E85 I cannot get rid of this knock.

[TheBoz]

So here are the basics.

2.0 9000rpm rev limit
37r @ 25psi
AEM EMS
Cali E85

So for the last week or so I have been fighting this knock on e85. I have tried everything under the son to get this knock.

I have gone from 12.0 afrs - 13.0afr's
I have gone from BRP7ES @.020 - BR8ES @ .024-.018
I have run lots of timing and very little timing. I am kinda at my witts end here. Any advice will be helpful.

Also if you want the full log file I can email it to you.

As you can see from the log below, the car will start to knock pretty bad at 8200rpm and 12.50 AFR and 14.3* of timing. It starts to missfire and then by about 8500rpm the will buck and just start to loose tons of power.

Current conditions during this run.
BR8ES @ .018
25psi
3* @ peek boost
16* @ peek rpm

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[rstchris]

This is knock voltage, why not knok count or sum? Are you sure you are over the knock threshold? What do the plugs look like after a pull like this? I run a similar sutup but smaller, 3071e, e85, cams, I run 12.0 and 24* up top 0 knock. You should be fine with this setup.

 

[95blackGsTurbo]

That is VERY rich on E85 Chris. I am very surprised you aren't getting knock from excessive fuel. I would look at valvetrain noise. Typically most cars down here are running in the mid-high 12's for AFR. Is your head built to take 8500+ RPM's. Were all clearances in the head exact for such a high revving setup?

 

[rstchris]

That is VERY rich on E85 Chris. I am very surprised you aren't getting knock from excessive fuel. I would look at valvetrain noise. Typically most cars down here are running in the mid-high 12's for AFR. Is your head built to take 8500+ RPM's. Were all clearances in the head exact for such a high revving setup?

I tried 12.8 afr but saw knock @21* so I dumped a bit more fuel and jack the timing, that's where the power's at. I may fine tune to about 12.2 though.

 

[TheBoz]

That batch of engine noise does not exist on Q16. My logs from the race track the day before show much cleaner knock up past 8200rpm then on E85. I am 100% sure this is an e85 related issue. I am now shooting for about 12.3-12.4afr. That seems to work pretty well on my car. I am also going to opne up the gap on the plugs a little bit.

So over the weekend, I am literly going to keep the AFR's right where they are at, and use my BR8ES plugs and just try different gaps on them.

I will do a baseline pull, at .018 and start increasing the gap from there.

I will let everyone know the results.

Thanks for all the help.

 

[95blackGsTurbo]

Have you run the car on the streets on E85. The dyno could be loading the car too much causing the knock as well.

 

[TheBoz]

That is VERY rich on E85 Chris. I am very surprised you aren't getting knock from excessive fuel. I would look at valvetrain noise. Typically most cars down here are running in the mid-high 12's for AFR. Is your head built to take 8500+ RPM's. Were all clearances in the head exact for such a high revving setup?

Yes, motor should be good to rev to about 9500rpm. I have been spinning this motor to 9k for months now. At least 100 3rd gear pulls all the way to 9k. As soon as I switched to e85 is when the noise up top showed up. On CA 91, and Q16 it does not exist.

I will also pull the valve cover and check inspect everything this weekend. I mgiht drop the oil pan and take a look there also. It is possible that I have just beat on the car too much .

Have you run the car on the streets on E85. The dyno could be loading the car too much causing the knock as well.

I have yet to take it to a dyno. This is all street tuning. Hell I am thinking about putting a good 1g knock sensor into the car . Ditch the 2g knock sensor, it is too sensitive .