My collector pipe is 2.5"... would there be any particular issues with using a reducer so I can run a silencer with a 2.25" inlet?

The reducer would be just before the silencer.

what engine and power you looking to run?

Audi RS4 V8... hopefully 400(ish)bhp.

(2 x collector pipes to 2 x silencers)

[Edited on 7/12/08 by scootz]

Area of cross section increases as the square of the radius, so any decrease in diameter is undesirable from the power point of view.

However, it might be interesting to know what the original exhaust system consisted of, for comparison purposes.

How does you projected output compare with original? and if you are expecting more power, is that purely from improvements in the induction and exhaust or are you changing something else?

John

John

It will run but you while lose some performance. In a RS4 these engines make 370ish on a dyno so don't be surprised if your down to 350-360 on a dyno. Only heard/seen one make more that 410bhp and that had 3" pipes all the way through.

Was aware of the OEM bhp anomaly Jeff.

There's been a few RS4 engines used in Ultima's and these have been healthily over 400bhp once all the emission cack and ancillary drives have been removed.

Scootz I'm running the same power with 2.5" pipes no problem. Would be doubtfull about running any smaller though they glow red hot as it is and a restriction, to my mind, would make it worse.

Powerflow make 2.5" bore silencers and 2 of them on my car came in at 109.5 dBA - OK for track but iffy for road. If you have room you could double up for the SVA or do as I did and stuff summat up the pipes for the test!!

Cheers!