Knock issue with stock tune

[mrpaul55]

Hi everybody I have a 2009 gen 4 6.0 liter in a 1994 c3500. The issue is with knock at low speeds and on light acceleration. This a stock motor with headers. I use it for towing my boat. Any help on this would help a lot! Thanks

[5FDP]

From the factory they do have alot of predicted knock built into the calibrations and the stock knock sensor settings are pretty sensative and kind of annoying on the GEN 4 computers.

I like to cut the burst knock tables in half for sure. The base vs cyl air delta is what I am talking about. And the knock retard decay rate table, taking the 2000-8000rpm and doubling it. If you look at the numbers and how small they are, going double is still a small change when you think about it.

I also prefer to run 89 octane at least over 87, they seem to run alot stronger and it can help reduce knock. For the 10-12 cents per gallon it's worth it to me.

[mrpaul55]

Thank you your comments. I will try that.

[mrpaul55]

I did try your suggesting's with no help. Still showing 10 degrees of knock retard at tip in. The truck is also rich if that tells you anything.
Thanks

[5FDP]

Without a wideband you won't know if it's running rich or not.

I don't see one in the scan you provided and I don't see a commanded AFR pid to see if it's dipping down into PE. But just looking at the o2 sensors it's just switching back and forth like normal and the fuel trims are a little off still likely because you added headers.

[mrpaul55]

I have a wideband hooked up but not to HP Tuners, its a gauge on the dash. Cruising it runs 14.9 - 16. WOT it reads 9

[schpenxel]

A. that's too rich
B. cruising around in steady state / closed loop you should be seeing closer to 14.7:1, +/-, though headers can do some weird things to this sometimes.
C. both of my GM vehicles regular showed knock retard with the factory tune, even on 93. I can't explain it, but it was there.. and they both have over 150K on them now and are just fine

[mrpaul55]

unable to sync cam /crank could that cause problems?

[Aaron407]

Something doesn't look right. At 50% throttle, it's showing your MAP at 97 kPa, which is essentially wide open throttle for most NA builds. However, your O2 sensors are still bouncing around, which tells me that you're not in power enrichment. Either the TPS or your MAP doesn't seem to be reading correctly. Were you WOT in your scan when you had the high KR levels? Your PE throttle/pedal table might be limiting you entering power enrichment as it's set to 87% throttle. However, it's odd if that's the case and you say you're running an AFR of 9 at WOT.

A couple of other things:

-Your PE delay is set to 8192 RPM, which means that PE will always be delayed.
-You could try boosting up your enrichment ramp-in.
-Your KR decay values are incredibly slow for higher RPM (e.g., 0.05 degrees/second).

[Aaron407]

Also, what MAP sensor are you running? If you have one in place that doesn't match the linear and offset values in the tune, it'll throw off your VE lookups and screw with your fueling. It'll also affect the injector flow rate lookup, further messing with the fuel calculations.

[mrpaul55]

The map sensor is a stock 09 Chevrolet Express map sensor. Thanks for the reply. Here is latest tune and scan. Its better but I agree with you map is weird.62016MASSADJUST.hpt62016518.hpl

[mrpaul55]

Tip in is where most kr happens.

[Aaron407]

The map sensor is a stock 09 Chevrolet Express map sensor.

What engine is in it? e.g., L96, etc. Can you read the part number from your MAP sensor to ensure that it's set correctly for liner and offset values?

[mrpaul55]

AC DELCO 12644228 map sensor. I double checked with GM parts and verified correct map sensor. The motor is a L96 out of a 2009 Chevrolet Express van 6.0. Where do you set the values for map in HP? Thanks for reply.

[Aaron407]

I found a stock L96 tune, and it looks like your MAP sensor data is correct by comparison. However, the injector flow rate data is quite different. Do you know what injectors you have? Your tune shows them at about 34 lb/hr @ 60 psi, whereas the stock truck tune that I found has them at about 55 lb/hr.

[mrpaul55]

The tune file for stock 09 express is 34lb/hr@60. That was from GM programming when I programmed the PCM. I saw that tune and I tried 55 lb/hr and it ran very bad. I just installed a new map and will post a new scan after a test drive. Setting the injector size to 55 lb/hr would make it richer across the table correct?

[schpenxel]

No, opposite of what you would think. Larger injectors would need to open a shorter period of time, so it will open them for shorter period of time which would mean leaner. Fuel trims will obviously try to correct you back to stoich if you're in closed loop.