E30 Club SA: AFM to MAF swap - E30 Club SA

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AFM to MAF swap

#1 User is offline   Sp33dy Icon

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Posted 28 April 2007 - 09:20 AM

I've decided, for the sake of scientific endeavour, to undertake the much hyped M20 air flow meter to mass air flow meter swap.

I will do pre and post swap dyno runs to do some objective assessment as to whether the exercise is worthwhile.

I have acquired the following parts:

Siemens MAF (p/n 1 703 275) out of an E36 328i
Siemens MAF to ECU connecting plug
M20 air temperature sensor from AFM
M20 4 pin male plug off M20 AFM

A while ago, possibly on the old forum, Stevin posted a wiring diagram for the manufacturing of a new adaptor harness which allows you to use a MAF in the Motronic ECU. I have used this wiring diagram to make a new mini harness for the MAF.

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Here are some pics up to this point:

Comparison between bore of AFM and MAF

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New adaptor wiring harness

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MAF and wiring harness

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The advantage of having a piggy back ECU such as the Perfect Power unit is that it is very easy to manipulate the signal comming from the MAF. The Motronic system will be able to function as normal and properly setup should feel like a factory installation..
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#2 User is offline   Andreas Icon

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Posted 28 April 2007 - 06:32 PM

Hey Sp33dy, nice project. I know that you can be relied on for a proper before / after evaluation. Not sure how you would objectively test it but I would be interested to know if the engine becomes more responsive to sudden acceleration.

Considering that you took the unit from a 328i, the diameter of the housing should be pretty perfect for your 2.7 However a thought has entered my mind and I am not sure whether it is just a dumb idea or actually something worth considering.

Here goes : I am just wondering about your before and after pipe diameters. If they differ somewhat and you make adapters to connect them to the MAF housing, you might be creating a venturi effect and the sensor in the middle of the "pipe" may not get accurate airflow readings.

It's probably irrelevant since you're having it re-programmed anyway. Hmmm, I may just have answered my own question with this last sentence.
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#3 User is offline   Sp33dy Icon

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Posted 28 April 2007 - 07:31 PM

Thanks Andreas, I'm quite keen to see if there is really an improvement.

The venturi effect would come into play, but the tuning facility of the piggy back would correct for that.. The only issue is that the effect wouldn't be linear, so I would have to fiddle with the fuelling across the whole rev, and throttle postion range.

The pic below shows the fuelling adjustment screen of the Perfect Power software.. You can see how many load sites and rev ranges need adjustment, but it's really easy to use and adjust using a wideband exhaust gas analyser.

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I'm hoping that the improvement in throttle response will be noticeable. You'll recall that in my old setup, before the 2.7 conversion, I used a Gotech Pro stand-alone system... This uses a MAP sensor, and I had a straight stainless steel pipe attached to the rubber elbow. At the end of the pipe was a cone filter. The throttle response was as close to instant as I could feel, and is definitely better than the moving flap of the AFM.

Do you think I should also make up an stainless steel elbow to replace the rubber one? Then I could make a smooth transition of air right from the filter, all the way through to the throttle..

Something like this:

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What is your view?
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#4 User is offline   Andreas Icon

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Posted 28 April 2007 - 08:34 PM

Definitely use the steel elbow. Looks awesome and is smooth on the inside whereas the OE rubber is ribbed and thus has substantially more drag which will decrease airflow into the engine ever so slightly. But hey, if it is a free 0.5% of power we will take it, right ?
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#5 User is offline   Sp33dy Icon

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Posted 28 April 2007 - 09:46 PM

...one example of where ribbed does not equal extra pleasure.. :lol:
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#6 User is offline   kreem_y Icon

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Posted 29 April 2007 - 12:03 AM

Sp33dy said:

...one example of where ribbed does not equal extra pleasure.. :lol:


sp33dy your posts are always entertaining........in more ways than one. :lol:

i may never get around to attempting half the technical projects you guys get to enjoy......but it's great learning from your
xperiences. looking 4ward to the results.
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#7 User is offline   Kobus325is Icon

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Posted 29 April 2007 - 07:52 AM

I 2'nd that kreem_y. I liike to learn more about these vehicles, and vehicles in general, so that one can do some stuff on your own, and not always be so dependant on others.
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#8 User is offline   Sp33dy Icon

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Posted 29 April 2007 - 09:25 AM

Andreas said:

Considering that you took the unit from a 328i, the diameter of the housing should be pretty perfect for your 2.7


I've just run the part number through the ETK, and it looks like they used the same MAF on the US version of the E36 M3.... so it should be able to support 240hp.. I think that's what the detuned US version made?
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#9 User is offline   Andreas Icon

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Posted 29 April 2007 - 06:53 PM

Sp33dy said:

I've just run the part number through the ETK, and it looks like they used the same MAF on the US version of the E36 M3.... so it should be able to support 240hp.. I think that's what the detuned US version made?


