When some blower motors are idling, there is a significant RPM fluctuation.

What causes that fluctuation ?

Running rich causes it. Leaning it out to make the Air/Fuel ratio correct will stop the surging.

Yup, exactly

I like that sound.

http://media.putfile.com/388MOV04062

Best sounding blower setup EVER.

http://www.sorcererboating.com/images/new.htm

The sound of pure evil.

Rodney's Skater sure would get the vote for the most baddest azz sounding powertrain. As bad azz as it sounds, I'd sure hate to have to do the maintenance on it.

With carburetors, a balanced A/F ratio at idle,when RPM comes off idle, does the risk of lean increase vs. fat idle ?

At idle, the throttle plates are closed and very little air is passing. Therefore, as the engine surges,does high pressure transfer from the bottom of the rotors to the top of the rotors ? If yes, how much gear and rotor slap is occurring ? With those questions asked, would a flapper or blow off valve connecting the top and bottom of the case seem prudent ?

Also, at high RPM,when the throttle is closed and inertia is at work from the drive train, is there enough A/F turbulence to encourage detonation as the throttles are reopened ?

My motors have a pretty big surge, 800-1200RPM's. But with Bravo style drives, this actually helps me shift easily into gear. I simply wait for the downside of the surge and it clicks into gear. If I want to shift them at the same time I rev the motors a bit and it will syncronize the surge and when the revs fall ckick they go.


Darrell.

Leaning will smooth the idle, but if you lean them too much, the engines will die easily when shifting into gear.

LE could you use a bypass valve assembly like Whipple's? See their web site. I believe that their carb blower setups idle good with the bypass.
JE