Noise levels

SimonExtreme · Sep 22, 2006

I am trying to colate some data on how noisy different exhausts are. In particular, I would like to know the static noise level on the standard system and the same system with a decat. In addition, any other system combinations would be welcomed.

The purpose of this is to be able to identify the perfect system for trackdays. I know of somebody who has just ordered a Hayward and Scott rear box (across the back) and we are all hoping that might be the answer for the best combo of silencing and power. They claim 98 db but with a cat and I cannot find any figures for the box with decat.

To start this off...........

My car
105db (if I am lucky [

]) with decat and cup pipe

jason · Sep 22, 2006

I was 108db with almost straight through system including cat bypass and cup leaving only small silencer at back, when tested from half a metre behind exhaust.

Had to swap cup pipe back to standard to get below limits as was not prepared to run the risk - lost some of the aural enjoyment but keeps me on track so makes up for it 1,000,000%......as the GT3 boys will tell you...as I passed most of them at Croft yesterday[

]

lee fulford · Sep 22, 2006

Simon I have a full cargraphic system complete with manlyfolds, I reckon it sounds good and never a problem on track days.................and before anyone tries to be funny, yes it has been on track.[8D]

timbarber · Sep 22, 2006

I don't think there's a definite answer to this. One of the key things is what revs the car is doing when the measurement is done. I have a standard 64RS exhaust and I don't remember the exact revs but at Castle Combe at about 4800 I was 99db. At Goodwood at around 5500, I was 105db. The Castle Combe day was a quiet day and it could be that they were being generous?[

]

I've been told that holding the clutch down also helps reduce the noise reading.

tomas johansson · Sep 22, 2006

I'm driving decat and with cup-pipe. The car is generally noisy and at the Oulton RS day I had the same reading as Jason (ie 108). This being the case I have still managed to drive at both Bedford and Donnington when limit was 98 and noise was also checked drive by. It seems that as long as I can get on the track things are OK. I can also mention that I have not been short shifting to keep the noise level down. I once tried to resolve the matter and bought the big muffler to replace the cup-pipe. A couple of times for "quiet" days I replaced the cup-pipe with the muffler but I am not bothering with this anymore. My take on this is that the 964 RS static noise level is high relative to the drive by.

Melv · Sep 29, 2006

Simon -since you asked:

100 cell race cat, Cup pipe, final silencer IRO 106-107db @ 75% max revs.

100 cell race cat, C2 rear silencer, final silencer IRO 103-105db @ 75% max revs.

+ Merlin Motorsports tailpipe silencer -take off 2db.

But, as time goes on, the baffles in the final silncer are wearing out and it's getting noisier again!!

However, as pointed out above, depends where and how the noise is measured. Combe is .75m from tailpipe, Goodwood 1m, both at 75% max revs.

Dipping the clutch also helps, as does ensuring the engine is really hot and you are not near any buildings!