Hey guys,
I've been having this issue while tuning my car on e85. From spool-up to peak torque I have a single count of knock even with very very conservative tuning. It's gotten to the point where I've dialed everything between 2500-5000 back to 0 degrees of advance just to see if it's a timing issue. The load seems to be pretty high for such a low level of boost, where there is knock. Car is a IX MR w/ stock turbo. I've attached a snapshot of my log from 2000-3500rpm. I was thinking maybe boost leak, but the car tests just fine. I'm all out of ideas.

Mods are as follows:
TBE exhaust, catless, Titek v2 o2 housing
non-CDI COP kit
Forge adjustable WGA
GM 3port BCS
Synchronic BOV
Kelford 272
Supertech valvetrain
Nisei LICP
T-bolt clamps all around
New TB shaft seals
FIC 1350cc injectors
Walbro 255lph
Omni 4bar map sensor
Tephra v5 and direct boost control

 

I dont see anything wrong with that. even with e85 the knock sensor is going to pick up engine noise. 1 or 2 counts is not really knock. IMO you need a good bit more timing. i see a bunch of 0's where you should probably have at least 3-4.

 

I dialed the timing down to 0 because w/ 3-4 degrees of timing I was getting knock, so I wanted to see if it would still happen with less timing. W/ 3-4 degress of timing the 1 count is more consistent throughout spoolup (happening at almost every data point from 2500-4000)

 

You may want to add some fuel. Seems a bit lean to me IMO.

 

I thought that high 12 on spool-up is ideal for e85?

 

I'm guessing it's most likely valvetrain noise that you're picking up; you've pretty much ruled out that it's real detonation by running low timing. If it were my car I would go back to running normal timing advance and adjust the knock filters to reduce the chance of picking up false knock.

 

What do you think about the load spike to 280 with only 21psi though? Isn't that kind of odd? I have other logs with more realistic timing that I can post that have load spiking to 290-300 with only 22-23psi.

 

What happens to your knock count if you add timing one degree at a time to those areas that are now -1 degree?

You should not need negative timing. I'm running 6 degrees at peak and 24 degrees out the top at 20psi on E85 with no knock.

If you can add timing and the knock count stays the same (meaning 1 count or less), then it's not really knock. Then, I'd agree it is likely valve train noise.

 

I posted a log from last night. With a little more aggressive timing, I was still getting a random 1, and occasional 2 count. I did notice that when the car "knocks" it feels like it's hesitating. Is that a result of the ecu seeing the "knock" and pulling timing? You'll notice that where there's knock, the timing advance drops.

 

What happens to the knock counts if you add enough fuel in the area that is now 12.4 AFR to make it 12.2?

Have you considered going to Tephra ver 7? The big maps can make a big difference (sometimes) in avoiding knock.

 

can you rev the car in neutral and produce knocksum in the troublesome areas?

be careful when tuning with e85 man.. its not like regular octane fuels. you cant tune it based on just knocksum.. you must monitor each degree you add to the car with virtual dyno and confirm its making the same hp/tq increment per degree added.. you can easily give a car to much timing on e85 with zero knocksum. be aware AFR plays a huge roll when MBT is hit or missed as well.