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Tutorial-MAF Scaling for High Horsepower Setups

Old 10-13-2017, 11:53 AM
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Originally Posted by turbolx View Post
Thanks for the kind words, guys. Hopefully, you'll find that the science doesn't age, so the lessons presented in my books and videos can still be applied today the same as they were when published. It's just the interface (HPT, EFILive) that gets updated and the control system (ECU) that may add an extra layer over and above the basics with time.

Basic MAF calibration is covered in my first "GM Tuning Beginners Guide" DVD. I also did a segment on it in the "Advanced Tuning Series" BLu-Ray too.

Scaling the MAF (and injectors) to deal with the hard coded limits on the older ECUs is covered in my second "GM Tuning Advanced Guide" DVD with a step by step walk through of the process that proves how it really works. Following these instructions will also help prevent some of the common issues with transmission controls that some people have when taking shortcuts on scaling.

I don't sell them directly to end users, but there is a link on my website to our partners at Detroit Technical Media. The discs are also in stock at Summit Racing Equipment as well.
I take it thats you Greg? Didn't recognize the username since its different over on EFI Live. Thanks for helping explain how some of this stuff works and answering pm's. I hope the sticky did you justice. Would you care to offer your opinion on why we don't modify the idle air tables by the same percentage as the rest of the scaled tune?
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Old 10-13-2017, 01:23 PM
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Greg actually has two books on Amazon.
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Old 10-13-2017, 02:04 PM
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Originally Posted by joecar View Post
Greg actually has two books on Amazon.
Yeah I've got both of them. The guide to tuning fuel injected engine and then the advanced book that G mentioned. And both DVDs lol.
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Old 10-18-2017, 01:50 PM
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Originally Posted by ddnspider View Post
I take it thats you Greg? Didn't recognize the username since its different over on EFI Live.
It's me. I've had this account for a while...

Would you care to offer your opinion on why we don't modify the idle air tables by the same percentage as the rest of the scaled tune?
I don't think I said not to scale target idle airflow. In the DVD, I clearly showed how we scale EVERYTHING with g, g/s, g/cyl, and torque. This would include the minimum running airflow or target idle airflow tables (depending on the year of the ECU). If you did the idle control correctly later, this would come out in the wash anyway as you match target airflow to whatever was the stable indicated airflow at idle. Scaling the table initially makes the first guess closer, that's all.
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Old 10-18-2017, 04:15 PM
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Originally Posted by turbolx View Post
It's me. I've had this account for a while...


I don't think I said not to scale target idle airflow. In the DVD, I clearly showed how we scale EVERYTHING with g, g/s, g/cyl, and torque. This would include the minimum running airflow or target idle airflow tables (depending on the year of the ECU). If you did the idle control correctly later, this would come out in the wash anyway as you match target airflow to whatever was the stable indicated airflow at idle. Scaling the table initially makes the first guess closer, that's all.
Cool didn't know you were on here. Sorry I should clarify my statement. You completely said to scale the idle tables....my comment was that when I did scale the idle tables I could never get it to idle right without the iac trying to make huge adjustments. If I scaled the idle tables by a smaller amount then it would start up and idle with minimal iac action. I was curious if you knew why that would be.
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Old 03-19-2018, 08:23 AM
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Just bumping this as I've struggled to get the closed loop (especially idle) not to do some crazy stuff like go rich at idle. Put the CLMODE table back to factory and it appears to have cleaned up on back to back driving OL to CL. I may tweak the O2 switchpoint at low airflow some, but otherwise its acting like it should now and I'm scaled ~40%. This was the last thing in the tune that was giving me fits and it looks like I got it finally.
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Old 03-26-2018, 01:19 PM
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Sorry I'm not familiar with the build, but did you also dial in the speed density model (scaled, of course) in addition to the MAF? This helps a TON with idle control, even if you *think* it is running "MAF only".
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Old 03-26-2018, 01:24 PM
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Originally Posted by turbolx View Post
Sorry I'm not familiar with the build, but did you also dial in the speed density model (scaled, of course) in addition to the MAF? This helps a TON with idle control, even if you *think* it is running "MAF only".
I've got the RPM threshold for airflow calc's set to 1 rpm so I am pretty confident that I am in MAF only.....unless you're telling me that there are still conditions where the PCM will look at the VE table and ignore that Maybe I should consider a VE only at idle and set the MAF only to something like 1500 rpms or something. I'm pretty happy with my CLMAF now, but if it helps " a ton" maybe I should try it
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Old 03-26-2018, 04:36 PM
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Originally Posted by ddnspider View Post
I've got the RPM threshold for airflow calc's set to 1 rpm so I am pretty confident that I am in MAF only.....unless you're telling me that there are still conditions where the PCM will look at the VE table and ignore that
Not "ignore", but blend... The weighting is variable, so best practice is just to make sure both models are correct.
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Old 03-26-2018, 04:41 PM
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Originally Posted by turbolx View Post
Not "ignore", but blend... The weighting is variable, so best practice is just to make sure both models are correct.
LOL, interesting. I was under the impression it was completely ignored if B0201 is set to 0. Then again I was going off the EFI Live description shown below.


