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Thread: Open Loop Maf Tuning

  1. #1
    Senior Tuner Russ K's Avatar
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    Open Loop Maf Tuning

    There seems to be allot of methods to tune the AFR on the V6 cars. Since these cars don't yet have an open loop table like the V8's and the V6 (4.3) trucks, the commanded AFR while in open loop is all over the place when not in PE. In PE the commanded AFR will be were you set it.

    This is what I found is the best way to tune these cars. First leave the VE table stock. Then zero out the Power Enrichment PE Enable > Delay vs. TPS table (some models will already have this table zeroed out). Set the PE Enable TPS > Hot to 0% (at all rpms). Set the Base AFR vs. ECT to 14.7 at all temps. Zero the Add vs. Tps (note the values in this table add to the Base AFR vs. ECT and leans the AFR). Then zero out the Add vs. Rpm table.

    Now install the wideband in place of the stock front 02 sensor, or the right front if a rear drive car (this will put the car in open loop). Flash this new file, then warm the engine to operating temp. Start scanning and reset the fuel trims. Now the commanded AFR will be steady at 14.7. With the Maf AFR histogram open, drive the car at part throttle to fill the histogram up to ~7500 hz. Try to accel & decel smoothly. Then copy & paste the Maf error % histogram to the Maf table using paste special multiply by %. Once you get the AFR close to 14.7, then use paste special multiply by % - half. For the low end of the Maf table that you didn't enter, just enter the error % from the lowest airflow hz cell that you did enter. So by now the part throttle AFR will be ~ 14.7.

    Now change the PE Enable TPS back to stock (or were you what it as some models have the low rpm enable at 100%). Change the Base AFR vs. ECT to 13.0 at all temps for NA, or 11.0 for a boosted engine. Flash this new file, connect the scanner and check & reset the fuel trims. Bring the car to a dead stop, use the VCM controls to put the trans in 2nd gear. Now go wot till your max rpm desired. Then copy & paste the Maf AFR error % to the 7625 hz & higher part of the Maf table. For the freq. hz cells that the scanner skipped over, just average these cells. For the higher freq hz cells of the table that you didn't enter, just enter the error % from the highest airflow hz cell that you did enter. Once you get the AFR close, use paste special multiply by % - half.

    Unlike the V8's and V6 trucks, if the part throttle fuel trims are negative by even a small %, you could have negative LTFT at wot. This is why you need to get the open loop part throttle AFR close to 14.7 BEFORE wot tuning the AFR.

    When going to wot from a dead stop there will be a lean spike at first (under 7500 hz) that is normal if you first got you part throttle AFR right, this is caused by the split sec. delay for the richer exhaust to reach the wide band.

    Now install the stock O2 sensor. If you did everything right, your LTFT's should be close and will lock at 0% @ wot.

    Russ Kemp
    Last edited by Russ K; 03-09-2011 at 02:14 PM.

  2. #2
    Russ , what a great guide.

    I have a few questions tho:
    Set the PE Enable TPS > Hot to 0% (at all rpms).
    you mean to PE enable TPS to 0% or to 100%? (you are trying to disable PE mode here , right?)
    Now install the wideband in place of the stock front 02 sensor, or the right front if a rear drive car (this will put the car in open loop)
    I dont understand what is this that will put car in open loop. NB error code? or? I have both o2 connected and WB in the Y pipe. by using VCM Controls I can command open loop, or this doesn’t do the job?
    On NA vehicle you have to rev up to the red line to hit 7500Hz. I wouldn’t recommend doing that with PE disabled.

    Russ again, great stuff
    www.turbofirebird.com tuned with HPT MPVI Pro, LC-1.

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  4. #4
    Senior Tuner Russ K's Avatar
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    iGoRa,

    Yes you set the PE to 0% (this is so the commanded AFR at all TPS% will be the value you entered in the Base AFR vs. ECT) So this is why the TPS% table is to be 0's, so your always in PE, but commanding a 14.7 AFR. Now the commanded AFR stay at 14.7 so you can set the Maf table up to 7500 hz. You don't need much over 2000 rpm to hit 7500 hz, you need more load on the engine (use 2nd gear if an auto, or 2nd or 3rd gear if a manual)
    Since the V6 cars don't yet have an open loop table, this is by far the best way to do the part throttle/none PE fuel tuning.

