What exhaust/mufflers are you guys running for tracks like Laguna which have dB limits? I am building a Pro 7 car and looking at exhaust systems but want to make sure that they will stay under the dB limit.
Any suggestions?

Thanks,
Mark

 

I'm curious myself.. My car runs a Magnaflow muffler, 2 1/2" piping from the header all the way back.. I left a bit of length on the back so if I needed to add additional muffling or a turn down, I could.. But I have no idea if this will pass DB at Laguna.. Fortunately SCCA has rather high DB limits (101 and 103, depending on the time of day), but NASA gets stuck with 90-92db..

PaulC

 

I would guess dual N1's would be out of the question then

I love that left right at the top of the hill. I miss running the BMW's I used to race out there.

 

On our first gen IT7 car we run a 2 into one header going to a 3 inch oval NASCAR style pipe to a DynoMax muffler with 3" in/out. We use a 90 deg turn down to direct the sound away from the sound detection device.

If the turn down isn't enough just make sure you lift when you go by sound check. I have a friend running no muffler and dumping the exhaust out right in front of the pass side rear tire. he has never failed sound. That car is way Louder than ours.

BTW, sound limit is 98db at Road Atlanta.


MIke

 

The problem with lifting for the sound booth at Laguna is that it's placed just before a fairly big hill, and a huge acceleration zone going up to the 'screw.. Lift there, and you pay..

I can do it with the Trans Am, I got the torque to recover, but we'll see with the RX-7..

Yeah, the sound limit at Laguna is a joke... I heard that one time neighbors called up the city complaining about a lot of exhaust noise from the track.. The city called the track, only to find out there was NOTHING going on at the track, the people were hearing noise from Hwy 68..

#@%*

PaulC

 

there building houses right next to the track now too, how long is it going to take before they complain?
on the pro7 cars we used to run 1 of those round dynomax cans, but those have the stock manifold so they aent as loud to start

mike

 

Why the hell would anyone move next to a racce track? Thats like moveing next to the airport and bitching about the planes making noise.

Your right. You should not lift where your sound booth is. That sucks.
Lucky for us, our sound check is at the end of a fairly long straight. You can get away with lifting to maybe half throttle at Road Atlanta if you need to. But luckly we don't need to.

The best trick I know is get that 90 deg turn down and face it away from the sound booth.

Good luck,
Mike

 

welcome to california!

mike

 

nothing wrong with moving next to a race track especially one as nice as Laguna Seca. problem is the people who are moving there aren't aware or don't realise the sounds that are generated at the track. the area used to be a naval target range so the track should be a alot quieter. unfortunately for laguna lifting and turn downs are not enough. recently they have been using a roving sound meter as well as the "shack". A near stock exhaust is needed for RX7's. I have seen 3rd gens black flagged because the BOV was over the limit. 90db is very low. I used two very restrictive turbo type mufflers on our old Porsche 944 race car to get it low enough. for the turbo cars a large straight through muffler should be enough. the ported N/A cars are going to need more though maybe the turn down and a supertrap. unfortunately this is going to cost HP

 

Hey, I've heard nothing but good things about Pro 7's,... super economical, good fun, competitive field. I am in envy. Check mazdamotorsports.com, this is the factory support site. They'll most likely have a spec exhaust they run that Db levels have been researched on etc.

 

On my 12app that i run on the street i use a 37" long round muffler that is 2 and 1/2 inch piping through it. It is a diesel stack muffler but its steel packed and it works realy well. Long but effective, and the packing has held up pretty good. I got it from NAPA, and at $50 you cant beat it.

CJG

 

Borla XR-1's are the way to go. They are suppose to drop dB levels by 8dB or more per muffler, and this is a straight through design.