Added M50 injectors and the car runs like ish!

[dickerdeville]

I just put in some M50 injectors that were cleaned and flow tested and my car would barely run at first.

Here's a run down of what I'm working with:

89 325i.
128k miles Well Maintained
Mark D 91 oct stock injector chip.
Stock AFM (have an M30 afm ready to go in)
91 octane gas
Recently Adjusted Valves (mechanic did it to .011 cold ??? Too cheap to pay him to do .010 and he's a friend so I don't want to be a dick either)

I got the injectors in and then touched the battery cables together to clear the memory on the DME.

Started the car for the first time. Runs bad, a bit of black smoke, idles rough, CEL. stumbles off idle, ticks louder than usual, on the overrun it died out, a bit of fuel out of the tailpipe too.

Started it again and let it run with the AC on (idles fine with the AC on) then shut the AC off and let it idle. Idle's decently, CEL at idle. if I rev it the idle goes off.

Then I drove it around, feels ok, seemed louder than it was before, no CEL while driving, pulls harder over 6k :D

Parked it and then drove it again, feels ok, ticks a little louder than usual but feels strong.

I have about 3 cycles on it and about a total of 12 miles.

How long does it usually take the DME to get used to these injectors? Anything sound unusual to you guys? Should I put the M30 AFM in now instead of having to go through this again? Is the stock inj Mark D chip worse off than the stock M20 chip in this case?

[jlevie]

It will take 50-100 miles of driving at various speeds for full adaptation. For the DME to properly adapt the O2 sensor needs to be good, which means one withe less than 100k on it.

[shiboujin]

Wait... you have an M20? On a stock motronics ECU (NOT an M50 DME)? With a chip not designed for those injectors? And you expect it to "learn" the injectors?

BWAHAHAHAHAHAHAHA

[nando]

your O2 is probably bad, or you have some other problem that the injectors are bringing to light.

also if none of the above is true, you need to take it out and drive the piss out of it for a while. don't expect it to run perfectly right away.

Wait... you have an M20? On a stock motronics ECU (NOT an M50 DME)? With a chip not designed for those injectors? And you expect it to "learn" the injectors?

BWAHAHAHAHAHAHAHA

Everyone seems to have a wierd idea as to what Motronic is capable of. No, it can't detect the size of the injectors - but it does have a short term (not stored, only closed loop) and a long term (stored, applies to all fuel maps) fuel trim that it bases off O2 feedback. But it needs enough records of valid O2 data for it to work, and that's not going to happen in 12 miles of sitting at idle with the AC on.

[shiboujin]

Even at that Motronic only has a specific amount it can correct. It won't give you peak power or even more power. Any more power you feel is all just that, feelings. The M20 is already a well tuned motor, a chip will give you a bit more, and intake and an exhaust will give you a bit more than that. Otherwise, this whole "M30 AFM + 19# injectors + chip" BS is snake oil.

[nando]

17 or even 19# are well within it's range

I know, because I did the injector swap long before most people here even had an E30 or knew what it was. I've also collected a lot of information on early motronic and similar EFI systems. ;)

and no, it really doesn't give you more power, except that stock 180k mile injectors are probably gunked to hell, and the single pintle design isn't very good at atomization. ideally you could get a 14.5# 4 pintle injector and drop it in.

the reason it tends to not work out for a lot of people is they have an engine that had a problem or wasn't running right to begin with. Now you've added a huge change and it just falls apart. O2 sensors don't last forever either, and I doubt many people have spent the $80 or whatever for a new one.

[Sagaris]

Immediately after installing my chip and injectors (M50) my car ran like the timing was off. I took it on a late night spirited 20 mile loop and by the end of the drive it was feeling nice and normal, It seems like about a week later the car started running even better (by a very small margin). But that could just be all in my head.

