I am under the gun sort of..... i paid for an exhaust from a guy in Florida but he hasn't confirmed shipping it yet..... so.. just in case it doesn't get here by next weekend.....

I am running stock header and a test pipe..... i was at 104db and need to be at 102db or less.

Can i stick some loose fiberglass into the test pipe, then drill a hole or two to put pins in to hold it in place?

They said they are going to be VERY strict on the db readings.... you go over once and they warn you....go over twice and you are done......this is all new

Will this affect my a/f ratio?

Thanks for the help..... hopefully my single sided spugen exhaust shows up and I don't have to worry about this, but........

 

Go to home depot etc and get a double walled adjustable stove pipe elbow of a diameter that will fit over your exhaust outlet. Then get a 1/4" bolt longer than the outer diameter of the pipe and use that and 2 nuts to secure the pipe to the exhaust.

Thats what i did. I call it my Sears Point elbow. It brought my 104db down to 102, below the new 103db limit at SP.

ps: Dont use the single walled elbows. Ask me how i know

 

Most organizations next year are going to limit noise to 103db at all tracks.


FYI

 

dave.... all i am running is header - test pipe.... i would need a pipe bigger than the flange to get it to stay on the test pipe.?

did you just turn it away from the side they were measuring the sound?

I am just hoping my exhaust shows up, but will sure try some kind of elbow if it doesn't......

anyone else have any ideas too?

 

check your intake. it frequently makes more noise than the exhaust.

 

i have a PRM intake that is hooked directly up to a pipe/hose that goes through my passenger side headlight.....

i just got rid of my stock box, so I can't even switch it back.

 

Ahhh... For some reason i thought you were running a racing exhaust like the spoon or somesuch. My speed racing (spoon knockoff) exhaust has like a 3 or 4" tip that i attached the elbow to.

 

OK first: where is the measurement being taken? Just one place out on the track? What is the metric, SPL dBA?

Next, what are your noise sources? Probably exhaust and/or inlet dominate. Which one is louder? That's the one that you have to treat.

I would try the elbow-type redirection of the exhaust before I tried to fabricate some sort of muffler. Mufflers are harder to design than you might think (I have designed several for Boeing). Just some directional shielding might give you 3 or so dB off that source (but only in one direction, of course).

As for "limiting the noise to 103 dB at all tracks" that is a meaningless comment unless it comes with more information. Sound pressure or sound power? Weighted? Measured where? Measured how?

-Mike (former noise control engineer)

 

they were on the right side of the track last weekend at summit...... at pit out...which is right about where i switch to 6th gear....so i was probably at about 6000rpm ish...... i guess they could move, etc......

I ***need*** to race because I need the points..... i am currently in 2nd place and need to stay there.....

thanks for all the help..... i am still working on it....

 

Well, one simple (but not very satisfactory) solution is to just back off the throttle a little when passing the sound check station. Otherwise, try the elbow noise deflector thing. Treating the inlet noise will be more problematical, so hopefully it's not the inlet. It doesn't help that they were on the same side of the track as your inlet air intake.