Air flow meter tests

[august]

Did not know if anyone answered the question about 5 or 7pins on the AFM? Here it goes anyway;

The old ones with 7 pins the two last pins are for the fuelpump-shutoff, during motorbraking. The newer ones that is built in in the tps and the Ecu.

//Peder

thanks for the info Peder, and welcome to the forum. interesting about the fuel pump shutoff, havne't heard that before.

I measured a Bosch 0 280 202 044 AFM from my Turbo #2, European 505 Turbo Injection 1985 (N9TE). The AFM has a blue plastic cover and the pin numbering is 6 9 8 7 27. So, I measured between pins 6 and 7.

Fully closed: 140 ohm

Fully open: 480 ohm

Peak: 1100 ohm

I haven't measured AFM from my white Turbo #1 or from the Turbo #3 (parts car) yet.

I've seen pictures of the AFM's with the blue covers, but didn't know they had a different part number as well..

does anyone know the difference between the "0 280 202 044" and the "0 280 202 057"? I think that's the next big question. I'd have to say its just due to the emissions control stuff, but i'm really not sure. V-M?

you can see on atp they list the 044 as being a for a 82-88 L-Jet equipped 505: link

[Toni Lindroos]

I've seen pictures of the AFM's with the blue covers, but didn't know they had a different part number as well..

does anyone know the difference between the "0 280 202 044" and the "0 280 202 057"? I think that's the next big question. I'd have to say its just due to the emissions control stuff, but i'm really not sure. V-M?

you can see on atp they list the 044 as being a for a 82-88 L-Jet equipped 505: link

I'm not sure if AFM with part number 044 always has a blue cover or not.

Here's a Bosch catalog too:

http://ecat-online.bosch.de/toc/

0 280 202 044 Airflow Meter:

CITROËN 1920 29

CITROËN 9151 454 780

PEUGEOT 1920 29

PEUGEOT 9151 454 780

Description Model Year Fitted Period kW HP cc

PEUGEOT - 505 (551A) - 2.2 Turbo Injection 03.84-10.88 -06.88 114 155 2155

0 280 202 057 Airflow Meter:

CITROËN 1920 49

CITROËN 9151 819 480

PEUGEOT 1920 49

PEUGEOT 9151 819 480

Description Model Year Fitted Period kW HP cc

PEUGEOT - 505 (551A) - 2.2 Turbo Injection 01.86-12.87 - 110 150 2155

PEUGEOT - 505 (551A) - 2.2 Turbo Injection 06.87-12.88 - 128 174 2155

I'm not sure why that catalog also lists Citroen part numbers but no Citroen vehichles... Obviously it doesn't list 505 US models at all.

But here's a Bosch catalog system that has only US models:

https://www.rockauto.com/dbphp/mfr,BOSCH

But I didn't get much information out of it...

[Guest adegnes]

I'm not sure if AFM with part number 044 always has a blue cover or not.

Both my ...044 cover's are black, never seen a blue one in real life.

Would be fun if someone could post a picture of the inside of a 057 AFM, could compare with my 044... ( dont think there is any seable differences thoug...)

[Johnny]

The number on my US spec N9TEA (0 280 202 057), which is obviously the same as yours Johnny. I'm assuming your 88 N9TEA has a lamda sensor, eh?

adegnes: 130 is a little high, but not considering your peak is 1280 (which is really high).

Yes, my car has lambda.

And about the fully closed reading:

I don't think that it's that important because when the engine is running, the flap is never fully closed. And at least when I tested my AFM, the resistance dropped when opening the flap a little bit (approx. that much it would be opened at idle).

the peak ohms seem to be when the flap is about 3/4 depressed. the only thing i / we can come up with is this is the position where the flap would be under full load conditions. i think this is one of the reasons that causes the ecu to throw errors under much higher then normal boost conditions. the flap is open more then it should, yet things arent matching up and the ecu's are freaking out. this seems to start happening on the N9TEA around 20psi. now maybe if we used a AFM that didn't peak at 1000 ohms, we could have managed 23psi without codes (get what i'm saying?). in any case, for more info on HP and AFM's read some of the posts in the beginning of this thread.

That sure is interesting!

This would mean that when you raise the boost so much that the flap opens past peak resistance (giving less voltage) and thus the ECU would think that the engine sucks in less air then actully it is. This in turn would mean that the engine runs lean, hurting performance and possibly causing detonation.

Just a theory.

[Guest adegnes]

Yes, my car has lambda.

And about the fully closed reading:

I don't think that it's that important because when the engine is running, the flap is never fully closed. And at least when I tested my AFM, the resistance dropped when opening the flap a little bit (approx. that much it would be opened at idle).

That sure is interesting!

This would mean that when you raise the boost so much that the flap opens past peak resistance (giving less voltage) and thus the ECU would think that the engine sucks in less air then actully it is. This in turn would mean that the engine runs lean, hurting performance and possibly causing detonation.

