rear exhaust

[jesfirth]

My back box has died and I seem to recall when I fitted it that it weighed the same as a small planet.

Does anyone know of alternative back boxes, like the sports exhausts, but which DO NOT increase the dB volume. The car is decatted so I already have to use add on silencers for places like goodwood etc with a stanadrd box to achieve 100dB

[JensenA]

As far as I know all the Sports Exhausts do increase the dB. The SP is advertised as a Track Day friendly exhaust - but it isn't, and it's expensive. I know a Guy in Leeds who does custom exhausts and can make them as quiet/noisy as you like. He's had a look at mine, an SP one, and says it is no problem at all to make a copy, that performs/sounds to your spec.

http://www.tonybanks.co.uk/

[hoppo4.2]

dose anyone no of a company that can make custome system in the midlands area (leicester).

i no that powerflow do it at mr tyres but ive seen the workmanship and im not won over.?

[ridds]

You could try Blue Flame. Good quality and should be able to make it as quiet as you need.

Be ready for the price though.

[jesfirth]

Ok next stupid question. Why did TVR design such a huge back box surely it cant be completely filled with pipes and lagging?

[ridds]

I think it's just a couple of perforated tubes that have half the box each.

i.e. Straight perf tube in, another perf tube straight out and the gas has to find it's way across.

Don't quote me on that though.

They're definitely separate for each bank though.

[BCA]

I believe TrackCar is coming up with such an exhaust (quiet!) Worth a call?

[Byker28i]

My old SP exhaust rear box alone weighed much more than than my whole exhaust system from ACT I replaced it with. The other advantage was I gained a huge amount of clearance again as the silencing cans were much smaller, so could lower the car again. I'd had to jack it up substantially to clear road humps. I'm guessing the original exhaust had the same issues.

I'm decatted with ACT's quiet system that's 106db, 97-98db with trackday silencers. SP's was 109db on mine decatted. I know Graham's just had the SP back box fitted but had to leave the cats in to meet trackday noises. The 98db claim was on a 4.2 catted car (i.e. no link pipes).

[HarryW]

Though goodwood was 105dBs on a 'noisy' sprint day with no more than 5 cars out at a time and 98dBs with 10 car track days .
All in all a very sad compromise the circuit had to make with the local nimby's to allow days like the Revival go 'unrestricted'.

Back on topic, Byker are those figures for the system with silencers int eh centre section to ,I have a big bore system that is a little noisy that I'm thinking about trying a quiet centre section first (i already have the cat cherry bombs).

[dean_ratpac]

i believe act do a range of silencers to go with there range. although i never even considered these.

[Byker28i]

HarryW said:

Though goodwood was 105dBs on a 'noisy' sprint day with no more than 5 cars out at a time and 98dBs with 10 car track days .
All in all a very sad compromise the circuit had to make with the local nimby's to allow days like the Revival go 'unrestricted'.

Back on topic, Byker are those figures for the system with silencers int eh centre section to ,I have a big bore system that is a little noisy that I'm thinking about trying a quiet centre section first (i already have the cat cherry bombs).

Yup - my ACT system looks like:



Silencing in the straight pipes, and tailpipes as well as the main boxes. The cherry bomb silencing would probably mean I wouldn't need trackday silencing as well, but it's a nice compromise at the moment.

[alderley]

ridds said:

I think it's just a couple of perforated tubes that have half the box each.

i.e. Straight perf tube in, another perf tube straight out and the gas has to find it's way across.

Don't quote me on that though.

They're definitely separate for each bank though.

There are perforated tubes (which can snap) surrounded by steel wool then glass fibre insulation. The same perforated pipe is welded to the pipe that enters, bends through about 60 degrees and continues straight, then bends back and is welded to the tail pipe which leaves the box. I packed mine with extra glass thinking it would become more 'straight through' and noisier. To my surprise, the extra packing absorbed more sound. At sprints it came out at 99 to 101 decibels. You can buy the perforated tube from Demon Tweeks as well as stainless steel sleeves to weld into the inlet of the back box but which take the rear of the middle section. Yes the back box is rally set up as two separate boxes from the exhaust gas point of view.

[ro_butler]

Byker28i said:

SP's was 109db on mine decatted.

Eh?! How did you manage that? I went to Snetterton in mid December '08 and got a reading of 99db at just under 5000 rpm. It was nearly 0 degrees C and sleet was falling
but I doubt this makes much difference. I also managed to squeak onto Bedford early last year but got kicked off for failing the drive-by limit.
If the noise limit is 98-99 db then I can't get on but 105db days I can manage easily.

I am in no way knocking your numbers, just curious as to what conditions it was measured under.