AFAIK the US M3 did make 240 hp. Is that what you are aiming for - 176 real kilowatts ? That would be about 20 kw more.

I think as long as the inside diameter is bigger than your throttle body you should be fine. I also don't think that you need to worry about it being too big since the "air speed" issue for mid-range torque will still be sorted out by the long runners of the standard M20 intake manifold.
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#10 User is offline   Sp33dy Icon

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Posted 29 April 2007 - 07:29 PM

I've got no real goals with this exercise, it's more a case of doing it just because I felt like it.. that, and the fact that the management map needs some more tweaking to make it smooth in some areas since the 535i AFM was installed.

So I thought that I might as well change to the MAF and sort out the fine- tuning at the same time. I'm finding it easier to tune the engine at full throttle on the dyno, than to sort out the light throttle map when the engine is cold for example.

Ultimately I can see myself wanting ITB's. Something with a plenum and and a cone air filter with the MAF inline... I don't really have the courage to run open ram tubes, and I can see the flap type AFM really restricting that kind of setup..
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#11 User is offline   Andreas Icon

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Posted 29 April 2007 - 09:37 PM

Sp33dy said:

Ultimately I can see myself wanting ITB's.


Aha, the real reason behind the AFM deletion comes out.

Excuse me for shaking my head whilst wearing an evil grin. Been there done that, i.e. standing over my engine compartment, looking at my M20 and thinking that my baby deserves some ITBs after all that good service. I hold my hand out, thumb and forefinger spaced out a few centimeters and take some rough measurements by eye - hmmm, yeah everything should fit in real easy.

I go out and buy the ITBs, they look real good and they're sooo big. Man my motor will look so wicked. R8,000 later I hold the ITBs against the engine and guess what - now all I see is problems. How am I going to solve this ? How am I going to work around that ?

I thought designing an airbox will be easy. What can be so difficult ? Then I had to go and read how F1 teams spend huge amounts of money to design and test their ram airboxes. Turns out there is this potential problem of turbulent eddies within the airbox and/or high pressures developing at the mouth of the airbox. Race teams test their airboxes in the wind tunnel by taking pressure readings in several places within the airbox and in all runners. Guess I won't be removing my one headlight for ram air after all.

I think the angle at which the ITBs direct airflow into the head is important - you just have to study what they did on the E46 M3. Most ITB conversions on M20s that I've seen on the Internet are bolted on 90 deg to the head, leaving the airflow with a sharp turn before going past the valve.

There are many "little" things that you would want to make perfect and they all add up. I mean the last thing you want is an ITB conversion like the dBilas one : costs roughly 2,500 Euros for a gain of 15 hp.

And therein lies the rub my friend. That is why I am smiling like an imp. Only once you try to think of how to make all the little things perfect, will you realize what a huge job ITBs represent. Somehow I think cutting off your existing M20 manifold and using that as the basis for an ITB conversion is NOT the way to go.

On numerous occassions I have thought to myself : "I wish that I had never bought those damned ITBs" :cry:
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#12 User is offline   Sp33dy Icon

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Posted 30 April 2007 - 07:47 AM

Thanks for the heads up! I'm getting loathe to throw more money at things which offer minimal return.. especially if the hassle factor to make it work is high....

Call it personal choice, but I really like the factory engine management system, especially the idle control valve. :D So all my future mods will endevour to keep this stuff intact. As my car is predominantly a road car, I place a high value on smoothness and tractability.. I probably won't achieve that with throttles..

Another thing is that I've been struggling to find more than 2 references to ITBs on the M20 in the net.. maybe I'm not using the right keywords? Could be it's not a popular enhancement after all...

