MAF
Turbo Mini Forums

Purely for data logging, not for the fueling equation.....

Not my idea, Graham started this :)

But we now both have some non-genuine Bosch MAFs to experiment with.

This one is mine.



They are large - to get the mass flow we want to measure - so a pain to fit in but we will log the data through Jean's IOx and MS2.

The ones we have chosen are Bosch HMF 5-6.4 so read up to 640kg/hr.

That should be good for logging up to ~240BHP (depending on how you do all the other calcs and the assumptions you make - the idea of this is to remove some of the assumptions).

Just gathering more data really before anyone asks why.....

Schrödinger's cat - so which one am I ???

if there non gen dont trust there readings in an absolute sence, i fitted a non-genuine one to my old rover 75 and it gave the exact same outputs as a genuine pierburg maf(a common retrofit with an adapter box of tricks). Needless to say this was nowhere near what the genuine bosch one i later purchased was showing for given conditions. guess it dpends on how good your non-gen maf's are though. the one i tried came from Euro car parts. and as a benefit of the doubt i bought another later for another car and had the same issues which were resolved with a genuine bosch sensor. if you can get someone with a flow bench to confirm the absolute readings fair play, but if its just to compare between one known car and an unknown then the absolute readings shouldnt matter

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Good idea. What you need is a mad scientist with a cobbled together flowbench to calibrate it for you.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Depends on the flowbench and how that is calibrated in the first place.

I'm guessing this is just for datalogging rather than fueling control?

Is it a resistance device or will it give a voltage output?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Just for data logging, as per the first line of my post :)

No need for a mad scientist - if there was a need for a mad scientist it would be me.... but we have the calibration curves / data tables for this.

It's basically a Bosch sensor (HFM 5 series) as fitted to thousands of engines that use an MAF.

It's a hot film resistor type rather than the older hot wire types. Gives a 0-5V output for the IOx.

Schrödinger's cat - so which one am I ???

rod, unless its genuine bosch i wouldnt trust the voltage Vs Airflow curve. To compare before and after modifications would be fine but as an absolute reading i would take it with a pinch of salt unless you can confirm with some calibrated equipment. Hope you dont think im being an arse, just had a few eye opening expereinces. Tbo a manometer, vacuum cleaner and thermometer would get you there lol

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

The required level of accuracy depends what you are ging to do with the data. If you are plotting air flow on compressor maps, then I would not get too hung up on it.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Schrödinger's cat - so which one am I ???

No worries, like i say i have had three aftermarket maf's now that were so far out of spec the car ran notably worse, were talking +- 100cfm according to live data on the one i had to measure to prove to ECP it wasn't fit for purpose. it was particularly bad tbf the other two the car just didnt feel quite right. looking forward to the results if you share lol Iv always wanted to use an old MAF to measure blowby to see if it could be used to extrapolate cylinder pressure.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

So, are you trying to verify the AFR from actual air and fuel measurement?

Given that the A-Series does not conform to accepted optimum AFRs, that's a bit idealistic isn't it?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

be very interesting to know the deviation though! and would also allow for more accurate simulations of a current engine spec.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Edited by Rod S on 18th Oct, 2012.

Schrödinger's cat - so which one am I ???

I suspect you picked up on my error of the units in my previous post, realised i had it wrong when i woke up this morning (youd think i had better things to think about) cannot remember the actual units off hand but was approx a .5v deviation in the analogue output, so im glad your checking the calibration, you could very easily have good sensors w.r.t the bosch data-sheet but not worth the risk if you want to stand by your results :)

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Schrödinger's cat - so which one am I ???

Sounds like fun :)

So we'll need pictures or a video of the setup.

Edited by jbelanger on 18th Oct, 2012.

http://www.jbperf.com/

Schrödinger's cat - so which one am I ???

happy to help if i can rod .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I've been looking at this for a while, and what concrned me was the lack of any sort of bell mouth on the inlet side of the meter. Mainly it depends where you put it in the inlet tract, but having the air filter clamped right onto it, depending on its construction, might give funny readings.

At the very least check the air filter has a nice curved lead into the meter, like the 57i K&N I bought has.

Couldn't you bite your tongue a bit and go scrap yard and get a genuine on off a car? just to try ?

Robert,

Thanks for the offer, I'll be reading your flowbench thread again tonight then I should have some questions.

Colin,

Initially I would have thought the same but it seems they don't want any sort of a lead in.
My photo doesn't show it because 1/3 of it is in the filter but heres the genuine Bosch picture



As you can see it's flanged to bolt into an airbox and it's own inlet is quite deliberately square (the grids apparently are to try to make the flow as laminar as possible at the measuring venturi).

Now this isn't a one-off, 90% of this range are flanged in some manner (so obviously mount into airboxes) and 100% of the range, even the few that do fit in pipes, have the same square edge and square edged grid.....
I can't explain why, but that 's the way they are.
Unfortunately cramming it into the air filter is the only place I have room.

Chalkie,
After a few hour on many VW/Audi/Seat forums tracking down the connector codes, the consensus was even the Bosch ones don't last much more than 70k miles before they drift or fail. So a high probability that a breakers yard one could be non-genuine or on the way out anyway.


EDIT....

Colin,
One other thing with potential flow restriction - This particular series of meters are in 5 different sizes to cover 5 different flow ranges.
To get the range we wanted (640kg/hr) the physical size of the meter tube bore is ~70mm
My inlet piping is 57mm or 2 1/4" whereas I think most people use 2" so although the inlet profile isn't ideal (but I think that is for a specific reason) it certainly isn't a restriction overall.

Edited by Rod S on 19th Oct, 2012.

Schrödinger's cat - so which one am I ???

Rod, looking at a VAG airbox that takes this sort of MAF sensor, there is clearly a bell mouth built into the box itself, as can be seen in this pic

Colin, nice pic...

It looks as if the recess where the meter fits may even be stepped to match the bore of the meter.

I'll have a re-think but I'm struggling for space.

Having said that, the grid (as you can see in the Bosch photo) is all square edged - now for a plastic moulding it would have been dead easy to radius those edges ???

Schrödinger's cat - so which one am I ???

Right Colin, I think it probably is doeable.

Looking down the other way (lousy picture I'm afraid) I think there is enough difference in diameter between the MAF and the inner cone of the filter to put a small bellmouth directly on the MAF.

I'll do some detailed measurements to be sure but I think 3-5mm should be possible. Any more and I couldn't force it through the rubber neck of the filter anyway......

Schrödinger's cat - so which one am I ???

As long as it isnt mounted too close to the turbo, I wouldnt be overly concerned.
The airflow within say 150mm of the turbo will be very turbulent.

You arent referencing this to fuel, or for an exact airflow figure. Just to see if it is flowing more, or less.

If you max the unit out, simply fit it into a larger diameter housing. Or use a bypass so all air doesnt flow through the meter.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

The lack of a bellmouth on the inlet should not be a particular problem if you calibrate it as an assembly.

The air filter will stabilise inlet conditions and minimise any entry effects that may disturb the velocity profile at the sensor.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."