KR, Cant seem to get rid of it!

[bmuir]

Hey Guys,

I have a 2001 Sierra C3 6.0 Stock LQ4, Radix with 2.9 Pulley(7 psi), 90mm TB conversion, LT and Corsa, running 94 octane. I went to the track the other night and did a bunch of logging, but keep getting KR and I want to know what needs to be done to fix it. I am running the stock 2001 LQ4 knock sensitivity.

My timing (from what Ive read) isn't really high, at 2800 its at 13.5 ish and ramps to 15.5-16 at 6000. I am running at AFR of 11.4-11.6, the logs show slightly higher than what is read on the wideband.

On the first log i got KR right from the launch, on the second i pulled about 1.5-2 degrees of timing from the entire map at WOT and still got KR, but it was not as bad. The final log only has about 12 degree of timing ramping to 14.5.

Is this all real knock, and if so do I need to run even richer and pull more timing to combat this? Am I not able to run much timing because of the stock cam? I will be putting a cam in soon...but for now need to get rid of the knock!

If it helps, ive also include a log of street driving where i get some KR once and a while.

Thanks for the help!

[joecar]

Hi Brian,

In the race1 log, KR looks like it's around peak torque, and also during an upshift (in one instance)...

IAT is high, I don't know how the Radix is laid out, is there a way to introduce an intercooler...?

Is there any chance that the engine is pulling in oil from anywhere...?

Also, your MAF is pegging out, but that doesn't appear to coincide with knock.

Also, your MAP appears to peg at 104 kPa... how much boost do you have...? Shouldn't you be using a 2-bar or 3-bar MAP sensor...?

[bmuir]

Thanks for the reply!

My IAT are high, but so are all Radix's when you pulley down. It is intercooled, but the intercooler sits under the blower and is water to air via a heat exchanger mounted at the front of the truck, there isnt much more I can do on IAT's other than a newer style 1900 or 2300 blower which are not so much of blow torches.

I am running the stock 1 bar sensor, thats why it pegs at 104kPA, i should be going to a 2 bar, but haven't really researched what is involved in setting the tune up for 2 bar. Also the MAF is pegged, but i guess there isnt anything i can do about that other than go SD?

You talk about oil, and im not sure if its pulling oil in..i wonder??? I guess I could pull the intake tube and check. Where would the oil be pulled from and will that contribute to the knock?

I also did notice the KR during the upshift. What would cause that? Is it actually knocking or is that shift noise being picked up?

thanks again!
-Brian

[ScarabEpic22]

Brian, go 2 BAR asap! You're guessing at best right now once you get into boost...

Also, Im at school so I cant view your tune but is it a stock OS or are you running COS 3 or 5? You should be running a COS to have accurate spark and fueling over 1 BAR.

P.S. I usually head to Whistler over Winter break and meet up with 4 or 5 TrailBlazer guys in Vancouver, Ill hit you up if I go up this year!

[joecar]

Install the 2-bar or 3-bar sensor (somewhere there are part numbers for suitable sensors), and edit the MAP scaler parameters in the Engine Diagnostics section of the tune.

If there is a crankcase vent tube going to the manifold, check it for oil... also check the back of the throttle blade for oil.

Oil lowers the effective octane number of the fuel... so it more easily allows knock, and it coats the pistion tops with gunk (which in turn causes more knock).

The knock during an upshift can be various things:
- going into the next gear places more load on engine,
- maybe the exhaust/something bumped the chassis a little,
- maybe a motor mount moved a little,
- maybe the transmission made a loud noise which transmitted to the engine block;

The knock sensor logic/algorithm in the PCM is supposed to filter out non-knock occurances, but it's not foolproof.

[bmuir]

Brian, go 2 BAR asap! You're guessing at best right now once you get into boost...

Also, Im at school so I cant view your tune but is it a stock OS or are you running COS 3 or 5? You should be running a COS to have accurate spark and fueling over 1 BAR.

P.S. I usually head to Whistler over Winter break and meet up with 4 or 5 TrailBlazer guys in Vancouver, Ill hit you up if I go up this year!

I am running the stock OS. If I can run a two bar right now with the stock OC, then move into a COS sooner than later that would be great. Can I just add a two bar in now and modify the MAP scalers like Joecar said or do i need to go to a COS before any of that? I'll have to look into COS 3 and 5, but for now would like to use the maf. Do i have to go OL SD with the COS's?

If you are coming up to Vancouver let me know, that log was taken going to Whistler while i was doing a job and commuting up there this summer, but I do get up to ski a couple times a year usually too.

[bmuir]

Install the 2-bar or 3-bar sensor (somewhere there are part numbers for suitable sensors), and edit the MAP scaler parameters in the Engine Diagnostics section of the tune.

If there is a crankcase vent tube going to the manifold, check it for oil... also check the back of the throttle blade for oil.

Oil lowers the effective octane number of the fuel... so it more easily allows knock, and it coats the pistion tops with gunk (which in turn causes more knock).

The knock during an upshift can be various things:
- going into the next gear places more load on engine,
- maybe the exhaust/something bumped the chassis a little,
- maybe a motor mount moved a little,
- maybe the transmission made a loud noise which transmitted to the engine block;

The knock sensor logic/algorithm in the PCM is supposed to filter out non-knock occurances, but it's not foolproof.

Thanks for that info Joecar, good to know!

Ill check for oil in the areas you specified, i have been consuming more oil with the blower...so maybe thats the issue?

I guess i need to get these issues checked before i touch the knock sensor sensitivity as it seems like the KR is real?

[joecar]

With the COS you can run MAF/CL.

[bmuir]

With the COS you can run MAF/CL.

OK, ill be looking into that for sure then. Thanks.