centre silencer removal

[loko]

my 2.8T saab has a twin exit exhaust setup but also has a middle silencer, now in my quest to make it sound a bit sportier i was toying with the idea of removing the centre box and just leaving the 2 rear silencers, would this be overly loud/boomy or just make it sound a bit deeper
any thoughts?

[SooperDan]

I would imagine it would be a lot louder, not just a little. You'll notice a difference in fuel consumption too. But I can only assume

[redgriff500]

Best to ask on the relevent forum.

But I have frequently removed, front, centre, rear boxes or all of them.

Usually the noise is only a subtle increase just removing one box.

Worst case senario has been a horrid dull resonance around 2k and that was after fitting a genuine Schnitzer back box !

Best was deleting ALL the boxes on a V8 Soarer - it sounds glorious.

If you pick an easy box to delete (on a straight run) then it's pretty simple to refit it using a couple of joining pieces so worst case is you lose a couple of hours and £20.

[buggalugs]

As said hard to say unless someone's actually done it on that specific car. Turbo exhausts are usually quite quiet anyway though.

[maniac0796]

SooperDan said:

I would imagine it would be a lot louder, not just a little. You'll notice a difference in fuel consumption too. But I can only assume

Divulge?

[jimxms]

maniac0796 said:

Divulge?

x2...I can't possibly fathom out how removing the silencer, a steel pipe with some baffle material around it could change the fuel consumption.

Also the silencers tend to just remove some of the drone. Its normally the back box that mutes the cars exhaust the most.

[davepoth]

On a NA car it's possible if the centre silencer has been designed to provide significant back pressure for cylinder scavenging purposes, but that won't happen on a turbo car. It may possibly be because you'll end up going through tunnels several times though.

[P I Staker]

davepoth said:

On a NA car it's possible if the centre silencer has been designed to provide significant back pressure for cylinder scavenging purposes, but that won't happen on a turbo car. It may possibly be because you'll end up going through tunnels several times though.

I haven't heard of this before? Googling for it was exhausting.

[swansea v6]

I removed the centre silencer pipe on my v6 vectra and it made it sound awesome!!! pops and bangs on demand, although I had to remove the sports back box and fit one from a GSI as it was just too loud!! Even when I had it MOT'd the tester put down VERY loud exhaust as an advisory.....fuel consumption actually improved tho??

[davepoth]

P I Staker said:

I haven't heard of this before? Googling for it was exhausting.

Usually the exhaust manifold is "tuned" by having the runners a certain length, so that at particular engine speeds the exhaust charge of one cylinder is "sucked" out of the manifold a little bit by the previous cylinder's charge. It's a similar effect to the way the air pressure changes in a deep level underground station when a train goes through.

Anyway, the effect is dependent upon the gas being in the right place in the exhaust system at a certain time, and if there's not the right restriction in the exhaust system, it may be a little further through the system than expected, which will reduce power. It may move the power band a little further up the rev range but that's something you'd need a dyno to check.

[redgriff500]

davepoth said:

Usually the exhaust manifold is "tuned" by having the runners a certain length, so that at particular engine speeds the exhaust charge of one cylinder is "sucked" out of the manifold a little bit by the previous cylinder's charge. It's a similar effect to the way the air pressure changes in a deep level underground station when a train goes through.

Anyway, the effect is dependent upon the gas being in the right place in the exhaust system at a certain time, and if there's not the right restriction in the exhaust system, it may be a little further through the system than expected, which will reduce power. It may move the power band a little further up the rev range but that's something you'd need a dyno to check.

In theory in an NA sports / race cars the manifold is tuned but in a run of the mill car they just fit any old crap that's cheap & fits.

Turbo / FI cars it's pretty irrelevant, just minimal back pressure for performance but then they have to pass noise limits too.

[Oilchange]

I'd imagine the centre section silencer is also there to keep in cabin noise down. Also they put funny airboxes on the inlet pipework which act as 'resonators' (absorb some engine intake noise) to keep under bonnet noise down. Don't know if they do anything else but I would have thought laminar airflow was best for the intake??

I, on the other hand, replace both with straight through pipes and release the rather glorious sounds that the factory muted.

[loko]

redgriff500 said:

Best to ask on the relevent forum.

i would have but i wanted an answer this month

[loko]

Oilchange said:

release the rather glorious sounds that the factory muted.

thats what i,m hoping for


looking at vxr online it seems the vectra vxr and the saab V6 are the same engine and it would seem obvious that the exhaust systems run along the same lines, a common mod on the vxr is to remove the centre silencer and the 2nd cat which sits in front of it leaving the pre cat on the downpipe in place to pass the MOT emissions test
good or bad? never messed with cats before so a bit unsure

[richie barry]

if you wanna know what a 2.8 v6 without the silencer sounds like have a listen to this http://www.youtube.com/watch?v=iZ71s_OAdUE

[SooperDan]

jimxms said:

maniac0796 said:

Divulge?

x2...I can't possibly fathom out how removing the silencer, a steel pipe with some baffle material around it could change the fuel consumption.

Also the silencers tend to just remove some of the drone. Its normally the back box that mutes the cars exhaust the most.

SooperDan said:

I would imagine it would be a lot louder, not just a little. You'll notice a difference in fuel consumption too. But I can only assume

...

[LuS1fer]

Long pipe runs are instrumental in generating drone so you are likely to experience an increase. That said, many cars don't have one and sound just fine.

[P I Staker]

davepoth said:

P I Staker said:

I haven't heard of this before? Googling for it was exhausting.

Usually the exhaust manifold is "tuned" by having the runners a certain length, so that at particular engine speeds the exhaust charge of one cylinder is "sucked" out of the manifold a little bit by the previous cylinder's charge. It's a similar effect to the way the air pressure changes in a deep level underground station when a train goes through.

Anyway, the effect is dependent upon the gas being in the right place in the exhaust system at a certain time, and if there's not the right restriction in the exhaust system, it may be a little further through the system than expected, which will reduce power. It may move the power band a little further up the rev range but that's something you'd need a dyno to check.

Thats interesting, thanks. I imagine though that the majority of the time a performance manifold and exhaust system would give benefits?

[GroundEffect]

davepoth said:

P I Staker said:

I haven't heard of this before? Googling for it was exhausting.

Usually the exhaust manifold is "tuned" by having the runners a certain length, so that at particular engine speeds the exhaust charge of one cylinder is "sucked" out of the manifold a little bit by the previous cylinder's charge. It's a similar effect to the way the air pressure changes in a deep level underground station when a train goes through.

Anyway, the effect is dependent upon the gas being in the right place in the exhaust system at a certain time, and if there's not the right restriction in the exhaust system, it may be a little further through the system than expected, which will reduce power. It may move the power band a little further up the rev range but that's something you'd need a dyno to check.

Nice explanation.

The thing however is that it's the primary and secondary lengths that make the biggest difference - a silencer half way down the pipe wont have the biggest effect on the resonance.

[SturdyJ]

I know on the GTV, the centre silencer is the key to unlocking the beast. Opted for a small one in the end given the unsilenced rear, apparently otherwise it is unpleasantly loud...

So curious though...