Passing sound

[quadzjr]

Is there a cheap way to test for sound? I was working out the exhaust system on the ITB MR2 and was thinking on running a 2" hushmaster on it. I don't want to weld it up, then find out that it is completely useless since if it don't pass sound. Since it's first trip will be to RRR I don't want to get kicked out, or worse fined. I want to say it is 103db limit there.

[ITA_honda]

I have a 1990 Honda civic in ITA.
Im running a straight pipe exhaust that exits underneath the car.
no resinator, no muffler.
i average about 80-90db. (depending on the weather ofcourse)

so you will (should) have no problem passing sound WITH or WITHOUT a muffler

[lateapex911]

If you really want to know for sure, get a friend, and go to radio shack. Buy their meter for $70.

Read the GCR, and set up the meter on an appropriate road. Have your friend watch the meter as you drive by. Make sure the meter is set up to the right weighting, distance, height, etc as described in the gcr.

If you don't have a friend, use a lawnchair, some clamps and a video camera to record the pass.

Return the meter if you are so inclined. Buy something else to be nice, like a ton of batteries.

[mc-integra111]

I don't think it is for sure, but I agree, I think you are safe. I recorded a 93, 94, and 95 dB(A) reading at Road America (SCCA regional event) in the rain with a single, flow-through concentric tube resonator of ~8" length and 3" diameter. I think I would still be less than 103 even without the resonator, but I don't want to take it out and find out I have to put it back.

I have confirmed these number myself using my own sound meter. You can get a sound meter from an electronics store (Radio Shack) for like $30-$40. Not too expensive and interesting to have around for various tests for curiosity.

[raceita]

Steve

I run a Mk1 MR-2 (ITB for '09) with about 7' of straight pipe. Pipe routing/exit follows stock routing/exit (complete with 180 degree bend). Don't recall size of pipe, but large-ish. No muffler - no restriction at all. Loudest I've recorded at Blackhawk Farms is 93 db. Where sound is at I think I'm around 5,000 rpm.

Never had any problem at any other track. Road America, Gingerman, Autobahn.

I don't think I could get to 103db no matter what I do!

Steve Burns
#38 Midwestern Council

[Ron Earp]

Steve, I think you're going to be fine at RRR. I run a 260Z with an open pipe - no muffler, and generally am 8 dB below the limit at RRR. Mr. Young's TR8 is one of the loudest cars in the IT group down there and it is always below the limit too, with a very minimal expansion chamber. Ditto Parrish's 240Z which is one of the louder Z cars I've ever heard on track - his is an open pipe like mine, no sound problems.

All three of us have side exit exhausts that exits on the passenger side of the car - they check sound on the driver's side of the car. If you have a rear exit put yourself a little turn tip on there that points to the passenger side of the car.

You'll be ok and come by and have a beer on Sat.

Ron

[joeg]

Don't buy a sound meter. You cannot duplicate readings for all tracks and atmospheric conditions.

If you had a Mazda with a rotary engine you would have problems; otherwise, take a chance.

[tom_sprecher]

I have a Mazda with a rotary engine and I don't have any problems...

Well... at least not related to passing sound checks.

Other stuff, that's another story.

[joeg]

Tom--You telling us you are running w/o any mufflers....YEOWW!

[quadzjr]

The reason why I ask is my current exhaust is a long 4-1 header right into a 3" inlet bullet muffler that has a 3.5" outlet that is approx 12" long and dumps after that dumps. no bends total exhaust system including header primaries is only about 5-6' no bends straight out the back. It is noticbly louder than my racing quad that had to pass sound test at XC and some hare scrambles and it ranges between 98 and 100db.

Unfortunatly the car won't be ready for the regional for the double weekend. I will be working on my buddies Honda ITA car and Honda FP car. I am going to hopefully be breaking the car in at the Darkside DE the following weekend. But it is getting there! My dad is plannign on entering it in at the sebring driver school. We have dubed it the "cheap date". (cheapest way we can muster to get onteh track, and everybody gets a ride)

I will still take you up on the beer however!

[tom_sprecher]

Tom--You telling us you are running w/o any mufflers....YEOWW!

The whole system is 3" with what I guess is some type of expansion chamber fairly close to the header and a big Dynamax muffler tucked up under the rear quarter panel.

So it's not so much a YEOWW as it is a RAPP RAPP RAPP.

[ddewhurst]

On my ITA/7 1st gen with an ISC system (similar to Tom) I was 98/100 db on cool crisp days at the Blackhawk Farm.

[ITA_honda]

The whole system is 3" with what I guess is some type of expansion chamber fairly close to the header and a big Dynamax muffler tucked up under the rear quarter panel.

So it's not so much a YEOWW as it is a RAPP RAPP RAPP.

you've got that right, im just one of those regular Honda boys who hear the sound of loud rotary engines in my sleep after a day at the race track!!! AHHHH!:eek:

LOL

[tom_sprecher]

you've got that right, im just one of those regular Honda boys who hear the sound of loud rotary engines in my sleep after a day at the race track!!! AHHHH!:eek:

LOL

On behalf of all my fellow rotarians I'd like to say we're just glad to prolong the whole race track experience for you and can only hope you will hear our engines for two days after your race.

[CSPRX7]

After hearing the 3 cylinder 2 cycle Saab with straight pipes, people don't complain about my 12A.