silencers

[strat6v]

I'm still scratching my head regarding silencers and cats. The thought of bike parts keep springing to mind. Our favourite market place has plenty of cans coming up for sale all the time, most with cats in them already. A pair of immaculate cans(with cats) can be had for £100.00. They should also be quiet enough to pass sva etc.

A Yamaha r1 has a single can for a one litre engine capacity. This engine revs to something like 13000rpm, so if i used a pair on my alfa 24v limited to say 7500 rpm i should get enough flow for a three litre capacity? With the :D 'cat in the can', i wouldn't have a packaging problem for the pipework.

Does anyone have any thoughts on this before i go and spend the hardearned on something useless?

[mudhut]

Does anyone have any thoughts on this before i go and spend the hardearned on something useless?

I've heard (source unknown although it came via my son who possibly got it from MaxPower - but he's grown up now) that bike silencers produce more back pressure on the engine than is really desirable and this might be used by the makers to limit performance. The effect may not be significant at the exhaust flow rate you'll have, but if true, then this becomes increasingly important as the flow rate increases.

Guy Croft reckons that any silencing system worth its money should not produce more than 4 lb in -2 (4 psi) of static back pressure (i.e. measured at idle at the skin of the exhaust pipe after the collector). He makes the point that any back pressure is not conducive to good engine breathing, after all if it can't get out, it can't get in.

FWIW my son is about to have a new custom exhaust fitted to his VX220. The maker is going to use a sports cat (may be imported from germany where they are supposedly cheaper). These seem to be rated by power. The one being used is supposed to be good for up to 400bhp and costs around £250.

Seems to me that you either mount two silencer cans or you mount one cat and one silencer. I think I'd go for the latter.

I'm not an expert on these matters though - just my immediate thoughts.