maf tuning thoughts

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maf tuning thoughts

Postby techsalvager » Fri Mar 30, 2012 5:10 pm

This thread will host my info and understanding on maf tuning and issues.

Also a quick background
Why I like the idea of using maf is because imo it has a better sense of airflow though the engine.
and like most stuff there is pros and cons.
Personally I have two people lined up to transfer over to maf based ms2extra, one is a turbo bmw, the other is a stock Nissan hardbody. They both run diypnp units. I think the Nissan hardbody is a very prime candidate for this type of work due to it being all stock. Once I have the curve of its stock sensor setup then mostly anyone with that hardbody should be good to use that curve in the setup. Maf is in the throttle body anyways.
Also I have made a simple guide so far.
https://docs.google.com/document/d/10h4 ... prli4/edit


I'll start by saying maf usage requires proper fuel injector settings or else you will have issues.
With proper fuel injector settings, a good starting transfer function and wideband you can get a running car done very quickly.


If the car has a turbo setup its best to run a diverter valve if you plan to use the maf infront of the turbo.
Also you should have a good amount of piping space between the maf and any bends and before the filter.
Do not cut out any mesh screens as they are for keeping flow laminar though the maf elements and do their job well.

If you want to understand maf tuning even more I suggest this book
http://www.amazon.com/Engine-Management ... 1932494421
I use it as reference material for any issues I have.


I only use MAF for fueling as primary alogthrim. With this you will not tune a VE table, instead you tune what is know as a transfer function.
A map sensor has a transfer function as well, but its linear, if you know min and max you can plot the rest of the area. With a maf sensor its an exponetional curve. So knowing two end values can't get you a transfer function that easy, but there is ways to figure out the curve with some math.
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Re: maf tuning thoughts

Postby techsalvager » Sat Mar 31, 2012 7:14 pm

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Re: maf tuning thoughts

Postby techsalvager » Sun Apr 01, 2012 2:29 pm

hows a 30MB datalog sound?
2 hour+ driving datalog of driving up to atlanta, ga on maf.
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Re: maf tuning thoughts

Postby Peter Florance » Sun Apr 01, 2012 4:32 pm

techsalvager wrote:hows a 30MB datalog sound?
2 hour+ driving datalog of driving up to atlanta, ga on maf.

I have a BMW MAF I'm going to try...
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Re: maf tuning thoughts

Postby techsalvager » Sun Apr 01, 2012 5:14 pm

how do you plan to plumb it into the intake?
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Re: maf tuning thoughts

Postby Peter Florance » Mon Apr 02, 2012 3:10 am

techsalvager wrote:how do you plan to plumb it into the intake?

I think it is pretty close in size to what is already there (tube that replaced Ljet AFM)
Probably just silicone couplers etc.
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Re: maf tuning thoughts

Postby techsalvager » Tue Apr 03, 2012 6:29 am

Image
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Re: maf tuning thoughts

Postby techsalvager » Thu Apr 05, 2012 11:49 pm

issues

maf correction table
The way it is currently implemented is terrible. correcting a defined value with a defined value. It needs to be changed to be used correctly and make it easier to use. X axis should be based on ADC and not grams a second.

lag factors
Where are they? From what I hear the lag factors for maf is the same as the map one. Well what happens when one uses maf and map for their setup?
They can't tune the maf lag factor without effecting the map lag factor. Needs separate lag factors
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Re: maf tuning thoughts

Postby techsalvager » Fri Apr 13, 2012 5:35 am

I was looking over ms3 firmware and both MS2 and MS3 have the same issues that should be fixed.
Improper correction table.
lack of a separate maf lag factor.

Also I noticed one can't use the stock map sensor slot for running a maf in ms2 or if they leave the stock map sensor in the stock location they can't use it for real time barometric.
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Re: maf tuning thoughts

Postby techsalvager » Wed Apr 18, 2012 8:19 pm

the stock way maf is done on ms2extra is that it uses the AFR target table for its commanded fuel, unfourntaly this is the same table used for closed loop fuel control. the issue becomes now that both your commanded fuel and commanded closed loop control are together.
I could see one way to solve this is to take the stock VE table in maf mode and dump it and turn it into the commanded AFR table so you have a 16x16 fuel map
and use the afrtarget table for your closed loop fuel table.
besides in maf mode GVE is locked at 100 and the VE table 1 is useless.
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Re: maf tuning thoughts

Postby techsalvager » Sun Apr 22, 2012 5:11 pm

the only current way to seperate closed loop operation from the main fuel table is to use narrowband to target stoich.
That way you can u se the afrtarget table as your main commanded fuel table and it won't impact closed loop fueling as well.
viewtopic.php?f=101&t=44836
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Re: maf tuning thoughts

Postby techsalvager » Tue Jul 17, 2012 7:45 pm

back to running on maf again, so much better then using speed density

I really like this n62 maf so far.

inc file of the stock suppode transfer function
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Re: maf tuning thoughts

Postby techsalvager » Sat Jul 21, 2012 7:00 am

Image
2nd gear 2200 wot to 6800
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Re: maf tuning thoughts

Postby techsalvager » Wed Aug 15, 2012 7:05 am

If you have no diverter valve turbocharged, put a elbow on the inlet to the turbo from the maf. This will help keep the maf from reading reversion of the compressor surge. Used the maf sized properly for the application. Intake changes before and after the maf affect the maf readings.
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