Makes me want to try the idle portion of the VE and see what happens.
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Old 09-05-2018, 08:05 AM
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Originally Posted by ddnspider View Post
Cool didn't know you were on here. Sorry I should clarify my statement. You completely said to scale the idle tables....my comment was that when I did scale the idle tables I could never get it to idle right without the iac trying to make huge adjustments. If I scaled the idle tables by a smaller amount then it would start up and idle with minimal iac action. I was curious if you knew why that would be.
Originally Posted by ddnspider View Post
Just bumping this as I've struggled to get the closed loop (especially idle) not to do some crazy stuff like go rich at idle. Put the CLMODE table back to factory and it appears to have cleaned up on back to back driving OL to CL. I may tweak the O2 switchpoint at low airflow some, but otherwise its acting like it should now and I'm scaled ~40%. This was the last thing in the tune that was giving me fits and it looks like I got it finally.
Followed this thread's instructions, and can't thank you enough. I did learn a few additional things that are not on the list, and I thought I would put them up for discussion:

1. The proportional fuel constants needed to be cut way back. I was getting large rich/lean swings on wideband. Factory numbers are 128. I'm now at 11. Typically, this is done for larger injectors anyway, but I found it needed further adjustments after scaling the tune with the same injectors. not so much for a 25% scale, but the 50% scale swung wildly.

2. The fuel integrator also needed to be slowed down and smaller adjustments are needed. Remember, it's moving twice as fast as the ECU thinks.

3. The IAC effective area table. It's still commanding the IAC position based on a non-scaled tune. I found that I can leave all my idle commanded stuff alone (not scaled), and it runs fine, if maybe a tad rich at idle for now. When i cut all the idle airflows in half, it tried to idle too low, recovered, overcompensated, etc. I think that the idle commanded stuff is completely separate from the dynamic air, MAF, and cylinder airmass readings. So, if you are going to scale your idle tuning, I think you also need to heavily modify the IAC effective area table. With electronic throttle, I'm sure this is completely different, but I don't have an ETC car that requires scaling. For now, I have my commanded idle air, PID, etc, all unscaled so the IAC table still works as a reference.

Flame away!
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Old 09-05-2018, 08:30 AM
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Originally Posted by Darth_V8r View Post
Followed this thread's instructions, and can't thank you enough. I did learn a few additional things that are not on the list, and I thought I would put them up for discussion:

1. The proportional fuel constants needed to be cut way back. I was getting large rich/lean swings on wideband. Factory numbers are 128. I'm now at 11. Typically, this is done for larger injectors anyway, but I found it needed further adjustments after scaling the tune with the same injectors. not so much for a 25% scale, but the 50% scale swung wildly.

2. The fuel integrator also needed to be slowed down and smaller adjustments are needed. Remember, it's moving twice as fast as the ECU thinks.

