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Discussion Starter · #1 ·
Recently went back to a full exhaust system and am suddenly getting knock. I didn't change anything, I tried adjusting the T+ back 2 degrees on the timng and it doesn't help. TUrning boost down to 18ish lbs does eliminate it. Usually I run up to 26 on pump gas with alky injection though. Haven't really changed anything else in the combo but exhaust. Could this be causeing the knock?

The exhaust is pretty restrictive 2.5" non mandrel all the way back to a cheapo turbo muffler. Only running a 2.5 inch hooker DP as well.

I have already ordered a cutout and plan to run that when racing but I wanted a nice quiet ride for street use.

Thanks
 

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I believe it could,given the levels you're running it at.
 

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26psi on pump gas and you wonder why it's knocking? Turn the alcohol off and fill up with 110oct. The craziest thing will happen, no knock! :rolleyes:
 

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Discussion Starter · #4 ·
That would make sense. Except, as I said, when running open DP before at 26psi and alky i wasn't getting any detoantion. :eek:

I did just fill up the gas tank last time I was returning from the track. Maybe I got some bad gas. once the cutout is back on I'll let U all know.
 

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VxTurboxV said:
Recently went back to a full exhaust system and am suddenly getting knock. I didn't change anything, I tried adjusting the T+ back 2 degrees on the timng and it doesn't help.
I'd bet your EGTs are higher.
Duel 3's, with ultraflows, with a cross-over at the rear, can be *dead* quiet.
 

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Discussion Starter · #8 · (Edited)
My car is pretty whisper quiet now.

I've got this on order...





So hopefully is solves my problems. And I can have the best of both worlds as far as exhaust is concerned.. Thanks for the input everyone!
 

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I believe this is a turbo engine. In that case, the exhaust system is downstream from the turbo, and will reduce turbo output slightly. That will give less boost. At the same time, the pressure in the headers upstream of the turbo might increase a little, so that there is more residual exhaust gas left in the cylinder- less oxygen. Less boost, and a richer mixture. Unless what you are getting is "rich knock" it's hard to see how the exhaust system is responsible.
 
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