Production Light Exhaust

[XXL]

With about 10 days left before we need to leave for Idaho, and a car that is just getting the interior painted tomorrow. I'm wondering about what to do about the exhaust system. Here's what I'm thinking, tuck it up high but not too high, stainless steel cat, and a Supertrapp 4" muffler. Move the cat towards the rear near the muffler. My question is should the exhaust pipe be made in 2 1/4" or 2 1/2"? Any helpful advise?

[KevinWelker]

If I remember correctly you've got a turbo, so I would go as big as you can. And would likely just put the cat right at the bumper and not do a muffler at all. Try it that way, and if you don't like it, move the cat up just enough to fit the supertrap.

Yes, tuck it up by the driveshaft as much as you can.

[XXL]

Thanks Kevin,
It's a non turbo 2.5 RS. I'm also looking at Megan racing muffler, but you still think that I can eliminate the muffler all togeather? That would save some money and weight but will it pass a sound test?

[KevinWelker]

sound test? are you running RA national events? Otherwise find out about sound tests at the rallys you plan to run. I have not run a rally yet that actually sound tests. On our open light car we just use a straight pipe in place of the muffler. OEM from the engine back though, so the restricive stock cats make it quieter, but it's still loud and sounds awesome.

[XXL]

Getting ready for Idaho Rally its a NASA national and my first rally. If they don't test for sound then I think I'll try the cat only option. Production class rules requires the stock header but open past there with the exception of it must have a cat and pass the sound check.

[KevinWelker]

PM or email Dick Rockrohr, he is the organizer for Idaho. Great guy and he will give you the straight story if you are honest & up front with him. His username on specialstage is BUELLRACER1

There's lots of rules in them there books, not all of them are enforced. Figuring out which are and which are not is part of the fun and what you can learn from veterans, all you have to do is ask.

[UP2MTNS]

I've never seen any techs do a sound test at any of the events I've run. I've run Idaho two times now; this year will be my first driving my car :headbang:

see you there.

[409industries]

Are you asking about the rules for Open Light?

There aren't any light / heavy designations for Production class AFAIK.

[A1337STI]

Prescott, a USRC National Did do sound testing i think in 09, but it might have been 08.

You should build your car to comply with the rules whether you feel they are being enforced or not.

It will be a lot of fun to have an overly loud exhaust ... But your car might generate a lot of complaints that will ultimately get taken out on the rally organizer (not cool)


The maximum permitted noise level from the exhaust system shall be
86 db (A scale) with the engine idling at 3500 RPM, measured from a
distance of 50 feet in an area 45 degrees either side from the
center-line of the exhaust outlet. The test shall be on level ground and
be free from any obstructions.


86 DBs at a 3500 Idle from 50 feet away is Pretty damn loud.

Also if you have any intercom issues you will be hating a loud exhaust (ask me how i know!!! LOL) a Quiet exhaust is a performance benefit if your intercom goes out.

I'm running a hi flow cat, in the factory position, along with an STI muffler. my car isn't much louder than a stock wrx. Maybe at some point i'll get a turn down made for it , just so i can do some testing to see if i lose anything from being quiet.


Also Organizers have to deal with noise complaints from time to time, no reason to give people more things to complain about.


Lastly , Never purposefully Break the rules because you don't think they are being enforced.

Its one thing to accidentally violate a rule. but please don't set out to break them, even if you are relatively certain you won't get caught.
Its just super lame!


Production class you have to keep the factory exhaust manifold, any Open class headers are free. in either class you can make a custom exhaust After the exhaust manifold.
:)

and the Cat as your Muffler does seem to be all the rage these days!

[kturner]

RA did a sound check at STPR this past weekend. We passed at 81 dB at the RA 20" :-).... then we tore a big hole in the exhaust. Guess which one was better during transits?

[A1337STI]

BTW a harley davidson exhaust is about 90 Dbs, and it takes about a 3 DB difference for people to be able to notice a loudness difference.

So if a harley Davidson is noticeably louder than your exhaust(as in people would point to the bike as being louder) you should be fine. If some how you make something where you drown out Harleys, you have a problem. lol

[hoche]

I've had soundchecks done at several events, but I think they were all RA Nationals.

For what it's worth, I hear NNR will be doing soundchecks on any turbo-charged Subarus missing more than half a bumper.

[UP2MTNS]

I've had soundchecks done at several events, but I think they were all RA Nationals.

For what it's worth, I hear NNR will be doing soundchecks on any turbo-charged Subarus missing more than half a bumper.

Haw-haw....And that's why I still have a resonator in my mid-pipe, hoche, I know u like to pick on me ;)
My car is relatively quiet, especially at idle. The cat actually reduces sound quite a bit.

My car w/just the catless downpipe is friggin loud.....like, bill holmes' truck loud. It's awesome....I've got it on video somewhere.

[A1337STI]

My car w/just the catless downpipe is friggin loud.....like, bill holmes' truck loud. It's awesome....I've got it on video somewhere.

Bill's truck sounds great, along with Camero Jims' uh .. .Camero. (neither is harley loud)

If you like loud, go for it, it is your car, but with in reason :headbang: 86 at 50 feet is actually pretty damn loud. hehe

[XXL]

Thanks everyone for your input, maybe I wasn't clear on my original question so I'll try again. I would like to know what size of exhaust pipe to use 2 1/4" or 2 1/2" on a stock header production car 2.5L Impreza RS. I'm thinking of using either a Megan or Supertrapp muffler along with the stainless cat.
By the way, there's not even going to be a production light class at Idaho so we will either be in the Production GT or Open Lights. I'm thinking Open Light, but either way were going to learn, have fun and hopefully be able to drive the car onto the trailer when were finished.

[biggreen96]

The motoIQ guys say 2100cc-2500cc motors- 2.25 inch. Plus it would be that much easier to get tucked up out of the way.