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Old 08-08-2007, 10:09 AM   #1
thummel26
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2004 STi
WR Blue

Default New Cold Air Intake idea

So, here i am mulling over my MAF table (got a CAI), never satisifed. Being an engineer i start thinking there has GOT to be a hardware fix, instead of constantly fine tuning all of the scaling. So, here is an idea:

-the MAF sensor is actually an air VELOCITY sensor
-MAF is based on the VELOCITY of the air flowing through an orifice (pipe) of a fixed diameter.
-the MAF scaling table translates the velocity value into an air flow value, this, once the math is done, is a non-linear relationship.
-The reason why we always have to tune for an intake is because the diameter of the pipe has changed from stock.
-so why not use the stock diameter pipe for the MAF housing section of the intake?

The idea is simply, i dont want to say hack job, but u do have to use a hacksaw. Cut out the MAF housing from the stock intake system, and cut out, the same length, the section of the CAI where the MAF is placed. Simply use silicone couplers and reaplce the CAI maf housing, with the stock maf housing. The length of the housing that should be removied should be 2-3 diameters of the STOCK MAF housing. ONce this is done use the stock MAF table and u should have peice of mind, while still gett'n that sweet, sweet air.....
keep in mind that the only engine mods I have is the CAI and catless TB. Tuning using enginuity.
I havnt done this mod yet, but i plan on it at some point int he next few days when i get some time. Let me know what u guys think....


Tom
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Old 08-08-2007, 10:54 AM   #2
bren wrx
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'10 E92 M3 M-DCT
brentuning.com/blog

Default

its already been done, being an engineer you maybe should have considered the velocity stack in the stock air box's role in proper maf readings and the flow characteristics of the open element filter in the piping before causing turbulence. may want to go back to the drawing board.
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Old 08-08-2007, 11:25 AM   #3
djpast
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Just an FYI, Buchurs intake uses the same size piping for the maf section as stock.

The ebay knock off of their intake is the exact same. I am running the ebay intake with NO changes to my maf scaling or tables and my ST2 tune is spot on. with my fuel trims nearly dead on.
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Old 08-08-2007, 02:09 PM   #4
thummel26
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cool, ill look at that can i get pics of that intake? thanks. i didnt know if it has been done beofre thats y i posted. And yes, i did consider the velocity stack, think about what a velocity stack is. It is merley a trumpet which trades air pressure for velocity. there are pressure compensation tables, which yes u CAN compansate for that, however, since the diameter change that forms the velocity stack is much less than the diameter of the pipe, for the purposes of raod tuning this can assumed to be negligible. since the we are measureing the velocity right before it enters the turbo inlet pipe, the effects of the velocity stack is a measured, not calibrated value.
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Old 08-08-2007, 02:28 PM   #5
djpast
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Old 08-09-2007, 10:42 AM   #6
thummel26
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yeah that looks EXACTLY like mine. Hmmm i seem to be running into AFR issues tho. my wideband is saying im running way rich in the top end...more then what the table calls for of course...like its running 10.2 when i want a 10.9. What kind of AFR correction learning values are u getting?
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Old 08-09-2007, 11:00 AM   #7
djpast
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~ 0 to -0.78 usually.
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