Fatman

I've got a full ScoobySport decat exhaust (Janspeed-made backbox), and in the last couple of months it's started sounding too 'raspy'. If I were to guess the source of the noise, I'd say it was something loose in the backbox. Does this ever happen?

garethbrunt

sounds to me like the baffles have come loose in the back box. Can you gat the back box to rattle if you tap/shake it on its mounts?

Gareth.

Fatman

No, it doesn't make an obvious rattling sound if it's shaken on it's mounts. I don't know what the internals of these backboxes are like. I imagine, though, that a simple shake of the 'box wouldn't necessarily show up any loose internals. Perhaps I ought to take it along to Janspeed and see if they'll take a look...?

garethbrunt

A shake would usually show it up, although it could be the gas is just catching it enough to make it rasp....as you say the best bet is to let them fix it.

Gareth.

Fatman

...one reason I suggest it may not 'find' the rattle is that the raspy sound seems throttle sensitive. On a light throttle, but at high revs it may not sound. However, at lower revs but more throttle, the 'rasp' may be provoked into sounding. <smart-ar$e mode=ON>That, and I studied physics so have a notion of harmonics<smart-ar$e mode=OFF> I'll see what Janspeed have to say.

Jolly Green Monster

iTrader: (4)

check the joints have not worked loose or blown the gasket...

JGM

Pavlo

Perhaps whatever rodent that has been resident in your exhaust has been blown out recently? I had a similar problem with a feline...

Paul

Fatman

Damn... how big is that backbox if you can fit a cat in it?

JGM: which gasget?

Pavlo

not all cats have fur!

Jolly Green Monster

iTrader: (4)

Dartford tunnel..

All gaskets..

there is one between backbox and centre which periodically needs tightenning on my car.. there is then one between centre and downpipe.. downpipe to turbo.. turbo to uppipe, uppipe to headers, headers to link pipe, link pipe to headers and headers to heads both sides.

Most likely the backbox to centre though.

JGM

Jolly Green Monster

iTrader: (4)

especially not once they have been blown out the exhaust... lol

Fatman

Actually I've had to tighten the centre/downpipe join before, so you may well be right there. I'll check the bolts.

I'll keep an eye out for bits of singed fur, too.

RON

Mine started making a strange noise tonight on the way home from work, it normally does it after it's been ragged, it sounds like mine's a heatshield that's rattling when excessively hot, it does it more when you lift off, but it goes away once it's been sat for a while and cooled off.