Stock Class Exhaust Regs

[Kurt Rahn]

"Any part of the exhaust system beyond (downstream from) the header/manifold or catalytic converter, if so equipped, may be
substituted or removed provided the system meets the requirements of 3.5 and 3.3.3.B.15. Stainless steel heat exchangers are
permitted only if the physical dimensions and configuration remain unchanged.
<snip>
Removal of a portion of the stock exhaust can be considered a substitution. The resulting cat-back exhaust system is not required
to exit in the stock location. However, the requirements of section 3.3.3.B.15, and 3.5 must still be met."

I read this to mean that you can do whatever passes sound regs as long as it's downstream of the cat(s). Is that the case? Could I run basically a straight pipe after the cat with a supertrapp or something to muffle the sound sufficiently, as long as it exited behind the driver and passed sound? I'm not stuck buying a heavier pre-fab catback system?

[Steve Lepper]

Yes. Anything behing the last stock catalyst (and sub-O2 sensor, if equipped) is fair game. If it met sound, you could run open pipe back until just behind the driver's seat. I've seen some stock class cars where the exhaust is not much more than that with a turn-down at the end... there's a stock class Miata in my shop right now where the entire cat-back exhaust is only about two feet long.

[KJ Christopher]

I believe that "after the cat" is after what ever pipe the cat is welded to. I don't think you can cut an exhaust just behind the cat if the stock system includes, say a 2 foot section after it before the next flange.

[Kurt Rahn]

I believe that "after the cat" is after what ever pipe the cat is welded to. I don't think you can cut an exhaust just behind the cat if the stock system includes, say a 2 foot section after it before the next flange.

Why do you say that? Is there something that you're reading in the rules that I'm not seeing? Not trying to be argumentative, just curious.

[Steve Ekstrand]

I believe that "after the cat" is after what ever pipe the cat is welded to. I don't think you can cut an exhaust just behind the cat if the stock system includes, say a 2 foot section after it before the next flange.

Guess again.

[Will Kalman]

Guys, there's a place where they make these rules and any member is welcome to join in the process.

Simply drive to the midwest in Spetember and bring what you think is legal according to the written rulebook. They'll introduce new words to you that you never saw in the book. Like "Flange" and "Stock Location" or "OE Type". But don't worry about what appears to be a random on-the-fly process, these changes are trustwrothy. In fact the advisory committees are so enamored with the establishment of these new words and concepts, they'll reminisce about them in their meetings for at least four years!

** BONUS: If you attend a National Tour event or a Divisional, they cut you a break on the rule making attendance fee that year! Sweet!

[Sebastian Rios]

Guys, there's a place where they make these rules and any member is welcome to join in the process.

Simply drive to the midwest in Spetember and bring what you think is legal according to the written rulebook. They'll introduce new words to you that you never saw in the book. Like "Flange" and "Stock Location" or "OE Type". But don't worry about what appears to be a random on-the-fly process, these changes are trustwrothy. In fact the advisory committees are so enamored with the establishment of these new words and concepts, they'll reminisce about them in their meetings for at least four years!

** BONUS: If you attend a National Tour event or a Divisional, they cut you a break on the rule making attendance fee that year! Sweet!

But "You're done" being bitter about it right? ;)

J/K Will, I can't imagine how horrible that must have been.

[Will Kalman]

Actually, I can deal with the protest but I didn't like (1) How it came about behind the scenes, and (2) How the protest committee made up rules that day. "Flanges", "bolt-in", "OE Type", and "stock location" were all added to the rule and/or defined on the spot and applied retroactively.

[Steve Ekstrand]

I love the videos of Will's STS performance that sad year. You can clearly hear him going flat or nearly flat in sections the other top cars are coasting through. So, all that low end power must have been a real, wait, this doesn't make any sense....

[Jason Uyeda]

Actually, I can deal with the protest but I didn't like (1) How it came about behind the scenes, and (2) How the protest committee made up rules that day. "Flanges", "bolt-in", "OE Type", and "stock location" were all added to the rule and/or defined on the spot and applied retroactively.

OK, I hate to continue to drag this off-topic and I realize that this is a touchy subject for some, but I have to ask... Will, since you yourself have said that the car was illegal, surely you must feel that the car violated some rule/s that weren't, "made up", right?

[Will Kalman]

OK, I hate to continue to drag this off-topic and I realize that this is a touchy subject for some, but I have to ask... Will, since you yourself have said that the car was illegal, surely you must feel that the car violated some rule/s that weren't, "made up", right?

This snuck through and I didn't see it...

Yes, I accepted that the rule did not allow relocation and that the cat was relocated. Or, I should say, they interpreted the term "stock location" in the strictest sense.

What really bothered me about the protest shed discussions was having it explained to me that they wanted to see flanges in stock flange locations. The word "flange" was nowhere in the rule. Further, the chief of protest told me *directly* that they realized that aftermarket cat "bricks" were often of different dimensions than OE "bricks" and they they'd allow that non-OE-sized brick to be located *anywhere* between those flanges in the stock flange location.

Well, if that isn't "relocation", then I don't know what is. So why did they measure form the Chassis to the brick location on the car in 2005 if it was the almighty flange that defined things? What if we'd installed a big flange right in the stock location with four holes in it for the primaries with the collector after this super flange?

That's what bothers me. They were making up rules and conditions in the protest shed.

The other extreme would have been to say that "OE Type" means three-way catalyst and that "stock location" means "in the same basic area as stock". I can make a clear logical case about a cat moved 9" as being in the "stock location" but I also realized that their strict interpretation is just as valid (if misguided, another topic altogether that they still struggle with).