Extreme loss of power at 7100 rpm. Help needed!
 

Hey guys wondering if anyone is having problems with their sc stage 1 or 2, at 7100 rpm my boost and power just plummet. It is about *100 whp and +1 lb of *boost of loss every dyno pull and this always occurs *like clockwork at 7100 rpm. Seb and I are racking our brains trying to figure it out. We believe it's a software issue. I believe we are going to send the logs to uprev / Sam on Monday.
Please let me know if anyone has any knowledge / experience / advice.

Note: I have a gtm sc stage 2

It would probably help if you posted what type of SC kit you were using. Stillen, GTM, etc?

what's the last thing you guys messed with? pulley change, retune, etc

Updated OP with the kit I have.


This issue occurred when we swapped to the ark exhaust from
Invidia (which was more restrictive). We have also swapped the pulley to a 92 mm one but the sharp decline started once the exhaust was swapped out.

weird, i swapped my HKS out back to stock without retune and still runs the same.

did you retune it after the pulley change though?

He did a few changes as far is timing. But this sudden drop of power occurred before pulley swap and it was just after a new exhaust. I don't think the ark is a bad exhaust but I'm think something is just not sitting right in the tune/ecu. Not to mention that coop has one on his TT g37.

We went from 460 whp peak to 340 And then it shows to start building up power again

I dunno. When I first bolted on the ARK Grip exhaust there was no dramatic reduction, although from a nearly flow through GTM exhaust to that, I did not feel a gain. Possibly a slight loss, but not 100 whp, and they were able to tune it back up. We did not do a back-to-back.

That said, a drop of this caliber sounds very much like a fuel cut in some form. One of the better changes I made was when I asked Sam to raise the fuel cut (RPM limiter in effect) to 7800 RPM from 7500. The car wanted that extra and it used it. He did NOT want to go this high, but I assumed all responsibility.

Got a graph?

Coop

Perhaps your belt may be slipping

It would help if you data logged via UpRev so that you can determine what your MAF is reading , timing adjustments, as well as what your A/F ratio is reading. Two things come to mind; one that a coupling is leaking and a less restrictive exhaust or even a major exhaust leak could be the cause. But a 100 HP loss is staggering and I would expect something else related to the A/F ratio. First things is to datalog, as the data will always show the problem.

My tuner seb data logged the runs the maf is reading 4.0+ volts? Like 4.5

That sucks man. Hopefully it can get fixed. Let's hope the tranny can be able to hold that extra power. You might see a slight gain not much using a different pulley.

Well in only making 8.9 psi max

Is your transmission or torque convertor shot?
I assume you have a automatic transmission.

+ or - 0.5 volts on your MAF air flow is a huge difference. Expecially with the 3" intake piping. Plus if your boost is low, I would automatically be looking for a boost/vacumn leak in your couplings/connections or the boost relief valve could be sticking.

I doubt my trannys shot it shifts fine and no matter what hp or gear pull its always 7100 rpm. No matter if it's 350 who or 410 or 390 or 450

Anyway I'm confident in gtm uprev and my tuner. Im just hoping I can make this problem go away quicker

I'd have to agree with with what Zat Zuma is saying about checking for boost leaks. I've already had to retighten some of my couplers on my GTM Stage 1 kit. What kind of AFR's #'s are you getting?