ORIGINAL: djlyon

Hi Dar

I looked at those numbers and don't understand any of them. I was not running a Rossi Q500 motor. Mine is just a standard 3 port 40. On an older 3 port motor I could get 16.5 with a 9/6 apc using the old pop rivet muffler. The PS muffler (Nelson Ultra thrust) I was using was the sport racing. It is the same as the racing I believe (I never measured the inner pipe) except for the header which fits engines like the TT40 PRO and slightly cants the muffler away from the fuselage. It fits the Rossi using an adapter plate made by SG. I don't believe he makes an adapter plate that will fit the regular Nelson racing muffler to a Rossi. Hole spacing.

A TT40 PRO with it's stock expansion chamber muffler (baffle in) properly broke in with appropriate shim changes will typically turn a 9/6 at 16.8 to 17.2 on the ground. If it doesn't you set it aside for a practice motor . At least all that is true in California air. Put on the Ultra thrust sport racing and it goes up to 18.2 to 18.4. I use that configuration for first flights on a new quickie before putting a Nelson on just to get the rough trim and check to make sure nothing ugly is going to happen.

I'm stumped by his numbers. It could be that the Rossi Q500 is just not ported for what he was trying to do. But if it was a real Q500 motor it should have been able to get on the pipe with a 9/6. I wonder about vibration with that stand he was using. I just don't know.

Denis