Exhaust Drone

[surypap3]

ok. i understand

[surypap3]

I did bring the engine up to the RPM range 3500 and 4000. Listened thru a ratchet extension. Nothing rattle or seemed out of norm in the intermediate pipe and muffler. Just got loud.

[jbcollier]

Well, now you know it's the lack of "muffling" that's the issue.  Try a different muffler or fit an end can.

[surypap3]

Don't try to add a resonator in the intermediate pipe?

[jbcollier]

The first thing I would try is a different muffler.  Magnaflows have a good rep.  Mine is "straight-through" but has a lot of space for sound waves to expand and be diminished.

Exhaust design is complicated.  The "exhaust system" starts at the air intake, through the engine, all the way to the end of the outlet.  My old boss and I both have Ducati singles.  His is a stock 450 with a straight pipe, no muffler at all.  Mine is only a 250 but it is ported, wild-cam-ed, large carbed, with a baffled, reverse megaphone exhaust.  His is a pussy cat.  Mine barks and snarls and sets off car alarms.

Is yours an otherwise stock engine?  Or, has it been breathed upon?

[surypap3]

Work was done by the prior owner. Exactly what, I do not know. He said it was brought up to approx 145 hp. My son tracked it at a LOTUS Owners annual and it ran well against the Elises for what that is worth.

[jbcollier]

145hp is pretty healthy.