MAF screens removal

[windym]

Hi guys quick question, we all know the more air into the engine the more fuel the better the performance. The engine in the z3 m52tu has been strangled by the manifold, so I have changed this and it has made one hell of a difference.

So I started working out how much the MAF screens block airflow, I have, and this is not entirely accurate as I got a bit bored doing it but my calcs are between 37 and 43% of the through space is taken up with plastic. Which in my opinion may not need to be there.

So my question, we have air filters so why the need for this plastic air reducing grid, I will be removing the plastic at the weekend regardless just to see.

So any ideas or definite answers would be good.

Andy

 

[ZTec]

This’ll be interesting.

 

[gookah]

I would suggest this is more to even out the flow of air over the sensor, rather than as a filtering screen. but I could be wrong.

 

[windym]

I would suggest this is more to even out the flow of air over the sensor, rather than as a filtering screen. but I could be wrong.

That would make sense into the maf but how would that be applied to the screen out of the maf. As the air exiting will have been metered, so would that make the second screen redundant?

Andy

 

[Stevo7682]

Was reading this thread got me interested so went online to look at a few things came across this link
Guy makes a few valid points
http://www.gmtips.com/3rd-degree/dox/tips/maf/maf-screen.htm

 

[5harp3y]

I would suggest this is more to even out the flow of air over the sensor, rather than as a filtering screen. but I could be wrong.

It's this

It's to create consistent flow across the sensor. Leave it be.

Plus even if you did see a difference it would be 1bhp or less .

Which of course you would never notice / feel

 

[Ianmc]

Logic says there must be a reason for it (its been designed and manufactured at a cost). The reason can't be a filter as its too course for that.
I'd leave well alone but will be interested in your findings.

 

[Pingu]

@windym I am probably the saddest person on this website for testing items - and I agree with you - there would be a difference if you removed BOTH meshes, but...

I built a manometer and this was one of the things that I measured.

Below is the unmodified video that I used to measure the pressure changes with different MAF screens removed, It shows the setup that I used. Previous test that I did with air filters (Simota and OEM) were confirmed by rolling road results - so the manometer gives valid results.

The comments about the screens smoothing the flow are valid, but I think the downstream screen can be removed without affecting airflow (as it is downstream of the sensor). The flow into the engine from the MAF, through the plenum, into the engine is so turbulent, removal of the screen will make little difference.

The pressure difference across the MAF with both meshes in place was 2.5cm H2O.
The pressure difference across the MAF with no meshes in place was 2.0cm H2O.
The pressure difference across the MAF with just the fine (upstream) mesh in place was 2.5cm H2O.

I never tested it with only the coarse (downstream) mesh fitted.

From the manometer data it is only worth doing if you remove BOTH screens, but the upstream screen is used to smooth the air flow over the MAF.

 

[5harp3y]

Holy testing batman

 

[5harp3y]

But doesn't tell you the impact of maf readings

 

[windym]

@Pingu Hi, thanks I had been reading the water drop test in other forums quite impressed that you had done the same. Looking at other data it appears a honeycomb mesh is the most efficient in smoothing turbulent flow. One criticism of the mesh BMW have used is drag behind the mesh due to the depth of the holes the air travels through.

In complete agreement the rear mesh can go, as you say what good will it do after the sensor, this covers or blocks around 18-23% of the free space. I will look at removing the rear and replacing the front with the deeper honeycomb style mesh and see what happens.

Andy

 

[Pingu]

@Pingu In complete agreement the rear mesh can go, as you say what good will it do after the sensor, this covers or blocks around 18-23% of the free space. I will look at removing the rear and replacing the front with the deeper honeycomb style mesh and see what happens.

Andy

It sounds like a reasonable idea. You've seen my rig, so you can see how easy it is to make. Crack on and let's see the results.

I'm going to investigate honeycomb (and other) smoothing screens over the winter.

I'll need to have a think about the easiest way to make a smoke machine.

 

[windym]

@Pingu here is a vid of just that

View: https://youtu.be/mjJFx99YYPc


Andy

 

[Pingu]

But doesn't tell you the impact of maf readings

Correct, but I was only testing the effect of removing the screens. As I decided that it was only worth it if I removed both screens, I decided to remove neither. If I had, I would investigate the actual flow through the MAF. That's what I will be looking at over the winter.

But before that, I will be looking at improving the flowrate through the airbox and from the MAF through the plenum into the cylinders.



As an aside, I'm currently experimenting with extended trumpets on the inlet throats and bypassed exhausts, but it looks like I will need to completely design the plenum - nothing ventured, nothing gained

 

[Pingu]

@Pingu here is a vid of just that

View: https://youtu.be/mjJFx99YYPc


Andy

It certainly seems to keep the airflow straighter for longer.

I think that my 3D printer will be busy over the winter

 

[gookah]

@Pingu here is a vid of just that

View: https://youtu.be/mjJFx99YYPc


Andy

Obviously the improvement is equally as good with different colour air, as everyone also needed that to be shown
In fact that would have been my next question, "but what if the air is coloured red?"

 

[windym]

Will be ordering one of these at the weekend, just have to measure the internal bore of the MAF.

https://www.boostunited.net/fabrica...44/treadstone-honeycomb-maf-straightener-76mm

Andy

 

[Pingu]

I would test and compare flowrates before fitting.

No good having a more accurate MAF reading, but strangling the engine.

 

[Ianmc]

Never heard of these before, maybe just me. If it gives a notable improvement in "air flow straightening", will this offset the reduced airflow by using the straightener? As this technology was available 20 or more years ago, why did in not get designed in in the first place? I suspect the answer is that the MAF housing, as designed, is a compromise between air flow and straightening. Will be interesting to see your further results.

 

[Pingu]

@Ianmc - the current MAF has a straightener (all MAFs do). The potential improvement is to improve volumetric airflow, but still keep the flow straight. BMW used an off-the-shelf Bosch MAF. @windym and I will be investigating using different straightener shapes, but with reduced cross-sectional area.