Attempted M30 afm swap gone wrong, is it actually possible?

[whitebulat22]

I think I have a unique problem happening. Ive searched the internet extensively, found conflicting successes and failures, and I learned that the M30 afm thing was tired a while ago, but not so much the specific thing happening to me.

Baseline M20 is a 2.7i that has always run near perfect. M30 afm was said to work beautifully on its old m30, and I verified this by handing it to a local m30 owner. Trying to mate this to a stock ecu changing nothing else, it runs so awful that its not even safe to drive (17 lb injects did nothing to help). It doesn't learn over time either, stays awful, and then goes from unsafe to undrivable after 10 minutes and stays that way until shut off for a bit.

Now I've put it through a couple of good tunes matching my engine, it still runs like it has the runs on start up, but then it gets closer over time until it suddenly again becomes completely undrivable, barely able to even rev similar to how it "dies" with no tune. It "dies" the second it sees a lot of load no matter what.

I'm not terribly bothered to fix this when the stock afm is zero headaches, but I do remember the unique sound and pull it had a moment and I still have the (most likely) good tune and afm laying around. I've seen the consensus being that stock tune plus different afm results in crappy but drivable car, but I've never even gotten to that stage. It is an 027 unit I'm using and tested good on an m30b35. Is there anything non obvious I could've missed during 4 attempts?

[modernist]

If you used the ECU, AFM, and stock sized injectors from an M30 on the M20, for example, it would at least get mixture close, because the ECU is still programmed to match the same voltages to the same injector pulse, putting out the same amount of fuel per air, regardless of the engine it's attached to.

So yeah, that would run like shit; the poor ECU is being fed misinformation by an alien AFM.

[nando]

why even bother with this in this day and age? There's basically no gain from it. Even deleting the AFM entirely has been shown to be only a couple HP difference on an otherwise stock M20.

[digger]

yeah m30 AFM is like early 2000's thinking. my stock m20 ran a whole bunch better with m20 AFM and tune

[whitebulat22]

why even bother with this in this day and age? There's basically no gain from it. Even deleting the AFM entirely has been shown to be only a couple HP difference on an otherwise stock M20.

Good to know, I didn't know taking away the whole thing was still basically nothing!

It was tempting at the time because I was buying a tune anyway, I figured it would be "bolt on" straight away, and the original one seems much smaller than the throttle. Ah well, 1 hp can't make up the time saved boiling the intake boot over it. At this point I'm just wondering why it's not going for scientific purposes.

[mazzo]

I don't remember M30 AFM mod works 2.7 stroker engine out of the box (I assume 2.7i means you stroke it, right?). I use M30 AFM on my 2.5i with 19lb and SSSquid chip which has the specific tune for my combo. You may want to contact them for your need...

[Bullet Ride]

Now I've put it through a couple of good tunes matching my engine, it still runs like it has the runs on start up, but then it gets closer over time until it suddenly again becomes completely undrivable, barely able to even rev similar to how it "dies" with no tune. It "dies" the second it sees a lot of load no matter what.

I'm not terribly bothered to fix this when the stock afm is zero headaches, but I do remember the unique sound and pull it had a moment and I still have the (most likely) good tune and afm laying around. I've seen the consensus being that stock tune plus different afm results in crappy but drivable car, but I've never even gotten to that stage. It is an 027 unit I'm using and tested good on an m30b35. Is there anything non obvious I could've missed during 4 attempts?

As mentioned by Nando, it's not really worth the hassle, but just to put in my experience with it:

I installed a wideband O2 on my E30 bone stock, drove it around and got an idea of what the typical AFRs were (I wanted to see if it was leaning out on the top end to see if my injectors needed cleaning).

Then I installed an M30 AFM and on the initial drive the AFRs were maybe half a point leaner, meaning that the car was getting more air, and after some driving the fuel trim adapted and AFRs were normal.



The car wasn't noticeably quicker, maybe a bit peppier, but nothing to write home about. Then occasionally I'd notice a check engine when idling at a stop light, which was remedied by tweaking the spring tension a couple teeth on the gear (I'm sure you've read about it). After that I never had any issues with the swap.

After that I installed 19# injectors and a MarkD chip, there was a noticeable improvement, but again, nothing earth shattering and definitely a bit underwhelming based on what people were saying about it on the forums.