Quote Originally Posted by anthony1k View Post
I don't see any references to AFM in STU. Does that mean that they can be replaced with an aftermarket MAF?
Yes, they can. Or even removed entirely. Or so I'm told.

Here's where the fun begins.

In IT parlance, "metering" means "measuring"; here's how the IT regs words it:

"All air must also pass through the stock air metering device, eg MAF, or AFM, etc. if so equipped."

So in that case the AFM has to be there, be stock, and air must pass through it.

However, the applicable STU rule states:

"All cars shall use the installed engine’s stock air metering device (e.g., throttle body) and intake manifold, unless noted otherwise."

In that context, "metering" means "restricting", as in a device intentional to meter - or restrict - the flow of air at the command of the driver. Now, it has always been my understanding that the word "meter" when used as a verb describes the process of measuring something; e.g., I am "metering" the cost of postage as the letters go through the system to see how much money we're spending. It's to that context that the IT rules refer. However, I am told that the STAC intends the word "metering" in the context of STx to mean what I describe above; e.g., I am "metering" (restricting) the volume of letters that are flowing through the system so that we do not exceed the available postage budget.

So, to my personal understanding as a competitor, AFMs can be replaced or removed in STx, but I suggest this might be a good letter for someone to submit to the STAC for discussion/verification/clarification.

GA