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I'm trying to find out more about what silencer exit diameter works best on the Aprilia motor. I have an Aprilia RSC Ti silencer (albeit shorter than standard) with a 45mm exit, and an Arrow Ti silencer with a 54mm exit.

Short of doing work on the dyno (which I will do as we get closer to the start of the season), anybody know what diameter works best? Obviously, smaller throttle bodies and exhaust diameters favour bottom end performance, while larger diameters favour top end.

Anybody done any dyno work to prove either way that the theory stacks up with the reality on the Rotax lump?

Dunno what size they are but I'd put my money on Jorge having found the optimum.

Not sure tbh ben - all I will say is that the larger throttle bodies kick in on my bike at around 5000 revs - then it's almost lime a supercharger hits.... And all of the effective peformance cans I have seen - renegade, akra et all seem to have wide exits....

What I would suggest for you that may well make a big difference is a Mille exhaust system with the renegade mid section mod to give more mid range ooomph

Hey Pete/Paul,

it's already got a Mille pipe installed. It's the early Mille pipe with the collector that joins the primaries earlier. Apparently they don't get the same boost from the header mod (because they've joined earlier already). I do have a set of the later Mille headers/collector that I could get done and then try it.

Good call though. I'm just wondering if the 54mm exit silencer will be better at the top-end biased tracks, and the 45mm exit better at the tighter tracks. I will put both pipes on the bike and dyno them at some point before the season starts to work out where I'm going with it (I'll have the PCIII custom mapped to both pipes at the same time).

B