cai

[Jackpine]

Originally Posted by rednoved

I stand corrected. I had a feeling I would learn a few things on this forum. Does the MAF sensor adjust because the filter is still after the MAF sensor? And it doesn't adjust on a CAI because the filter is before the MAF sensor?

I believe it's more than that, but I haven't studied any of the commercial CAIs beyond looking at pictures of them installed. It appears to me that the whole intake system is replaced up to the throttle body. And, if the sensor is "calibrated" for a specific cross section and air flow characteristic, it's going to "see" something different there. I think to really work properly without a custom tune, the sensor would have to be redesigned a bit for the new environment. (I think it's essentially a heated resistance wire that's cooled by airflow, and that's a pretty simple analogue device, if I'm right).

In the stock setup, the sensor is AFTER the filter, above and behind it on the driver's side, in my truck. All the changes done to the intake in the "Gotts" style mod are way before that location, and are limited to allowing extra air in. By the time airflow reaches the sensor, the flow pattern is the same as always (more or less), but potentially, there's more of it. In a commercial setup, everything is different all the way to the throttle body. The simple sensor can't really account for all the differences.

What I've just said is mostly based on discussions with Bill on this system.

- Jack

[88Racing]

Good points Jack!

Another thing Bill looks at when writing tunes for cai's is that each mfgr places them "generally" in the same area. But when the cai went through r+d the mfg looked for the optimum placement of the maf in it's cai. From what I understand of looking for their specs the placement may differ an inch or two or three from which ever mfg you chose. Thus the flow of air may be different at that area. Also alot of mfgs test at WOT. Find a cai mfg that tests all the way through the rpms and for DDs not for racing.

Lars

[Jackpine]

Thanks for adding to this Lars. I thought perhaps I'd over simplified.

- Jack

[88Racing]

Here's another one I just was reminded about.
Mfgs also use different size intake tubes.
So if mfg a tube is the same size as mfg b tube no adjustments should be needed. But if mfg c has a larger tube than mfg a then the tune may need tweeking. The same would go for the reverse, if mfg c tube and down sizing to mfg a tube.

Lars

[Power Hungry]

Just a quick note...

Larger tube = Leaner
Smaller tube = Richer

So, for example, an AF1 3½" intake is going to run considerably leaner than an AF1 3" and is going to require a bit more tweaking.