Low boost knock issue

[czimpel]

I've been trying to track down a knock issue since I got my car running this spring. I'm pretty sure it's not a lean detonation issue. Currently running E85 @20 psi TT 5.7 E85 chip for 120's and 30 psi boost. No knock at full boost(20 psi 10.5 afr), but at times up to 7˚ transitional knock from nothing to WOT full boost.

Here's something new I found in the last couple weeks.

If I ease into the throttle and hold the boost at about 10-12 psi, this is where the knock happens. AEM wideband is bottomed out at 10.0, so it's obviously pig rich at this boost level. I read a couple posts that said that a rich condition can also cause knock.

Problem is, there is no adjustment that I know of in my chip to change my fuel maps at anything other than WOT. Is there anything else that can be done? How low can I run my fuel pressure?

 

[Eric Stage I]

With that chip, I would need to adjust that by reprogramming it, unless you have a MAF Translator. In that case there may be some slight tweaks you could do with that.

 

[psycho6cyl]

well if youre pig rich maybe try removing fuel @wot vey little at a time. im far from expert but id lay w it and see if theres a difference

 

[psycho6cyl]

oh never mind lol

 

[czimpel]

Eric, how long does it take and how much does it cost to reprogram the chip? Can I lower fuel pressure at all to see if it helps, if so, how low can I go?

 

[Eric Stage I]

Yes you can try lowering the fuel pressure. You can go as low as you want, as long as it runs and starts ok, and has enough fuel at WOT.

There is no cost to make a small adjustment like that. I would need info on the airflow reading and rpm range, when the rich condition is occurring.

 

[czimpel]

I'll try the FP first, if I can't get it dialed in I will send the chip in.

 

[87chrisss]

It could also be false knock wheel hop or something else you shouldn't be having any knock on Ethanol. Did you test the batch your using for true 85% content?

 

[czimpel]

Eric, Just went out and did some more testing.
Spits, sputters, and jerks when holding the RPM at 3000 at about 5 psi boost while driving. Doesn't do it with no boost.
• Turned the FP down to 35 static.
• Trans in 3rd gear.
• AF 200-210 on Scanmaster.
• RPM 3000-3200
• A/F 10.0-10.1
• 5 psi Boost
• KR 1˚-4˚

Is this the type of info you need?

 

[czimpel]

It could also be false knock wheel hop or something else you shouldn't be having any knock on Ethanol. Did you test the batch your using for true 85% content?

I can get KR while just easing the throttle to hold it at 10 PSI. Not hammering on it at all.

 

[Eric Stage I]

Ok, that's good info. Your MAF reading is too high for that RPM and boost level. What are you using for a MAF?

 

[czimpel]

Stock one.

 

[Eric Stage I]

My opinion is that the MAF is reading too high at that boost level, which will cause it to be richer than intended. Normally a boost level of 10-12psi matches up with 200-220 gr/sec airflow (depending on the car).
I can still try to lean out the chip in that area, but it might a little "funky" because I don't know at what areas the MAF is reading correctly or not.
If you still have 2 screens in the MAF, you can try removing one, which will lean it out a little.
Eric

 

[czimpel]

Will a translator and lt1 maf fix the issue?

 

[czimpel]

Only one screen in the MAF.


Posted from the TurboBuick.Com mobile app

 

[czimpel]

Just received the MAF Translator from Dave Husek. Picked up a Junk Yard 3" MAF and this solved my problem. Runs stronger than ever now.

Thanks for the help.