Technical Feasability

[m42technic]

i thought the AFM was 0-5 volts? its that or somewhat in between

The reference is 5v. The signal voltage range is 0-5v.

[ragehardintothebendies]

It could be done easily if you can find a MAF with a linear voltage output, I know when researching Subaru MAF issues I found a few with a linear curve.
Not sure what from though, may have been a FD?

[peerless]

Ok So I learned that the reference voltage is 5v for the AFM. I also read a very good article on MAF sensors. Here the link,

http://www.allfordmustangs.com/Detailed/583.shtml

Which brings up the question, What is the outcome of converting to a MAF system?
From what Im reading, not much. The reasoning behind this is that you can have all the
air flow you can get, but unless the ECM knows about it all it can do is give the same stock mappings. For instance the MAF is telling the computer that there is 900cfm flowing through, but the computer maxed out at 600cfm because thats the max it was programmed with.

So in order for this project to be successful a custom chip is required. I have always wanted to learn how to program eproms. I think I will start a seperate topic for that.

I am still looking for more AFM information.

Robert
85' 325e

[nando]

it's not just more airflow. the AFM itself is very restrictive by the way it works - a big door on a spring that blocks the intake. removing the door is where most of the gains are, you're not going to get more air than the throttle body can flow anyway.

[mspiegle]

Heres what i can tell you from my experience...

most AFMs work the same way. You input a voltage, the door is connected to a potentiometer-like wheel, as the door opens, it changes resistance and outputs a new voltage @ the signal wire based on that resistance. The temp sensor is a separate circuit in almost all AFMs i'm pretty sure.

Not all MAFs are the same. You have to find a very specific MAF, and stick with it. I believe a MAF already compensates for temperature as PART of the circuit - but I don't know that to be true for ALL MAFs. I think this is the way it works by design (cooler air will cool the hotwire better/faster)

The signal a MAF puts out is the same as an AFM's, except it runs on a different scale. You shouldn't have to mess with digital-to-analog conversion if you get the right MAF. I don't even know if they make MAFs that run on digital signals... if they do, it seems like something that might be in the newest cars.

I visited the idea of fabbing up a circuit that would work with 1 specific MAF and allow for an easy conversion, but its a pain in the ass unless you have some electrical engineering experience to back you up.

With the group-buy prices of SMT6s running around 250-275, and with the increased functionality - it is a better option as it allows FAR MORE FLEXIBILITY than that simple circuit could ever provide unless you start pouring money and time into it.

If you happen to find a MAF that uses a very linear scale that is simliar to an AFM, it could be as simple as a few resistors to make the voltages match up enough to work.

[peerless]

Well I sourced an 90 Mustang 55mm MAF, I should have it next week. I will start testing.
If what you say is true and the BMW ECM reads the voltage and not the resistance then I might get lucky and not have to convert the signal. That should make it much easier.

I was also checking out Aftermarket ECM's last night and I agree they are the way to go.
A Motec would be absolutely bitchen. I also found one that uses a MAP sensor and measure speed density and does not even need a metering device at all. Image that airflow. Only the throttlebody resiricts you at that point. I also read an article about a guy getting much improved throttle repsonse and a slight HP/Torque improvement via a larger T/B.

Very Cool,
Robert
85' 325e

[mspiegle]

well, full on standalone management is best... but at a cost. The SMT6 is nothing more than a signal converter/conditioner. That's why its so cheap.

I believe you will have good luck with that MAF.

As a test, power the MAF properly, get a digital meter, tap the signal, and blow into the MAF. On my 328i MAF, when you blow on it, it went from .9v to about 2.5v or something like that. That proves it works on a standard voltage system.

[ptownTSI]

so how did this end up working out.

[Kip]

View Profile: peerlesspeerless
Member
Last Activity: 02-24-2004 08:22 PM


I guess it worked so well, he went dark to protect the patent...

[EtaSport]

whoa.. holy thread ressurection. There is a guy on an m42 forum who is making the convertor board to run a MAF on his his 318. I believe it can be done.