Tuning for 3" MAF housing

sporadic · 05-13-2010, 01:03 PM

I currently have a MAFia and a stock MAF with a draw-through configuration.
I'm moving to a 3" housing and blow-through with no MAFia.
I know this will end up being a drastic change in the MAF Transfer table, which I can handle.
What I'd like is a suggestion on a starter tune for adjusting to the 3".

My thought was to reload the MTF and manifold volume back to stock, and then add 10% fuel to the MTF just to get started and see how it runs.
Perhaps load a 5%, 10% and 15% richer MTF tables into the xcal to save some time.

So my questions:
1) What can you all suggest as a starter MTF for the 3" housing?
2) What oddities should I expect to run into? (aside from leaner AFR due to lack of metering of the extra air)
3) Will any idle functions need adjusted?

All tips I'm looking for are regarding N/A tune.
However, if anyone has a suggestions for boost and 3" MAF tube I'll welcome those too.
My plan is to run with the wastegate open until the base tune is where I want it.
By then I should have enough data to make educated adjustments to the upper portion of the MTF table and start running boost again.
I should also mention my car is already tuned for 9.5psi boost with the draw-through setup.

Thanks all.

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illinipo · 05-13-2010, 02:02 PM

PM me your email I can send you a value file with my 3" maf data to start you off

illinipo · 05-13-2010, 02:08 PM

Quote:

Originally Posted by sporadic

(aside from leaner AFR due to lack of metering of the extra air)

What extra air?

Also dont forget to de-scale your injectors and engine displacement, and manifold volume if that was scaled before as well

I had no change in any idle or dashpot functions when I went 3", but you are also changing your piping configuration so there might be some tweaking to do there

When I did mine I went by the r2^2/r1^2 multiplier compared to stock which is I believe (3/2)^2/(2.16/2)^2 = 1.93, and it was WAY off I had to pull back like 25% from that.

sporadic · 05-13-2010, 02:11 PM

Quote:

Originally Posted by illinipo

What extra air?

Also dont forget to de-scale your injectors and engine displacement, and manifold volume if that was scaled before as well

I had no change in any idle or dashpot functions when I went 3", but you are also changing your piping configuration so there might be some tweaking to do there

When I did mine I went by the r2^2/r1^2 multiplier compared to stock which is I believe (3/2)^2/(2.16/2)^2 = 1.93, and it was WAY off I had to pull back like 25% from that.

Oh, I didn't mean literally more air, just that there will be a certain volume of air that will "escape" around the meter causing a lean condition.
Hmm I'll look into the scaling done to the injectors.
They are 55#, and Don LaSota originally did my tune.
There are values such as timing tables and injector values I have not had to change since I bought the PRP and built off his tune.

illinipo · 05-13-2010, 02:14 PM

Fortunately the MAF doesnt measure volume, it mostly cares about the speed of the air going past it, which changes how much the wire gets cooled. Bigger maf tube means slower air, so you get more range on the maf. But lower resolution.

sporadic · 05-13-2010, 02:17 PM

Quote:

Originally Posted by illinipo

Fortunately the MAF doesnt measure volume, it mostly cares about the speed of the air going past it, which changes how much the wire gets cooled. Bigger maf tube means slower air, so you get more range on the maf. But lower resolution.

Yeah, but the whole idea of going with a larger housing is to "fool" the sensor, thus permitting a greater volume of air to get past.

illinipo · 05-13-2010, 02:20 PM

Not exactly. Bigger tube means slower air velocity in the maf tube which cools the wire less. It's called a MASS airflow sensor not a volume airflow sensor.

http://en.wikipedia.org/wiki/Mass_fl...nsor_.28MAF.29

Also I just realized you have a duratec. So my file will likely not even be close to what you need but it will be closer than a stock MTF.

sporadic · 05-13-2010, 02:24 PM

OK, I just learned something.
That's downright embarrassing to be working on MAF vehicles for this long and even tuning and not know how a MAF actually works.

Quote:

Originally Posted by illinipo

Not exactly. Bigger tube means slower air velocity in the maf tube which cools the wire less.

http://en.wikipedia.org/wiki/Mass_fl...nsor_.28MAF.29

Also I just realized you have a duratec. So my file will likely not even be close to yours but it will be closer than a stock MTF.

tb1999 · 05-13-2010, 09:37 PM

Quote:

Originally Posted by illinipo

PM me your email I can send you a value file with my 3" maf data to start you off

I had a 3" MAF Tube on my duratec for a while when I first started playing with the SCT PRP.

If you PM me, I can e-mail you my value files if you want. They should work better than illinipo's zetec files.

It worked OK for me, but I was still running stock cams at the time so the resolution was crappy at idle/low RPM and very hard to tune below 2000 RPM.

I ultimately settled on a 2.75" MAF.