VE SS UTE KR Issue Help

[Dazza]

Hi

So new to this forum and to tuning GM E38's - our workshop VE SS Ute only has full exhaust and OTR - as you can see from the dyno run attached its falling over earlier than stock baseline run. Ive attached the scanner data from the tuned run and you will see the KR activity is robbing power. I've scaled lean cruise and WOT maf but not VVE - from the histogram it looks pretty close anyhow but would this cause knock?

I cant hear any knock but dont have a standalone knock sensor.

Ive also attached stock and the tuned file the dyno and scan log was done with.

Any help would be appreciated.

[andrew1988]

when i tuned my ve ss L76 with just an exhaust i couldnt get anymore than 17 degrees in it without it seeing knock

[Dazza]

when i tuned my ve ss L76 with just an exhaust i couldnt get anymore than 17 degrees in it without it seeing knock

Yeah this is pretty similar - L98. Some workshops are quoting 280rwkW with this configuration (with same mainline dyno)

[Jason W]

I have a stroked L76 block and have found that I can't push the timing anywhere near what I had on the LS1. I would have thought you would have been able to get a bit more than 20 degrees before knock though.
How is the VE table in those ranges without PE/open loop enabled? If it's leaning out there is possibility of this causing knock.
Another thought is that the exhaust could be causing false knock to the sensors? I don't know if this is possible, but could the sound level coming through the header walls could vibrate the sensor?
You could possibly back off the amount the Knock Retard comes in and see if you can hear it pinging? You'll know it when you hear it and you can always back off straight away. It's only knocking 2-3 degrees out at those points so I don't think you could hurt too much by backing off the KR levels. Mind you, I would get some other more experienced peoples opinions on doing this before blindly following my suggestions! I will do these things on my car cause I am the one that suffers the consequences I don't want to cause others to damage their cars by following any of my advise!
I hope any of this helps.

[subsonic_79]

I had similar amounts of knock with my stock cam VE SS L98. Couldn't get anymore than 18-19 degrees at WOT without knock at high revs @12.5 AFR. I pulled a few degrees out from peak torque up to redline, and while I couldn't get it on a dyno at the time, it was definitely stronger up top with less timing.

The GenIV's do not need or tolerate much timing at all, even at part throttle. Pull a few degrees out and see how it goes.

[Dazza]

Thanks, yeah I pulled a few to stop knock and the power really suffered. I'll try again with a different brand of 98

Does anyone know why it's falling over earlier in the rpm than stock?

[andrew1988]

what are your afrs? also your maf hz are going up and down rapidly across the pull

[BigDaddyCool]

Hi

So new to this forum and to tuning GM E38's - our workshop VE SS Ute only has full exhaust and OTR - as you can see from the dyno run attached its falling over earlier than stock baseline run. Ive attached the scanner data from the tuned run and you will see the KR activity is robbing power. I've scaled lean cruise and WOT maf but not VVE - from the histogram it looks pretty close anyhow but would this cause knock?

I cant hear any knock but dont have a standalone knock sensor.

Ive also attached stock and the tuned file the dyno and scan log was done with.

Any help would be appreciated.

Roll up a maf only and see if it will hold. A professional mafless tune on mine ran around 17 degree's.... with maf only i find i can run around 22 at peak torque and 24 at 6000..... so it seems to handle a few more degree's as it's faster to respond to the airflow changes i guess. I've also made minor adjustments to the injector offsets etc to correct fueling and keep fueling consistent across the varying conditions to help ensure i dont get knock retard. I have a big stereo and I think it messes with my injectors so. Mine has hsv headers, 200 cell hi flow cats, underdrive, x-force 2.5 system with stock ends. Running a 12.5 AFR...

Actualy I just had a look at your log, you should always log engine torque.. something to keep in mind but pull some timing out of the top..... Clearly the car just doesn't want to run it without some fine tuning. Take notice of the 5600rpm area it's jumping between two timing cells..... make sure they are the same or that could be the cause there...... either that or drop some timing as previously stated.

[IARLLC]

I have seen major improvements in knock resistance on GEN4s by tuning the VVE table. Just sayin