[garyd85gt]

I searched and although their is info, no one seems posts a transfer function for the new 05 Mustang MAFs. And I saw the HPX excel sheet, but someone said the VPX sensors have a resistor to raise the values??!!

So...does anyone have a transfer function for an 05 Mustang slot sensor in a 3" blow through tube?? Thanks

[85GT]

This is the stock 06 mustang curve from EA. It's suppose to be a 79mm which is 3.11"
In a 3" tube you'll run a tad richer and then can dial in the MAF as needed. And you probably want to adjust the top and bottom cells for 0 volts and 16 volts if using GUFx

PS - the curve is not much more then your Pro M 19#. Would recommend a bigger tube like decipha said if you can fit it.

[garyd85gt]

Thank you so much !!!! Now I have a starting point...

[garyd85gt]

What would transfer be if I move up to 4"??

[decipha]

just multiply the curve by 1.83

[12siko]

The sample port of the MAF stays the same. So if you put the electronics in a different size pipe you just divide the original pipe area into your new pipe area (area=Pi x radius squared). So going from a 3.11” to a 4” is 12.56 sqin divided by 7.59 sqin or a ratio of 1.65. You then multiple you entire MAF curve (air flow) by 1.65 (65% more airflow at a given voltage).

Going from a 3.11” pipe to a 3” is 7.065 sqin divided by 7.59 sqin or a ratio of .93. You then multiple you entire MAF curve (air flow) by .93 (7% less airflow at a given voltage).

Factory MAFs are extremely accurate and I have used this method several times. I recently put a 05 GT MAF in a 5’ pipe and was with 8% using this method. This is useful, as most pipes are OD and you need to use the ID to determine airflow – a 4’pipe is more likely 3 7/8”...

[85GT]

You're on the right track with the area scaling but you need to use actual area between the two.
You neglected to account for the sensor area. Without measuring, I estimate the sensor to be about 10mm by 50mm.

With this factored in, your 1.654 becomes 1.728

The remain factor I have still to get my hand wrapped around is the affect of sensor itself.

[garyd85gt]

NOOOO,not MATH !!!! LOL, not my best subject...

[12siko]

The area of the electronics unit is a constant (the area does not change) so that area does not figure into the equation. This method is the same used by the HPX MAFs, as the sensor comes with a spreadsheet and you enter pipe size to generate the MAF table. Be warned thou, just like with any other large MAF you lose low end resolution as the pipe size increases.

My 5" setup practically doesn’t read at idle, but on the dyno it was dead on above 3K with no adjustments. I only went with a large intake pipe because the root style superchargers don't like to suck...I had to use the low flow Ford MAF as the HPX flow was way to high (7360 kghr!!!!!).

Most of the late model (05 up) Fords (Crown Vic, Trucks, Vans, Mustang GT and V6...) use the same sensor, it’s just mounted in a different size tube. I've used truck and crown vic sensors, you can pick um up on ebay for under 20 bucks! You can buy the GM aluminum mount that works for HPX and 05 up ford slot type MAF, GM part # 19166574, at Summit Racing for around $12.

attached is a xls to help in the calculations. I’ve been wanting to build a spreadsheet and this post forced me to go ahead and do it.

[85GT]

The area of the electronics unit is a constant (the area does not change) so that area does not figure into the equation. This method is the same used by the HPX MAFs, as the sensor comes with a spreadsheet and you enter pipe size to generate the MAF table. Be warned thou, just like with any other large MAF you lose low end resolution as the pipe size increases.

Agree it is constant. But, don't understand why you don't think it matters in the equation...

Yup, the HPX do it the same way. And, I don't think their curves are quite right either. ;)

[garyd85gt]

anybody know what size tube the GT500 has the sensor in???

[bender460]

You're on the right track with the area scaling but you need to use actual area between the two.
You neglected to account for the sensor area. Without measuring, I estimate the sensor to be about 10mm by 50mm.

With this factored in, your 1.654 becomes 1.728

The remain factor I have still to get my hand wrapped around is the affect of sensor itself.

Tube area versus sensor area would not be constant. That makes sense. So the bigger the tube area from stock the leaner things get?

[12siko]

The area of the electronics unit is a constant (the area does not change) so that area does not figure into the equation. This method is the same used by the HPX MAFs, as the sensor comes with a spreadsheet and you enter pipe size to generate the MAF table. Be warned thou, just like with any other large MAF you lose low end resolution as the pipe size increases.

Agree it is constant. But, don't understand why you don't think it matters in the equation...

Yup, the HPX do it the same way. And, I don't think their curves are quite right either. ;)

I agree the body of the MAF will block less air (percentage wise) as the tubing size increases. But you are talking a small percentage (around 5% for the 3” to 3.5” example). In my real world experience, this will still be closer than any of the standard style MAFs I’ tried to tune…

[85GT]

You're on the right track with the area scaling but you need to use actual area between the two.
You neglected to account for the sensor area. Without measuring, I estimate the sensor to be about 10mm by 50mm.

With this factored in, your 1.654 becomes 1.728

The remain factor I have still to get my hand wrapped around is the affect of sensor itself.

Tube area versus sensor area would not be constant. That makes sense. So the bigger the tube area from stock the leaner things get?

BINGO!

[85GT]

The area of the electronics unit is a constant (the area does not change) so that area does not figure into the equation. This method is the same used by the HPX MAFs, as the sensor comes with a spreadsheet and you enter pipe size to generate the MAF table. Be warned thou, just like with any other large MAF you lose low end resolution as the pipe size increases.