I checked out the dbilas site. They are offering 15kw on their M20 ITBs. I must say though, 15kw more on a NA setup is quite nice! Wouldn't turn my nose up at that if it came for less than 2500 euros though... Unfortunately no pics on their site..
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#13 User is offline   Andreas Icon

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Posted 30 April 2007 - 12:18 PM

dBilas said:

Hallo,

vielen Dank f?r das Interesse an unseren Produkten.

F?r den BMW 325i E30 mit dem M20 Motor bieten wir Ihnen wie folgt an:

Leistungsstufen f?r den BMW M20B25 Motor
bei Verwendung einer Einzeldrosseleinspritzanlage


Stufe I : Leistungssteigerung auf 141kW / 192PS
bestehend aus:
? Einzeldrosselklappeneinspritzung 2076,--
? Anpassung der Motorelektronik 355,--

? Einbau der Einspritzanlage 391,--
bei dbilas dynamic

Komplettpreis mit Einbau bei dbilas dynamic 2750,--
Sie sparen 72,--

Stufe II : Leistungssteigerung auf 147kW / 200PS
bestehend aus:
? Einzeldrosselklappeneinspritzung 2076,--
? Sportnockenwelle 320,--
? Anpassung der Motorelektronik 355,--

? Einbau der Einspritzanlage 391,--
? Einbau der Sportnockenwelle 326,--
bei dbilas dynamic

Komplettpreis mit Einbau bei dbilas dynamic 3350,--
Sie sparen 118,--

Stufe III : Leistungssteigerung auf 154kW / 210PS
bestehend aus:
? Einzeldrosselklappeneinspritzung 2076,--
? Sportnockenwelle 320,--
? Zylinderkopfbearbeitung 863,--
? Anpassung der Motorelektronik 355,--

? Einbau der Einspritzanlage 391,--
? Aus- und Einbau des Zylinderkopfs 783,--
und der Sportnockenwelle
bei dbilas dynamic

Komplettpreis mit Einbau bei dbilas dynamic 4620,--
Sie sparen 168,--

Stufe IV : Leistungssteigerung auf 162kW / 220PS
bestehend aus:
? Einzeldrosselklappeneinspritzung 2076,--
? Sportnockenwelle 320,--
? Zylinderkopfbearbeitung 863,--
? Anpassung der Motorelektronik 355,--
? a/N 2000 Zusatzsteuerger?t um den 889,--
Luftmassenmesser zu ersetzen

? Einbau der Einspritzanlage 391,--
? Aus- und Einbau des Zylinderkopfs 783,--
und der Sportnockenwelle
bei dbilas dynamic

Komplettpreis mit Einbau bei dbilas dynamic 5500,--
Sie sparen 177,--

Preise sind in EURO und inkl. gesetzlicher MwSt.


Anbei erhalten Sie ein paar Fotos von der Einzeldrosselanlage.

F?r weitere Fragen stehen wir Ihnen gern zur Verf?gung.
Mit freundlichen Gr??en,

dbilas dynamic

Maybachstr. 3

63322 R?dermark

Tel:+49(0)6074-93328
Fax:+49(0)6074-93316


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As you can see, ITBs do have potential. The Stage 4 upgrade takes the 2.5 M20 engine from 125kw to 162kw which is of course impressive. But just look how many other things you have to do (and what its costs) to get the most out of ITBs.

Now surely you would not want to go through all the effort of just installing them and then leaving everything else (except changing maps) as is. You'd be missing out on 21kw (difference between Stage 1 and 4).
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#14 User is offline   Stevin Icon

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Posted 30 April 2007 - 01:06 PM

For the english speakers... what does the stage 4 consist of ?

I've also been thinkin a lot about this MAF conversion... for a long time now, aswell. I'm really curious to hear how the throttle response is. From readin some of the stuff from the UK, there isn't much gain in power, maybe 3-4kw , most of the guys have reported about 10nm increase in torque...


I figure I will do it when I get around to making that plenium, with the big TB, I will do the MAF, and I will see what else needs to me done to make it fit, and work (hence why I got that other intake manifold)

I dont plan on running itb's as such... as Andreas said it will be a real hassle, to setup in the most effective position.

My main worry is losing to much mid range, with the new plenium as I dont think I will ever get the runners as long as the std intake manifold... I think some of the loss in mid range we might be able to gain back on the exhaust side of things.