    The car will stay in open loop with the O2 unplugged because closed loop will not be enabled until there is a changing voltage (above & below ~450 mv). Since the O2 will be removed for wideband testing, there will only be a steady ~450 mv from the reference circuit of the vcm. So yes, sometimes the check engine light will come during tuning.

    Using the VCM controls to put the car in open loop works also, but slows down the data logging speed (since you may also be commanded 2nd gear) And you just need to reset the fuel trims after the first flash.

    Russ Kemp
    Last edited by Russ K; 11-07-2006 at 10:50 PM.

  5. #5
    got it. I was about to ask another question , but you got it covered.
    I know what to do , if everything will go smooth will finish my writeup!
    www.turbofirebird.com tuned with HPT MPVI Pro, LC-1.

  6. #6
    Advanced Tuner xonelith's Avatar
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    Russ, great guide!!! Would you have an alternate method that wouldn't require the swapping of the narrow with the wideband sensor? I have them installled separately... unless I am misunderstanding your guide (very possible.. i'm not that bright).

    My afr's in open loop aren't that great (13.9 - 15.2), usually in the lower range. I expect that your method above will help me out... Note that I have an aftermarket cam.
    All Motor 2001 GA GT1




  7. #7
    yes , you can do it thru VCM Controls. check out my site.
    www.turbofirebird.com tuned with HPT MPVI Pro, LC-1.

  8. #8
    Senior Tuner Russ K's Avatar
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    The question about using the VCM controls to disable open loop was asked a while ago. The problem with that method is that the average AFR will be affected because the car is running and your scanning until you disable open loop and reset the fuel trims. Just unplug the B1S1 O2 sensor before starting the engine, then just reset the fuel trims, then hit the space bar to stop scanning.

    Now once the engine is at operating temp, start scanning. This way the average AFR will not be skewed because of the fuel trims not being 0 and or being in closed loop.

    Russ Kemp

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    That comment was for Xon I think. With both 02's in place(NB & WB) he will need to reach under and "physically" unplug his NB. That will put his application into the open loop that he needs to tune his lower MAF values.

  10. #10
    Senior Tuner Russ K's Avatar
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    Quote Originally Posted by slow6
    ehhh??? B1S1 having no sensor in it is gonna be one hell of an exhaust leak...lol
    I know you meant to say, put the WB in B1S1
    I said unplug the B1S1, not remove it. Of course if you don't have a bung for the wideband, you install it in place of the stock B1S1.

    Russ Kemp

  11. #11
    Advanced Tuner xonelith's Avatar
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    Thanks Russ... makes sense. Just unplugging it...LOL. A novel idea Didn't think of that!! (Must be the cold air here)
    All Motor 2001 GA GT1




  12. #12
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    yea sorry russ
    reading comprehension > me
    unplug not disconnect

  13. #13
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    Russ, one question with regard to this method.
    When your done the MAF table will be correct for a a/f ratio of 14.7:1 per the wideband.
    What happens when you plug the narrowband back in and it reads different than the wideband?

  14. #14
    Senior Tuner Russ K's Avatar
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    Quote Originally Posted by Perforator
    Russ, one question with regard to this method.
    When your done the MAF table will be correct for a a/f ratio of 14.7:1 per the wideband.
    What happens when you plug the narrowband back in and it reads different than the wideband?
    I've tuned several V6 cars this way. Once the O2 sensor is plugged in/installed, the LTFT's were very close to 0. If the LTFT's are out more than ~3% positive or negative, you could fine tune the maf table. The problem is most likely an inaccurate wideband in that case.

    Russ Kemp

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    Russ,
    What do you think about the addition(possibly) of the closed loop enable temp? Would this do the same thing as unplugging the sensor? The way you would tune an LS1? If that makes sense.

    Tim

  16. #16
    Senior Tuner Russ K's Avatar
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    Yes that would disable closed loop also, but I always install the wideband in place of B1S1 while tuning. No reason to install another O2 bung.