Agree it is constant. But, don't understand why you don't think it matters in the equation...

Yup, the HPX do it the same way. And, I don't think their curves are quite right either. ;)

I agree the body of the MAF will block less air (percentage wise) as the tubing size increases. But you are talking a small percentage (around 5% for the 3” to 3.5” example). In my real world experience, this will still be closer than any of the standard style MAFs I’ tried to tune…

It's that few percent we're trying to nail down. Why not start closer.

If it were a perfect sensor that offered zero impedance to the air flow, then a straight area to area ratio would be exactly right, if you assume uniform airflow across the entire area. Which it isn't either.

[bender460]

If some one can measure there sensor I'll see what I can come up with. Here is a spread sheet I created some time back. I'm sure I can come up with something.

[85GT]

If some one can measure there sensor I'll see what I can come up with. Here is a spread sheet I created some time back. I'm sure I can come up with something.

If someone doesn't have it, I'll get it tomorrow.

We talked about your spreadsheet a while back.
The area of the sensor affects the area to area ratio, the first order of the equation. Still need to quantify the part of the equation for the non idea sensor. My degree didn't go that deep into this subject :). I'll see if some of the aero engineers at work can point us in the right direction.

[12siko]

Here’s a revised spreadsheet that takes in account the approximate area of the sensor. I say approximate as it has the hole in it but it’s not straight through. In this revision the area of the sensor is subtracted from each total area before the ratio is figured. You can comare this to the earlier spreadsheet, if interested.

[85GT]

Here’s a revised spreadsheet that takes in account the approximate area of the sensor. I say approximate as it has the hole in it but it’s not straight through. In this revision the area of the sensor is subtracted from each total area before the ratio is figured. You can comare this to the earlier spreadsheet, if interested.

Yes, very good! That's how I start.

Your approximation of the sensor is right in the ball park of about what I guessed. I used 10mm x 50mm as I'm using mm as the original curve is from a 79mm stock mustang and my VMP housing is 88mm I'm working with currently. If we put in that original 4", our numbers a pretty close from the earlier posts.

This takes care of actual flow area between the two different diameters.

The part that needs to be tackled next it the sensor sample area to actual flow area ratio. That sensor opening is, from memory, about maybe 1/8" by 3/8".

If that opening grew at the same ratio as the actual flow area grew, we'd be golden and done. But it doesn't.

This ratio gets higher with a bigger housing which means that the sensor is actually sampling less a percentage of the actual flow area. It reads 'leaner' because of this, as bender460 correctly stated.
Or if the housing got very small, it would be sampling much more of the airflow. This needs to be addressed.

What I tried for the 88mm housing, I took the stock housing ratio and divided it by the new housing ratio. I then multiplied the curve by that. This is the part I'm not sure is that simple. But...

This got my curve very very close to a 90mm LMAF. Which worked very well. When I used the curve from bender's spreadsheet, it was leaving me very lean. His is in principle the same type of calculation as ours.

Thoughts?

[decipha]

aww fuck man just plug in some damn numbers and hope for the best, good enough for government work

[85GT]

LOL, I was starting to think the same afterwords. Maybe the first scaling is enough, then tune.

[12siko]

The truth is, there ain’t no magic formula. Due to clocking, location relative to bends and other variables (that I don’t even know or understand), all MAFs table will require tweaking. As long as we are close enough not to do damage in the process is good enough for me.

[bender460]

[garyd85gt]

Well, that was interesting reading-....So would I be better off putting the sensor in the 4" Intake tube as a draw through, as opposed to placing it in the 3" discharge tube as a blow through, so that I gain a higher kg/hr flow rate??

[decipha]

im one for size :)

[garyd85gt]

LOL

[stout95]

I have the pmas hpx blow through 3 inch. i have the cd and maf transfers looking for them ill post as soon as i find it. but with your mods i dont see you ever pegging it. i run it in my 95 turbo car and have not pegged it.

[garyd85gt]

I have the pmas hpx blow through 3 inch. i have the cd and maf transfers looking for them ill post as soon as i find it. but with your mods i dont see you ever pegging it. i run it in my 95 turbo car and have not pegged it.

From what I understand, the HPX is "calibrated" in some way to provide a higher reading MAF kg/hr limit....The stock Ford 05 MAF in 3" tube pegs at about 1007 kg/hr, where the HPX is Wayyyy higher

[awdgsx]

Sorry I'm soo late to the party. this is the ACTUAL flow data from the slot sensor in the 05 mustang airbox. I see some of you are doing some curve fitting.. you should be using an 8th or 9th order.

Ps. this is Nick from PMAS

""volts flow KG/HR
0.311 4.83
0.474 9.28
0.564 11.09
0.656 13.08
0.719 14.89
0.792 17.28
0.847 19.09
0.918 21.88
0.984 24.52
1.088 29.34
1.175 33.8
1.274 39.42
1.386 46.66
1.486 53.87
1.604 62.92
1.74 74.09
1.877 85.88
2.022 100.38
2.133 116.63
2.269 135.55
2.423 159.02
2.577 185.44
2.735 216.32
2.904 252.66
3.07 293.72
3.249 342.42
3.44 400.41
3.64 466.52
3.856 544.7
4.079 635.91
4.308 742.09
4.542 864.63
4.713 963.29

[Paulie]

Do you have actual flow data for the stock 05 sensor in a 4" housing?