Could anyone who has had their exhaust noise tested post up what db reading they got?

Standard way of testing in the UK is 45 degrees at a distance of 0.5m from the exhaust at 4.5k rpm, but any db values would be informative.

I need to get my car below 95db for the above test. I'm currently running a custom dual tip exhaust that is well above the target figure (sound meter heading my way so I can measure it) with a silenced midpipe, downpipe and BNRs non-seq on a ported engine. The car is making over 400rwhp, so need good flow along with minimal noise.

Have spent hours searching and found lots of posts about what people think is quiet (RB and possibly M2 duals) but a distinct lack of numbers to back these up. A local FD is running an RB dual and while it is quieter than many aftermarket systems it is still vastly louder than the stock setup.

Thanks for any input

 

Using my radioshack db tester I was getting around 110db+ (straight 3")+greddy muffler...Getting below 95 is kinda hard to do with aftermarket kits...of course cats help quite things down a lot--so if you still have them thats a plus on the sound side! Of course so many things come into play when you measure that getting accurate readings is hard...Altitude, temperature, pressure, surroundings, air density and a few more....but anyway you can get a guesstimate so I will stop rambling on!

 

Ported engine? 400+ horsepower? No cats? I wouldn't think you'd have a chance of getting under 95 decibles. 4500rmps in neutral isn't too bad for sound but only half a meter from the exhaust is pretty darn close.

I think you're just going to have to accept a horsepower loss (read put the stock cat back on or stock muffler) to get that quiet.

When my bone stock FD still had the stock main cat and a racing beat dual tip exhaust I was in the 94 to 95 decible range at full throttle measured from a bit over 100 feet (~30 Meters) away.

 

Just cheat...

Swap back to your stock exhaust and put your cat back on, pass the test, put your aftermarket exhaust and midpipe back on.....

 

Thanks guys, most tracks have drive-by noise tests on the circuit so cheating isn't really an option (unfortunately). My stock cat-back rusted away years ago, but may try to borrow one so I can get a low noise benchmark.

I'm hoping it is less than 110db at the moment... Still had the stock cat-back when my silenced midpipe was fitted, and it was no louder (to my ear) than the dead cat it replaced, however, the cat-back changed the volume fairly spectacularly :o

 

Tested it today:
102db

Also tested a stock FD with Feed silenced midpipe and Racing Beat dual tip:
91db

 

In case anyone is interested I got a new backbox from SMB which is a 3" dual tip. Fitted it to the car tonight and the drop in noise level is simply astonishing. As it hasn't had time to bed in these can only be approx figures at the moment:

Idle: 83db (88db)
4.5k rpm: 90db (102db)
6k rpm: 93db (106db)

Figures in brackets for my old twin exhaust. All tests at 0.5m 45 degrees from the exhaust.

I'm delighted as the car is now almost as quiet as a factory car. SMB were a delight to deal with and couldn't have been more helpful.

As reference these figures are on a par with the Racing Beat dual on a non-ported, sequential car - so the SMB is IMHO quite a bit quieter. Ideal for anyone after a quiet road car, or who has to comply with tight noise limits

 

Do you know where the noisesensors are placed? Some guys who drive at Laguna Seca actually run a pipe to direct the sound away from that side of the track when they go by. I saw apic once. It looked like a 3" right angle pipe stuck on the end of their cat back.

 

Christ, I have to be pumping 110+ db with my single. I should go pick up a db tester, it's a port with 4" straightpipe. LOUD!!!! It gets annoying, i need to put a high flow cat on to shut it up, lol.

 

When I raced my GT2 and GT3 SCCA RX-7 with a Bridgeported engine I always used a 3", 90 degree tip that I attached to the outlet of the Mazdasport lavarock racing muffler. It made a huge difference.

One day at the Thunderhill racetrack I forgot to attach the 90 and got called for sound violation during a practice session. I came in, attached the 90 pipe so that it pointed AWAY from the sound station and my DB dropped close to 10 db. The sound guy came over to my pit after the session to ask me what I did to lower the level so much. He could not believe that the 90 degree pipe made that much difference.