PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Stuck the MAF back in to test bucking at takeoff

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Old Feb 26, 2005 | 11:11 AM
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Default Stuck the MAF back in to test bucking at takeoff

Well that #$%^!@ MAF is back in.

Pros:
1) Appears to have fixed bucking at takeoff

Cons:
1) Screwed up LTFTs, even with the Holden table (not surprised)
2) That stupid bucking at steady cruise is back
3) WAY down on power, even at part-throttle, I definitely had to lay into the pedal more at cruise

As soon as my MAF ends get here I will rebuild the MAF table. I think that may fix the bucking at cruise when it matches the VE table more. I did turn proportional idle back on, so that may be what is hurting me though. We shall see....
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Old Feb 26, 2005 | 12:10 PM
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My car just plain runs better (smoother) with the MAF. I've noticed spikes in the Dynamic airflow calculation which might be why our cars don't run so well without the MAF. Of course we make more power without the MAF because the fueling falls in line.
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Old Feb 26, 2005 | 07:45 PM
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you guys love a needless headache. Leave the maf on and let the pcm do all the work
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Old Feb 27, 2005 | 12:20 AM
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Originally Posted by cablebandit
you guys love a needless headache. Leave the maf on and let the pcm do all the work
No. I just like knowing how it all works. Eventually, my car will drive just like from the factory with a hotcam. Now I am just back to this silly surging at cruise...however...I now know that can be tuned out, I just need to tinker with that...
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Old Feb 27, 2005 | 04:59 AM
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ahh....good luck in your quest
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Old Feb 27, 2005 | 05:16 AM
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Yes I must admit It makes me LOL to see people tossing there MAFs again
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Old Feb 27, 2005 | 09:13 AM
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Originally Posted by TwoFast4Lv
Yes I must admit It makes me LOL to see people tossing there MAFs again
I don't understand the laughing part. It does make more power. A considerable amount of power. But if I can find a better way to do it with the MAF, then that is what I am going to do. So goes the evolution of PCM tuning....
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Old Feb 27, 2005 | 02:43 PM
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I decided to update my MAF table today, because my trims are way too far off to stick ported ends on the MAF. It could have maxed out the LTFTs for sure. The MAF frequency to 0 thing certainly did the trick. I made an interesting observation. The MAF table was almost exactly one cell off all the way down the table. (shifting them to the left)
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Old Feb 27, 2005 | 08:05 PM
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You better change that avitar...

So did you get the MAF table nailed down so that your trims with MAF match the ones you were getting SD?
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Old Feb 27, 2005 | 10:28 PM
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Originally Posted by Scooter70
You better change that avitar...

So did you get the MAF table nailed down so that your trims with MAF match the ones you were getting SD?
The trims are still slightly off (+4 instead of +14 at low rpm/kpa), but, I did turn proportional idle back on. Most of the table does match though. I am watching my trims, and I am still seeing the same trimming problems as before. I am turning it back off in my next tune and then I will make some runs. It is actually pretty weird. You can drive the car after a trim reset and cruise feels perfect. Once those trims start to learn it starts to buck at steady cruise. I think the STFTs and LTFTs are fighting each other or something. The requirements for proportional idle and actually being in the idle FTC are two completely different things, and I think the proportional idle has some issues after installing a cam. Anyways, enough rambling, it is getting turned off. Hopefully my trims will fall back in line (or at least closer). But the takeoff bucking is definitely gone, so it is defintely caused by unstable dynamic airflow calculation by the PCM.
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Old Feb 27, 2005 | 11:28 PM
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https://ls1tech.com/forums/showthrea...41#post2526741
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Old Feb 28, 2005 | 04:44 AM
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That is pretty much what I did. That is how I came up with my values.
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Old Feb 28, 2005 | 05:14 AM
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In circumstances like this I will go back to the stock MAF cal, Idle airflow and all other airflow calcs and retune. Its hard to hit a target when you don't know where it is. Change one thing at a time. By all means keep your current tune safely stored. Use it when you have isolated the problem.

It is unquestionably fuel related caused by dodgy airflow calcs, but without knowing much about your car (cam etc.) it could be anything. I knwo its obvious, but check your O2 sensors and log your airlfow readings at idle and into moving closed loop.
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Old Feb 28, 2005 | 09:22 AM
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Originally Posted by MNR-0
In circumstances like this I will go back to the stock MAF cal, Idle airflow and all other airflow calcs and retune. Its hard to hit a target when you don't know where it is. Change one thing at a time. By all means keep your current tune safely stored. Use it when you have isolated the problem.

It is unquestionably fuel related caused by dodgy airflow calcs, but without knowing much about your car (cam etc.) it could be anything. I knwo its obvious, but check your O2 sensors and log your airlfow readings at idle and into moving closed loop.
I am. I just changed those two main things because I went back from scratch with a stock tune and re-added all my changes to remove anything I might have missed. I have always noticed a big difference in idle and cruise fueling with proportional idle enabled. Basically I stuck the MAF back in, and removed most of my changes so I could re-add them one at a time again. I was just hoping once the VE and MAF tables were in sync the proportional idle would start to work right, but apparently it is more sinister than that...
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