cliftyhanger
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| posted on 24/5/17 at 07:31 PM |
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Quiet exhaust options
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?
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gremlin1234
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| posted on 24/5/17 at 07:43 PM |
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an old style 'cherry bomb' silencer could be fitted between the chassis rails under the prop shaft. then back boxes behind
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cliftyhanger
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| posted on 24/5/17 at 07:59 PM |
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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"
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Daf
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| posted on 24/5/17 at 09:51 PM |
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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.
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snapper
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| posted on 24/5/17 at 10:46 PM |
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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"
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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cliftyhanger
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| posted on 25/5/17 at 05:36 AM |
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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!
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SJ
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| posted on 25/5/17 at 06:38 AM |
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quote:
Seems that exhausts are a black art.
Years ago I fitted a smaller Alfasud back box to my Cirtoen GSA instead of the big standard one and it sounded great. I then decided more was better,
and as it was a flat 4 I split the exhaust where it joined at the Y piece and fitted two 'Sud back boxes - one to each bank of cylinders. From
inside the car it sounded like a squadron of Halifax bombers was following me! Really loud and not that nice.
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