHT STEEL FLYWHEEL (Racing Beat ) Quicker throttle response and improved accelleration. Doesn't create MORE HP it just reduces the parasitic energy normally used to spin up a heavy flywheel. There is NO difficulty when starting from stop with a light steel flywheel . . . maybe with a super-light aluminum one there is, dunno. Pricy but worth it in my opinion. Quality flywheel/counterweight package.

WAS TII FUEL PUMP/ NOW A WALBRO 255 LPH: Gives more FLOW for modified NAs and is a straight swap for NA OE pump (except for trimming the rubber isolator a bit for the TII). First swap took over an hour, fourth time (that's a long story) took less than twenty minutes. YMMV.

BONEZ STAGE 1 PADS AND BONEZ SS BRAKE LINES: (Rotary Performance) Good combination for firmer pedal and improved braking No noise, little dust and requires minimal warm-up to function. Bleed, bleed, bleed.

EBC GREENSTUFF BRAKE PADS: Obtained from EBC via phone to their sales office in Las Vegas as referred from a magazine ad. These replaced the Bonez to see if brakes could be even FURTHER improved. They could. The EBCs take less pedal pressure to affect the forward motion, not exactly GRABBY but quick to engage. I don't use them on the track but DID run to interstate speeds and back to zero several times in a couple of minutes. No fade or increased pedal pressure. These were installed in parallel with-

BREMBO SLOTTED / CROSS-DRILLED ROTORS: These rotors were obtained by auction for a price that couldn't be ignored. Went on simply and work well. I have no way to measure performance gain - if any - but they haven't warped with several 100 mph. sequential stops. At the least, they look sexy.

PORTING: Templates for enlarging the 6-port 13B (Mazdatrix) come as a sheet of aluminum with Dychem squares painted on it which are etched for port shapes. You need to cut out the port shapes in order to transfer the shapes to your (Dychem stained) irons. Actual port enlargements are conservative but this is just what I wanted with a boosted, high compression engine. Mazdatrix is NOT eager to support porting projects and are unlikely to answer porting questions.

INJECTORS: I am using 460 cc. primaries and 550 cc. (ShaneRacing) secondaries to support high end boosted-flow requirements. For cleaning and flow-testing Marren Motor Sports is okay (but slow). Clean injectors minimze flood tendencies and assure even/expected flow. Marren advertises 2 day turnaround . . . my experience puts their turnaround between 2 to 3 weeks. Not really recommended - but the options are limited. . . you might try RC Engineering for quicker turnaround. My set of 720 cc. GSL-SE injectors I'm going to have cleaned / tested at a local diesel & machine shop. Stay tuned.

OIL SYSTEM MODS: I replaced the stock rear oil regulator with an 80 psi. one (RB), replaced eccentric oil injection springs and balls with Weber 2mm. jets (Racing Beat) and replaced the stock oil pump with a TII one. . . I also replaced the eccentric bypass oil plug with a non-bypass plug (Mazdatrix) which puts oil through the engine ALL the time (I'd rather have a slow warm-up WITH oil than find I have a quick warm up and NO oil circulating). I removed oil injection system all together, plugging injector holes with bolts/washers and the injector pump opening with a cover plate. Overall engine oil flow should be increased significantly, oil temps. should be reduced and the amount of heat carried out of the engine should be improved. With premix being used in lieu of dirty engine oil in the intake charge - engine should remain cleaner. All difficult to prove but looks good on paper. The 80 lb. regulator makes the stock oil pressure gauge read about 95 lbs - but there are no observed ill effects. I intend to add a quality oil temp and oil pressure gauge (the stock oil pressure gauge is VERY suspect) but the question is where to mount them.

OIL COOLER TO BLOCK STAINLESS STEEL BRAIDED LINES: Replacement lines from Mazdatrix were a perfect fit and sealed fine. Original lines failed at 126,000 miles near the oil cooler banjo (top). Took only 15 seconds to empty 3 quarts of 20w 50 on the street. When you need replacement lines you need 'em Cost less than Mazda rubber / nylon lines. Go stainless.

