Still getting knock with low boost and meth
Thread Starter
I need a gauge for that
iTrader: (37)
Joined: Jan 2006
Posts: 10,921
Likes: 3
From: Huntsville, AL
Still getting knock with low boost and meth This is getting frustrating, I still havent been able to give my truck more than 60% throttle without getting a lot of knock, even with a twin nozzle alky control kit with 100% meth.
Specs on the build:
stock 99 silverado PCM
402 iron shortblock built by LME
WCCH L92 heads, LS9 gaskets
truck L92 intake, NW 90mm TB
FIC 96lb injections, nasty performance billet rails, dual denso 1020 pumps
KB turbo pipes, pt88 t4, 4" downpipe
JGS 50mm wastegate, 6lb spring, eboost street controller
yank pt3200, ace racing 4l80e
stock truck coils, taylor 10mm wires, tr6 plugs at 0.028"
M15 and M10 nozzles alky control meth kit, 100% meth
226/226 117 cam with stock rockers
Basically whenever I get near or into boost I get knock, sometimes only 1 degree, other times up to the max of 8 degrees. I thought it might be false knock so I turned the meth on and it still knocks (albeit, less). I can't hear the knock but ive destroyed an engine because of detonation so im determined for that not to happen again.
You will notice in the log that the meth is off in the first part, and on in the second half, hence why the wb is showing richer.
I have some BR7EF plugs on the way to try out, but I wanted to see if anyone had any other ideas in case thats not the solution.
Specs on the build:
stock 99 silverado PCM
402 iron shortblock built by LME
WCCH L92 heads, LS9 gaskets
truck L92 intake, NW 90mm TB
FIC 96lb injections, nasty performance billet rails, dual denso 1020 pumps
KB turbo pipes, pt88 t4, 4" downpipe
JGS 50mm wastegate, 6lb spring, eboost street controller
yank pt3200, ace racing 4l80e
stock truck coils, taylor 10mm wires, tr6 plugs at 0.028"
M15 and M10 nozzles alky control meth kit, 100% meth
226/226 117 cam with stock rockers
Basically whenever I get near or into boost I get knock, sometimes only 1 degree, other times up to the max of 8 degrees. I thought it might be false knock so I turned the meth on and it still knocks (albeit, less). I can't hear the knock but ive destroyed an engine because of detonation so im determined for that not to happen again.
You will notice in the log that the meth is off in the first part, and on in the second half, hence why the wb is showing richer.
I have some BR7EF plugs on the way to try out, but I wanted to see if anyone had any other ideas in case thats not the solution.
Last edited by Atomic; Mar 19, 2012 at 11:36 PM.
Thread Starter
I need a gauge for that
iTrader: (37)
Joined: Jan 2006
Posts: 10,921
Likes: 3
From: Huntsville, AL
The exhaust is very tight against the frame, but so much so that it doesnt rattle, its just wedged in there (4" exhaust is very tight). I dont really think thats the issue. I suppose I could test that by running an open downpipe, but I remember there being knock when I was doing that anyway.
Timing is less than 20 in medium load areas (80kpa to 110) and around 10 I think up from there. Knock starts sometimes as early as 80kpa or sometimes 120kpa. Often if I get a little knock at first, and I hold the current boost it will decay, then I give it more throttle (and more boost) and its alright.
Timing is less than 20 in medium load areas (80kpa to 110) and around 10 I think up from there. Knock starts sometimes as early as 80kpa or sometimes 120kpa. Often if I get a little knock at first, and I hold the current boost it will decay, then I give it more throttle (and more boost) and its alright.
What's the compression?
What's the AFR when this is happening?
Is burst knock tuned out?
I can't see your tune or logs because I don't have HPT...
too little timing and/or too much fuel can cause knock - common mistake on forced induction cars is to yank out a bunch of timing and/or dump in a bunch of extra fuel too soon or too big of a step...
What's the AFR when this is happening?
Is burst knock tuned out?
I can't see your tune or logs because I don't have HPT...
too little timing and/or too much fuel can cause knock - common mistake on forced induction cars is to yank out a bunch of timing and/or dump in a bunch of extra fuel too soon or too big of a step...
Thread Starter
I need a gauge for that
iTrader: (37)
Joined: Jan 2006
Posts: 10,921
Likes: 3
From: Huntsville, AL
9.5 compression
AFR is going from stoich to 11.8 from 85kpa to 125kpa then down to 10.7 after that
burst knock is indeed tuned out
timing is 10 degrees
AFR is going from stoich to 11.8 from 85kpa to 125kpa then down to 10.7 after that
burst knock is indeed tuned out
timing is 10 degrees
I was gonna say burst knock....but thats out
50 water and 50 meth is better cooling....actually straight distill is better cooling if you have enough fuel already. You should be into water meth anyways yet....It should really come on around 3 psi or higher.
Its very common for pcm s to have false knock on the transition to boost, but my experience is that its very repeatable...like alway 92-94 kpa....light load, ussually heavy load, big throttle transition they pass thru.
The exhuast could....be doing it. 10 degrees....and 11 to 1 should just be fat and retarded.....a good place to start ussually.
I run the iat about 6-10 inches up the pipe from the last nozzle, so I can measure the temp drop. I dont think your issue is water/meth related at all, and I wouldnt spray that low....as you can bend a rod loading it up in light load low rpm .
I bet if you start limiting the knock tables.....its still there.
50 water and 50 meth is better cooling....actually straight distill is better cooling if you have enough fuel already. You should be into water meth anyways yet....It should really come on around 3 psi or higher.
Its very common for pcm s to have false knock on the transition to boost, but my experience is that its very repeatable...like alway 92-94 kpa....light load, ussually heavy load, big throttle transition they pass thru.
The exhuast could....be doing it. 10 degrees....and 11 to 1 should just be fat and retarded.....a good place to start ussually.
I run the iat about 6-10 inches up the pipe from the last nozzle, so I can measure the temp drop. I dont think your issue is water/meth related at all, and I wouldnt spray that low....as you can bend a rod loading it up in light load low rpm .
I bet if you start limiting the knock tables.....its still there.
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Thread Starter
I need a gauge for that
iTrader: (37)
Joined: Jan 2006
Posts: 10,921
Likes: 3
From: Huntsville, AL
I plan to use the meth as a safety net, but as of right now I keep it off. I had it on just to try to see if it was real knock or not. I have it coming on around 3psi, and the IAT sensor is about 8 inches upstream of both nozzles.
But really, the meth isnt what im concerned with, I just mentioned it to try to eliminate the "bad fuel" theory.
But really, the meth isnt what im concerned with, I just mentioned it to try to eliminate the "bad fuel" theory.
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Thread Starter
I need a gauge for that
iTrader: (37)
Joined: Jan 2006
Posts: 10,921
Likes: 3
From: Huntsville, AL
Like I said above, I changed pcms to a 2002 model and commanded slightly less fuel (11 instead of 10.7) and the knock is gone. I even used more sensitive knock sensor settings than previous, and hotter plugs (tr6 instead of br7ef). So I am sure it is not burst knock.
Does burst knock show up under the "total timing retard" pid?
Who is Brent?
Does burst knock show up under the "total timing retard" pid?
Who is Brent?
