I finally got my st170 powered Spitfire on the road a couple of weeks ago. And had the ME221 ecu mapped by ME. Still a work in progress there.....
Anyway, I made a 2 1/4" exhaust system, and single 4x10", 14" long straight through box (think it is 2 1/2" bore) but it is
incredibly loud. So much so when I took the car to Sap for the classiclast weekend I fitted a 1.5" bore box just to get it bearable, but the
effect on performance was marked.
So, I have had a few thoughts. Because of "packaging" issues, I can only get a box under the boot floor. So that limits it to 5"
diameter box.
Realistically I could split the exhaust and run a pair of boxes in parallel. I reckon 1.75" bore gives an overall area a bit more than teh 2 1/4
pipe, and each silencer could be 18" long.
Plan b is to use 2 2 1/4" silencers, again 5" diameter, one after the other but joined by a 180 degree link pipe. One could be max 18",
the other up to 30", giving a total length of 48"
Either of those sound a winner?? or other good ideas?
an old style 'cherry bomb' silencer could be fitted between the chassis rails under the prop shaft. then back boxes behind
I considered that, but not sure if that would be effective. I could get a 3" cherry bomb in there but the difference in diameter between the pipe
and the outer case is small, about 8mm gap.. Not a lot of space available.... (most spitfires use 1 1/2 pipe, and sports exhausts about 1 3/4"
Have you considered a DB killer? I have an ST170 engine in my car and a DB killer took it down from 106dB to 97db after it failed it's first IVA on noise. It still made 175hp on the rollers with it fitted.
Deb killers are bhp killers
Tuned Spitfires often used twin silenced end pipes.
Having just replaced the rotten exhaust on an 06 plate Fiesta ST I would be looking for a resonating back box as the non resonating box I fitted is
unbearable inside the car "Doh"
So what is a "resonator" box? Chambered or baffled?
Seems that exhausts are a black art. I know with straight through silencers longer is quieter, and larger outer casing is quieter. And smaller bore
too....
And yes, the twin "wheelbarrow" exhaust has been very popular, . But most of those cars are in the 75-100bhp category. And some of them are
VERY loud!
quote:
Seems that exhausts are a black art.