M30 AFM Observations

[rcko]

Here are some more data pts regarding the effects of the M30 air flow meter in a M20. Keep in mind these was installed on a M20 with 19lb injectors and a 93 Octane DSylva chip. Weather was in the mid 90's deg F. Fuel was 93 Octane Shell.

I had to fabed the bracketry to mount the M30 meter and installed the thing using a stock M20 bellow which I heated and stretched over the port on the M30 meter.

Idle was fine and mid throttle events were fine. The only issue encountered was detonation under heavy load at >4k rpms. I switched the back the stock meter, ei same weather conditions and fuel, and the detonation was not there even with the AC on. Plug the bigger meter, and the detonation returned.

Apparently the fuel mixture does lean out with the bigger meter, thats the only reason I can think that the detonation is present. Since the chip I am running already has a pretty well tweaked and aggressive timing curve I am guessing the bigger meter just takes the A/F ratio over the edge. I wrote to DSylva with my observations and asked for his suggstions.

From reading online the one thing that I can do is up the fuel pressure to richen the mixture. I will need an adjustable fuel pressure regulator which cheapest I found is $150 from IE. Then I would have to hit a dyno to tune A/F.

The bigger meter gave the car a nicer intake sound as well as made the idle throttle response crispier. The later maybe is a side affect of the lean mixture. Another side effect was higher fuel milage in the 28mpg vs the avg 24mpg,

[redhatpat]

You could also install an air:fuel meter and just tune it on the road as you drive.

[rcko]

I decided to return to the stock M20 AFM and airbox setup. It would take about $200 to get a regulator + tuning to only gain ~5hp more. Not a decent hp/$ rate. So I am selling the M30 AFM.

For those considering this upgrade, please do not regard this observation as negative. The issue I ran into is having an already tuned fuel/ignition map that accounted for the 19b injectors. The folks I have spoken with running the baseline M20 chip with 19 injectors and M30 intake have not had any issues and got updgraded performance from their cars.

[dark89e30]

I put mine in and it runs rich as hell. There are 3 adjustment points on the afm and with a bit of patience, you should be able to get some decent power. You really need to play with all 3 adjustment points. Hint: run a soft door...

[Jordan]

Adjusting the spring tension of any AFM ruins the close tolerance laser trimming that was done by BOSCH at the factory. I really don't understand why people insist on doing it.

The M30 AFM really isn't much if any better anyways. I tried that for a couple days and then tossed it to the curb in favor of a HFM setup.

[nando]

M30 afm is a waste of time. unless you are going to do serious mods to your M20 and tune it with standalone, just leave the stock setup alone.

[delatlanta1281]

I like my m30 afm
I have
Mark d chip tuned for the swap.
19lb injectors
Porsche afpr with gauge
Split second air/ fuel ratio meter.
027 afm with m30 box and k&n filter.


My car is faster than my friends' e30's by a bit.
It sounds cooler.
I will say that my motor will have an upgraded cam by December 30th this year, so I can imagine it would be better with the head work and my IE headers (I know they don't make a huge difference in comparison to stock).

[dark89e30]

M30 afm is a waste of time. unless you are going to do serious mods to your M20 and tune it with standalone, just leave the stock setup alone.

Yes it is a huge waste of time, if you just expect to throw it in and have it work tits/ don't know what the hell you're doing. And who the F runs an AFM with standalone? That is a waste of time...

[rcko]

delatlanta1281 : you mentioned the use of a Porsche afpr. Is this a 4-4.5 bar regulator? Could you please post a part number for it?

Regarding the Mark d chip tuned for the swap. I spoke to Mark before purchasing my chip and it sounded like the 19lb chip was for the stock M20 not the M30. He said he knew what to do to tweak one for the M30. Is that what you got? Is your DSylva chip a 6900 rev limit unit or the 7k limit unit?

[ja burna]

with m30 afm, your going to need dyno time to get it right. Don't mess with the AFM as Jordan said.. All your going to do is mess it up. Bottom line is don't cut corners, if you wanna use it, use it right and get it tuned properly.

[nando]

Yes it is a huge waste of time, if you just expect to throw it in and have it work tits/ don't know what the hell you're doing. And who the F runs an AFM with standalone? That is a waste of time...

I never said that you would want to run an AFM with standalone. that is kindof my point though.. there really is no point in doing it at all. go big or go home.

you might get lucky and it will work okay for you, but unless you put it on a dyno you're just taking a chance that your AFRs are anywhere near correct. and dyno time isn't cheap, so why waste $100/hr+ for a $30 mod that gives you maybe 5hp?

[rcko]

... why waste $100/hr+ for a $30 mod that gives you maybe 5hp?

My thoughs exactly, but still tempting to do. Actually more like a $90 mod due to parts I bought but still... If I can find an affordable regulator I would give this a try again.

[rcko]

I just got reading a book on Bosch FI ignitions including L-Jettronic ei systems using the L shape trpa door AFM like ours and our Motronic system.

The book went into some pretty sweat detail of the systems, how to troubleshoot them, modified them etc, and apparently they aint much that can be done on the motronic besides a chip... Everyting else is peanuts.

The limiting factor is the injector timing ei how long they stay open and squirting as well as the throthle butterfly itself not so much the AFM. Apparently anything above 3.5k to 4k the L shape door is fully open and the AFM is sending a wide open signal to the ECU. SO the larger AFM is sending more air through, maybe bottle necking at the throtle body butterfly valve maybe not, and then the injectors are doing their thing at their max pressure controlled by the regulator and whatever the capacity of the fuel pump is. So if we assume the throttle body is not the choke pt then the M30 AFM will be sending more air mass through the system at anything above 3.5k rpm. The DME increases injector duty cycle for as long as it can depending on what it is reading from the o2 sensor. However, if the injectors cant squirt enough fuel the mixture will lean out. NOthing that can be done at the AFM end will fix this besides resorting back to the stock AFM. THe answer is more fuel via upping the fuel line pressure which is not controlled by the DME only by the fuel regulator and pump capacity. The duty cycle remains the same as needed based on o2 sensor input to the DME but due to the higher pressure more fuel will be squirted out by the injectors thus enrichening the mixture.

The book went on to basically said that bigger injectors and bigger afm offer marginal performance increases over stock. Only on engines build to produce more power or force inducted will these items increase performance. One item that was mentioned was a rising rate pressure regulator that bias pressure based on manifold pressure changes ei vacuum. It maintains whatever dial in setting is set up for idle and then increases that setting as vacuum pressure changes typically 0.5 psi fuel to 1psi vacuum. I found one of these and it runs ... $200 so it is the same and the main benefit is claimed to be improved throttle response.

Hope this thread helps those dealing with this device. Apparently it works and will produce a bit more power but like it has been said it will need some "tuning" to make sure A/F ratio is mantained.

[AlarmedBread]

From the dead!

My results for m30 afm + 19lb injectors + stock chip 173 ecu = fail


AFR average 11.17 130tq/115hp
Runs way too rich, a tune is required. Put stock parts back on and made 160.

[nando]

ouch, that's really weak. I just saw a Pro3 car dyno today that was running 15:1 at WOT and he made a good 140whp.