DME question, Advice, help

[mccor023]

So I see a lot of folks in the classifieds selling different DME's. Colors, numbers, etc.
I have searched but I cant find specs on the differences, and advantages of one over another.
Ideally I would like suggestions and opinions on which I should be using.
I have a late model, m20 with m50 afm and 19# injectors to offset.
I bought a used dme from here bc I was told it had a MarkD chip in it to match my mods. Being too afraid to pop the dme open, I never checked.
I wanted to give the car time to learn, but now believe I had better power w my stock DME than I do now. Better fuel/air mixture.
Any recommendations would be great.
Thanks

[Sagaris]

any DME from an e30 325i or 325is or 325ix or vert will work. From my understanding the 153 was updated and replaced by the 173 and so the 153 is less desirable.

173, 524, 525 work including some other numbers I am not directly familiar with.
I am running a chip made for a 173 manual trans car on a 524 ecu in an automatic car. No sweat (auto trans is fully mechanical, not controlled by the DME in any way)

I believe you mean you have an M30 AFM. I think the best way to go would be with a W.A.R. chip which would let you fine tune things to get them working right.

The original DME and maps bases all of its injector pulse width calculations off of the stock injectors and stock AFM. If there is a plug and play chip for this specific combo then I haven't seen it, but what you are essentially dealing with is an AFM and injector setup that the oxygen sensor is able to compensate for and keep the car running.

This is not the way to go if you want best performance.

You want to get your base fuel map and air/fuel ratios as close to optimal without the help of the oxygen sensor, then when you have the oxygen sensor helping it out, the air/fuel ratio is closer to being correct and the DME does not need to compensate much. You end up with better more consistent performance. Since the WAR chip allows you to adjust the fuel maps, I suggest that route.

adjusting AFM spring tension may give the car decent air/fuel ratios at a certain RPM range but you may lean out or go rich at other points of the range.

[E30-325iS]

+1 for the WAR chip and I would also replace the AFM with a MAF.

[mccor023]

Im confused, whats the difference between the m30 afm and a MAF?
Is miller the only one that makes one?

[Sagaris]

M30 AFM (Vane Airflow Meter) off of an M30 engine (ex. E28 535i)

Looks like this inside



M50 MAF (Mass Airflow Sensor) off of an M50 engine (ex. E36 325i)

Looks like this inside


Both output different signals to the ECU and are not interchangable without changing the software in the ECU (W.A.R. chip can do this)

There have been others in the past such as "Split Second" MAF conversions and perhaps others but it seems that all the older ones are more problematic than the new stuff that Miller makes (based off of peoples MAF conversion problem threads on the forums I have read over the years)