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/gmpowertrain/engines/specialized/industrial/2006_8100_industrial.pdf#search=%228.1L%20integral %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.

[Dirk Diggler]

Ok cool no problem

[joecar]

Can you check the inside of your intake manifold for signs of oil (pooling on manifold floor, backside of TB blade wet with oil, etc...).

[Whippled 496]

Throttle body is on the blower now, but when i had the intake adapter off about 2 weeks ago there was no sign of anything in there, looked very clean. I could see in about 6 or 8 inches i guess. I was shining the light in there to make sure there was no debris before i put the flange back on.

[Whippled 496]

I would just be anxious to see if anyone has any logs of a moddified or even a stock 8.1L tune to see how much KR they normaly have. Maybe the 8.1L is prone to knocking?

[dc_justin]

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.

Sometimes I can hear a 3* KR spike, other times can't hear a 6*+. :nixweiss:

I'm going to beat my dead horse here and point out the IATs and the fact that timing isn't being pulled as a result (IAT Correction = 0). We definitely tried this with the Knock sensor filter being inaccurate, but not aftwards. :)

[Whippled 496]

Sometimes I can hear a 3* KR spike, other times can't hear a 6*+. :nixweiss:

I'm going to beat my dead horse here and point out the IATs and the fact that timing isn't being pulled as a result (IAT Correction = 0). We definitely tried this with the Knock sensor filter being inaccurate, but not aftwards. :)

Beat that sucker, you can borrow my bat......i will give that a shot tonight. I will just copy and paste your IAT table to the tune i am using now. I dont wanna keep switching tunes because it makes it hard to compare logs. Unless you think i shoud start out with that last tune you made for me with the incredibly low timing table?

[dc_justin]

Beat that sucker, you can borrow my bat......i will give that a shot tonight. I will just copy and paste your IAT table to the tune i am using now. I dont wanna keep switching tunes because it makes it hard to compare logs. Unless you think i shoud start out with that last tune you made for me with the incredibly low timing table?

It wasn't incredibly low, it was the IAT table pulling it all out. ;)

I'd use a less aggressive IAT table to start with to just see if it has an impact... maybe 50% of the table I had set up. Leave the rest of the tune the same, so that you can attribute any results to that specific change.

[Whippled 496]

Yea, seems like i have a lot of things to try now...:). I will take them one at a time. Looks like a roadrunner would help me out a lot ...LOL

[SinisterSS]

How many miles does the 8.1 have on it?

How prone are the 8.1s to main or rod bearing knock?

Or the eternal GM cold-piston slap?

Ever had the heads off or are they still torqued from the original factory assembly?

Is the KR value higher or lower when the engine is cold?

Is the VE table within +/- 2% in all loads/rpms?

In SD mode is the KR more, less or too simlar to tell?

What color/condition are the spark plugs? Using AC Delco irridiums but in one step cooler, correct? How do NGK TR6 plugs behave? Same KR?

With the torque converter locked, what's the KR look like?

[Whippled 496]

How many miles does the 8.1 have on it?

24,000 miles



How prone are the 8.1s to main or rod bearing knock?

no clue



Or the eternal GM cold-piston slap?

I can hear a little noise at start up, but quickly disapates



Ever had the heads off or are they still torqued from the original factory assembly?
never been off, still factory torqued



Is the KR value higher or lower when the engine is cold?
doesnt seem to be a difference



Is the VE table within +/- 2% in all loads/rpms?
yes, it can be seen with the logs i posted.



In SD mode is the KR more, less or too simlar to tell?
never had it in SD mode



What color/condition are the spark plugs? Using AC Delco irridiums but in one step cooler, correct? How do NGK TR6 plugs behave? Same KR?
Yes one step colder AC delco's, not irridiums though. Never tried the TR6's.



With the torque converter locked, what's the KR look like?
never tried to manually lock it and log.