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Just a note. I sent an email to Doug Gill at SCCA and received a reply with his opinion. Can't fault his logic.

You can not trim the diffuser for an exhaust on the Elise and be legal in stock class. You could do this if it came that way from England as a factory option. But not as a dealer option.
 

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Randy, just a FYI but I'm having a shop here in atlanta make me a catback straight pipe. It is going to cost around 100 out of mild steel or 150ish out of stainless. You do not need to alter the difuser. I'm only having them make 1, but I'm sure any decent muffler/performance shop could make one pretty easy.
 

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On SCCA legality...this is primarily an issue if you are competing Nationally, trying for a National title and so forth. Or on an SCCA board, so you must be squeaky clean.

Trimming an 1/8 inch from the diffuser exhaust port is sorta like trimming a bit of plastic edge from a bumper cover so you can fit the exact exhaust tip whose appearance you prefer without getting some ugly plastic burns. In local autocross something like this would never be protested and provides no performance benefit whatsoever, and is not cheating or whatever. Some National guys would freak out if you remove those *nasty* looking air bag warning stickers from the sunvisors for example. I mean, they are supposed to be there and all that. So to avoid weanie protest bait National folks need to be very careful about things like this.

I think I have removed about 7-8 stickers from the car so far. I think it looks purer and is less distracting not having them around. I also remove those tags from pillows and mattresses. You know... the ones that say do not remove under penalty of law.
 

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A straight pipe may reduce your power and torque. A fellow Miata driver dynoed his car to determine whether a straight pipe was worth it, and the car lost power and torque at all speeds with the muffler removed, compared to the Enthuza sports muffler.

Randy, you could get the Stage 2 and weld on tips that fit through the stock holes.

Stan, I don't think that airbag warning stickers are protestable. That's really a C&C item (for the comfort of not having to see an ugly yellow sticker in your field of view at all times), and it doesn't really remove weight or increase performance. There are things that SCCA people get pretty anal about, but warning labels is a bit of an exaggeration.
 

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>>>There are things that SCCA people get pretty anal about, but warning labels is a bit of an exxageration.<<<

I've heard all sorts of stories. I once sold a set of black plastic liner / water shield thingeys weighing about 3 ounces or so that go behind the headlights on old BMWs. The buyer was afraid of a protest and was happy to purchase them as they are apparently NLA from the Dealer. Another BMW at Nationals last year was missing the little cover for the fuse box, and was being questioned about it while sweating bullets. Turns out he finished mid pack and was not protested. It's a shame that some folks who got beaten by a fraction of a second start focussing on minutiae to protest. On older cars this can be a concern as some of this stuff is hard to find or, for that matter, it can be difficult to even realize that something is missing in the first place. Some of this sort of stuff may not lead to a DQ but it can sure burst your having-fun-bubble in a hurry.
 

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There was an S2000 at nationals last year that unhooked their rear view mirror and put it in the arm rest holder. He got protested and was DSQ.


As far as the straight pipe goes after it gets finished if backpressure is an issue and it makes less HP they can always adjust that with a plate at the exhaust exit. The only reason I'm talking about this is I don't particularly want to spend alot of money on a catback nor do I want to alter my rear difuser in anyway. I don't think any catback is going to really make a difference as far as HP goes. My main goal is to have the loudest exhaust I can, so I can hear it through my helmet. I really helps me know where I am in the RPM range without looking at the guages.
 

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Discussion Starter #7
del105 said:
I really helps me know where I am in the RPM range without looking at the guages.
Agreed, but I am finding this is not a problem with the stock exhaust (as it is on other cars I have driven).

I am now mainly trying to shave off weight and yet stay within the rules and not be so loud that the car is a pain to drive in my neighborhood... and not lose power.

Removing a rear view mirror is indeed a bad thing at Nationals. As is removing the silly sun visors (Miatas have been protested for this IIRC).