Just a theory.

Maybe adjustment (tightening) of the spring holding the flap will allow even more boost...?

This may reduce driveabillity thoug, if the spring is too stiff, and the flap only opens enough when full boost...

[Johnny]

Maybe adjustment (tightening) of the spring holding the flap will allow even more boost...?

This may reduce driveabillity thoug, if the spring is too stiff, and the flap only opens enough when full boost...

I think if you rise fuelpressure and/or install larger injectors (and adjust idling mixture), this would compensate for the signal dropping a bit.

This would cause the engine to run richer on full boost, but that is what you want if you raise the boost.

This should apply if the spring is fairly linear.

But can the spring be tightened without damaging the afm?

It's an interesting thought though...

Joe Grubbs might know more about this... I saw that he has/had an experimental afm earlier in this thread so if you are reading this Joe, maybe you would be willing to share your experience in the subject?

[Guest adegnes]

I think if you rise fuelpressure and/or install larger injectors (and adjust idling mixture), this would compensate for the signal dropping a bit.

This would cause the engine to run richer on full boost, but that is what you want if you raise the boost.

This should apply if the spring is fairly linear.

But can the spring be tightened without damaging the afm?

It's an interesting thought though...

Joe Grubbs might know more about this... I saw that he has/had an experimental afm earlier in this thread so if you are reading this Joe, maybe you would be willing to share your experience in the subject?

Yepp, the spring can be tightened without damaging the AFM.

I know non-turbo engines often achive better throttle response by loosening the spring slightly, too much makes it go beyond the peak at full throttel (not good...). Maybe a little tightening on the n9t will give more power on high boost, but allso bad response...

[Johnny]

Yepp, the spring can be tightened without damaging the AFM.

I know non-turbo engines often achive better throttle response by loosening the spring slightly, too much makes it go beyond the peak at full throttel (not good...). Maybe a little tightening on the n9t will give more power on high boost, but allso bad response...

Sounds like it's a job for one lucky pioneer

But how do one adjust the spring then? Is the case openable without using violence?

[august]

yeah, you can get the cover off without much trouble. it's just being held on by some sort of silicon rtv or something. get out the exactly, then do some gentle even prying and it should come off pretty easily.

adjusting the spring tension is no problem, its know how much i think is the tricky part.

it'd be fun to spend some time with this, maybe on the dyno. it would be hard to find the 'sweet spot' as far as boost goes though unless you could watch the resistance while doing a run. then try and get the resistance in the in the peak area during full boost.

an electrical engineer friend of mine drew up a map on how to get a constant voltage reading, rather then have to look at the logrhythmic resistance reading (which is as hassle to figure out as anyone knows who's done the factory electrical checks on these things). I'll have to dig it up, and try to setup some sort of bench test.

on another note, why couldn't we apply some sort of constant vacuum to an afm, which would equal say, 15psi in the manifold. if this could be an accurate way of adjusting, it'd be a helluva lot easier then doing it in the car.

[Johnny]

Yes, alot dyno-testing and fiddling sure would be fun. To bad I dont have a dyno at home, or a car that's drivable for that matter.

Maybe you could hook up a quality voltmeter that could draw graphs or one that remember the peak value?

This way you could see afterwards what the peak value you got, and compare it to the peak value you got when bench-testing.

When you have the AFM spring adjusted correctly these values should be really close, but you'll probably want the reading in the car to be slightly less (for some safety-margin).

About that vacuum-idea you have, couldn't we build something from old vacuum-cleaners?

Ghetto!

[august]

About that vacuum-idea you have, couldn't we build something from old vacuum-cleaners?

Ghetto!

hahahha ghetto is right, but wouldn't it be fun? I can just see it now, vacuum cleaner nozzle with regulator and vacuum gauge hooked up with a T to measure the pressure.

[Johnny]

hahahha ghetto is right, but wouldn't it be fun? I can just see it now, vacuum cleaner nozzle with regulator and vacuum gauge hooked up with a T to measure the pressure.

I actully think it would work if we just figure out which vacuum that equals a given boost in the manifold. I would like to think that the pressure would be -1 bar for 1 bar boost, but I don't think that it's so easy.

The compression heats up the air, and this affects the boost pressure.... I'll try to look into it.

If we can't figure it out theoreticly, we could always measure the vacuum at the AFM when we have a car set to a specific boost.

[V-M]

Well... In old times vacum cleaner was (is) used when cylinder heads were (are) "tuned"

Some of old tuners are still using those (I have one old model Hoover waiting inspiration)

V-M

[Johnny]

Btw, when I saw this picture:

I took another look at the afm and those numbers were there, only covered in dirt .

I'm going to talk to my teacher today about that vacuum-thing and see what he can come up with, hopefully I'll have something to post in the evening .

[Johnny]

I've talked to my teacher today, and it will be very hard to calculate how airflow affects the flap without any real data on the afm's geometry.

