pilchardthecat's MAF screen mod

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exdos
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Re: pilchardthecat's MAF screen mod

Post by exdos » Tue Jun 25, 2013 7:27 pm

After the initial datalogging of the Honeycomb MAF screen, I wanted to see what the ECU does to adjust to the increase in airflow which the Honeycomb screen allows, so I did some more datalogging looking at Ignition Timing and Equivalence Ratios. The Equivalence Ratio is equal to 1 when the Air Fuel Ratio is at the stoichiometric mix of 14.7:1, so when the AFR is at, say, 13:1, the Equivalenace Ratio is 0.88.

I've produced the graph below by first running the car with the Honeycomb MAF screen and then swapping back to the OEM MAF screen and then repeating the same runs.


Image

As the graph shows, the engine acceleration is more linear at the upper RPMs and the airflow is higher at all stages of acceleration with the Honeycomb screen. The Equivalence ratios are very similar but with the Honeycomb screen the AFR might be at, say, 13.2:1, whereas in OEM it might be at 13:1 at the same RPM. Likewise, the timing is similar, except at the highest RPM with the Honeycomb screen, the timing advances as the redline is approached: this seems to smooth out the "stuttering" that normally appears at around 7300rpm. I have previously suggested that the dip in performance at around 7300rpm might be caused by resonant effects, specific to the Z4M's air-intake, but it would now appear that the problem is more likely to be caused by turbulent effects caused by the OEM MAF screen. I shall now look in more detail at individual parameters at 7000rpm and above to see if the MAF screen is the problem.

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Re: pilchardthecat's MAF screen mod

Post by pilchardthecat » Thu Jun 27, 2013 10:59 am

Very interesting, and entirely in keeping with my arse-dyno & theorising - it definitely feels like it breathes better at the upper part of the range.

I appreciate the time spent testing.
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Re: pilchardthecat's MAF screen mod

Post by Mark-Z4 » Thu Jun 27, 2013 10:05 pm

Is this a mod that works for the Z4M or could it be done on other models.


That graph is quite impressive for a mod that's straight forward and cheap to do.
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Re: pilchardthecat's MAF screen mod

Post by AlienZed » Fri Jun 28, 2013 8:05 am

pilchardthecat wrote:Very interesting, and entirely in keeping with my arse-dyno & theorising - it definitely feels like it breathes better at the upper part of the range.

I appreciate the time spent testing.
Same here at first seemed flat at low revs but now feels better across the rev range.
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Re: pilchardthecat's MAF screen mod

Post by pilchardthecat » Fri Jun 28, 2013 9:15 am

Mark-Z4 wrote:Is this a mod that works for the Z4M or could it be done on other models.


That graph is quite impressive for a mod that's straight forward and cheap to do.
Try it and see :)

I haven't looked at the intake system for the other models, but i think some parts are common between the M and the 3.0
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Re: pilchardthecat's MAF screen mod

Post by exdos » Fri Jun 28, 2013 11:04 am

Mark-Z4 wrote:Is this a mod that works for the Z4M or could it be done on other models.


That graph is quite impressive for a mod that's straight forward and cheap to do.
If your air intake has a screen in front of the MAF like the Z4M (which I expect it does) then this mod will work for you. :thumbsup:

Below is a photo showing the OEM MAF screen of the Z4M on the left and on the right is a photo of the Honeycomb screen fitted in the air-filter box lid.

Image

The OEM Screen has both a plastic mesh and a wire mesh, where the thickness of the wire is 0.23mm and the plastic mesh is 0.43mm. There are 42 wires across the 87.1mm aperture of the MAF screen so the total thickness of wire across the screen is 9.66mm and there are 17 plastic wires, with a total width of 7.31mm: That's a total reduction in aperture width of (9.66mm + 7.31mm =) 16.97mm or 19.4%.

In comparison the honeycomb walls are 0.08mm thick and there are 28 cells across the maximum aperture of the MAF, this represents a total thickness of cell wall of (28 x 0.08 )+25% = 2.8mm or 3.2%. Clearly, the Honeycomb MAF screen impedes the flow of air less than the OEM MAF screen with the added advantage that it "straightens" the air as it flows past the MAF, giving more consistent readings from the MAF.

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Re: pilchardthecat's MAF screen mod

Post by Mark-Z4 » Sat Jun 29, 2013 11:08 am

Thanks :thumbsup: I'm definitely going to have a look at this.
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Re: pilchardthecat's MAF screen mod

Post by gwatson » Thu Nov 07, 2013 11:38 am

I fancy giving this a go for some cheap induction noise :)

Do you guys think a 0.5mm sheet will be about right?

http://www.ebay.co.uk/itm/3K-Carbon-Fib ... 2331deb581
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Re: pilchardthecat's MAF screen mod

Post by gwatson » Thu Nov 07, 2013 11:43 am

This kit also looks very interesting:

http://www.ebay.co.uk/itm/Carbon-Fibre- ... 1373325126
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Re: pilchardthecat's MAF screen mod

Post by Lower » Thu Nov 07, 2013 10:03 pm

Don't forget that the honeycomb will change the flow characteristics across the width of the intake. The MAF only measures airflow where its in the airflow, ie the centre of the intake, so don't assume that just because you're seeing an increase in airflow over the MAF you are necessarily getting more air into the engine.
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Re: pilchardthecat's MAF screen mod

Post by exdos » Fri Nov 08, 2013 9:42 pm

Lower wrote:Don't forget that the honeycomb will change the flow characteristics across the width of the intake. The MAF only measures airflow where its in the airflow, ie the centre of the intake, so don't assume that just because you're seeing an increase in airflow over the MAF you are necessarily getting more air into the engine.
I agree with that point but my datalogging of other parameters shows that there is a performance increase which, to my mind, shows that the recorded increased flow through the MAF is genuine.

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Re: pilchardthecat's MAF screen mod

Post by gwatson » Sun Dec 01, 2013 10:35 pm

Guys,

Finally getting round to this, apologies if I've missed the answer in the above discussion, but do I need to trim the new MAF screen in terms of depth\thickness?

Where does it sit? In the con-caved section, or where I cut the mesh from? Should I fix\bond it somehow?

Image

Image

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Re: pilchardthecat's MAF screen mod

Post by exdos » Sun Dec 01, 2013 11:24 pm

It's hard to explain how you should fit this, but the OEM plastic rim in your photo has to fit in exactly the same way with the honeycomb screen as does the OEM MAF screen. So you need to cut a rebate around the edge of the honeycomb screen. To do this, I stuck a few pieces of masking tape onto one face of the honeycomb and then traced around the plastic rim. I then used a Dremel with a diamond cutting disc to cut the circle marked on the masking tape to fit within the plastic rim, BUT I ONLY CUT about 5mm into the honeycomb I then cut from the side of the honeycomb just enough to remove the honeycomb to produce the rebate. Does this make sense?

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Re: pilchardthecat's MAF screen mod

Post by gwatson » Sun Dec 01, 2013 11:47 pm

Yeah I think so :-) I tried cutting it with thin tin cutters, but at the mercy of the honeycomb structure, so stopped, really hard to do it neatly. I wonder where my dremel is!!
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Re: pilchardthecat's MAF screen mod

Post by exdos » Sun Dec 01, 2013 11:55 pm

gwatson wrote:Yeah I think so :-) I tried cutting it with thin tin cutters, but at the mercy of the honeycomb structure, so stopped, really hard to do it neatly. I wonder where my dremel is!!
The honeycomb is thin enough to cut with a pair of nail-scissors. Just don't tell your wife you've used them. :wink:

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