How loud?

[Dave 53]

I've got a WRX engine and the exhaust has only a cat. No muffler. How loud in dB might this be? Looking at future track days with 90dB limit.

[NAZ]

Don't guess, get an app for your smart phone and test it yourself -- you can find free ones or almost free.

[Ajzride]

Mine measured at 95 dB 4 foot away with factory cat. 2.5 Turbo from
A 2006.

[Bob_n_Cincy]

I've got a WRX engine and the exhaust has only a cat. No muffler. How loud in dB might this be? Looking at future track days with 90dB limit.

I'm running a up-pipe cant and a down-pipe cat with no muffler.
I passed the NCM track DB limit with no problem. The small tdo4 turbo really quiets it down.

We can still talk in the car.
https://www.youtube.com/watch?v=dxbXW_77muc

[Sgt.Gator]

I'm running a up-pipe cant and a down-pipe cat with no muffler.
I passed the NCM track DB limit with no problem. The small tdo4 turbo really quiets it down.

We can still talk in the car.

Bob I think you mean an up-pipe cat. You need to swap that out for a non-cat up-pipe. When the cat starts to come apart it will take out your turbo.

For the OP, I have no cats and a small muffler, it's quiet. I've never checked with track officials about my sound readings.

[fletch]

Both the front and rear cats are after the turbo.

[mikeb75]

I run a resonator and straight pipe after the turbo and I measured 93 dB at 5K RPM (unloaded)... but I also have an EJ207 dual scroll, so there is less Subaru boxer rumble with that setup, I believe that affects peak SPL because of how the exhaust pulses interfere...

Also, try running an exhaust outlet that angles down, if the SPL measurements are made at hand height... I believe this deflection can help... but that's total internet conjecture on my part.

[Sgt.Gator]

Both the front and rear cats are after the turbo.

There were versions with a cat in the uppipe. They are notorious for disintegrating and taking out the turbo.
All 02-05 USDM WRX's (2.0L's) have cats in the up pipes. Also Forrester XT, 2005-06 Legacy GT...Subaru realized the problem and the 2007 Legacy GT has the cats after the turbo..many threads about the problem on NASIOC, Legacy GT, IWISTI.

Dave 53 if you are going to drive Laguna Seca you are probably going to need a muffler. They are incredibly strict.

[Mitch Wright]

With a JDM header and Twin Scroll Turbo with a 3" exhaust and 12" Dyno Max Racing Muffler I was 95-98DB at 50' at 6500rpm at NCM. Atmospheric conditions play a roll on any given day, a cool crisp day will be louder than a warm/hot day as an example.
90db how far from the edge of the track and what scale is being used?

Some good suggestions in the previous post.

[Dave 53]

Quote...If you go to Laguna Seca, the paddock is quite an interesting location to be. You probably won’t ever see as many cars with ridiculous home-brew, DIY muffler extensions as the pits at Laguna Seca.

Do a Google image search for "Laguna pipe". 143745143746143747

[Mitch Wright]

I see a theme there, point the exhaust exit away from the sound station.

[DSR-3]

Laguna has an official sound booth on the right side. Unfortunately they or SCCA would sometimes put one on the left side too. Both are in (uphill) areas where lifting-off is not much of an option (if you're trying to go fast). I tried lot's of solutions on my 2 race cars, cause having a good qualifying time tossed was so painful in a 70 car field!