I need some big brain help here, hopefully an ADMIN ir EFILive creator

[Whippled 496]

I was considering just shooting off an Email, but in the hopes that this may help others, i decided to just make it a thread first. I am having some very strange and difficult to resolve issues with knock. I have a whipple supercharged 2003 8.1L/Allison and there does not seem to be a whole lot in the way of information on these suckers and its making tuning very very difficult. I have tried tunes with single digit timing numbers, I have tried 110 octane CAM2 fuel, I have my AFR and VE tables dialed in tight. I am still getting consistant knock as high as 7* sometimes through out my RPM range. I have my burst knock table zero'ed out and for the most part the tune is pretty conservative. I have nothing in the engine bay clanging or banging that would induce any false knock, and the engine runs strong otherwise. Thats the story. One thing I found is that on all LS1 stock and modified tunes that i looked at, table B6227 (knock sensor filter) had the sensor filter set at 4.70. Mine was set at 7.90, not sure why or what effect that has. Would the 7.90 setting make my sensor more or less sensitive? it that a setting that should even be adjusted at all? And what effect would making adjustements in that table have? I set mine back to 4.70 and it seemed to clear up a little of the knock, but not a whole lot. I would very much like to see a tune of a modified 8.1L truck if anyone has one or has any intimate knowledge of tuning them. Here are 2 logs and the tune i used for those logs. One log is with CAM2 and the other is not. If anyone can see anything here that stands out to them please let me know....Thanks

Jimmie

[TAQuickness]

any chance you run a catch can on your PCV system? At one point in time, I had an ass load of knock induced by oil sucking thru the PCV.

[Whippled 496]

any chance you run a catch can on your PCV system? At one point in time, I had an ass load of knock induced by oil sucking thru the PCV.

The 8.1L has no PCV valve on it. It is integral, inside the manifold.

http://www.gm.com/automotive/gmpower...egral%20PCV%22

[Dirk Diggler]

I would try the Fbody tables from the FBody but so far what you have explain sounds like over sensitive KS. If you trust your fueling and all that is dialed in try using less sentive values and see if that cures it

[Whippled 496]

I would try the Fbody tables from the FBody but so far what you have explain sounds like over sensitive KS. If you trust your fueling and all that is dialed in try using less sentive values and see if that cures it

I have them set at 4.70 now, where they used to be set at 7.90. Which is more sensitive? Should i try them at 2.50? Thats the next step down, but i have never seen them that low on any other tunes.

[Dirk Diggler]

I have them set at 4.70 now, where they used to be set at 7.90. Which is more sensitive? Should i try them at 2.50? Thats the next step down, but i have never seen them that low on any other tunes.

Is the 4.70's still giving you problems

[Whippled 496]

yes, those logs i posted were both done with the sensor set at 4.70. One of those logs was with CAM2 also. Still a bunch of knock in there, i can never hear it though, and you would think at 5*+ you would hear something.

[Whippled 496]

You're a maryland guy arent you Larry? I will gladly pay you $14.37 to stop over my house and clear this up for me.........just kidding, but this is getting a little crazy!

[Dirk Diggler]

I sure am. I will be down at Fbody Central Tonight in Bmore tuning a car you are welcome to come on by so I can take a look see

[Whippled 496]

WOW!, thanks man, thats awful nice of ya. I dont wanna step on your toes though Larry, i really appreciate the offer, but i dont want to impose. Brett is actually the one who set up my original tune. If you get a chance to pop open that tune and log file i attached a few posts back and see if anything pops out at you, that would be great. I am gonna work on it a little more myself. I have some good guys a that are scanning the logs and giving me some help online (a lot of help actually) but we just cant figure out where this knock is coming from. Maybe after i rip all my hair out i will give you a ring...LOL.