Help. Getting massive knock at low rpms and can't figure out why.
08-30-2012, 06:28 AM
#1
Help. Getting massive knock at low rpms and can't figure out why. Here's all the details about the car.
PI (MAST) 215 cylinder heads, small bore, ls1 cathedral port.
227/235 113lsa cam ~600/600 lift.
60lb/h injectors.
Twin intank fuel pumps.
D1SC procharger, FMIC, SD tune.
Pistons are -3cc diamonds.
Spark plugs are NGK 7's, non-projected tips.
I've attached my scan and tune, and can't figure out why when I roll into the throttle I'm getting a lot of knock. My timing is low, afr is good, cool plugs, fresh 93 octane gas. I can actually hear the knock, so it's got me worried.
PI (MAST) 215 cylinder heads, small bore, ls1 cathedral port.
227/235 113lsa cam ~600/600 lift.
60lb/h injectors.
Twin intank fuel pumps.
D1SC procharger, FMIC, SD tune.
Pistons are -3cc diamonds.
Spark plugs are NGK 7's, non-projected tips.
I've attached my scan and tune, and can't figure out why when I roll into the throttle I'm getting a lot of knock. My timing is low, afr is good, cool plugs, fresh 93 octane gas. I can actually hear the knock, so it's got me worried.
08-30-2012, 07:43 AM
#3
TECH Junkie
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how many degres of knock , i know before i had my two fans i would get hot in the city and taking off from a light or sign easy would result in knock . a low rpms and low load. I could never hear it just saw it light up my aeroforce .
08-30-2012, 08:11 AM
#4
A lot of knock, like from 4-10 degrees. This happened this morning coming into work when it was 57 degrees outside, IAT was less than 70 degrees the whole time.
I hear this. I'm not sure if it's the knock I'm hearing, or the motor breaking up because it's pulling so much timing, or it could be a mechanical vibration somewhere. I had the kmember and motor mounts off recently replacing the oil pan gasket, so I might have a loose bolt somewhere and I'm getting virbation playing havic with my knock sensors.
I hear this. I'm not sure if it's the knock I'm hearing, or the motor breaking up because it's pulling so much timing, or it could be a mechanical vibration somewhere. I had the kmember and motor mounts off recently replacing the oil pan gasket, so I might have a loose bolt somewhere and I'm getting virbation playing havic with my knock sensors.
08-30-2012, 10:45 AM
#6
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When you say "degrees", that's a result, not a basis. The
knock retard attack and decay want to be modified if you
haven't already (try 1/2 and 2X respectively) to get to where
you can see anything but a massive cover-up.
If you do this, check the reality, and then subtract 2 degrees
of timing and see no corresponding 2 degrees of decrease in
the KR, then it's false (mechanical) knock.
knock retard attack and decay want to be modified if you
haven't already (try 1/2 and 2X respectively) to get to where
you can see anything but a massive cover-up.
If you do this, check the reality, and then subtract 2 degrees
of timing and see no corresponding 2 degrees of decrease in
the KR, then it's false (mechanical) knock.
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08-30-2012, 05:26 PM
#9
Originally Posted by Slowhawk
just had a car do that. Bad gas.
Had a truck last week pulling hard, cam was advanced too much.
Had a truck last week pulling hard, cam was advanced too much.
Posted from LS1Tech.com App for Android
08-31-2012, 04:21 PM
#10
I think I got a bad tank of gas, combined with too agressive of a tune that didn't have enough taken out of the low octane table.... so it was a combo, and here's why I say that.
Here's the knock table the morning I was hearing the motor break up with tip-in at low rpm. As you can see, on my 20 mile commute to work, I never got into it or went up in the rpms, but I got massive ammounts of knock. This one is the max amount.
Here's what it looked like this afternoon after going back to an old tune that I logs of not getting any knock earlier this summer. The thought was, maybe I messed up the tune and caused this knock issue. It's better, and the motor definitely sounded crisper and healthier, but I still got some audible knock, and the logs showed it as well.
Here's the average, much better.
And here is after I put in 5 gallons of 100 octane gas. Unfortunately, I was messing around with the blow off valve the night before, adjusting the positioning of it, and I guess it popped loose at some point, so I didn't get into boost, but as you can see, I only have one instance of knock and it was due to a stumble in the 600rpm range.
Here it's all but gone away. I'm guessing it took a little bit before I purged the line of 'bad' gas before the 100 was fully mixed.
So, honestly, I don't remember the last time I got gas, it was in the beginning of August, but I think I got gas in Jersey where they pump it for you. I'm searching for the receipt, because I think he might have put in 87 instead of 93. It would make sense.
Needless to say, I'll be getting gas in PA where I pump the gas myself.
Here's the knock table the morning I was hearing the motor break up with tip-in at low rpm. As you can see, on my 20 mile commute to work, I never got into it or went up in the rpms, but I got massive ammounts of knock. This one is the max amount.
Here's what it looked like this afternoon after going back to an old tune that I logs of not getting any knock earlier this summer. The thought was, maybe I messed up the tune and caused this knock issue. It's better, and the motor definitely sounded crisper and healthier, but I still got some audible knock, and the logs showed it as well.
Here's the average, much better.
And here is after I put in 5 gallons of 100 octane gas. Unfortunately, I was messing around with the blow off valve the night before, adjusting the positioning of it, and I guess it popped loose at some point, so I didn't get into boost, but as you can see, I only have one instance of knock and it was due to a stumble in the 600rpm range.
Here it's all but gone away. I'm guessing it took a little bit before I purged the line of 'bad' gas before the 100 was fully mixed.
So, honestly, I don't remember the last time I got gas, it was in the beginning of August, but I think I got gas in Jersey where they pump it for you. I'm searching for the receipt, because I think he might have put in 87 instead of 93. It would make sense.
Needless to say, I'll be getting gas in PA where I pump the gas myself.
