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Thread: How to correct WOT for each gear?

  1. #1
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    Default How to correct WOT for each gear?

    I am having an issue regulating the AFR in each gear. I usually tune in third from 2,500 to 6,700. But what I notice is when I get a good 13.00 AFR in that gear 1st and 2nd are lean and 4th is rich. 1st will be off by as much as half a point where 2nd will be 2 to 3 tenths off. Now 4th will be rich by 2-4 tenths. I figured it may be a MAP KPA issue but it isn't that. So I looked at my MAF freq. Nothing there. The car basicly runs in the same place in both tables in all gears at WOT. What am I missing? Why doesn't the car run the same AFR at WOT in all gears?

  2. #2
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    Seems to me that 1 & 2 will climb RPM's faster & 4 could climb RPM's slower, depending upon beginning RPM & gear ratio. Perhaps, the airflow acceleration (g/s^2) is a bit faster in 1 & 2; slower in 4. Peak airflow (g/s) itself may be the same, but, the acceleration of the air (g/s^2) to get to the peak airflow (g/s) is likely higher in 1 & 2, slower in 4. Am thinking that the airflow acceleration (g/s^2) could possibly lean out 1 & 2 & make rich 4.

  3. #3
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    That makes sense but is there a way to compensate for it? I want to make peak power in each gear. I also don't like running lean ever. Especially in my two low, high Dincyl, gears where knock could be present. But I don't want to be rich in my two running gears when I am trying to beat the guy next to me. I can't be the only one experiencing this. There has to be a fix some where in the system.

  4. #4
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    As to tuning, I am a newb. So, please keep that in mind.

    Just went through the tuning options & found only one area that may help, as there appears to be verry little tunning for accelerated airflow values.

    Under "learning" & then "filtered" RPM airflow correction," there is described "RPM rate of change" or (accel/deccel). The filter is used to correct over & under shooting RPM. It's used for RPM rate of change corrections & may end up causing an RPM issue, even if it works to help the A/F ratio. Anyway, it looks like you may be able to use this table to help w/ the lean condition. Description says, "airflow subtracted during (accelerated) RPM." So, maybe if you enter a negative value, then perhaps the filter table will add (neg & neg = positive) airflow to the MAF reading. If this is the case, then the PCM should add more fuel during 1 & 2. Unfortuneately, (& if this even works) the same cannot be done to 4. It's either/or; either go w/ the negative values in the filter table in an effort to add air flow to the MAF table in order to help 1 & 2 or use positive numbers & further lean out 1 & 2 in order to help with 4.

    For this to work, the software will need to have the ability to recognize that when subtracting a negative number, the answer is positive.

    I'm getting ready to fine tune my basic tune & am going to try this as well. Hope this helps. Also, if you find something that works, please let us know.

  5. #5
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    pray, mine is all the same... same afr throught every gear.. i used olsd w/ cos5. i had that problem when i had a maf tune.. w/ sd not any more
    01 Z06, 4L60E CONVERSION, L92/L76 TOP END, 72# LS3 INJECTORS (THANKS FIC), DRY NITROUS, COS5

  6. #6
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    I will have to go back and look at my logs but I think it does in both OLSD and MAF. I am going to check it again. I am just having a problem with my stupid clutch now so banging gears is not an option. Thanks for the imput guys.

    Brett

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