mega

I searched and I can't find the exact answer I'm looking for.

I have Stock Seq Twins, TRUST SMIC, HKS RS Intake, DP, Stock Main CAT, TRUST 3'' Exhaust, No Airpump, Indigo pulleys, upgraded fuel pump, stock injectors, Profec-B II, with a GFORCE ECU running pretty rich, obviously. I've only had the car on a dyno jet once (before I had the lightened pulleys on) and it put down 309RWHP and 270 LB/FT at just about 15 psi (93 octane).

I want to replace my stock cat pipe with an RX7 Store resonated MP with a davesport HF metallic CAT welded into it (right after the resonator). I think it will flow a little better than the stock CAT, but it won't be as drastic as just a strait MP would be. Does that sound right? How much of an increase in flow do you think I should expect with that set up?
Would the GFORCE be able to deal with the extra flow or would it have to be reprogrammed? I would still plan on getting it dynoed afterwards and hooked up to a wideband just to be sure that my A/F was good. I just want to know if I should even consider doing this at all while running a GFORCE or just wait till I get a PFC and have it tuned and all at the same time.
Thanks for any input. Also, If anyone can point me to any good threads that apply, I'd appreciate it, thanks.

mega

I am posting this for informational purposes only in case anyone was wondering:

Since no one wanted to touch this thread, I PM'd a very knowledgeable senior forum member and this was his response:
Ideally yes, you would want to have the fuel maps adjusted for the better exhaust flow. However, pretty much all the rechipped ECU's (GForce, M2, Pettit) all only use one fuel map.

GForce was the oldest of the bunch. There maps were typically fairly conservative compared to maps like Pettit. Pettit is really the only rechipped ECU you would want to use with a midpipe.

The ECU won't self-adjust. Whatever is programmed is whatever is used (hence the MAP system). Some of the ECU's are tuned "richer" for safety, in which case adding more flow mods won't put you in a danger zone, just a little further outside the safe zone.

The problem is, without proper monitoring with thinks like a wideband O2 sensor and an Air/Fuel guage, it's all guessing.

I would suggest that if you want to run a midpipe, use the Pettit ECU or go with a fully programmable replacement like the PowerFC.

As far as adding a cat back into the midpipe, I still recommend the above. Even though you are still putting a cat back in place, the overall exhaust piping as increased from 2.5" to 3" so you are still increasing the flow even with a cat welded in.

Hope that helps.