93 Octane = 9* KR...100 Octane = 0 KR, now what?
11-18-2003, 08:32 PM
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93 Octane = 9* KR...100 Octane = 0 KR, now what? I am helping a friend tune his Car...its a 01 A4 Trans-Am. He is getting some major KR.
As soon as he hits 1700+ RPM he gets 4* of KR also as his MAF starts to flow more the KR increases.
While cruising (1200 rpm) he is at 0* knock if he accelerates a little and the rpms rise the KR comes in. I noticed the KR show when his MAF starts to flow 4.5 lb/min and up.
When he gets to 2000+ RPMs he is getting 9* of knock all the way up to his rev limiter, which is anywhere from 6lbs/min to 30lbs/min on the MAF.
He is running a stock tuning minus the basic LS1Edit stuff like rev limiter, shift points etc. The timing tables are still stock, the PE/rpm has been adjusted a little to meet 13.0 AFR. He is still running the stock MAF as well.
Here is a list of his mods:
2.05/1.57 ported heads
212/218 Xtreme cam 558int/563ex 115 lsa
SLP Lid, LS6 intake, !EGR, !AIR, !FRA
MAC headers and ORY, Flowmaster Cat-Back
Now what I had him do is put some 100 octane unleaded gas in his car and re-ATAP it. The knock was almost completely gone. A few .1's here and there.
My question is what is the best way to fix him up so he can run pump gas? I tried lower the timing in the High/Low Octane tables in the rpm/MAF g/sec where he was getting knock but that didn't help any at all.
Any ideas?
Thanks,
Lee
As soon as he hits 1700+ RPM he gets 4* of KR also as his MAF starts to flow more the KR increases.
While cruising (1200 rpm) he is at 0* knock if he accelerates a little and the rpms rise the KR comes in. I noticed the KR show when his MAF starts to flow 4.5 lb/min and up.
When he gets to 2000+ RPMs he is getting 9* of knock all the way up to his rev limiter, which is anywhere from 6lbs/min to 30lbs/min on the MAF.
He is running a stock tuning minus the basic LS1Edit stuff like rev limiter, shift points etc. The timing tables are still stock, the PE/rpm has been adjusted a little to meet 13.0 AFR. He is still running the stock MAF as well.
Here is a list of his mods:
2.05/1.57 ported heads
212/218 Xtreme cam 558int/563ex 115 lsa
SLP Lid, LS6 intake, !EGR, !AIR, !FRA
MAC headers and ORY, Flowmaster Cat-Back
Now what I had him do is put some 100 octane unleaded gas in his car and re-ATAP it. The knock was almost completely gone. A few .1's here and there.
My question is what is the best way to fix him up so he can run pump gas? I tried lower the timing in the High/Low Octane tables in the rpm/MAF g/sec where he was getting knock but that didn't help any at all.
Any ideas?
Thanks,
Lee
11-18-2003, 08:40 PM
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When you say that the PE/rpms have been adjusted "a little" how much is that. Was the 13 AFR done with a wideband o2? If not that may be where your trouble is at. You may be leaner at PE than you think you are and may have to richen up that PE/rpms some.
11-19-2003, 07:57 AM
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Yes this was on a wide band 02 Dyno.. The Power Enrichment table was only lowered by 3% in a few rpm cells to lean out to 13.0 AFR.
Has anyone had this happen to them, knock goes away with high octane gas? What did you fix to be able to run 93 octane with no KR?
Has anyone had this happen to them, knock goes away with high octane gas? What did you fix to be able to run 93 octane with no KR?
11-19-2003, 09:10 AM
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This is all my friend knows about his heads.. 2.05/1.57 ported heads
I don't think they are milled and CR should still be close to stock 10:1 (stock pistons). I was thinking he might have a littler higher than stock CR, but if I lowered the timing he should be able to still run on pump gas even with 11:1 CR. I was able to run on 93 octane with my 11.2:1 CR @ 28* timing with no problems.
He got ATAP + LS1Edit after he did his H/C on his car and has had KR ever since. At first he thought it was just false knock, but as soon as his MAF is flowing +5lb/min or more the knock starts at 4* and goes up to 9*, it doesn't go higher than 9* even at WOT up to the rev limiter.
He has been through many full tanks of gas at different gas stations around town. So far the only cure for his KR was 100 Octane.
Could it be a faulty MAF sensor maybe? I suggested he switch another stock MAF with one of his friends just to see if there was any change.
What do you think?
I don't think they are milled and CR should still be close to stock 10:1 (stock pistons). I was thinking he might have a littler higher than stock CR, but if I lowered the timing he should be able to still run on pump gas even with 11:1 CR. I was able to run on 93 octane with my 11.2:1 CR @ 28* timing with no problems.
He got ATAP + LS1Edit after he did his H/C on his car and has had KR ever since. At first he thought it was just false knock, but as soon as his MAF is flowing +5lb/min or more the knock starts at 4* and goes up to 9*, it doesn't go higher than 9* even at WOT up to the rev limiter.
He has been through many full tanks of gas at different gas stations around town. So far the only cure for his KR was 100 Octane.
Could it be a faulty MAF sensor maybe? I suggested he switch another stock MAF with one of his friends just to see if there was any change.
What do you think?
11-19-2003, 10:26 AM
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If octane fixes it, it's all about burn rate vs advance.
The advance may be coming in too soon (ping/KR at
4000-5000RPM) or the mixture might be too lean.
You can play with the combination of mixture & spark
(if dyno time is free, heh) to see where the best power
is made. Mixture messing changes burn time (rich=slow)
and spark advance makes it back up. Other variables are
inlet & coolant temps, spark plug heat range too. He may
just be at the limits of detonation from improved cylinder
filling, cylinder preignition pressure also speeds up burn.
Lastly, one cylinder that's hotter or leaner or has one
more carbon glow spot that the rest, determines the
onset of knock. Look for any one cylinder having knock
or misfire counts that are out-of-bed with the rest? This
might respond to injector balance / cleaning, top end
clean, fresh colder-range plugs, etc.
The advance may be coming in too soon (ping/KR at
4000-5000RPM) or the mixture might be too lean.
You can play with the combination of mixture & spark
(if dyno time is free, heh) to see where the best power
is made. Mixture messing changes burn time (rich=slow)
and spark advance makes it back up. Other variables are
inlet & coolant temps, spark plug heat range too. He may
just be at the limits of detonation from improved cylinder
filling, cylinder preignition pressure also speeds up burn.
Lastly, one cylinder that's hotter or leaner or has one
more carbon glow spot that the rest, determines the
onset of knock. Look for any one cylinder having knock
or misfire counts that are out-of-bed with the rest? This
might respond to injector balance / cleaning, top end
clean, fresh colder-range plugs, etc.
