AFM in STU

anthony1k

anthony1k

New member
I don't see any references to AFM in STU. Does that mean that they can be replaced with an aftermarket MAF?
TIA
 
Since ECUs are free and there's no mention of it elsewhere, I don't see any reason why not.
the only stipulation is the STU rules state the engine must use it's factory supplied "air metering device, e.g. throttle body."
some tech people could construe air metering to be a MAF, some could consider it a throttle body/carb butterfly.
 
anthony1k said:
I don't see any references to AFM in STU. Does that mean that they can be replaced with an aftermarket MAF?
Click to expand...
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
 
Greg Amy said:
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
Click to expand...

I agree with your understanding and definitely this is something that needs to be spelled out in the rules. In cars like mine it makes a HUGE difference. I'll try to send out a letter to STAC this weekend.
 
Wow, I would have assumed the answer would be 'no'. nearly identical rules with very different outcomes, or intents.
It's an odd 'place' they wind up with the STx rule....Half the intake passage is "free", but half is not. In some cars, you win, some you lose....

Seems to me that the formula classes car by displacement to weight, which is an assumed HP basis. Yet the rules leave in place HP restricting items like Airflow metering devices, intake manifolds, and heads. That eliminates a lot of cars from being competitive as the items that prevent the car from reaching the "theoretical golden number" are left in place oon many. Removing one aspect of that is good, I guess, because it might increase the number of cars that have a chance at hitting the "theoretical golden number". But it does make it important to have intimate knowledge of an engines limitations going in. (Not much different than picking a car for any class I guess)
 
lateapex911 said:
Seems to me that the formula classes car by displacement to weight, which is an assumed HP basis.
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Actually, while you're inferentially correct ("displacement to weight, with assumed HP") I think you're off the mark in that while you are assuming it's based off of stock output/displacement, the category is actually assuming relatively-equal modified (resulting) output/displacement. Removing non-standard restrictions such as varying AFMs would tend to equalize that.

Get past that IT mindset and it "kinda" makes more sense...ain't sayin' you'll agree, just sayin'... - GA

On edit: Actually, in re-reading your response, I think you're saying the same thing. Were one to take that concept further, then the category could remove other reasonable non-standard restrictions, such as intake manifolds and equalizing throttle bodies...in the end, you'll never make different engines with equal output no matter how hard you try, but the variables are minimized.
 
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while removing the stock "measuring" devices is a good thing for parity, the variation of intakes, TBs, head, and overall engine designs will certainly yield big winners and big loosers.

this is why I am a big fan of the alternate minimum weight for known over/under performing engines. the tables in STU are a good start, but don't address swaps (kind of a big deal in STx). GTL would be a better place to look for the type of list I am thinking of where allowed mods are all equal but the toyoter 4A-GE would be, say 1900 lbs in STL vs. the honda B16 (same bore, stroke, displacement) at a higher 2200. obviously, this would need some run-time to develope and can't just be thrown out there with any hope of success. but the idea I think has merit. it would make the "forbidden" motors legal, but heavy, and the stuff that hasn't got a prayer currently a potentially competitive mill given an appropriate chassis.

agreed in that the term "metering" needs to be rethaught. a CRB ruling, new term for the alternate definition, and having BOTH in the glossary in the GCR would be a wise decision.
 
I suggest a better wording of the rule might be:

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

GA
 
carbs meter fuel AND air and are known to have metering screws which do not measure anything, they control the flow...

They used an example to avert confusion and there is still an issue?

meter and measure are not one and the same...

Maybe the IT guys misused the word and caused the confusion in the first place? :shrug:
 
CRallo said:
carbs meter fuel AND air and are known to have metering screws which do not measure anything, they control the flow...

They used an example to avert confusion and there is still an issue?

meter and measure are not one and the same...

Maybe the IT guys misused the word and caused the confusion in the first place? :shrug:
Click to expand...

http://www.neo.ne.gov/phase1/glossary.htm

Metering:
The process and methods of utilizing devices to measure the amount and direction of electrical energy flow; particularly for end-use.
 
Greg Amy said:
I suggest a better wording of the rule might be:

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

GA
Click to expand...

Request to adapt the wording above was sent to the CRB.

GA, thank you for the suggestion.
 
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