EIBACH PRO SPRINGS: "Pro" means progressive . . . these springs are soft when gently cruising but as they compress they become much firmer. NOT for racing where linear feel is preferred but these are GREAT for the street. (Mazdatrix) Lowers the car 3/4" and does not make daily driving any harsher (perhaps a little softer) but firm up immediately under use. Again, I recommend using a shop and lift. Lowers CG and reduces roll.

TOKICO HP STRUTS blue: (Mazdatrix) Good replacement for stock shocks. Slightly firmer, non-adjustable, economical. For racing the tokico 5-way adjustables are possibly better and the KYB AGX are almost certainly so.

GAUGES: A/F gauge is Intellitronix (Summit Racing ) and utilizes a series of LEDs. It functions well enough - tapping into the stock O2 sensor - but is cheap. I had to re-solder after the faceplate popped off of its own accord. NOT recommended. Oil Temp, Oil Pressure and Water Temp are VDO gauges also from Summit. You need to be careful to order the right senders seperately from the gauges. These three are mounted in the old ash tray area. Boost gauge is from VDO (Pegasus Racing) and is the only one I could find with a 0-15 lb. scale w/no vacuum. With the supercharger the needle sweep uses 2/3 of the scale where most other gauges with 30 lb. scales & vacuum would only register 25% sweep (for the 0 to 10 lbs of boost) - too small a sweep to be significant. I took a "T" in the boost line to the BDFPR. The EGT is Westach (Pegasus Racing) and reads 700 degrees F. to 1700 degrees F. allowing for hot RX-7 exhaust (1400 degrees F. at 3500 rpm lean cruise). I used the 3/16 probe and SS hose clamp installation kit instead of tapping the exhaust collector. Life expectancy results will follow. Pegasus Racing is just that - a racing supplier. Good products, good info but not very rotary-wise.

PLUG WIRES Magnecor 10mm. (Rotary Performance) wires are probably overkill but I was concerned with underhood temperatures with the supercharger. After 2 years they are still delivering spark, are still pliable and still fat.

FUEL LINES Aeroquip AN -6 Stainless Steel (Summit Racing) OE steel fuel lines rotted out at 15 years age and 146,000 miles - starting to actually leak behind the passenger bins. It is necessary to drop the rear sub-member and the fuel tank in order to install new OE bent-steel lines (ask me how I know this) so it makes sense to just fabricate new from flexible stainless steel braided. The Aeroquip lines went together easily (if you are careful and take your time). Fuel feed line is about 7' and the fuel return is about 8' so you can get the two out of a 15' length if you are careful. Pain to have to convert from AN to socketless barbs to go into the fuel tank though.

VACUUM LINES All vacuum lines have been replaced with silicone (Baker Precision , Summit Racing , AgriBusiness Supply ). About 10' of 3mm. about 4' of the 6mm. about 4' of the 8mm and a few feet of 10mm. CAUTION: Some suppliers are starting to ship silicone hose that is thin wall . . . I recommend using only 3mm. id. hose that has a wall thickness of 3mm. also (9mm. diameter vac hose for 3mm id.) Thin wall, small diameter, hose WILL kink. T-Bar clamps, which are good at holding high boost without cutting silicone hose, are hard to find. I had to go to an agricultural supply house in Iowa!

A'PEXi SUPER AFC: (ShaneRacing ) Ray Lochead of SR offers outstanding customer support. He's a top racer (9.89 in stock body 3rd gen) and still is willing to support his sales personally. The S-AFC (Super Air Flow Converter) allows tuning the flow of the 550s when the ECU thinks that they are 460s . . . then again, the ECU doesn't know that it is being blown either.

MSD 6A Ignition - This capacitive discharge / multiple spark ignition system was installed in about an hour and was chosen to provide a hotter spark to the dense (supercharged) gas/air mix at boost. Frankly, I have seen virtually NO difference between the MSD and stock ignition performance and I sometimes leave the 6A off the car for weeks at a time without realizing that I have forgotten to re-install. YMMV.

WHEELS Stock wheels with the '88 GTU are 15" "bologna slicers." The initial upgrade was to 16" turbines (from an '87 TII) but these are pretty heavy. I got lucky and finally located a set of 16" GTUs wheels (honey comb ala BBS) which are about 16# each. A very nice improvement over the 21# each for the TIIs. Also not so common as aftermarket wheels (okay, I'm a snob)