Battling Knock Retard... Is if False?
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On The Tree
Joined: Dec 2001
Posts: 154
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From: Burlington, ON
Battling Knock Retard... Is if False? I have been having knock retard problems now for quite awhile. It starts around 4000rpm at WOT and will keep building all the way until I shift. On the street when its cool out I will only see 3-5 degrees, but when its warm or I am at the track I will see up to 7-9 degrees of KR.
When I am at the track I run Sunoco 94 with a bottle of NOS Off-Road Octane Boost, my engine is 11.5 CR, and I have LS1edit so I have played with the timing advance and set it anywhere from 24 degrees down to 19 degrees from 4200rpm - 5500rpm and the KR still happens. Even though I get quite a bit of KR, I NEVER EVER hear a sound out of the engine, and I cannot feel it stumble like an engine normally does when detonating.
Does anyone feel this might be false knock retard? Where would I start looking if it was? Would it be wrong for when I go to the track to turn down the Max KR by RPM to like 3 degrees?
When I am at the track, with 8-9 degrees of KR, I am only pulling like 12 degrees timing advance which is terribly ripping down my trap speeds by at least 5 or 6mph.
Anyone else ever encounter a problem like this? Any experiences someone could share would be greatly appreciated
When I am at the track I run Sunoco 94 with a bottle of NOS Off-Road Octane Boost, my engine is 11.5 CR, and I have LS1edit so I have played with the timing advance and set it anywhere from 24 degrees down to 19 degrees from 4200rpm - 5500rpm and the KR still happens. Even though I get quite a bit of KR, I NEVER EVER hear a sound out of the engine, and I cannot feel it stumble like an engine normally does when detonating.
Does anyone feel this might be false knock retard? Where would I start looking if it was? Would it be wrong for when I go to the track to turn down the Max KR by RPM to like 3 degrees?
When I am at the track, with 8-9 degrees of KR, I am only pulling like 12 degrees timing advance which is terribly ripping down my trap speeds by at least 5 or 6mph.
Anyone else ever encounter a problem like this? Any experiences someone could share would be greatly appreciated
TECH Apprentice
Joined: Jan 2002
Posts: 364
Likes: 0
From: Princeton, IN
Re: Battling Knock Retard... Is if False? I have spent sometime fighting KR also, when I seem to have it I don’t... I went back to a paper filter. That seemed to help I think the car runs a little better all around with the frame!! I don’t think I have ever got over 3.9 degrease pulled out at one time. Mine shows up at WOT and Part Throttle,
I removed my lid, 85mm maf, htpp tuning, iat!, and holly air filter.
I have used two cans of gm top engine cleaner. One can of seafoam and added a can to my gas. I think the seafoam works the best, I could tell a difference in the way the car runs.
One thing you must do is stop the oil from getting in to the intake. I tried smh mod “it help but did not stop all of the oil” I have an air compressor filter installed right now and it seems to work. I can send you some pictures if you like.
I removed my lid, 85mm maf, htpp tuning, iat!, and holly air filter.
I have used two cans of gm top engine cleaner. One can of seafoam and added a can to my gas. I think the seafoam works the best, I could tell a difference in the way the car runs.
One thing you must do is stop the oil from getting in to the intake. I tried smh mod “it help but did not stop all of the oil” I have an air compressor filter installed right now and it seems to work. I can send you some pictures if you like.
TECH Apprentice
Joined: Apr 2002
Posts: 373
Likes: 0
From: Hickory, NC
Re: Battling Knock Retard... Is if False? You may want to run some unleaded 100 octane or, in your case with increased compression, try unleaded 110 octane. This is one of the best ways to determine if it's false knock or not. There's a good chance that it is false since you don't audibly hear the motor ping when you see 7 to 9 degrees (that's some serious knock retard).
Re: Battling Knock Retard... Is if False? just some ideas:
-hook up a fuel pressure gauge to fuel rail; make sure you are seeing over 50 lbs., preferably around 55.
- check injector pulse width with atap. under WOT i think you want to see 19-22.
if both of these tests are within safe zones, you should check to see if any exhaust components or suspension pieces are banging the chassis. if still nothing, try nineballs KO box to desensitize the knock sensors.
good luck!!!!!!!!
-hook up a fuel pressure gauge to fuel rail; make sure you are seeing over 50 lbs., preferably around 55.
- check injector pulse width with atap. under WOT i think you want to see 19-22.
if both of these tests are within safe zones, you should check to see if any exhaust components or suspension pieces are banging the chassis. if still nothing, try nineballs KO box to desensitize the knock sensors.
good luck!!!!!!!!
Re: Battling Knock Retard... Is if False? IF, you are sure it is false knock, here are several things that you can immediately do to restore power:
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</font>
- <font size="2" face="Verdana, Helvetica, sans-serif">reduce the total number of degrees that the knock retard can take out of your timing (max retard vs. load table)</font></li>
- <font size="2" face="Verdana, Helvetica, sans-serif">increase the "Decay vs. RPM" values by ~150% to return to stock timing faster once KR is sensed</font></li>
- <font size="2" face="Verdana, Helvetica, sans-serif">Reduce values in "attack vs. RPM by ~50% to slow down how much the KR comes on</font></li>
- <font size="2" face="Verdana, Helvetica, sans-serif">copy the values from your high octane table and type these into your low octane table (this is a pain because you cannot import the numbers, they have to be typed in)</font></li>
On The Tree
Joined: Nov 2001
Posts: 175
Likes: 0
From: Cincinnati, OH
Re: Battling Knock Retard... Is if False? Depending on the year of your vehicle, GM released several PCM updates that address the issue of overly aggresive knock retard. I have the web address at work that will allow you to input your VIN. The site will come back to you with a list of PCM updates for your car (assuming a "relatively" stock automobile). I'll post the address Tuesday morning unless someone else has it handy.
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TECH Addict
Joined: Nov 2001
Posts: 2,207
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From: College Station, Tx
Re: Battling Knock Retard... Is if False? If you are running lean at WOT you can even be seeing spark pre-ignition at 13-15 degrees of timing. If you have access to a wideband that would be a good tool. Otherwise I would
1) Try richening the PE vs RPM by a fixed amount (so you can take it back out later if needed). Say increase it by 110-115 percent. This should knock you down a full a/f point richer.
2) Fill up with 104 unleaded.
If you are running verifiably rich and with 104 and still getting the same amount of knock retard I would suggest some sort of false reading. First I would replace the knock sensors and torque them to spec. If that doesn't help I would start adressing an "overly sensitive" knock sensor through programming.
Chris
1) Try richening the PE vs RPM by a fixed amount (so you can take it back out later if needed). Say increase it by 110-115 percent. This should knock you down a full a/f point richer.
2) Fill up with 104 unleaded.
If you are running verifiably rich and with 104 and still getting the same amount of knock retard I would suggest some sort of false reading. First I would replace the knock sensors and torque them to spec. If that doesn't help I would start adressing an "overly sensitive" knock sensor through programming.
Chris
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TECH Enthusiast
Joined: Jan 2002
Posts: 597
Likes: 0
From: Orange Park, FL
Re: Battling Knock Retard... Is if False? I battled KR for over a month after my TR224 install. I swapped pulleys, ran race gas, tuned with Edit, did a top engine clean - basically went round and round with it (and lost!!) My dumbass finally got around to putting a fuel pressure gauge on it and found out that my stock pump is no longer running as designed. My pressure dropped to around 45psi at WOT in the top of 2nd and into 3rd. I would recommended checking your fuel pressure along with all of the other great ideas given earlier. I'm currently waiting on the Racetronix PnP for the 99's. Good Luck to you.
