Track-day Silencers
Discussion
C1RVY said:
Scuffers said:
and bolting on 'silencers' to the back of the exhaust usually is a really bad idea as it messes up the exhaust flow significantly and can screw the engine.
Are you sure?We used bolt-ons a lot with de-catted TVRs without problems ( maybe slight drop in power ).
TVR is a completely different kettle of fish, (although I still think it's a bad idea)
C1RVY said:
Why is it so different?
ones a lazy, big NA engine that's not hugely exhaust sensitive, the other is a small high output supercharged engine that's very exhaust sensitive.Look, if you ram something up the tail that's goign to make any significant difference to it's noise, it will involve adding significant restriction to the exhaust, this then knocks onto the engine and raised the pressures in the inlet as well as the exhaust, causing not only power loss, but huge increases in temps both withing the inlet and the combustion cambers to an engine that's already being pushed hard.
Now go do this on a race track and just think about how much a new engine costs.
Scuffers said:
ones a lazy, big NA engine that's not hugely exhaust sensitive, the other is a small high output supercharged engine that's very exhaust sensitive.
Look, if you ram something up the tail that's goign to make any significant difference to it's noise, it will involve adding significant restriction to the exhaust, this then knocks onto the engine and raised the pressures in the inlet as well as the exhaust, causing not only power loss, but huge increases in temps both withing the inlet and the combustion cambers to an engine that's already being pushed hard.
Now go do this on a race track and just think about how much a new engine costs.
I hear what you're saying, but i don't think you could call TVR engines lazy. My old AJP 8 was a fairly manic race-bred engine in a high state of tune. Despite flames, pops & 414BHP, bolt on cans never really caused any big power loss or any damage.Look, if you ram something up the tail that's goign to make any significant difference to it's noise, it will involve adding significant restriction to the exhaust, this then knocks onto the engine and raised the pressures in the inlet as well as the exhaust, causing not only power loss, but huge increases in temps both withing the inlet and the combustion cambers to an engine that's already being pushed hard.
Now go do this on a race track and just think about how much a new engine costs.
Additionally, we've now got companies on the market like Decibel-Devils who specialise in noise restricting inserts for race car exhausts. So it's clearly not quite so cut & dry.
Edited by C1RVY on Monday 20th May 16:11
Scuffers is right. He was not being nagative about the TVR motor but it's not that stressed.
On a high reving SC 4 pot you need to get a lot of gas in and out at high speed. Putting a restriction on the gas will cause the flow to slow increasing heat and induction pressure.
Just changing from one manifold to another can make a big difference to the flow on these engines.
If you wnat to do track days just get a quiet 2bular or Tullet. many people with these are doing Goodwood and Bedford without probs.
Ex77
On a high reving SC 4 pot you need to get a lot of gas in and out at high speed. Putting a restriction on the gas will cause the flow to slow increasing heat and induction pressure.
Just changing from one manifold to another can make a big difference to the flow on these engines.
If you wnat to do track days just get a quiet 2bular or Tullet. many people with these are doing Goodwood and Bedford without probs.
Ex77
Scuffers said:
wrong on both counts
Interesting....Would a 911 Turbo or Gen 2 GT3 enngine be classed as big & lazy? I've got mates running these on track, & they regularly have to rely on bolt-on silencers to get through many of the trackday noise limits nowadays. Indeed, there are now companies specialising in the supply & manufacture of purpose-made bolt ons for such cars.
Seems at odds with the issues i might have with my 1.8 Toyota engined car!
Exige77 said:
Do some quick sums and see how many BHP/Litre a Porker GT3/Turbo is.
They're about the same, hence the comparison. We did some basic static noise testing over the weekend, & the 997 GT3 is about 2db louder than my Exige with the current set up ( it was basic too, we didn't really know how to use the meter Edited by Exige77 on Tuesday 21st May 10:44
)So now i'm thinking that the exhaust may not be such a huge problem for me so long as i manage my revs a bit. In the past, i'm sure my issues were more SC whine than tailpipe noise. Problem is compounded by the SC intake being on the same side as the noise meters at my local circuit.
Cheers for the input btw
Edited by C1RVY on Tuesday 21st May 11:00
cirvy. i've seen ur car at donny so im guessing ur problems are donny and bedford, for donny just lift as you go past the meter on the back straight and build up til you're either flat out or black flagged at the end of the day, talk to the marshals as you go and see if your car sounds like a problem, a £130 evening session is an easy way to check it just be patient and build up
bedford's more of a pain since you have to lift at i think 4 points, and it's easier to fail in my experience, still i think it's worth going down and doing a day building up the revs at the meters and talking to the marshalls, if your car is a problem then worry about silencers afterwards
having looked into this myself (285bhp MY10 exige) i tried a decibel devil (had no impact on the static test) and i tried the merlin motorsport one which i've still got but it's pretty big, heavy and sticks right out the back, it's knocked a bit off the static but it wouldn't get me through either bedford or donny, tested the merlin on the dyno and with or without it the power curve was the same so i'd guess it had negligable effect on back pressure, i looked at soundtrapps or supertraps whatever they're called and was put off by the back pressure, pretty sure they'd wreck my engine, John JSR seemed sure they were a bad idea
in the end Jim 2bular built me a one off 2nd silencer and it's 99% effective, though stage 2 is your starting point which is a lot louder that my i think 24*8 gt3 with silencer decat
bedford's more of a pain since you have to lift at i think 4 points, and it's easier to fail in my experience, still i think it's worth going down and doing a day building up the revs at the meters and talking to the marshalls, if your car is a problem then worry about silencers afterwards
having looked into this myself (285bhp MY10 exige) i tried a decibel devil (had no impact on the static test) and i tried the merlin motorsport one which i've still got but it's pretty big, heavy and sticks right out the back, it's knocked a bit off the static but it wouldn't get me through either bedford or donny, tested the merlin on the dyno and with or without it the power curve was the same so i'd guess it had negligable effect on back pressure, i looked at soundtrapps or supertraps whatever they're called and was put off by the back pressure, pretty sure they'd wreck my engine, John JSR seemed sure they were a bad idea
in the end Jim 2bular built me a one off 2nd silencer and it's 99% effective, though stage 2 is your starting point which is a lot louder that my i think 24*8 gt3 with silencer decat
I did loads of trackdays in my old Exige 240pp with a stage 3 and a TRD airbox and it never failed the noise test (always 100db limits) although once or twice measured 99.9999999999 according to the marshall..!
Just make sure the engine is nice and warm and increase the revs gradually as it's very often the 'spike' of revving it up too quickly that upsets the meter.
Cheers
240
Just make sure the engine is nice and warm and increase the revs gradually as it's very often the 'spike' of revving it up too quickly that upsets the meter.
Cheers
240
when mine was an unmodified 240s + stage 3 it was fine static everywhere but failed the driveby at donny and bedford miserably, at a guess it'd fail goodwood, combe and croft on the first lap
saying that it was fine at silverstone, anglesey, oulton and rockingham where driveby isn't really an issue
saying that it was fine at silverstone, anglesey, oulton and rockingham where driveby isn't really an issue
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