Tuning warning
07-13-2007, 01:07 PM
#21
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A lot of people think , more fuel=more power , more fuel=less knock , more fuel=throw fuel at knock makes more power .
From what I understand there is a point where air , fuel and spark come together to make the most power , tune for air , fuel then spark because one will effect the other , add to the VE it changes fuel mixture (richer) change fuel mixture (lean) it changes spark properties and can cause knock .
From what I understand there is a point where air , fuel and spark come together to make the most power , tune for air , fuel then spark because one will effect the other , add to the VE it changes fuel mixture (richer) change fuel mixture (lean) it changes spark properties and can cause knock .
Last edited by HD6.0l; 07-13-2007 at 01:16 PM.
07-13-2007, 09:23 PM
#22
I think the difference in winter air versus summer air is the actual oxygen content. See, atmosphere on average is only about 20% O2.
Your MAF doesnt know how much of the 'air' its measuring is oxygen.
So, in the summertime, you may have an O2 level of 19.8/19.9, while in the winter, you may have an O2 level of 21%+ (accurate O2 readings, another benefit of tuning with a 5 gas!!). You're engine is concentrating on the O2, and is basically displacing the rest of the crap. Mainly nitrogen.
So, while you would think cooler air, less prone to knock, you actually have more oxygen to mix with XX amount of fuel, and you end up with a leaner charge. Again, remember its the O2 we're focusing on.
And how do we lean a mixture? Remove fuel, or add oxygen.
And, BTW, anybody doing any amount of tuning needs to realize all motors have a 'sweet spot', where you get maximum power, within a couple HP, where there is virtually no gain or loss going a couple degrees each way. This is the area where you want to reduce the ignition timing to right before a significant power loss.
Just did a car today, and 3-4 degrees made damn near 30 HP. Talk about a sweet spot!! 1-2 degrees more did absolutely nothing. Zero KR. So, we took that back out. No need leaving it like that.
Your MAF doesnt know how much of the 'air' its measuring is oxygen.
So, in the summertime, you may have an O2 level of 19.8/19.9, while in the winter, you may have an O2 level of 21%+ (accurate O2 readings, another benefit of tuning with a 5 gas!!). You're engine is concentrating on the O2, and is basically displacing the rest of the crap. Mainly nitrogen.
So, while you would think cooler air, less prone to knock, you actually have more oxygen to mix with XX amount of fuel, and you end up with a leaner charge. Again, remember its the O2 we're focusing on.
And how do we lean a mixture? Remove fuel, or add oxygen.
And, BTW, anybody doing any amount of tuning needs to realize all motors have a 'sweet spot', where you get maximum power, within a couple HP, where there is virtually no gain or loss going a couple degrees each way. This is the area where you want to reduce the ignition timing to right before a significant power loss.
Just did a car today, and 3-4 degrees made damn near 30 HP. Talk about a sweet spot!! 1-2 degrees more did absolutely nothing. Zero KR. So, we took that back out. No need leaving it like that.
07-14-2007, 07:50 PM
#23
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Originally Posted by 5.7 ute
None of this really makes any sense.
If your sensors are reporting correctly & you have tuned properly for the variations then your AFR shouldnt change. Only if your sensors are giving bad info like with heatsoak not giving an accurate description of air temp should you have an issue.
I realise it isnt a perfect world but from what Ive seen in my car from an early morning log with the ambient air being around 0 degC to an afternoon temp of 28 degC is less than 1% variation on my Ben Maps. Not an engine destroying scenario.
If your sensors are reporting correctly & you have tuned properly for the variations then your AFR shouldnt change. Only if your sensors are giving bad info like with heatsoak not giving an accurate description of air temp should you have an issue.
I realise it isnt a perfect world but from what Ive seen in my car from an early morning log with the ambient air being around 0 degC to an afternoon temp of 28 degC is less than 1% variation on my Ben Maps. Not an engine destroying scenario.
07-15-2007, 02:47 PM
#24
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all you have to do is modify the IAT to timing table to get the timing correct for any temperature you will drive in.Its that simple really.If i tuned my car in 90* weather with 28* timing,then i will have it pull out a couple degrees when the iat sensor reads 65* ambient ait temps..Just be sure you iat sensor is not getting anything but ambient air temps.
07-15-2007, 06:07 PM
#25
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Such a warning to be noted. I had a Lightning in between my F-bods, and I can tell you...he couldnt be more right. Cold weather can push an FI motor into the danger zone fast. The colder months are when the Lightning community gains more members of the "vented block" club. Its one club you dont want a membership to. Keep an eye on things and datalog.. 
