Can't get rid of KR on a Procharged 98 C5..

[Redline Motorsports]

Working on a 98' C5 A4 with a D1SC blower. The car came in with a really bad tune and for a set of LT headers. The car has bad KR at 5000 that I can't seem to get under control. The timing I am down to is not timing that should be causing 6-9 degrees of KR. The AFR's are within check, 11.8-12.0 for boost. For some reason I seem to remember that there are known issues with 98's with respect to false KR.

I just don't see that the KR is real. I am only running 20 degrees at max advance so I just don't believe its real. If its an issue with the 98 black cloud its killing me! The car is still making decent power but the timing reduction is leaving a lot on the table.

Anyone recall this 98 problem?

Thanks

Howard

[98SS2836]

ya I have a 98 couldn't get rid of it for the life of me. I would get 4 degree's no matter what 100 octane. lower timing upgraded knock sensors every thing.
What I found it to be was they are two sensitive i was having a hard time finding the table. I had to do a lot of searching to find what table had control of it i don't know why but table B6245 controls the sensitivity. I changed the whole table to 4's. I never had a problem yet. the map from 65 up is 1 you can start by putting it to 2 and see if it helps or three. I've seen in posts that people will start at 4 and work there way down to just above knock.

Rob

[Doc]

ya I have a 98 couldn't get rid of it for the life of me. I would get 4 degree's no matter what 100 octane. lower timing upgraded knock sensors every thing.
What I found it to be was they are two sensitive i was having a hard time finding the table. I had to do a lot of searching to find what table had control of it i don't know why but table B6245 controls the sensitivity. I changed the whole table to 4's. I never had a problem yet. the map from 65 up is 1 you can start by putting it to 2 and see if it helps or three. I've seen in posts that people will start at 4 and work there way down to just above knock.

Rob


X2 with the caveat of reviewing and comparing window to cal window the 98 and 02 knock settings. I think you will find the variance you are looking for there, by this method.

[Redline Motorsports]

X2 with the caveat of reviewing and comparing window to cal window the 98 and 02 knock settings. I think you will find the variance you are looking for there, by this method.

H,

X2?

what?

[ScarabEpic22]

X2= times 2, or I wanna know as well!

[Doc]

Times two

[hquick]

To 'exume' and regenerate an old thread.....what have you guys since discovered along these lines of thinking/action?
I'm thinking of 'desensitizing' my knock sensors a little because I seem to be having the above issues.
Any advice?

Thanks

[brokenfly]

don't know if it will help as i am not boosted,but i got rid of a bunch of kr during low throttle light load areas by maxing out the B5954 burst knock delta airmass...

the knock i was getting was all during gear changes(auto) and during the stall's lockup rpm drops under light load...

i still can get a little knock at wide open throttle from time to time as usual,but up until i maxed out the airmass delta,all my knock was light load airflow kpa drops and never after the converter locked up in a higher gear even when i gave it a lot of throttle and loaded it up heavy...

[98 tigershark]

Hi Howard,
What is the compression ratio and quench if known. There is an issue but as far as I know its with aftermarket forged aluminum pistons imitating sound or knock. There are some other issues also that I cant recall. But some performance mods can imitate knock. Or you could have Knock, as the my 98 is more sensative to knock compared to op systems on later years. Check to see If they are set at factory also. Are they 98 Knock sensors or a later version. Good luck.

[hquick]

Thanks 98...I'm not sure of the comp ratio or quench. The motor is a stock 98 L31 5.7L in that dept...using the Hypereutectic pistons.
Intake manifold is different (mercruiser Marine manifold) and of course the Whipple is not stock.
Knock sensor is also the original from 98. I have heard some people say to use the sensor from the 2002 Express van from which the base tune comes so I might get one and try it out. Atleast if that turns out to be the issue...some of the other guys who've made this PCM swap will know it's OK to desensitize the 98 sensor a little.