Knock

[max_boost]

Today on the way to work I was doing some scanning on the expressway. The gauge recorded a few degrees of knock when going wot in third, no more than 1.3 degrees. Also when cruising at 65 in 5th gear I got quite a lot of knock when I would go wot. It hit as high as 3.5 around 3000-3500 rpm.

I have never got knock like this before even after the pulley install. I have an exhaust leak so I'm wondering if it is possible for it to cause the knock?

[jpapa]

The exhaust leak is more than likely the culprit, with the help of the pulley shoving more air in there. The leak would be disrupting the exhaust flow from the cylinders during the stroke, since it's not able to stroke at the designed/tuned pressures. So that can cause your knock. You're still on the stock exhaust, right? Where's the leak at?

[max_boost]

Originally Posted by jpapa

The exhaust leak is more than likely the culprit, with the help of the pulley shoving more air in there. The leak would be disrupting the exhaust flow from the cylinders during the stroke, since it's not able to stroke at the designed/tuned pressures. So that can cause your knock. You're still on the stock exhaust, right? Where's the leak at?

Yes it is the stock exhaust and the leak is after the resinator where the axle back bolts up.

[cvenom2122]

could be bad gas if you have never exoerience it that bad before that is probably the answer!

also i know you live in michigan and all but has it been warm lately? if so that could be another factor.... get some new gas, and reset your battery

[Sp00ner]

Some knock under sudden changes in engine load like that aren't totally uncommon. I can see a couple of degrees of knock just putting around town. For instance, 45mph, 5th gear, floor it.... you'll see plenty till the engine gets spinning a bit..

1.3 under full load, boost, and rpms, isn't too bad... although, with your mods, I can't imagine you should see any. Under normal conditions. I never see any, and engine wise, it looks the same...

[max_boost]

Thanks for the idea's guys. I just filled up yesterday at the same gas station I always do with Shell V-Power but I guess they could have gotten a bad batch. I'm taking her in this weekend to get the leak fixed so hopefully that will help with the knock.

Another think I didn't think of was that the knock that shows up in 3rd is right around the time the boost bypass opens up, maybe that is causing it also.