MAF Converter V3 Update!

[bmwman91]

Haha.  I WISH.  Unfortunately, while you potentially could stick a faster crstal oscillator, you would need to do a lot of software work to get all the timing right again.  Maybe if I put some Type R stickers on the unit it will work better.....

[Ramblin MAn]

So couldn't you just do an average of "X" number of polls from the MAF and feed that value to the DME? Maybe work in a delta factor so one value can not be more than +or- "Y" percent of the last value?

I mean you are  sampleing the MAF and converting it so you can do whatever you want with it right? The thing I've figured out is the DME expects certain values from the sensors and when they don't coincide with the expected values the damn thing shuts your injectors off.

Just like you said, the AFM sends a nice linear signal but you may have that MAF signal so snesetive that the software in the DME is flipping back and forth between maps or something and just basically getting confused.

Just adding to the the discussion.

[bmwman91]

Yes, I do suspect that at lower pulse/engine speeds the Motronic is seeing all sorts of junk values and shutting down the injectors.

Averaging this in software could be hard.  I would likely need some pulse-triggered hardware, then to use some interrupt-routines to captur ethe time between peaks & whatnot.  I think I have a simpler solution involving one additional componment on the input.  It could attenuate the input enough to give the Motronic something workable.  When I scoped this, it was prettymuch pulsing from 0V to 5V, which is the entire range of the covnerter!  Anyway, this will be interesting.  If this simple solution is a no-go, then software it is.  Lol, anyone have a function generator I could borrow...it would help a lot!

Too bad this is not a fully sinusoidal wave situation.  If it was, a simple integrator could do the trick!

[nobrakese36]

good luck!!

[D. Clay]

Now this is someplace past the point of where my knowledge ends. For most of the racing I was involved in a Holley carburetor was sufficient as the engine was in the top 20% of the power band almost all of the time. FI was a 50 pound weight penalty and not competitive.
I have sinus trouble and sometimes it's so bad I get suicidal. Is it something like that?

[AL GReeNeRy]

The noise is actually kinda fun lol.  I guess the only good way to run the cone would be with a heat shield...and I am definitely not going to look into manufacturing those.  Hand-building them would be a pain, and would hurt the cost considerably.  Don't worry though, I will test it with the airbox and without.

Yeah I got waaaay off onto some half-baked technical tangent there.  I was up late, and have been getting ~5-6 hours of sleep per night.  Unfortunately, my body likes 8 hours, so this leaves me in odd mental shape.

Anyway, I love learning.  I also love sharing things.  I was playing around in Excel with the various waveforms, and decided to export it to a PDF with notes to help folks understand what is going on.  Hopefully you will find this informative!

Adobe PDF, ~500kB
http://www.e30tuner.com/projects/aliasing.pdf

Might be typos in there.  I checked, but who knows what I missed in my half-asleep stupor!

i wouldnt expect you to make heatshields or provide the cone filter.  i just want the setup to be compatible with it =D keep up the good work and i hope this gets done in time for santa to pass em out!!!

[bmwman91]

I tested it more tonight.  The converter is now equipped with a filter to try and fix the weird engine-cut I was seeing.  The problem at 2400RPM weems to be gone, but the whole floored-at-1200RPM thing is still there.  Chances are that the filter has a hard time compensating properly for those intake pulses since they are so far apart.  I swear it feels like there is a slightly flat spot between 2800 and 3300RPM, but I might be imagining it.  It seemed to go away as I drove...maybe an ECU reset will help.  Anyway, I should proably toss it on a dyno soon to see exactly what is up.  Tomorrow I will look into logging some AFR's.

Speaking of ECU resets, the stupid car developed a new problem.  The Battery Check light now stays on after the car is off.  It is completely unrelated to the MAF converter...it must just be life testing me.  Stupid car, grumble grumble.

[rallycarcamshaft]

Hi there, i rally a 318is E30 in the UK and would be very interested in fitting an AFM. I have a rolling road so setting the ECU up would not be a problem (I have  a performance power piggy back ecu fitted, so if it requires AFR's changing / ignition timing or injector opening times this would not pose a problem). If you would be willing to sell me the compents / instructions to carry out the conversion please let me know and i will fit it and see what results I can get.

jon finch

[bmwman91]

The piggyback you run...do you have the stock AFM input going to it?  You could possibly get away with using a MAF and dummy-resistor to simulate the air temperature thermistor, and then tuning from there.  Let me know what piggyback you are using and I will look to see if it has the proper signal conditioning needed.  The MAF is basically TOO sensitive and is proving to be a real pain on the M42.  6-cylinder motors are easier to use with it since they have some overlap in the intake pulses.

By rolling road do you mean nice back-road, or a dynamometer?  I wish I had a dyno...

[rallycarcamshaft]

Hello there the piggy back unit is a "Perfect Power SMT 6", yes I have do have the stock AFM input going into it and by rolling road I mean a Dyno (lucky eh). If you think a dummy resistor may work, tell me what type and were to put it and i will give it a go.

[bmwman91]

Well, IIRC a 1.54kOhm resistor will simulate a temperature of 32.92 degrees Celcius.  If you are just tuning based on the dyno and AFR's, then you can pick prettymuch anything I guess.  Try to keep the resistance between 1.3k and 3k.

With the unit, do you basically have maps with the AFM voltage along one axis?

Again, adapting a MAF to the M42 is not as straightforward as even I would have thought originally.  Being 4 cylinders, the intake pulses actually cause issues at the MAF unit and additional conditioning is needed.  I am sure the SMT6 has something built in to deal with a noisy MAF...can you forward me some links to some literature?

I might be able to hook you up with the equivalence data between the 2 sensors for less then the cost of a converter unit since you have already gone to this much trouble.  PM/let me know!  At this point the information is proprietary just due to the ridiculous $ I have had to spend getting this far, and having done this initially with a partner.

[Ramblin MAn]

Well, I was going to ask for a copy of the paper you wrote for your senior project that explained how you were doing all of this but I guess thats not going to happen.

Would something like this help you?

http://www.thatcorp.com/4320desc.html

[bmwman91]

Yeah, the paper and a lot of the research is only 50% mine, so giving it away is not really possible.  All the new stuff if 100% mine, but much of the sensor data is shared, though I am working alone on this now.

[nickmpower]

well how does the m44 do it?

[bmwman91]

The M44's DME was designed to use it in conjunction with all the other engine controls, and Bosch has virtually unlimited resources as far as electrical engineering and software.  They also have engineers who have done this for a living for....oh hell, they are German, let's leave it at that!!!  Lol, it is good to be Bosch.

Now, I am not going to sit here & cry.  Once I get a new friggin alternator I can test more.  I will make a ~6" velocity stack to try and smooth things out a little.  I suspect trying to have this on the air box with that square to round transition plays all sorts of havoc.  I might have to toss the airbox compatibility goal.  While I wait for an alternator I al finishing up revising the code for my mini-datalogger so I can see exactly WTF is going on with the TPS, EGO, converter input and converter output.

Hokay, bed time!