Have a precat on 93 FD and Auto Transmission. Car came with no cat and Mickey Mouse Exhaust from previous owner.



Want to get rid of hacked up pre-cat and put a good exhuast system on the car. Ordered a down pipe but am afraid to run it without an ECU mod.



Running around 12 psi boost now with no mods to ECU sometimes it spikes to 14 psi between shifts. Worried about leaning the engine . Pettit told me to use a 67 orifice and limit boost to around 10 psi.

Be very worried - 11psi is the max I would allow without more fuel. I had intake, CB, DP and was only boosting 12 pounds and chipped an apex seal. Pettit gave you some good advice.

wait a sec. so you can't upgrade an Automatic 3rd Gen without upgrading the stock ECU?

Once you start to do alot of mods you need more fuel, A/T or 5 speed.

So what's going on with your car now?

All you did was put a DP and catback and it has 12psi of boost?

I have added a downpipe, Resonated midpipe, and cat back complete exhaust system. This all leans out the mixture and makes the boost go crazy. I am currently adding a mid sized intercooler to even complicate my problems more.



Right now with the Automatic transmisson the boost will creep to 15 psi or more if i didn't lift off of the pedal between shifts. This problem would not occour on a manual car since you lift at red line to shift gears. I am trying to tighten up the shifts but there are only a few transmission shops you can trust to do this. or you could sent the valve body to level 10 for modification, but the internal mods still should be done by a really good transmission specialist.



you have to add more fuel if you plan to modify your car. no one that i have found will modify the Automatic ECU, but there are several manufactures that offer a piggy back unit to control your fuel system. EFI sytems (also the PFS unit by Peter Ferrell) and a few others. the two I mentioned let you keep the hold function on your Automatic transmission car.



Even if you add the ECU you should have someone tune the car on a dyno and customize the fuel settings and timing etc. The more modifications the more obstacles you will encounter. I am working through over boost problems now and am tuning very conservatively with a EFI systems piggy back unit. I will schedule some Dyno time as soon as I get the problems worked out\



AK

The piggyback sytems are ok. I've heard of people using the PFS purple with a T-78.

yeah a few people have used the PFS but they aren't the best.....