Rules are rules at the serious level of Nationals. And always keep in mind that it's not that it's all that much of an advantage to not have 3 ounces of plastic...but it's a slippery slope. If it was legal to remove a fuse box cover, than why not an entire shroud? And if the shroud was legal, why not 20 pounds of bodywork?

But as Stan noted, locally this is not going to be an issue. I started this thread (and should have noted that) for National drivers. Locally or regionally, most people will not care. But at Nationals, there is a lot riding on the line. People invest thousands of dollars and a year of time. It can make them crazy. :)

It should also be noted that even at Nationals, a very large percentage of people will not file a weenie protest. But it only takes one.
 

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Not to mention:

Tire sponsorship - potentially worth thousands of dollars - and manufacturer prize money.

Ego might factor in this in some small way also...
 

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Are you allowed to modify the Stage II and replace the large tips with smaller ones that will fit through the stock diffuser?
 

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del105 said:
There was an S2000 at nationals last year that unhooked their rear view mirror and put it in the arm rest holder. He got protested and was DSQ.
There is a valid reason for this protest. The mirror, especially for taller drivers, is in the line of sight in an S2000. I'm only 5'10", it doesn't bother me. But my co-driver, who is 6'1, has an issue with it, and moves the mirror as far as possible to minimize it's cross-section in his field of view. It was, in this case, an advantage to remove the mirror...
 

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>>>There is a valid reason for this protest. The mirror, especially for taller drivers, is in the line of sight in an S2000. I'm only 5'10", it doesn't bother me. But my co-driver, who is 6'1, has an issue with it, and moves the mirror as far as possible to minimize it's cross-section in his field of view. It was, in this case, an advantage to remove the mirror...<<<

Yes but wasn't it also a vendetta protest between two guys who had a Hatfield / McCoy thing going?
 

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Always keep in mind not to worry too much about what is protested at the national level. But it is good to understand it and recognize it, should you run nationally some day... or if you run against some wheenie.

And if things like this bother anyone... just run in Street Prepared or Prepared classes. If you are there to have fun, you can have as much fun, if not more, with those looser rules.
 

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>>>Except I don't think a modified diffuser would be SP legal either. Probably ok for Prepared though...<<<

You know...this is really very comparable to someone with a normal performance type exhaust that comes too close to part of a urethane bumper cover. So they trim a bit off so it won't get a burn mark on it and it's not even visible unless you get down on your knees next to two otherwise identical cars. Many with Borlas on M3s have done something like this although that one doesn't burn but it can rub though. Around here noone would protest something like that. It's not a performance mod...it's just weenie protest bait.
 

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Trimming the diffuser allows you to use an exhaust that you couldn't otherwise install. Since an exhaust is clearly a performance part, trimming the diffuser gave you an illegal advantage.

Reminds me very much of the protest against Hoppe at Nationals this year.
 

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As explained to me by King Howie....

If I allowed you to trim a little to install your exhaust, the next guy can trim a little more. And then someone trims a hole directly in the side of his Porsche and has the exhaust exit out thru a pipe. You either allow it, or not. And not serves the membership better.

I can't argue with that.
 

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>>>Trimming the diffuser allows you to use an exhaust that you couldn't otherwise install. Since an exhaust is clearly a performance part, trimming the diffuser gave you an illegal advantage. <<<

Well sort of...the OE exhaust is already quite good performance-wise. And the Stage 2 tips do not affect it's output. It would only look different if smaller tips were installed on it They are not necessary for the Elise to act like it acts with a Stage 2. For SCCA purposes a 5-6 pound Ti or inconel setup would work well and there is plenty of room in the stock diffuser opening to allow any usefully sized tips to pass though. The Stage 2 mostly cuts weights and adds sound quality factors which some subjectively prefer. I have not seen a dyno test of it. I did dyno my car with it but don't have a before test..maybe someone else will dyno on a Mustang as I did so we can at least compare the shape of the curves. On the Mustang my output peaked at 8000 which is higher in RPMS than stock. If the exhaust only helps the extreme top end (and not by much if at all), it's useless for autocross anyway, especially if any low / mid drop off accompanies it.
 
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