I just installed my XS ecu (similar to the M2 stage 3 or pettit). I have full exhaust and an intake, running 11lbs. The car runs like a champ for most of the RPM range, but from 6500-8000 it feels like the car cant breathe. RPMs slow way down and it almost feels like the car is bogging. Im going to hit the dyno this weekend...but until then are there any suggestions on a fix for this? I have relatively new (5000 miles) spark plugs, 9s all around, 12k on new wires, pretty much everything is new since the motor was built 12k miles ago.

to me this seems like too much fuel, but i went from 8lbs to 10lbs, then to 11lbs and it didnt change it. i dont want to push it any further without knowing what is going on. thanks in advance.

 

also...i dont know if this would make a difference, but the ECU is from a 94 car i believe...and my car is a 93 non-cali.

 

Sounds like a clogged cat, but you have a midpipe...
so check the intake. One of the tubes may be collapsing on itself under high vac.
If you have hard pipes....then IDK.

Raj

 

hard pipes, no cats....

im starting to think it may be just drowning itself with fuel. or maybe its not getting enough spark. it pulls hard until those upper RPMs though.

 

I was gonna say sounds like an intake problem. Perhaps a clogged intake, or vacuum leak.

I would assume if it was a fuel problem you would feel it in the earlier rpm range as well. But I am just speculating.

 

a little more information in case it will help diagnose.

im running poor mans non-seq, 10lbs (sometimes 11lbs...crappy boost controller), and pull 18 in vac at idle. i dont think its a vaccum leak, or an intake/exhaust problem because i did not have this problem before putting in the ECU. this all happened with the ECU change. sometimes it does it worse than others, and sometimes it will do it, then from 7500-8000 it will stop and start pulling smooth and hard again. i am still on the stock IC, which could be causing some sort of problem.

could this be a boost leak? i've always had trouble holding 10lbs of boost....even with a free flowing exhaust and intake. i have a home depot ball/spring boost controller but i still have a hard time keeping 10lbs. lately the car has been stumbling at idle too. not always, not regularly, just every once in a while when i put the car i gear, or push in the clutch, it will stumble or die.

 

if boost normal before ECU swap. its the ECU problem.

 

The stumbling is most likely the Ecu being too rich. Nothing you can do, but live with that.

But, with intake and full exhaust...you have trouble holding 10psi?! You should easily be going to 14+. I have a high flow cat and saw 19.2 psi on my ECU controller once. There is a problem, boost leak, with not being able to make 10 with a full open breathing system.

I now think one of your couplers is cracked and leaking. Remember, you have to take them out and bend them all over or else the crack will stay compressed.
It has to be leaking somewhere.
Next, swap the ECU agian, and see if the problem goes with it.

Raj

 

well i messed with my boost controller, and am seeing 10lbs now. but it still runs really bad. could being really rich cause this? it pulls great until i hit 5500-6000 rpm, which is the transition point on the sequential system isnt it?

my wastegate line popped off last night and my boost gauge quickly shot up to 16-18lbs.....(i wish it always felt like that).....but anyways, there was definately no hesitation or bogging when it was boosting like that. im thinking that its just a rich ECU, and without an IC and y-pipe, which it was also tuned for, im running even richer. im going to try 12lbs and see if that gets rid of it.

 

Sounds like you are on the right track.

Transition for Seq. is 4500.

Raj