Toto111

Anyone know what the factory spec is on how loud the standard exhaust is?

I would imagine that it must be documented somewhere. Thanks.

EckFe1

According to the spec sheet I have, at standstill, 100dB at 1 meter distance from the tailpipe at 45 degrees and rev. at 2/3 of the rpm range in neutral.
Drive by is at 76 dB at around 4m distance at 50km/h flooring it in 2nd and 3rd gear at the moment the person with the mic on the side is at 90 degrees to the car.
Hope that makes sense the way I tried to explain it.
Ed

race911

As above, there are many ways to test.

At Laguna we generally have 92db sound days, though some are 90db. Particulars of the measurement are WOT at the high end of 3rd gear. No one fails with a stock exhaust. However, the first guy who showed up with a 993 Turbo back in '96 was sent home......... Surprised us, and the first time a 100% stock car failed, at least in our Porsche world.

(Oddball thing we figured out for the Olden Day dual carb/MFI cars was that most failed for intake noise.)

bruce7

While I don't have the factory standard exhaust, I do have the factory Motorsound
exhaust and did some sound level measurements.
I used the Extech sound level meter 407730. It is +/- 2dB accurate in the
300Hz to 8kHz frequency range. Meter was set to A weighting, slow response
and max hold.

Exterior exhaust sound levels measured 15 feet behind the car at 2 ft elevation:
At idle = 63 dB
At 4500 rpm = 86 dB

Interior sound levels measured in the cockpit:
At 70 mph in 6th gear = 75 dB
At 6000 rpm 3rd gear = 86 dB
At 40 mph at 2800 rpm = 74 dB
At idle = 59 dB

Note: My interior levels may be lower than standard due to installation of
Dynamat and VB-2 in door panels.

Here's some numbers for comparison to what others have measured of
non-standard exhausts. No info on type of meter or settings used.

FDMotorSports, measured 15 ft directly behind car:

Stage III w/stock cat.: Idle: 75.1 dB, @4500 rpm : 99.1 dB
Stage II w/sport cats.: Idle: 76.5 dB, @4500 rpm : 100.1 dB (200 Cell)
Stage III w/sport cats: Idle: 79.9 dB, @4500 rpm : 101.4 dB (200 Cell)

jhg41977, Fister 200 cell sport cat + Stage II mufflers measured in cockpit

Idle, windows up: 65-70 dB
70 mph, 6th gear: 75-80 dB
on the gas: 90 dB
6000 rpm: 89.7 dB


Attached are a couple of pictures. One of the sound level meter. Another of
a diagram illustrating how dB levels explain differences in sound level intensity.

From the this dB diagram and the measured levels at idle, you can see that
the FDMotorSports setup is 12-17 dB louder than the Motorsound setup
(63 dB vs. 75-80 dB). In other words it is more than 10x louder.

At 4500 rpm, the FDMotorSports setup is about 14 dB louder (86 dB vs 100 dB).
Again, more than 10x louder than a stock setup.

Remember that different sound level meters were used by different people
under different conditions. Nevertheless, the results are probably fairly accurate.
I haven't heard the FD setup in person, but I had the Fabspeed
Maxflo setup before the Motorsound and I can say that the Motorsound are way
quieter than the Fabspeed. Didn't have the meter then so I don't have
any measurements for the Fabspeed mufflers.

See also:

https://rennlist.com/forums/993-foru...at-videos.html

https://rennlist.com/forums/993-foru...installed.html

vincer77

Thanks Bruce, great information!

H.H.Chinn

Great information!! I'm a convert from factory motor sound to StageIII w/stock cats. Much more purposeful when you "get on it", but still allows you to have a conversation without screaming at each other.

Toto111

Thanks for the responses guys.

I have the pleasure of an EPA test coming up and need to get under 92db (90db for the exhaust plus a 2db allowance for rear engine) at 4525 RPM. I was reported for excessive noise.

steve porter

Hey Theo, I still have my stock mufflers if you want to borrow them

Toto111

Now why would I want to do that Mr Porter as that's what was in the car when it was reported...I think.

Pdyson4

59dB(A?) at idle is pretty good. I’m getting 60dBA and I have multiple foam and MLV layers on the bulkhead. Maybe it’s time to change engine mounts.