Quiet Silencers for LS 7?

[Rusti Evo]

Just planning the exhaust for the LS 7 and was looking for advice.

It is essential that the exhaust gives sub 98db to allow use at Goodwood and Top Gear. I believe that the LS 7 is naturally quiet with the cats but has anybody got any experience and sound figures?

The engine is bog standard (for reliability) and should have about 540bhp ish.

Stuart

[GTWayne]

Rusti Evo said:

sub 98db to allow use at Goodwood and Top Gear

I do believe that GTRSimons LS powered Ultima was remarkably quiet when tested at Stonleigh last month and that runs cats

Rusti Evo said:

...bog standard...540bhp ish...

How long have we been waiting to here that type of claim 'eh?

[LuckyP]

Have a chat with Charles Dunn. He seems to think (like a lot of peeps on here) that a cross over system is the way to go.

[Boosted LS1]

I like the idea of a cross over system and maybe some Borla's. Being more street biased they could be quieter?

[ROWDYRENAULT]

Hi Guys. Summit Racing sells a cone that goes into the back of the tail pipe it is pointed towards the engine an has a bunch of holes in it. Its made of stainless steel. Now I have no idea how much back pressure it builds but I can tell you that it made a difference in the sound level in my car. That said if you drilled and tapped the exhaust pipe you can install these in about 5 minutes. Might beat the heck out of missing a day at the track. Lee

[Steve_D]

ROWDYRENAULT said:

Hi Guys. Summit Racing sells a cone that goes into the back of the tail pipe it is pointed towards the engine an has a bunch of holes in it. Its made of stainless steel. Now I have no idea how much back pressure it builds but I can tell you that it made a difference in the sound level in my car. That said if you drilled and tapped the exhaust pipe you can install these in about 5 minutes. Might beat the heck out of missing a day at the track. Lee

That's been done.
The guinea pig is now the owner of a melted rear clip garden ornament.

Steve

[Rusti Evo]

ROWDYRENAULT said:

Hi Guys. Summit Racing sells a cone that goes into the back of the tail pipe it is pointed towards the engine an has a bunch of holes in it. Its made of stainless steel. Now I have no idea how much back pressure it builds but I can tell you that it made a difference in the sound level in my car. That said if you drilled and tapped the exhaust pipe you can install these in about 5 minutes. Might beat the heck out of missing a day at the track. Lee

Hi Lee. Are these SuperTrapps or has Summit got something new?

I have been experimenting with a set of 4inch trapps and as you say the noise reduction to the ear is very good - less so to the meter - only shows about 2db. I reckon I can feel a power reduction but am guessing most of that is just because the soundtrack is much softer.

Bill Lackey had great success with the 3inch size on his LS. However I'm guessing the 3inch must have had awesome backpressure

Stuart

[GTR One]

Rusti Evo said:

I believe that the LS 7 is naturally quiet with the cats but has anybody got any experience and sound figures?

Lol..My cat'd LS7 failed it's SVA yesterday on noise! 103dB

[Rusti Evo]

GTR One said:

Rusti Evo said:

I believe that the LS 7 is naturally quiet with the cats but has anybody got any experience and sound figures?

Lol..My cat'd LS7 failed it's SVA yesterday on noise! 103dB

Hell, that must have been very irritating. What exhaust do you have?

Also, what distance do they measure it at? I've been lead to believe they measure at 1m rather than the 0.5m used by trackday types.

[GTR One]

It's measured at 0.5m (at 45 deg angle) for the SVA.

Yeah, it was annoying! I have a Spectrum 5 exhaust with Edlebrock silencers. First fix is to fit a Jetex decibel insert for the SVA test. A cross link between the two banks would do a lot too I reckon.

Engine capacity has a lot do do with noise as the exhaust mass flow at a certain rpm will be higher, so more silencing required. Generally though, my LS7 has been reasonably quiet!

Liam