Extreme loss of power at 7100 rpm. Help needed!

kosstick

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

MattP725

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

weiboy718

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

kosstick

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.

weiboy718

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?

kosstick

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

SharpByCoop

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

__________________
Jim Cooper - (Retired: '08 Infiniti G37 Sport • TheShopCT built • 11.13 @ 123 mph (click for vid) • GTM Stage II Twin Turbo • 5-speed A/T Level Ten built • 591whp @17 lbs boost)

SharpByCoop

This would help us understand.

Coop

__________________
Jim Cooper - (Retired: '08 Infiniti G37 Sport • TheShopCT built • 11.13 @ 123 mph (click for vid) • GTM Stage II Twin Turbo • 5-speed A/T Level Ten built • 591whp @17 lbs boost)

kosstick

Will work on getting a chart Sorry didn't see your post earlier!

weiboy718

Perhaps your belt may be slipping

Zat_Zuma

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.

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[B]2009 & 2017 370Z Touring Sport Autos SOLD

kosstick

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

Jamaica

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.

kosstick

Well in only making 8.9 psi max

Zat_Zuma

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.

__________________
[B]2009 & 2017 370Z Touring Sport Autos SOLD