Strange Launch Issue PD Blown L76

[andrew1988]

We are having a problem with this car in first gear only launching at the track.
Right at 4000 rpm just as the engine starts to REALLY accelerate the rpms go dead flat for 100 rpm then pick back up again and the engine continues to accelerate.

It is like the car quits making power.
From what i can see is that it is not a torque management issue as the data shows that spark, fuel and throttle do not move from commanded.

The car has been tuned blended VE/maf to 2500 rpm then maf only onward.
I think that this might be my issue.

The set up is
2010 VE SS
Maggie 1900
DW injectors using DW data
216/232 115 cam
sbe
stock converter ect.
pump 98 w/ water meth

L76 stock engine e85 flex 216 232 cam ls7 maf XVP820 - 2 bar ve table magnuson 1900 90lb DW inje.hptheathcote 11.28 127.hpl

This one has me scratching my head and i think the car will knock over a 10 sec pass if we can get this sorted.
Thanks in advance for any help

[lukearmstrong1990]

you feeling this in the car or just going off data log?

disable injector desoot switch also.

[andrew1988]

I can feel it. Like someone cuts the power off for a second. It kills the 60ft pretty bad

[TCSS07]

i see it in a few spots in the last pull - start of - at 5500 and 6500 also where it slows down for a tick and then continues on ... i noticed in your tune you still a few torque management settings turned on so maybe shut them all off to make sure there no outside influence ... also the maf looks pretty rocky during the wot areas, i would definitely smooth those out a little better and having the maf/ve blend shouldn't matter for wot since maf takes over for fueling by then

[SUTTERERMAN85]

I’m having a similar issue on my e38 08 denali. I am going mag only at 2500 rpm also. I am only noticing it 1st gear also. Leads me to tq mgt also but logging it it not saying it’s on. Curious what others suggest.

[andrew1988]

i see it in a few spots in the last pull - start of - at 5500 and 6500 also where it slows down for a tick and then continues on ... i noticed in your tune you still a few torque management settings turned on so maybe shut them all off to make sure there no outside influence ... also the maf looks pretty rocky during the wot areas, i would definitely smooth those out a little better and having the maf/ve blend shouldn't matter for wot since maf takes over for fueling by then

My main concern is that because the ve after 2500rpm is stock it is too different from the maf curve caausing the problem.

What TM did you see that would be worth turning off?

[andrew1988]

I’m having a similar issue on my e38 08 denali. I am going mag only at 2500 rpm also. I am only noticing it 1st gear also. Leads me to tq mgt also but logging it it not saying it’s on. Curious what others suggest.

Is your VE table above 2500 untouched and stock also?

[SUTTERERMAN85]

It was and then I copy/pasted/smoothed some about 105kpa from a ZL1 and it didn't seem to change what it was doing.

[SUTTERERMAN85]

FWIW, I didn't have any of these problems with my LSA blower on my 07 Tahoe with a 5.3l Its an e38 also but 4l70e vs 6l80e and tq mgt work much differently on the 2.

[Tre-Cool]

how much fuel in the tank when your running? I've found the tank setup in commodores/camaro's do not like launching when running under 1/4 tank. They will launch then nose over then pick up again.

[David WS6]

I think your cylinder volume is a typo.

Never mind it's correct!

[10_SS]

At 11:19:20 (4000rpm in 1st gear) it looks like wheelspin to me since it picks up RPM much faster right around 3900rpm, then kinda hangs at 4000-4100rpm a bit, then is back in line and continues up the same slope. It happens again later on must be 2nd gear 11:19:22 but at 5900-6000rpm, starts increasing like wheelspin then tires get hot and rpm's actually come down to 5800rpm before continuing on up, you can see your speed looks like it follows the RPM drop so most likely it's wheel-spin.

Had this happen on the dyno one time, rpm's came up to around 4500rpm then just hung there.. I let off. The owner been doing it for 20yrs at this point, he thought something let go, or clutch slip. It was just wheel spin. Tires these days act different than they used too.. they get hot fast and start gripping, stopping wheelspin as it's happening. Creates strange thoughts about what is going on.

[andrew1988]

At 11:19:20 (4000rpm in 1st gear) it looks like wheelspin to me since it picks up RPM much faster right around 3900rpm, then kinda hangs at 4000-4100rpm a bit, then is back in line and continues up the same slope. It happens again later on must be 2nd gear 11:19:22 but at 5900-6000rpm, starts increasing like wheelspin then tires get hot and rpm's actually come down to 5800rpm before continuing on up, you can see your speed looks like it follows the RPM drop so most likely it's wheel-spin.

Had this happen on the dyno one time, rpm's came up to around 4500rpm then just hung there.. I let off. The owner been doing it for 20yrs at this point, he thought something let go, or clutch slip. It was just wheel spin. Tires these days act different than they used too.. they get hot fast and start gripping, stopping wheelspin as it's happening. Creates strange thoughts about what is going on.

You know i think you are right here. ive probably been over thinking it.

The rpm shoots straight up then goes flat. kind of the same after the 1-2 shift where it spins.