Exhaust Noise Level reduction ???
#16
Rennlist Member
Thread Starter
I think the 4,800 Rev request must have hit the sweet spot for resonance, hence why it registered so high on the DB reading. On the M40 return I was trying different speeds, gears and rpm ( I was bored) and the 4,800 was uncomfortable to the ears for any lengh of time.
#18
Racer
As another data point, a Decibel Devil (in a round exhaust tip) took me from 109 to 106 db at Bedford on the static test. My set up was g-pipe and decat, although I am now going to fit a standard rear silencer in place of the g-pipe for track days (in fact I will have the rear silence plus round tip as a swappable unit for the g-pipe and oval tip)
#19
Nordschleife Master
Thanks Boxsey, I baffle and pack both exits for the static test then pull them before I head out on track and never had any hassle with any drive by police.
Hot engine + dipped clutch + a smile a the noise tester usually helps too. My Mrs did the noise test for me this time and I think her smile got her off with a 4200 rev too.
#21
According to the owner Jev, who I've met before:
Thanks Boxsey, I baffle and pack both exits for the static test then pull them before I head out on track and never had any hassle with any drive by police.
Hot engine + dipped clutch + a smile a the noise tester usually helps too. My Mrs did the noise test for me this time and I think her smile got her off with a 4200 rev too.
Thanks Boxsey, I baffle and pack both exits for the static test then pull them before I head out on track and never had any hassle with any drive by police.
Hot engine + dipped clutch + a smile a the noise tester usually helps too. My Mrs did the noise test for me this time and I think her smile got her off with a 4200 rev too.
As you know the 3.2 runs a 993 3.6 and the exhaust is a magnaflow x-over box which is fairly small and light. It does bang a pop a lot but that doesnt seem to bother the sound tests/meters. It might be worth looking into for you 964 guys as other than flipping the flanges on a set of 993 HE's its a bolt on mod that should win you some power, save some weight, retains the standard heat stuff and also gives you easy baffle and bung options.
Heres a pic of the system before swapped the tailpipes:
And fitted:
#22
Burning Brakes
Nice 3.2 Jevvy....were you also at Silverstone on Sunday?
Does this go to show that static noise tests bear no relation to actual noise!?
Does this go to show that static noise tests bear no relation to actual noise!?
#23
Static noise tests are certainly harsh on a 911 and I've had a few close shaves over the years. I used to leave the baffles in after the noise test but the wire wool just sets on fire and the baffle inevitably falls out so I just pull them and have never tripped the drive by's. I think the theory of the x-flow box is the sounds from each bank whack into each other and kill some of the volume, heres a vid from when I first fitted it(excuse the tailpipes) - very loud at tickover but as the revs rise the volume seems to drop somewhat.
#24
Addict
Rennlist Member
Rennlist Member
#25
Burning Brakes
Static noise tests are certainly harsh on a 911 and I've had a few close shaves over the years. I used to leave the baffles in after the noise test but the wire wool just sets on fire and the baffle inevitably falls out so I just pull them and have never tripped the drive by's. I think the theory of the x-flow box is the sounds from each bank whack into each other and kill some of the volume,
Soz Barty if we've gone a bit