FEELER: Tunable MAF Conversion Interest?

[bmwman91]

Some of you know that I have been tinkering around with a MAF conversion for a few years now. Initially I wanted to develop it into a product, but that idea died when it became obvious that a MAF won't really do anything for the M42's power output. Well, I have been expanding some of my converter's functionality & decided to see if the current idea was popular.

At this point it might be a desirable replacement option for 20+ year old AFMs being that they can cost anywhere from $160 to $700 to replace (or $40 at a local wrecker, but you never know what you'll get). This may change, but I am looking at a ~$200US price point for the converter only (subject to change, up or down). The MAF sensor, & hardware to make it fit on the car, are not things I am planning to manufacture or sell at this point in time.


Here are the features I would start out with:

No-nonsense MAF conversion for M42 cars
- Some cutting of factory AFM harness
- Extra connector parts so that stock AFM could be plugged back in with minimal effort
- Overall design such that MAF / AFM could be interchanged in ~5 minutes with no need for tools
- About 20ms latency with filtered output

Selectable output variable
- Puts out either mass flow rate, or volumetric flow (AFM-emulation) rate
- Choice of filtered or unfiltered output (filtered is a good idea unless you know a LOT about the ECU you are working with, and is a must with Motronic)

Tunable output parameters
- With volumetric output (AFM-emulation), choice of stock-style logarithmic output or linear output
- - Tunable logarithmic & linear outputs
- With mass flow rate output, linear output
- - Tunable linear output

PC Graphical Interface
- Used to select output mode and tune output curve parameters
- Can log & plot filtered+unfiltered air flow and intake air temp in real-time
- - Thinking about having analog input for wide band & narrow band O2 sensors - not 100% sure yet
- Used to apply firmware updates (not 100% sure about this yet)


The current sensor can handle flows up to ~810 kg/hr (according to the data sheet), but I think that somewhere in the 500-600 kg/hr range is more reasonable. A stock M42 will generally flow ~350kg/hr at most.

When I say tunable output curves I mean:
- For linear output, Vout = m * FLOW + b with m & b being adjustable
- It's a similar deal for the log output - only 2 parameters to adjust

The purpose of the linear outputs would be to make tuning with things like the WAR chip / TunerPro and running MS easier.

The timeline for this would be a few months. I have a day job & I don't plan on quitting any time soon!

[jakeb]

I would be interested in at least one...maybe more.  If it will allow for more flow and then to be used with the warchip and in turn a turbo or SC setup then I would be all over it.  Let me know if you need someone to help test it.  

I do m42 swaps into 2002s and soon an e21 and have been wanting to add a bit more power....

[trackjunkie21]

very interested. this can help alot with my turbo build.

[Hey-u]

Very interested! Subscribed.

[bmwman91]

I just want to make sure that people are aware that a MAF will not really get them power gains. The AFM is not restrictive, believe me. Multiple dyno pulls proved that when I was developing an earlier version, years ago. You DO get better idle stability & throttle response though, particularly when coming off of idle.

M20 guys claim gains from a MAF, but that is only because the stock AFM was too small to begin with. The power gains from a MAF on the M20 are the same as putting an M30 AFM on. A certain other MAF conversion that will remain nameless claims gains too...but a chip comes as part of the package. The gains come from the chip, and are remarkably similar to the power gains seen when one adds JUST a chip.

I just want to be 100% up-front & honest with this. I don't want to sink a bunch of my own money into developing a product & then have people pissed off because they expected something & didn't get it!

[trackjunkie21]

I just want to make sure that people are aware that a MAF will not really get them power gains. The AFM is not restrictive, believe me. Multiple dyno pulls proved that when I was developing an earlier version, years ago. You DO get better idle stability & throttle response though, particularly when coming off of idle.

M20 guys claim gains from a MAF, but that is only because the stock AFM was too small to begin with. The power gains from a MAF on the M20 are the same as putting an M30 AFM on. A certain other MAF conversion that will remain nameless claims gains too...but a chip comes as part of the package. The gains come from the chip, and are remarkably similar to the power gains seen when one adds JUST a chip.

I just want to be 100% up-front & honest with this. I don't want to sink a bunch of my own money into developing a product & then have people pissed off because they expected something & didn't get it!

But with boost the AFM does become restrictive, or so I heard.

[bmwman91]

But with boost the AFM does become restrictive, or so I heard.

With boost, it is another story entirely.

a) The M42 AFM maxes out at ~400 m3/hr (stock M42s pull up to 360 m3/hr). If you put the AFM behind the turbo, you can sort of cheat since the density is higher, but you need to tune the fuel properly to account for that.

b) Yes, it probably is a restriction when pulling more than ~400 m3/hr. 400 m3/hr equates to ~1.7 PSI on an internally stock M42 lol.

[trackjunkie21]

With boost, it is another story entirely.

a) The M42 AFM maxes out at ~400 m3/hr (stock M42s pull up to 360 m3/hr). If you put the AFM behind the turbo, you can sort of cheat since the density is higher, but you need to tune the fuel properly to account for that.

b) Yes, it probably is a restriction when pulling more than ~400 m3/hr. 400 m3/hr equates to ~1.7 PSI on an internally stock M42 lol.

So what would be the ideal Maf the replace the AFM with? The m44 unit? or the m3 unit?

[Slick92GS-R]

not really looking for a m42 perfomance upgrade , but this sounds like i may want this for my project turbo m20.. put me down for interest there !!

[bmwman91]

So what would be the ideal Maf the replace the AFM with? The m44 unit? or the m3 unit?

The one I have been working with is a Bosch from a ~2003 Jetta Turbo. It is considerably cheaper than any of the ones used on BMWs (as far as I can tell). I was talking with another member about higher flow ones for FI use, and I may make it an option to use the $125 VW one (you could run ~9PSI boost at redline with it), OR the $260 one from something like a 540i (higher flow, not sure what the max is yet). Anyone who NEEDS the higher flow one has likely already dropped enough $ on their project that the extra $130 for the sensor probably won't be as much of an issue.

not really looking for a m42 perfomance upgrade , but this sounds like i may want this for my project turbo m20.. put me down for interest there !!

M20 stuff is definitely planned. Once I figure out exactly how many M20 AFM variants there were & get some data on them, it will be a relatively simple software update release to have this be PnP on M20 cars. Even before that, this thing will be tunable enough that someone with an M20 could make it work though. In linear output mode, you could basically use this on ANY car if you have a stand-alone or other ECU hacking/tuning hardware.

[jakeb]

I think something that might work for everyone is the MAF from a 95 m3....which is the same as the 325/525/etc etc  They can be bought used fairly inexpensively and brand new for right around $250.  Used around $100 or less.  There are some non Bosch units brand new for around $70 as well...  Not sure what the flow rate is on them tho.

The other options would be the one from a 540 or something that even allows more flow is the 803 maf which is from a 993 porsche (about $250 brand new).  The 803 will flow enough for over 400hp turboed.  So it might be a bit excessive.

[bmwman91]

Thanks for the information. It sounds like having two MAF options might be pretty popular. I can find a way to allow the unit to be switched between them in the control software. That way everyone is happy. I will see what I can dig up on the 540 & 993 MAFs.

[turbo 318]

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[bmwman91]

Maybe...but first you need to post up pictures!

[turbo 318]

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