Larger MAF housing

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mtsakmakis

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Hi all.

So I took the plunge and decided to fabricate a larger MAF housing. The decision came after reading (on other forums and websites) that noticeable gains can be found after such modification.

On a few American websites, there are larger ID MAF housings for sale, which is why I took the plunge and (considering I am kinda good with metal fabrications) decided to manufacture a 3.5" stainless steel tube into a MAF housing. No mean feet. Took a few hours to do in order to get the top hat square to the nominal tubing in order to get proper readings.

Anyway, today I decided to get it all together and actually see if the thing would work, and, well.....

IT DIDNT

Don't exactly know why, but car starts, then decides to run really low idle, then cut out.

I know theres something different that I should be doing, but dont for the life of me know what it is.

The mod goes hand-in-hand with other people out there who actually go out and buy a TT or VR6 MAF housing with a nominal ID of 3". I cant understand why 3.5" would make such a difference.

If there is anyone out there who understands why the housing would do such disheartening things, please input HERE!

I know that the MAF would be reading less air in comparison to the larger ID, but, I have no idea how to compensate. Any ideas?

The dimensions are:
3.5" Nominal Stainless Tubing at around 8" long (length shouldnt matter one bit)
30mm top hat extension (for sliding sensor into) @ 40mm diameter.
Adaptor flange for 2x screws (application wise) not extending top-hat length.

Anyone with fruitful input, dont be shy to post away.

Thanks in advance

/ubbthreads/images/graemlins/swear.gif /ubbthreads/images/graemlins/swear.gif /ubbthreads/images/graemlins/sleep.gif /ubbthreads/images/graemlins/swear.gif /ubbthreads/images/graemlins/swear.gif
 
US Tuning - Yeeeeehaaaaa!

This is a bodge for when you put bigger injectors in as well - you need to sort of match the more air flow you will get with bigger injectors or bigger FPR. It means if you are using a manual boost controller you have some more headroom to get more boost and power.
 
Ok. So I need a tighter FPR to compensate fuel pressure due to lower air mass sensitivity. I kinda knew that this was needed, but didnt realise that it was also necessary for use at idle without any engine load whatsoever.
Ok. This should be an easy fix for me. As for Fuel Pressure, am I correct in saying the standard for the 1.8T is around 3bar? Anyone out there know exactly?
 
Most 1.8T are 3 bar.

I would do some maths on the difference in air mass you are measuring and the difference you would need on the FPR.
 
Maths? I failed that in Secondary Schooling!!
If the normal OD for the MAF (standard) is 3", my OD is 3.5". So the difference (that I can pick) is roughly 60%. Is this correct or am I calculating things in a different matter? Mind you, Im trying to calculate overall flow difference rather than cylinder size.
 
A3 1.8T's are 3Bar... A4's are 4Bar... well at least the B5's are anyway... you can see it stamped on the side of you can access it.

I recently replaced mine with an adjustable type I bought from ATP turbo in the States.

Hope that helps a little, if at all! /ubbthreads/images/graemlins/smile.gif

T
 
Helping me out a little.
You say that the actual pressure the reg. works at is stamped to the side of the cannister? If so, then should make things easy. If not, then looks like I'll have to enquire about it with my "friend" who has the ETKA program....
 
Yes, it is stamped on the side or on the label... I don't remember which but it's definately there.
 
That looks awesome, good job /ubbthreads/images/graemlins/ok.gif
 
Thanks guys. Still a long way off sorting out a few niggling problems with it.

I had a close look at my FPR and its stamped with 4bar. I thought this was a little too high? Any ideas?
If I need to bump up my fuel pressure in order to counter the air density reading change, then I think the most I'd be happy pushing the standard fuel lines is to 5bar. Any ideas as to what pressure the fuel lines can handle? This is starting to get scary.
 
with a 3.5" maf, you may find the sensor is not sitting central enough to accurately calculate the air flow. There is also no real benefit in running a 3.5" maf... 3" is ample for S3/TT and for guys running big turbos (me) so with a K03 or even K04, you do not need a 3". I think thats where the problems stem from. It does look nice though!
 
Thanks for your input Rich.
As you might have guessed, the reason why I have decided to make a larger housing is because of the larger turbo I have. T-03 "P" trim with 0.64 turbine, 0.86 compressor housing (huge both ends). It has the ability to flow upwards of 400hp (as custom built by my mechanic). Thats essentially why I decided to go 3.5".
As for centrally locating the element, I can cut down the top-hat section in order to get the sensor reading linear through the housing. This is not a hard job and something I was thinking about doing. I guess I have to keep playing around with it.
 
[ QUOTE ]
Thanks for your input Rich.
As you might have guessed, the reason why I have decided to make a larger housing is because of the larger turbo I have. T-03 "P" trim with 0.64 turbine, 0.86 compressor housing (huge both ends). It has the ability to flow upwards of 400hp (as custom built by my mechanic). Thats essentially why I decided to go 3.5".
As for centrally locating the element, I can cut down the top-hat section in order to get the sensor reading linear through the housing. This is not a hard job and something I was thinking about doing. I guess I have to keep playing around with it.

[/ QUOTE ]

Ah ok! That explains that then! Yep, try and cut down the mounting plate so its more centrally located... This may solve the problem.

Rich
 
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