MAF Calibration 101

VersaTuner for Mazdaspeed6, Mazda 6 MPS, Mazdaspeed3, Mazda 3 MPS, CX7
EPTSpeed3
Posts: 17
Joined: February 20th, 2013, 8:30 pm

Re: MAF Calibration 101

Post by EPTSpeed3 »

Thanks for the great information! This is my first shot at tuning a vehicle. I tried EFI Live a few years back with an LS1 Engine but didnt get far. Ive learned so much these last few weeks emailing steve back and forth. The MAF Cal has always been something I had a hard time understanding so thank you for the great help! Im gonna give it a shot this friday at logging and trying to do my maf cal since I know I really need to get it done.

If only someone had a MAF cal for a sure sri and inlet pipe..... lol
EPTSpeed3
Posts: 17
Joined: February 20th, 2013, 8:30 pm

Re: MAF Calibration 101

Post by EPTSpeed3 »

So I went out tonight and tried to do some data logging for my shot at a maf cal. I did 3 WOT Logs and my Desired AFR matched my Actual AFR with the Stock MAF Cal.

One thing I dont understand is the Closed loop Logs only go up to about 2.847 Volts in 2nd Gear Logs before it goes into open loop. The Open loop Logs Start at about 3.393 volts. Is that what its supposed to be?

So What I got out of this is that my Open Loop is good with stock values. My Closed loop (everything under 2.847) needs a little tweaking. does this sound right?
mituc
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Re: MAF Calibration 101

Post by mituc »

If the WOT part of the MAF table matches the stock table then your intake flows like stock. I'd say, if the differences in closed loop are not significant leave them as they are now, having non-zero LTFTs means that the ECU did its job and learned the differences and knows exactly how much fuel to inject there. If the differences in closed loop are significant (above 12%) and the WOT maf cal is perfect then you may have a leak somewhere.

The points where the ECU goes in closed loop or switches back to open loop are defined in the tune -> Absolute Limits. There are Load thresholds and APP thresholds there, and they may differ per gear.
It's hard to understand what state your ECU is in when you mention the MAF voltage alone. Mentioning the absolute load value would have been helpful. Also, what are you looking at when you say "goes in open loop"? You see 0 LTFTs? if yes, then are you sure the ECU had enough time to learn the entire MAF curve? 2.8V is around 55-60g/s of air and that may be load 1 at ~2000rpm or load 0.5 at 4000rpm. So in both cases (based on rpm) you're above the threshold which determines the CL-OL transition - that if your OL-CL transition tables are stock(ish).
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
EPTSpeed3
Posts: 17
Joined: February 20th, 2013, 8:30 pm

Re: MAF Calibration 101

Post by EPTSpeed3 »

My LTFT are -5.46% the entire time I did the Logs. At that point today the more I read I realized the ECU might not have learned the MAF Curve.

Also, looking at the Tune, The CL/OL Transition Tables are all stock. I'm running a Base 91 Octane Tune for Gen 2 Speed2. I see the tables for the Load and APP transition. My Car doesnt go past 73% APP for some reason. The Tables Suggest that the Car Go into OL at 75% APP. Will the Load tables alone cause the CL/OL Transition or is the APP Tables keeping the transition from happening?
mituc
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Re: MAF Calibration 101

Post by mituc »

Yes, whichever parameter will go above some threshold first.
As for the APP, I assume you have a gen2: http://www.versatune.net/forum/viewtopic.php?f=17&t=362
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
EPTSpeed3
Posts: 17
Joined: February 20th, 2013, 8:30 pm

Re: MAF Calibration 101

Post by EPTSpeed3 »

Yes Gen2. Thanks for all your help with all this!!!
torquemaniac
Posts: 16
Joined: April 6th, 2013, 2:26 pm

Re: MAF Calibration 101

Post by torquemaniac »

mituc wrote:Yes, whichever parameter will go above some threshold first.
As for the APP, I assume you have a gen2: http://www.versatune.net/forum/viewtopic.php?f=17&t=362
Mituc,

There are 6 APP threshold tables, and 5 Load threshold tables (at least in the CX-7 tune)...are you saying that the ECU will transition to OL as soon as anyone of the values in those tables are reached?

Why so tables?
CX-7 beast : top mount Holset Hy35 / L2A intercooler / Aquamist HFS4 direct injection / modded transmission...etc
mituc
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Re: MAF Calibration 101

Post by mituc »

As far as I know only one load table and one APP table are taken into consideration at one moment. I don't know which of the APP tables (or load tables) are selected at some point, but this is how it works.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
Asthma
Posts: 6
Joined: March 4th, 2016, 7:36 am

Re: MAF Calibration 101

Post by Asthma »

Hi Guys,

I read some guides to do the MAF Cal, in all other how to's I read that only necessary to log the LTFT. In the help file of Versatuner it's recommended to work with the combinied fuel trim of LTFT and STFT. Which way is the best way? Because I'm getting high STFT (up to 30-35% by low or zero LTFT. Actual AFR and desired AFR are close to each other.

I didn't found any leaks in the hole system too.

Anyway, hope somebody could help me.

THX
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Steve @ VersaTune
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Re: MAF Calibration 101

Post by Steve @ VersaTune »

If you're getting 35% STFT, and 0% LTFT, your LTFTs have not settled yet or your have some very erratic MAF curve caused by poor MAF sensor location after a bend or some other flow obstruction causing turbulence. The combination of STFT and LTFT is what is applied to the actual injection calculation. You need both.
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