Knock problems
Thread Starter
12 Second Club
Joined: Sep 2002
Posts: 189
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From: Goldsboro NC
Knock problems Took my car to the track for the first time the other nite. Other than my crappy launches(spinning too much), my times where constant 9's in the 1/8 and 14's in the 1/4. I noticed it spark knocking in 2nd. Might be bad A/F mixture but im not sure. I think with all the induction mods i've done so far maybe making her run too lean. I thought about gettin a MAFT and playing with it to see if it made a difference. What do yall think? Haven't had any practice starting out from a complete stop so Im probably loosing some time there but could spark knocking be making a big difference? My 60ft times were 2.2 constant. Thx guys
Re: Knock problems From my experience audible detonation in my car usually means that my KR is up around 5.
Sooo, if you can hear it, then you are probably getting somewhere around or over 5 KR. This is going to drop your overall timing at WOT from ~27 to around ~22. Timing is kind of a cascade effect, and the more you loose the more hp you loose per deg. On my last dyno, I lost ~10 HP from 3-4 deg timing, because the car started to choke at 5300 rpm rather than pulling to my 6000 peak HP. With just a little KR, you can leave alot of HP on the table.
Running excessivly lean is a big contributor to KR. However, there are some other things that you may want to look at. I see that you are still using the stock valvetrain. On the stock valvetrain, I had some pretty bad float problems around my stock redline. Carbon buildup in the combustion chamber is another contributor, especially with the older LS1's. If your car burns oil, you may want to consider running some top-end cleaner to see if that eliminates the detonation.
And last but not least, you need A-tap or another form of data recording device if you purchase LS1 Edit or run an MAFT.
Good Luck
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Sooo, if you can hear it, then you are probably getting somewhere around or over 5 KR. This is going to drop your overall timing at WOT from ~27 to around ~22. Timing is kind of a cascade effect, and the more you loose the more hp you loose per deg. On my last dyno, I lost ~10 HP from 3-4 deg timing, because the car started to choke at 5300 rpm rather than pulling to my 6000 peak HP. With just a little KR, you can leave alot of HP on the table.
Running excessivly lean is a big contributor to KR. However, there are some other things that you may want to look at. I see that you are still using the stock valvetrain. On the stock valvetrain, I had some pretty bad float problems around my stock redline. Carbon buildup in the combustion chamber is another contributor, especially with the older LS1's. If your car burns oil, you may want to consider running some top-end cleaner to see if that eliminates the detonation.
And last but not least, you need A-tap or another form of data recording device if you purchase LS1 Edit or run an MAFT.
Good Luck
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Thread Starter
12 Second Club
Joined: Sep 2002
Posts: 189
Likes: 0
From: Goldsboro NC
Re: Knock problems Thanks NoGo.....is running the car with a knock damaging? I was told by someone else that it might be valve float but I would think I would notice in first too. What kind of valvetrain upgrade would fix valve float if it is the problem? I think i'll try the MAFT first since it can help further down the road if I get anything else done to the motor. Thx for your help
