Thread: getting some knock starting around 4800 rpm.. any suggestions?

Originally Posted by darkhorizon

Knock during tip in can be related to the trans and whatnot... the biggest fear of kr you want to have is stuff popping up after you have been in the throttle for awhile.

Is "tip in" meaning right when I start getting into the throttle?

to your second point, I believe that is the KR I am currently experiencing. I can stay in WOT and not see KR, but around 4800rpm, it starts to set in and increases to 3-4* before I shift around 5500rpm.

Maybe I should get more flow mods??? I still think that 17* on E85 with the mods I have shouldn't see any.. but I have worked this tune multiple times and feel like it is safe...

1st thing you have to learn is never trust ONE wideband. It can easily lie to you. I always have a backup A/F gauge and sensor.
We dyno tested hundreds of machines and it's crazy how often the customer's wideband gauge OR sensor was lying to us. I've saved face many times in front of a customer when his wideband was saying LEAN but he was DEAD rich or the opposite. You have to be careful do not 100% trust a gauge. With E85 the smell is different but with gasoline. With gasoline, if you have a keen sense of smell you can easily tell rich from lean, it's a totally different smell (when following the car) or on a dyno, which is easier.

I would try richening up just to see if knock will go away. Monitor power loss or acceleration loss. I always use GPS performance meters which makes it easy to know gains or losses even tiny amounts. If knock gets worse, I would lean a little at a time and see if it improves. Do not let it knock too much or too long. #1 killer of engines.

Appreciate all the comments. I went ahead and uploaded the stock high octane timing tables and took it for a drive this evening. Successfully achieved 0* KR throughout my WOT pulls. With that, I will probably add a degree or two, and do the same thing. I may also leave the stock high octane timing table alone and add a smaller pulley and see what that gets me. @ WOT, I am currently between 11 and 13* of advance, so nothing crazy, but that was the stock table so can't be too bad I guess?

I am thinking it will handle 14* of WOT timing just fine. We'll see how it does over the next few days!

Either way, I was seeing up to 9.6* of KR before E85 on the stock timing tables, and now I am seeing 0* on the stock timing tables. So that right there was worth the fuel switch in my limited opinion