3. The IAC effective area table. It's still commanding the IAC position based on a non-scaled tune. I found that I can leave all my idle commanded stuff alone (not scaled), and it runs fine, if maybe a tad rich at idle for now. When i cut all the idle airflows in half, it tried to idle too low, recovered, overcompensated, etc. I think that the idle commanded stuff is completely separate from the dynamic air, MAF, and cylinder airmass readings. So, if you are going to scale your idle tuning, I think you also need to heavily modify the IAC effective area table. With electronic throttle, I'm sure this is completely different, but I don't have an ETC car that requires scaling. For now, I have my commanded idle air, PID, etc, all unscaled so the IAC table still works as a reference.

Flame away!
Darth, good info! Can you throw up a couple of pics of items 1 and 2? I use EFI Live almost exclusively and they typically call certain tables by different names. If you throw up a few pics I can try to correlate what they're called in EFI Live from HPT. Glad to see you confirmed #3 that scaling the idle tables the same amount as air/fuel doesn't work so well.
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Old 09-05-2018, 10:02 AM
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Originally Posted by ddnspider View Post
Darth, good info! Can you throw up a couple of pics of items 1 and 2? I use EFI Live almost exclusively and they typically call certain tables by different names. If you throw up a few pics I can try to correlate what they're called in EFI Live from HPT. Glad to see you confirmed #3 that scaling the idle tables the same amount as air/fuel doesn't work so well.
Here you go. Not saying these are the "right" values, just where I ended up after screwing with it for a day or so in between other tasks.


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Old 09-06-2018, 03:20 PM
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Thanks for the pics, makes it easier to locate those tables in EFILive.
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Old 09-06-2018, 04:24 PM
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Originally Posted by joecar View Post
Thanks for the pics, makes it easier to locate those tables in EFILive.
Joe which tables are they in EFI Live? I've been looking and I don't see where they correlate in a Gen 3 pcm.
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Old 09-06-2018, 08:35 PM
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Originally Posted by ddnspider View Post
Joe which tables are they in EFI Live? I've been looking and I don't see where they correlate in a Gen 3 pcm.
I just started looking (again) thru some calibrations to see if I could find those tables...

so far, in my notes I have the following, none of which matches above pics:

B4512 - Filtered RPM Airflow Correction -> Derivative (looks at rate of change as errors approaches zero).

B4514 - Learned Airflow -> Integral (updates learned airflow based on error over B4508; this value is added to desired airflow based on conditions).

B4515 - Direct Airflow -> Proportional (makes direct airflow adjustment based on error over B4509).
I'm trying to see how these fit together with the Idle Learning parameters (B4501-B4511, B4322-B4328), and if the tables in Darth's pics above can be inferred from these.





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Old 09-07-2018, 07:39 AM
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Originally Posted by joecar View Post
I just started looking (again) thru some calibrations to see if I could find those tables...

so far, in my notes I have the following, none of which matches above pics:



I'm trying to see how these fit together with the Idle Learning parameters (B4501-B4511, B4322-B4328), and if the tables in Darth's pics above can be inferred from these.
The pics I took were the proportional FUELING, not proportional idle air correction. And the fueling correction integrator. it's in with the O2 sensor stuff. Sorry for the confusion.


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Old 09-07-2018, 07:45 AM
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I guess I thought the tables Darth posted were fueling tables, not airflow tables.
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Old 09-07-2018, 10:19 AM
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Originally Posted by Darth_V8r View Post
The pics I took were the proportional FUELING, not proportional idle air correction. And the fueling correction integrator. it's in with the O2 sensor stuff. Sorry for the confusion.

Yeah I dont think we have those tables in EFI on a GEN 3. We only have the CL mode table.
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Old 09-07-2018, 01:46 PM
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Darth,

Ah, I see, thanks

I think I found them under Fuel->Trim (I'll have to carefully look at each one):



Last edited by joecar; 09-07-2018 at 02:02 PM.
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