[jlevie]

I have yet to see any hard data (from a dyno) that supports a power increase from larger injectors, intake, or different AFM. That isn't surprising given how good the stock air box is and how the DME works. If you want to run the engine a bit richer (say 12.5-13:1 for best performance) you need to do something that changes the target fuel rate. Otherwise the DME will "learn" what fuel rate it takes to get back to stoich, thus negating anything you did.

The only ways of changing the target rates that aren't negated by adaptation that I'm aware of are to make the DME think that intake air and/or engine temp is lower than it is, intentionally run an aged O2 sensor, or to change the maps. Previously changing the maps was something that only a few tuners could do. But there are "DIY" methods now (MegaSquirt, WAR chip).

[dickerdeville]

I figured this would happen after reading other threads on it.

I did this mainly just to replace my injectors since they were old and everyone seemed to rave about the M50 injectors, then I figured while I was at it I would throw in an M30 maf as I've seen a few dyno charts showing 3whp or so, but everyone talks about the top end feeling a bit stronger (my car has been feeling like it drops off quite a bit after 6) After putting them in it does feel stronger at the top, but it could just be that I pulled some 130k mile injectors out of the car.

So the motronic (ecu? dme? piece of shit 80's computer what are we calling this thing?) needs about 50-100 miles to adjust the injector cycle correctly, assuming I have a good O2 sensor?

Thanks!

[nando]

it needs to be able to collect enough O2 feedback data, yes. even a newer ECU will be the same (except an OBD2 system would probably throw a code).

[shiboujin]

"pull harder past 6k"? You have like 500 rpms left anyway. You have an SOHC motor, it dies after 5k. Just look at dyno graphs. Some injector "upgrade" is not going to fix the inefficiencies of an sohc M20.

You spent all that money for 3whp? <_<

[nando]

"pull harder past 6k"? You have like 500 rpms left anyway. You have an SOHC motor, it dies after 5k. Just look at dyno graphs. Some injector "upgrade" is not going to fix the inefficiencies of an sohc M20.

You spent all that money for 3whp? <_<

SOHC has little to do with that. the stock intake/cam are tuned for a specific powerband with a peak at 5800. My engine peaks near 6500, but it's not stock. you can set it up for pretty well any power band you like.

and anyway, nobody should expect a power increase from the injectors, except that their old ones are probably pretty worn out. They're also an inefficient design compared to design II or III injectors.

[36brua]

17 or even 19# are well within it's range

I know, because I did the injector swap long before most people here even had an E30 or knew what it was. I've also collected a lot of information on early motronic and similar EFI systems. ;)

and no, it really doesn't give you more power, except that stock 180k mile injectors are probably gunked to hell, and the single pintle design isn't very good at atomization. ideally you could get a 14.5# 4 pintle injector and drop it in.

the reason it tends to not work out for a lot of people is they have an engine that had a problem or wasn't running right to begin with. Now you've added a huge change and it just falls apart. O2 sensors don't last forever either, and I doubt many people have spent the $80 or whatever for a new one.

noobie here ! what size/pattern are the M50 injectors vs. stk M20 Thanks

[Sagaris]

The stock M20 injectors are 14# the M50 are 17.5#. The M50 injectors I installed in my car (cannot speak for all M50's and all M20's) had a 4-pintle tip with air shrouds on the pintle caps, presumably to help with fuel atomization. Layman's terms: The ability to flow more fuel, and newer design features which may or may not be beneficial.

[dickerdeville]

Ok update.

I changed the O2 sensor ( bosch ford 4wire spliced to fit the connector for my car, $33) and the car seems the same as it was. I have only put about 15 miles on it since the most recent ECU reset so I'm going to be patient.

At this point I think I'm over the idea of installed the M30 AFM as this is just my daily beater, and the slowest car I own anyway.

I guess my last question is:

Will the motronic eventually adjust to run properly with the M50 injectors? I don't really feel like putting the M20 injectors back in as they have 130k miles on them and they looked pretty sorry when they came out.

If I can just leave the M50 ones in there and the car will be fine, that's great. If not, I think I'm just going to buy a set of cleaned M20 injectors and put those in.