    Russ Kemp

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    Quote Originally Posted by Russ K
    Yes that would disable closed loop also, but I always install the wideband in place of B1S1 while tuning. No reason to install another O2 bung.

    Russ Kemp
    That's the same way I'll start tuning the V6s. I just have my LC1 wired to simulate NB output and didn't want that to set the car back into close loop.

    Tim
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  18. #18
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    I have copied and printed that write-up Russ. That is going to help a lot.

  19. #19
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    Russ I like this idea, and am yet to try it but I have a very interesting question about this maf tuning method.... I have had HPT since ver. 1.2 when it first came out for the V6 Grand Prix guys and I have always manually edited the maf scale to fix fuel trims by driving and watching the fuels at different given areas and making adjustments until I am within a few percent of zero, since always keeping a constant zero seems near impossible with other variables outside of the car, nontheless this has worked great for me but I like your writeup and am sure it would ease tuning but here is my concern... If the front or B1 02 sensor is out of the loop and the car is run in open loop and you DONT have a wideband in place and have no idea of what the AFR is while driving, even if you set commanded afr at 14.7 and say installed a large cam, heads, and headers on the car and obviously airflow will be very far off from stock, sure the maf will show difference in the error table but how do you know this is what will put the cars fuel trims close to zero after a drive or two? What if the car is running very lean in open loop? I am not trying to complicate your great idea, I havent tried it yet and I know you install a wideband but it is not used by the pcm in any way for fuel trims. So I guess to simplify what I am trying to ask is this, How is the maf error % pasted into the maf table going to put fuel trims close to zero when the pcm cannot control fuel trims in open loop and probably wont be running the correct AFR to start with while in open loop? I know this works clearly as you have stated and I have read of other guys on other boards talking about it but I am just trying to reason with how the airflow differance on a car with incorrect afr is going to correct fuel trims. I do love the writup and next car I tune I am going to try this, and yes it will be with a wideband in place of the front 02. I still have the old serial cable and need to upgrade to the new one so I can put the WB input on my scans instead of eyeballing things sepearately. Thanks in advance!

    Dave

  20. #20
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    Quote Originally Posted by Trannyman95
    Russ I like this idea, and am yet to try it but I have a very interesting question about this maf tuning method.... I have had HPT since ver. 1.2 when it first came out for the V6 Grand Prix guys and I have always manually edited the maf scale to fix fuel trims by driving and watching the fuels at different given areas and making adjustments until I am within a few percent of zero, since always keeping a constant zero seems near impossible with other variables outside of the car, nontheless this has worked great for me but I like your writeup and am sure it would ease tuning but here is my concern... If the front or B1 02 sensor is out of the loop and the car is run in open loop and you DONT have a wideband in place and have no idea of what the AFR is while driving, even if you set commanded afr at 14.7 and say installed a large cam, heads, and headers on the car and obviously airflow will be very far off from stock, sure the maf will show difference in the error table but how do you know this is what will put the cars fuel trims close to zero after a drive or two? What if the car is running very lean in open loop? I am not trying to complicate your great idea, I havent tried it yet and I know you install a wideband but it is not used by the pcm in any way for fuel trims. So I guess to simplify what I am trying to ask is this, How is the maf error % pasted into the maf table going to put fuel trims close to zero when the pcm cannot control fuel trims in open loop and probably wont be running the correct AFR to start with while in open loop? I know this works clearly as you have stated and I have read of other guys on other boards talking about it but I am just trying to reason with how the airflow differance on a car with incorrect afr is going to correct fuel trims. I do love the writup and next car I tune I am going to try this, and yes it will be with a wideband in place of the front 02. I still have the old serial cable and need to upgrade to the new one so I can put the WB input on my scans instead of eyeballing things sepearately. Thanks in advance!

    Dave
    Sorry to beat a year old dead horse, but no replies since last year???? Any thoughts on this guys. Its that time of year to start getting my new build tuned in and I too want to make sure I understand the whys as well as the hows.
    2000 GTP- S2X, diamond forged 9.5:1, balanced, Lucas 42.5#, GenV w/N*, stage 3 heads, custom PCM, ZZP SS IC, TOGS, MPS 3.0, Intensified 3.69's tranny - low 12's!!!!