[Rootus]

Originally Posted by jaygoesfast

I pegged the stock MAF with my GT35R around 20psi. (probably around 400whp).

At 25psi and maybe 450ish whp it looks like I would be very close to pegging the MAF in the APS 70mm CAI.

Sounds like the 70mm APS would be a good option then, for what I'm planning at least. The BigMAF is out of consideration because of driveability concerns. I'm betting the APS doesn't have issues like that.

Dave

[keyser_soze]

Wolfman,
quick quesiton. What kind of turbo you got? The reason I'm asking this is that do you come close @all to near 4.5~5 volt area to know wheather or not your calibration is good up top?

Thanks.

[crystal_Imprezav]

Wolfs on the stock turbo.

[WolfPlayer]

Yea. Stock turbo.

1) I have some updates to this calibration that are not posted yet. I need to get those updates posted.

2) No way am I sure about the upper end of this curve. I will be later on when I get the bigger turbo ... but, for now, it is just a guestimate.

t

[WolfPlayer]

This post has been updated with my latest APS 70mm MAF table and the file is now attached to the post. The old file is still on my site.

t

[stretch]

Your results are interesting. I've worked with Custom Performance Engineering on some of their products, and they calibrate their big maf kits on a flow-bench so there's no guess-work. They built the machine to do it out of what they call a "leaf blower with 32 bits of precision", lol. Anyway, they hook up the stock airbox to the machine, followed by their prototype intake, and software does the rest. The big intake (usually 3 or 3.5 inch, the latter being 89mm!) is calibrated before it ever goes on the car.

Anyway, I mention this because your 16% figure for such a small increase surprises me. IIRC, the jumps I saw on their equipment were not much larger than that despite running much larger diameters. Thus, your correction is proportionately much higher than what I would have expected.

I theorized, having never taken fluid dynamics, that this was because the MAF remained near the center of the intake (in stock form), and regardless of intake diameter, the center of the tube will have the fastest flowing air. On the bigger pipe, the MAF can no longer sit dead-center, so the bigger pipes never need a proportional correction. On my own car (then, a Mazda6), it measured a 13-9% change going from a ~2.5" pipe to a 3" pipe- confirmed by dead-on fuel trims. The difference in air speed where the MAF is measuring was never as large as the increase in pipe cross-section area.

Anyway, one thing I can confirm for you is that the amount of correction jumps around a bit at low values, but it stays pretty flat at anything much above idle. You can pretty safely estimate the amount of correction at higher values based on what you're seeing lower.

Hope this helps. Another thing the CP-E guys always did was measure the pressure drop of an intake. It's pretty amazing how much power a MAF can rob simply by being an obstruction- that's why their intake kits (and BigMAF kits in general) work so well. Unfortunately, they sell their intake with their own custom tuner to recalibrate the MAF, which is very unnecessary for Cobb AP owners. Maybe they'll sell it seperately (but with the calibration data), as that's what I hope to run.

[WolfPlayer]

All I know is that my injectors are scaled appropriately (for 730cc injectors) and my intake was tuned on my vehicle and I have basically 0% fuel trims (depending on the weather). If my intake was scaled according to the information you just gave then the injector scalar would be way off for 730cc injectors.

Post their data before making evaluations if you can. IMHO, a 16% increase for a 76mm MAF (3") is ludicrous. It needs to be significantly larger if you want the injector scalar to be appropriate. EcuTek has done something similar. (http://www.ecutek.com/tuning/induction/). In some cases the values are 41% larger. So, I don't feel so bad

t