Knock retard in boost
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Knock retard in boost I am having knock when in boost from 120kpa to 205kpa. At 4000 to 6000 rpm. Its a L83, 5.3 with a port injected Whipple SC at 14#. 10.7 compression, all forged, pump 93, Fuel lab brushless pump, boost referenced. Knock starts about 11 psi boost and goes from .4 to 10 degrees.
I thought it might be lean and the wideband was wrong so I added 10% fuel from 4000 to 6800rpm, 127kpa to 255kpa. Still knocks. Latest tune and log attached. Is it time for better fuel? Is there any of the octane booster that is good for checking this? Thanks
I thought it might be lean and the wideband was wrong so I added 10% fuel from 4000 to 6800rpm, 127kpa to 255kpa. Still knocks. Latest tune and log attached. Is it time for better fuel? Is there any of the octane booster that is good for checking this? Thanks
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I got some octane booster, put it in, and should be about 98 octane now, and has about 1-2 degrees of knock. It switches to low octane table (I think, and spark is down to single digits. Where would you estimate the timing should be . Not having a dyno makes it tough. I guess I will be hunting E85.
There is some burst knock in there also.
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As a test, to see if it is false knock, or octane deficit you could splash in ( Blend ) 10% Toluene and 10% 100Low Lead aviation gasoline.
Such a blend:
80% 93 octane Mo-Gas
10% Toluene
10% 100LL
would result in ( calculated) 97.4 OCTane.
Such a blend:
80% 93 octane Mo-Gas
10% Toluene
10% 100LL
would result in ( calculated) 97.4 OCTane.
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One part is definitely octane deficit. I added enough octane booster to get to 98 octane and the knock was only 1-2 degrees----from 4 to 10 degrees previously. Need to reduce timing as Lorenzo said too.
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Verdad Gallardo Just for reference in my wifes yukon xl with l83 with lt4 blower on 93 I have 9-10 degrees wot on 8lbs. Its had the blower on it for 60k miles. We have built and tuned alot trucks with stock l83 with blowers and they all have timing close to that WOT. They make about 450rwhp on 93 and 500 on E85 but cant run e85 without lt4 pump and injectors. I know your port injected so dont have to worry about that but was just giving reference.
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Just for reference in my wifes yukon xl with l83 with lt4 blower on 93 I have 9-10 degrees wot on 8lbs. Its had the blower on it for 60k miles. We have built and tuned alot trucks with stock l83 with blowers and they all have timing close to that WOT. They make about 450rwhp on 93 and 500 on E85 but cant run e85 without lt4 pump and injectors. I know your port injected so dont have to worry about that but was just giving reference.
I lowered the timing on my tune, but I think I need to lower it some more if that's the direction that I need to go.
How the heck did I get by on the GTO engine for so long with no problems?
L83 and LS2 are completely different animals. Just look at stock tunes from a 98 LS1 and then look at a tune at LS3 and then a L86 and you'll see less and less timing. Higher compression and more efficient needs less timing.
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Gotcha---Changed wot timing to 10 degrees from 3500 up. Made two quick runs and only .4 knock on one of the runs. I will get my E85 sensor wired up and should be good to go. I reduced timing to 9.5 degrees from 5600rpm up in the last row. Now I can pull some of that fuel out.
Thanks guys, I was headed for BOOM.
Thanks guys, I was headed for BOOM.
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