I also would like to get hold of another head, and fit some M40 318i intake valves to it... Apparantly Budler did this once, and it gave him a gain of 5kw ...

I look foward to the before and after
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#15 User is offline   Andreas Icon

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Posted 30 April 2007 - 04:08 PM

Stevin said:

For the english speakers... what does the stage 4 consist of ?


Stage IV : Performance increase to 162KW / 220HP
consists of :

? Individual Throttle Body kit 2076,--
? sports camshaft 320,--
? cylinder head porting 863,--
? reprogramming of engine management 355,--
? Alpha-N 2000 piggy-back computer to replace the AFM 889,--


? installation of the ITBs 391,--
? removing cylinder head and re-installing cylinder head with sports cam 783,--


total price for all parts and installation at dbilas dynamic 5500,--
you save 177,--

prices are in EURO and incl. VAT
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#16 User is offline   Andreas Icon

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Posted 30 April 2007 - 04:14 PM

Stevin said:

My main worry is losing to much mid range, with the new plenium as I dont think I will ever get the runners as long as the std intake manifold... I think some of the loss in mid range we might be able to gain back on the exhaust side of things.


Look at all the modern BMW 6 cylinder engines, incl. the M3 engines. Do they have long intake runners like the M20 ? The E46 M3 only has quite short trumpets - no runners.

Personally I would not bother trying to emulate the length of the M20 original intake manifold runners. Do what you can with the space available and if mid range torque suffers too much, you can always change the cam.
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#17 User is offline   Stevin Icon

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Posted 30 April 2007 - 05:53 PM

Andreas said:

Stevin said:

My main worry is losing to much mid range, with the new plenium as I dont think I will ever get the runners as long as the std intake manifold... I think some of the loss in mid range we might be able to gain back on the exhaust side of things.


Look at all the modern BMW 6 cylinder engines, incl. the M3 engines. Do they have long intake runners like the M20 ? The E46 M3 only has quite short trumpets - no runners.

Personally I would not bother trying to emulate the length of the M20 original intake manifold runners. Do what you can with the space available and if mid range torque suffers too much, you can always change the cam.


Yes, but on the modern BMW engines you also have 24v and Vanos which helps with torgue in the midrange, especially the Vanos.
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#18 User is offline   Sp33dy Icon

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Posted 30 April 2007 - 07:11 PM

Today was D-Day for the demise of the Air Flow Meter....

The installation was fairly painless, with the only challenge being the stretching of the rubber elbow over the 80mm MAF end.

The engine started on the turn and ran easily.

Out on the road the difference is immediately noticeable. There is now a wicked whistle through the mid-range which turns unto a throaty bellow after 5000rpm all the way to 7000rpm...

The sound is AWESOME! Not quite in the CSL league, but intimidating none the less!

The throttle response has definitely improved and I'm sure with some dyno time, the horsepower will match the bark...

From what I can feel, the engine is now looking for more fuel, but I'll only know for sure when checking it out the exhaust gas..

It would take 10 mins to reinstall the AFM setup, so what I'll do is save the current tuning map in the Perfect Power chip as map B and retune the MAF as map A. This will allow me to freely swap between them should anything go wrong with the MAF in future..

Verdict at this stage (without hard evidence of a dyno run): HIGHLY RECOMMENDED... if only for the spine tingling induction roar.. :twisted:

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Next stage will be the construction of a box to enclose the air filter and a proper dyno tune...
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#19 User is offline   Andreas Icon

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Posted 30 April 2007 - 07:55 PM

Congratulations on the instant success. I am amazed that the AFM and the MAF return such similar signals that the car works well enough to drive without a major re-program.

Too bad that you're not an avid video poster. I would love to see and hear your car in action.

Stevin, you have to do this immediately, I want to hear and experience this.
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#20 User is offline   Sp33dy Icon

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Posted 30 April 2007 - 08:12 PM

Don't forget that I had the 535i AFM on before, and the fuelling map was substantially tweaked... The values on the Perfect Power screen shot I posted earlier in this thread are off my engine and you can see how far the fuelling has been juiced up...

As far as I can tell, with my limited skills with a multimeter, the voltages put out by the 535i AFM and the Siemens MAF are almost the same... I was amazed too!

Andreas I will make a video.. Knowing how partial you are to lots of noise! :lol:

I'm telling you the noise gives the hairs on the back of your neck an instant erection!
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