Please measure the ID of your MAF housing when you get some time...

Christian. · 06-21-2006, 03:49 PM

Would you mind measuring the inside diameters (in milimeters) of your aftermarket intakes. I am compiling a database of the various aftermarket intakes (MAF housings) and setting up an equation that will assist you with the generation of a global Intake Calibration multiplier so that you can more easily start your vehicle when using the StreetTUNER software to make a base calibration. This is what I have thus far...

Global Intake Calibration Multiplier 3.14159265358979 = pi
This calculation should only be used to assist you in the generation of a base map so that you can start your vehicle which has a MAF housing other than stock installed on it. Tuning your Intake Calibration table must be performed after you have started your vehicle. When switching your intake to an aftermarket you can use this multiplier to glabaly modify your Intake Calibration table based on the difference in diameters (surface area) between the two intakes, follow Step 1) below

66.5 Step 1) Enter the inside diameter for your stock MAF housing, choose from below list.
70.0 Step 2) Enter the inside diameter for aftermarket MAF housing.
=
1.0526 Step 3) Your Global Intake Calibration Multiplier
Step 4) Copy (CTRL+C) the data from cell B10 from this worksheet, highlight all of the lower cells in the Intake Calibration table, press the "m" key, then paste (CTRL+V) the copied value into the dialog box asking for a floating point value then press the Enter key.

Surface Area of a Sphere = 4 pi r 2
Intake Diameter Surface Area

66.5 mm ~ ID of stock 2002-2005 WRX MAF housing
66.5 mm ~ ID of stock USDM STi MAF housing
70.0 mm ~ ID of stock 2005+ Legacy GT MAF housing
65.0 mm ~ ID of APS Cold Air Intake System - 65mm, P/N APSWRX-HFA/01
70.0 mm ~ ID of APS Cold Air Intake System - 70mm, P/N APSWRX-HFA/02
~ ID of APS Pod Air Intake System - ??mm, P/N APSWRX-PAC/01

This is all set up in Excel and OpenOffice (freeware) so it has functional formulas and will look better.

Thanks,
Christian.

daemon · 06-21-2006, 04:47 PM

The Apexi short ram has an inner diameter of 70mm. However it also comes with a piece that goes in front of the MAF to direct air towards it. So if you put that in, all bets are off as far a quick diameter based formula.

***JDM-STI*** · 06-21-2006, 06:10 PM

Injen CAI is 65mm and the Perrin big MAF is 76mm.

06-21-2006, 03:49 PM	#1
Christian. STI Driver Car: 01 Subaru WRX STi Sp Fav Mod: Coming Soon Posts: 260 IWSTI Addict since: Aug 2005 Trader Rating: (0)	Please measure the ID of your MAF housing when you get some time... Would you mind measuring the inside diameters (in milimeters) of your aftermarket intakes. I am compiling a database of the various aftermarket intakes (MAF housings) and setting up an equation that will assist you with the generation of a global Intake Calibration multiplier so that you can more easily start your vehicle when using the StreetTUNER software to make a base calibration. This is what I have thus far... Global Intake Calibration Multiplier 3.14159265358979 = pi This calculation should only be used to assist you in the generation of a base map so that you can start your vehicle which has a MAF housing other than stock installed on it. Tuning your Intake Calibration table must be performed after you have started your vehicle. When switching your intake to an aftermarket you can use this multiplier to glabaly modify your Intake Calibration table based on the difference in diameters (surface area) between the two intakes, follow Step 1) below 66.5 Step 1) Enter the inside diameter for your stock MAF housing, choose from below list. 70.0 Step 2) Enter the inside diameter for aftermarket MAF housing. = 1.0526 Step 3) Your Global Intake Calibration Multiplier Step 4) Copy (CTRL+C) the data from cell B10 from this worksheet, highlight all of the lower cells in the Intake Calibration table, press the "m" key, then paste (CTRL+V) the copied value into the dialog box asking for a floating point value then press the Enter key. Surface Area of a Sphere = 4 pi r 2 Intake Diameter Surface Area 66.5 mm ~ ID of stock 2002-2005 WRX MAF housing 66.5 mm ~ ID of stock USDM STi MAF housing 70.0 mm ~ ID of stock 2005+ Legacy GT MAF housing 65.0 mm ~ ID of APS Cold Air Intake System - 65mm, P/N APSWRX-HFA/01 70.0 mm ~ ID of APS Cold Air Intake System - 70mm, P/N APSWRX-HFA/02 ~ ID of APS Pod Air Intake System - ??mm, P/N APSWRX-PAC/01 This is all set up in Excel and OpenOffice (freeware) so it has functional formulas and will look better. Thanks, Christian. This ad is not endorsed by this member. Please register or login to hide this ad.

06-21-2006, 06:10 PM	#3
*JDM-STI* Platinum Member Car: 2005 & 2008 STI Fav Mod: Scott Siegel Tuning!!! :D Location: Columbus, GA Posts: 2,017 IWSTI Addict since: Mar 2005 Trader Rating: (11)	Injen CAI is 65mm and the Perrin big MAF is 76mm. This ad is not endorsed by this member. Please register or login to hide this ad.

New To Site?	Need Help?	More
REGISTER FOR FREE! IWSTI Rules/Signature Rules Create a Member Journal Bookmark IWSTI Tell your friends about IWSTI	Frequently Asked Questions Did you forget your password? Make a suggestion or report a bug Mark Forums Read Contact Us	Member Journals Forum Pictures & Photography Forum GR Series (08+) Marketplace GD Series (03/04-07) Marketplace Hot eBay Deals Forum Beyond Off Topic

06-21-2006, 04:47 PM	#2
daemon The Next Petter Solberg Car: 2004 STi Location: Florida Posts: 894 IWSTI Addict since: Feb 2004 Trader Rating: (0)	The Apexi short ram has an inner diameter of 70mm. However it also comes with a piece that goes in front of the MAF to direct air towards it. So if you put that in, all bets are off as far a quick diameter based formula.