Is it possible to tune the low-octane timing table?
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From: PNW
Is it possible to tune the low-octane timing table? Seeing as I'll go through 5+ tanks of gas between events, it doesn't make sense to run hi-test all the time, so I run 87 in the meantime. Well I'm getting ready to build the engine - nothing crazy, most likely stay with the OEM 10:1 CR - but it will definitely require tuning and I would like to be able to continue this arrangement.
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From: AR
I'm kinda new to all of this so I may be thinking wrong here, but tune the high table for your 87 octane and then copy it to the low table. Put your existing high table (that you've already got where you want?) numbers back into the high table. You should have both high and low tuned at that point.
The only problem I see is if you're running 87, and your ecm has put you into the low table, and you get some real knock it doesn't have anything to reference at that point. It already thinks it is in the safe zone. I'm not sure if they computer will continue to pull timing even if you're 100% in low table?
The only problem I see is if you're running 87, and your ecm has put you into the low table, and you get some real knock it doesn't have anything to reference at that point. It already thinks it is in the safe zone. I'm not sure if they computer will continue to pull timing even if you're 100% in low table?
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From: Virginia
Tune the spark to run on 87. The PCM will always use the high table if you are not in SD. Take your new high table, copy it to the low table and pull out at least 5 degrees, if not more across the entire table. Reference a stock table and pull similar numbers. Not doing this will result in your PCM learning the knock over time (that will happen if not tuned to 87) and be added to "knock learn factor." Knock learn goes from 0-1, where 1=low octane table will be used, and 0=high octane. Anything between will be biased. Say your high octane is 20, and low octane is 10 and knock learn is 0.5. This would mean your PCM will set timing at 15, halfway between the tables.
Just tune it to run 87 with no knock, then set the low octane at least 5 degrees less, if not 10 in the higher rpms. That's up to you and your engine.
Just tune it to run 87 with no knock, then set the low octane at least 5 degrees less, if not 10 in the higher rpms. That's up to you and your engine.
Add up the difference in price between 93 and 87 times how many gallons of gas you use in a season. Find the difference between that and the cost of even one blown ringland. Then decide if this path is really even worth your time. Some of these discussions remind me of people who trade in a perfectly good car for one that costs 30k$ more because it gets 5mpg better mileage.
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From: Virginia
Add up the difference in price between 93 and 87 times how many gallons of gas you use in a season. Find the difference between that and the cost of even one blown ringland. Then decide if this path is really even worth your time. Some of these discussions remind me of people who trade in a perfectly good car for one that costs 30k$ more because it gets 5mpg better mileage.
i ran 87 in my stock L59 for couple years. would ping like a ************ hauling anything unless it dropped timing like 5* basically everywhere. IME even the "low compression" motors dont like anything but 92+ and even then the pisswater we get in the PNW for a "winter blend" will ping.
I understand that 1.00 is optimal Knock learn and 0.00 is running off the low octane table.
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Verdad Gallardo TECH Fanatic
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From: Virginia
If you have a knock learn of 1.00, then you have some issues with knock. I had a 98 pcm that used to show this as 1.00, couldn't get it to use the HO table at all in CL. After clearing up a MASSIVE amount of false knock, and tuning the sensors on race gas, it's 0.0. Not sure that the forum you cited is accurate. You know, it's a forum, just like this one, and people can be wrong. I never see knock learn be anything but 0.00 in my logs, and it uses HO on mine and every other car I've dealt with... well, unless it's knocking that is.
another one then
https://forum.hptuners.com/showthrea...k+learn+factor
i see threads with both, good catch, gotta pay attention
another one
https://forum.hptuners.com/showthrea...k+learn+factor
I even double triple checked with them because I wanted to be sure
https://forum.hptuners.com/showthrea...k+learn+factor
i see threads with both, good catch, gotta pay attention
another one
https://forum.hptuners.com/showthrea...k+learn+factor
Yes, 1 = Hi, 0 = low, and 0.5 would be halfway between....
Last edited by kingtal0n; Feb 10, 2018 at 03:08 PM.
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Joined: Oct 2014
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From: Virginia
another one then
https://forum.hptuners.com/showthrea...k+learn+factor
i see threads with both, good catch, gotta pay attention
another one
https://forum.hptuners.com/showthrea...k+learn+factor
I even double triple checked with them because I wanted to be sure
https://forum.hptuners.com/showthrea...k+learn+factor
i see threads with both, good catch, gotta pay attention
another one
https://forum.hptuners.com/showthrea...k+learn+factor
I even double triple checked with them because I wanted to be sure
It's very odd that in the video you see it climb (as I have myself witnessed) as knock occurs. Strange indeed.
Off to check some logs... lol.
