Tutorial-MAF Scaling for High Horsepower Setups
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.
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.
Launching!
Joined: Jan 2002
Posts: 299
Likes: 41
From: Detroit, Murder City
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?
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.
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.
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.
Launching!
Joined: Jan 2002
Posts: 299
Likes: 41
From: Detroit, Murder City
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".
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 LS1 Tech Stories
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Verdad Gallardo Launching!
Joined: Jan 2002
Posts: 299
Likes: 41
From: Detroit, Murder City
The weighting is variable, so best practice is just to make sure both models are correct. 
Makes me want to try the idle portion of the VE and see what happens.
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.
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.
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!
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!
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.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
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).
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 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.
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.
Yeah I dont think we have those tables in EFI on a GEN 3. We only have the CL mode table.
