I just got my 2nd new exhaust put on... I LOVE it.

Before I had a 3" dp and 2.5"MP - 2" duals - 2 ghetto dynomax mufflers.

it was loud and quick.

Now:
3"DP - 2.75" MP = 2.5"Y- 2.5" Duals - 2 stainless 3" all the way though open fartcans with removable silncers. with thie silencers in, its as quiet as stock. With them out, its about as loud as it was before.. maybe a bit louder. it was pretty bad before

With the silencers in (never gone WOT with them out) - the butt dyno sees a big difference. Before wasn't that quick, but was pretty damn good. Turbo spool in 1st is WAY beetter now.

if I go WOT in anything other than first, though.. it "cuts out".. it doesn't feel like fuel cut, and it sounds like the car is running on 1 rotor when it happens... it hapepens after 3-5 seconds.

I didn't hear any detonation... but an FD fuel pump is on the way that should help out. do I need to rewire it, or can I just use the stock wiring?

While I was under the car I also noticed a vacuum line off under the UIM, but I havent had a chance to fix it yet. Maybe tomorrow .

Anyone know what's going on here?

 

Check the voltage at the fuel pump connector on the left strut tower back near the pump at idle- if you're getting around 13 volts, I wouldn't worry about a rewire just yet...

I know this sounds strange, but give the ECU a couple of days to "learn" the new airflow and fuel scheduling requirements of the new exhaust. People say I'm crazy for thinking the ECU "learns", but I've seen it myself on my car, and I've heard other guys say the same thing...

Are your grounds in good shape? The OEM ones, of course...

 

there are no OEM grounds remaining on the car.

there's a 2/0 gauge wire going from the - terminal to the block (the engine removal hook) and a 4 gauge wire going from the - terminal to the chassis (at the leading coil).

I've seen the car "learn" too... I've been thinking about resetting the ECU and initializing the SAFC (it reads 0.4% on the MAF with the engine off ever since I changed it)

I put some 94 octane in it today and I haven't been able to duplicate the problem, but I haven't driven it at WOT in anything but 1st and 2nd.

 

OK, answer this simple question, and it will be all the flaming I'll do for now- what good does a 2/0 ground wire do if the power wires that complete the circuit are 16 gauge? The answer better be good, I'm giving a pop quiz tomorrow

I haven't had any luck "resetting" the ECU. J-Rat just might be right about the S4 ECU's, as far as that goes. I just drive her, and usually by the second day she seems to have found whatever "groove" she needs to find to run properly. Putting her on the "wide open exhaust" diet triggered one of these "learning" events. I can't explain it, but I know it happens...

Find a home for that vac line first, and after a couple of days if she's still giving you problems, we'll start the real troubleshooting...

 

that vacuum line is finding a home in about 10 minutes. I'm not sure which one it is, but I bet it connects to the back of the UIM by the throttle body..

I'll take it for a good drive today, and if it's still doing it, I'll reset the ECU, and initialize the SAFC.

Thanks for the help everyone

Thick ground wires help with starting and spark... I realize that they're a bit overkill, but I had the wire laying around doing nothing...

 

Self-learning was not a feature of 80's ECU's (first generation digital). It's very common in later models, but I highly doubt our cars do this.

You realise there are 26 ground points on the chassis? And if you remove them, nothing electrical works? Your comment doesn't make much sense...

 

okay... what I meant was the main engine bay grounds had been changed.

I got the vacuum line on.. it either went to the oil injectors or the fuel injectors.. not sure what. Either way, its on. If it was the OMP line maybe that's why my car was smoking?

car runs PERFECT now.. it's got a bit of 93 octane mixed in, maybe that's helping.

its creeping to like 13-14PSI now when I shift into 3rd from 7500 in 2nd.. I think that's a bit much for just SAFC.. no audible detonation. but I'm not going to take any chances.

Will just an upgraded fuel pump be enough for now or do I need to find injectors, too?

 

creep creep, port the wastegate :p

 

This still doesn't make much sense. You can't "change" grounds without completely rewiring the EFI loom. If you mean you've added some ground wires then that's something different.

The weak link is the pump, not the injectors. That's what should be upgraded first. More importantly, at that boost level the lifespan of the turbo won't be great due to over-speeding, and it's inefficiency will be increasing the intake temps past what the stock IC can effectively deal with. Get the wastegate ported and hold it at ~10psi.

 

wastegate is ported.. probably flows 3x origional. I'm going to a divided setup over the winter.

FD pump is on the way!
I raced a camaro last night.. 1990s IROC. I had a passanger and like 100lb of cargo.. kicked its *** made me happy.

 

You must have a FCD, right? I've hit fuel cut before but it was not even close to how other people described it. FCD solved that problem.

As for Porting the wastegate, did you see NZConvertable's thread on what he did? I would tend to think that would solve your problem.

 

I haven't seen that thread, no

I'll check it out tonight.. on my way to the autocross right now

it "cut out" on the highway again... I don't know it was.

yes, I do have an FCD... fuel cut is like hitting a brick wall... this is more like hitting styrafoam peanuts... or something.

it sounds like a WOT version of when you have a bad TPS and the car likes to run on one rotor, but I know the tps isn't the problem.. this one is perfect and almost new.

 

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/serious-s4-wastegate-porting%85-343788/