MAF rescale

[dieseladdiction23]

Hey guys, Im just about finished with my s475/stock install, and im wondering if im going to have to have the MAF sensor rescaled. The pipe its in now is rougly 4 3/4 inches ID. If so, does anybody know what I need to change the numbers to? I would like to save the $50 bucks for a tune change if possible. Thanks

 

[Fingers]

OEM => 4" or 12.566 sqin
New => 4.75" or 17.721 sqin

1.41 times bigger so air parcel will be moving 71% slower through the tube.

In the MAF table, multiply the grams/sec rate by 1.41

 

[dieseladdiction23]

OEM => 4" or 12.566 sqin
New => 4.75" or 17.721 sqin

1.41 times bigger so air parcel will be moving 71% slower through the tube.

In the MAF table, multiply the grams/sec rate by 1.41

Thanks man :thumb:

 

[dieseladdiction23]

OEM => 4" or 12.566 sqin
New => 4.75" or 17.721 sqin

1.41 times bigger so air parcel will be moving 71% slower through the tube.

In the MAF table, multiply the grams/sec rate by 1.41

Ok, I was just looking, which table do I do this in? Thanks

 

[SickLL7Crenshaw]

B0201

 

[dieseladdiction23]

So if these are my numbers, do I just multiply by 1.41 on all of them. Max is 66.14 so the last couple will be maxed is that ok. Because I drove it today and it is very laggy. Thanks guys
0.00
0.91
1.65
2.27
2.84
3.42
4.03
4.72
5.50
6.40
7.43
8.61
9.94
11.42
13.23
14.88
16.86
19.00
21.32
23.80
26.46
29.29
32.31
35.53
38.94
42.56
46.41
50.48
54.81
59.40
64.27
66.00
66.00

 

[Fingers]

Yes, multiply by 1.41 and "adjust" the values that exceed the table's max. 66.00 in your case is the max.

 

[dieseladdiction23]

Got it adjusted and no more lag, thanks a lot man!!!

 

[dracing70]

OEM => 4" or 12.566 sqin
New => 4.75" or 17.721 sqin

1.41 times bigger so air parcel will be moving 71% slower through the tube.

In the MAF table, multiply the grams/sec rate by 1.41

I have a question. How did u establish the 17.721 quantity. I understand everything else except how u came up with the new base number ???

 

[PACougar]

I have a question. How did u establish the 17.721 quantity. I understand everything else except how u came up with the new base number ???

That's the area of a 4.75" circle. π × r2 You simply calculate the area of the original intake pipe and then compare it to the area of the new pipe.

 

[S Phinney]

Using this math formula does not get MAF back in specs. Even though your truck may not be laggy take a reading of MAF at idle and WOT and you will see where you are. I adjust using percent differences of the readings not pipe size differences. I have tried the pipe difference before too.

Sent from my XT1080 using Tapatalk 2

 

[blue8135]

That's the area of a 4.75" circle. π × r2 You simply calculate the area of the original intake pipe and then compare it to the area of the new pipe.

I'm still confused. By my math, I can get the 12.566=(4*3.1416), but by the same formula 4.75*3.1416 does not equal the 17.721.

 

[dieseladdiction23]

Yea I'm gonna have to try something different, drove it to work today and it was kinda sputtering. So I did some more adjusting and now it has lag again.

 

[S Phinney]

The formula would be radius squared times 3.14. That hives you the 17.71. Just read your MAF at idle and see what you have before making any adjustments.

Sent from my XT1080 using Tapatalk 2

 

[dieseladdiction23]

What should it be at idle?

 

[SickLL7Crenshaw]

You sure it's your maf causing all of this? because there are more tables you have to revise after you put your kit on, not just the maf flow rate table.

 

[dieseladdiction23]

Well when I talked to Rob a couple months ago he said it didn't require a tune change for twins on the lb7.. So i don't know

 

[S Phinney]

What should it be at idle?

It should read 40 give or take a couple grams per sec.

Well when I talked to Rob a couple months ago he said it didn't require a tune change for twins on the lb7.. So i don't know

Anything that effects speed of air into the intake will change MAF readings.


Sent from my XT1080 using Tapatalk 2

 

[dieseladdiction23]

Ok thanks, I will check to see what it is.

 

[dracing70]

Using this math formula does not get MAF back in specs. Even though your truck may not be laggy take a reading of MAF at idle and WOT and you will see where you are. I adjust using percent differences of the readings not pipe size differences. I have tried the pipe difference before too.

Sent from my XT1080 using Tapatalk 2

This is how i base my changes also. I have had very positive results with percentage changes. that is why I was curious about how the new number was established. I never thought to use the formula for cylinder area. But its good to know thanks for the responses.