Julian's 12A Turbo RX7

 

1/4 mile best of 16.2 @ 81 MPH, with factory tiny dual exhaust. (All 1/4 times quoted are in full street trim - no weight reduction, special tyres or exhaust removal. Car only does 2.0 sec flat 60 ft times on a good day, so it's not set up as a drag car)

Fitted rebuilt 12A turbo motor 3 years ago. Motor ported, new seals & bearings. Microtech D5 computer & factory 12AT distributor. Light steel flywheel and 1 tonner clutch. After running in, boost was would up to 10 PSI with a simple bleed off on wastgate line. 2 1/2" press bend exhaust was fitted with single straight through muffler. In this form car did 14.0 @ 100 mph.

Found a mazda 4.44 LSD (rare & expensive!) about 8 months later and fitted it. Now would do 13.8 @ 100 mph.


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Turbo would drop boost after 4000 rpm. Obviously too small. Had the turbo high flowed (back cut exhaust and larger compressor wheel). Still dropped boost after 4000 rpm but now could get 13.3 @ 103 mph.

Fine and dandy for a while, but after a few laps of wanneroo raceway decided to check turbo, as it was leaking a bit of oil. After only 6 months of mostly gentle weekend driving (and some hard competition driving!) turbo bearings were flogged out and seals were not surviving! Warning for those who would hi-flow a 12 A turbo!

Found a T04B and intercooler (13B series 4/5) in the paper and brought it. Some guy had paid big dollars to set all this up and blew his motor on the dyno when they would 14 PSI boost into it! His loss was my gain, but turbo had to be completely recon (every moving part was replaced. Ouch!) Also added a Bosch blow off valve to try and minimise the lag.

Still running 10 PSI boost (will hold this boost till 8000 easy) car now does 12.8 @ 112 mph. Fairly dead below 4000 - 4500 rpm however. Turbo is fairly large (V trim compressor, 0.6 comp housing and large exhaust side - can't remember).

Plans: 4 spot RX-7 front brakes and bigger discs, lower heavy duty springs & 3" mandrel exhaust.

More boost is optional: there is a 3rd injector plumbed into the intake, but don't need to connect it yet. Not sure if motor would like much more boost, let alone the standard series 2 RX-7 gearbox.

Forgot to mention that computer was changed to Microtech Digi 2 a couple of years back.