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Equation for tuning fuel maps. Please help before I try to tune.

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Equation for tuning fuel maps. Please help before I try to tune.

Old 06-09-2005, 09:50 PM
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Default Equation for tuning fuel maps. Please help before I try to tune.

Sorry for the new thread about the formula but I was doing some math and something doesn't work out for me correctly and I figured people could throw their 2 cents in to give me a hand.

Shoot me if I'm wrong but if you use the formula of: % to change=[(known/calculated)/known]*100 then it works sometimes. Example: [(10/11.5)/10]*100=8.6% then you want to pull 8.6% of your fuel. True, this was already discussed in a previous topic. My problem is like this if you are at 10 and you want to hit 14.7 then according to the formula you only pull 6.8% of your fuel which wont even get you to the previously mentioned 11.5. Am I doing something wrong here or is the forumla flawed?
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Old 06-09-2005, 10:32 PM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

8.6% equals 1:1 AFR change, so if you're at 10.5:1 AFR and you pull 8.6%, you would then be at 11.5:1
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Old 06-09-2005, 11:59 PM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

I see, so in theory if i want to get from 10.5 to 14.7 I should pull about 35%, IN THEORY-I'm not going to pull that much fuel at once because of how much it could truely affect, but that is how it works, right?
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Old 06-10-2005, 12:02 AM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

Originally Posted by Darkelvis
I see, so in theory if i want to get from 10.5 to 14.7 I should pull about 35%, IN THEORY-I'm not going to pull that much fuel at once because of how much it could truely affect, but that is how it works, right?
if you have a map in part throttle that runs 10.5 AFR's you should seriously consider a starting with a better basemap.

what part of your rpm range are you trying to lean out that much?
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Old 06-10-2005, 07:43 AM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

That seems really way too rich for a scaled basemap.

I would lean out 5 or 10% at a time in problem areas until you get closer to your target and then start using that formula. 35% is a pretty big jump.
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Old 06-10-2005, 09:00 AM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

No... the forumula is perfect, very simple math.

If you're at 10.5, and you want to be at 14.7.. Do this:

10.5 / 14.7 = 0.71428571428571428571428571428571

(0.71428571428571428571428571428571 - 1) = -0.28571428571428571428571428571429

-0.28571428571428571428571428571429 * 100 = -28.571428571428571428571428571429


...then you take, -29% ...very simple.

I use that formula in an autotune routine in my datalogger... I get almost perfectly flat AFRs in 3-4 pulls on the dyno... ..so, do whatever you feel like you need to do.
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Old 06-10-2005, 09:51 AM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

I see, I just had my formula wrong, thank you very much. **** and 95redex 10.5 was just an example my map from xenocron is in the 11-13's range in vac.
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Old 06-11-2005, 06:05 PM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

Originally Posted by Darkelvis
I see, I just had my formula wrong, thank you very much. **** and 95redex 10.5 was just an example my map from xenocron is in the 11-13's range in vac.
ahh, you had me scurred for a minute there.
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Old 06-14-2005, 01:27 AM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

ok, say all that again for really stupid people
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Old 06-14-2005, 01:41 PM
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Default Re: Equation for tuning fuel maps. Please help before I try to tune.

[(where you are at/where you want to be) - 1] * 100

Example. your wideband reads 11.9 and you want to be at 14.7
11.9/14.7 = 0.809523809523

0.809523809523 - 1 = -0.190476190477

-0.190476190477 * 100 = -19.0476190477

So you highlight the area that you are at 11.9 and then pull 19% of your fuel from that area.
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