If we're going to do that we need to contact bosch and ask for drawings or some kind of report on the formulas used when they designed the afm.

What we can do is to measure the maximum vacuum after the afm when the engine is running and the boost is, say: 1bar.

Then it is possibly to make some kind of testing-device.

Ideally you would like to test how the vacuum changes with diffrent boost at a couple of points, say: 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 bar.

Another possibility is if we could get our hands on some data on the turbo, ideally how the vacuum changes then boost changes, but I think it would be possible to calculate vacuum if we know how much air it pushes/draws.

[Guest OB6D]

This seems to be a topic of interest. Didn't see the procedure for testing the AFM anywhere so far. So here's how it goes according to the documentation that i have:

Pin:

8 to 9 should read 160 to 300 Ohm Mine is: 222

8 to 6 should read 340 to 450 Ohm Mine is: 398

6 to 7 resistance is flap opening dependant

Closed it should be 60 to 180 Ohms Mine is: 112/138

Fully opened it should read 350 to 550 Ohms Mine is: 490

Flap on the move, resistance should not exceed, not go over 1K, 1000 Ohms, Mine didn't.

And then also here in my notes it says:

Pin: 6 to 27 is the build in air temp and at 20 degrees Celcius it should read between 2K and 3K, 2000 and 3000 Ohms.

Mine was: 3.18K but it was at 15ºC.

The procedure for testing the thing was plucked from a Dutch 505T manual. :-))

I believe i got the Bosch 0280.202.044

[Guest OB6D]

I was wondering something else. In the P505T the AFM is placed practicly vertical. I put mine horizontal. Is this bad in the way that gravity pulls on the door?

Or in other words, does the way you position the AFM effect your mixture? Upside down it would lean i guess...

Also i got this lambda thing with leds placed and while running idle, i brought the AFM from horizontal to an upright position and i noticed no difference. Agreed the method is quite sloppy...

Or maybe cuz the door is this two flaps in an angle, that one side of the rectangle compensates for the other and it doesn't give a damn how it's positioned.

Hehe, guess not, cuz when placed horizontal, that theory wouldn't work. You'd cancel this effect if it were so. So then there would be two good options, the way it was verticaly or upside down.

[Johnny]

I was wondering something else. In the P505T the AFM is placed practicly vertical. I put mine horizontal. Is this bad in the way that gravity pulls on the door?

Or in other words, does the way you position the AFM effect your mixture? Upside down it would lean i guess...

Also i got this lambda thing with leds placed and while running idle, i brought the AFM from horizontal to an upright position and i noticed no difference. Agreed the method is quite sloppy...

Or maybe cuz the door is this two flaps in an angle, that one side of the rectangle compensates for the other and it doesn't give a damn how it's positioned.

Hehe, guess not, cuz when placed horizontal, that theory wouldn't work. You'd cancel this effect if it were so. So then there would be two good options, the way it was verticaly or upside down.

I think that the flaps compensates for each other, unless you tilt it the other way. (if you know what I mean?)

When placed horisontally it wouldn't have any effect.

The reason the flaps are there in the first place is that the engine produces pressure-waves when closing the valves (I think).

And that pressure translates to a force on the flap, and therefore a momentum. But because there are 2 flaps the momentum's cancel each other out and the measuring is unaffected.

[Guest OB6D]

As far as i know, there's two flaps, so the curved part of the AFM body, functions as a damper. It has this [over] swing absorbtion function.

It makes a swing, when you kick the throttle. When it makes this swing, resistance is high and this gives you your acceleration enrichment.

And because resistance is high under these circumstances, it's why the manual says, that when test measuring your AFM, you should move the flap s l o w l y.

Anyways, i still think, when placed horizontal, that does make a difference. Because the forces on the flap are in a 90º angle with the force of gravity. Which imo means cancellation of that one side compensates the other effect, if it was meant to be that way in the first place.

Well, the effect is not cancelled, since the changed situation is the same for both sides of the flap, but the weight of the flap plays another [less important] role.

Hell, i don't know...

Just hate to admit it.

[Johnny]

As far as i know, there's two flaps, so the curved part of the AFM body, functions as a damper. It has this [over] swing absorbtion function.

It makes a swing, when you kick the throttle. When it makes this swing, resistance is high and this gives you your acceleration enrichment.

And because resistance is high under these circumstances, it's why the manual says, that when test measuring your AFM, you should move the flap s l o w l y.

I don't think that that is entirely correct.

I have read that when accelerating, the signal from the afm reaches the ecu faster than the air is actually drawn into the cylinders, and it's because of this you get the acceleration-enrichment.

As far as I know this has nothing to do with the extra flap or that the afm should give a greater resistance when opened fast.

I don't mean to be rude or anything and I'd be happy if you prove me wrong.

A great document of the L-jetronic can be found here:

http://bama.ua.edu/~darren/boschindex.html