I am currently looking at replacing the engine in my plane with a
rotary one. I had thought to use a single rotor unit but I have been
given the chance to get a almost new Renesis one (<10,000 Km). I have
looked up the net and found the spec of the engine I would set the
max revs at 4500 rpm (for take off) and  cruise < 4000.  Can anyone
suggest a ball park for fuel consumption given the average altitude
would be < 2000 Feet ABMSL Col Dale


Kind of heavy for direct drive and only 120 HP. A 4500 RPM prop or
ducted fan is very inefficient.

That means your MPG will be horrible. A rotary NEEDS a gear box.

Paul Lamar



Sorry Paul I didn't mention I would be using a gear box.  I plan on having the max prop revs at 2500.  Another identical a/c with a 106HP engine with 2500 RPM could exceed VNE of 140Kn  so I just took the figures of a published torque/HP graph for the Renesis  which is where I got the 4500 take off rpm and 4000 for cruise.  Do mean the engine running at the lighter load will be heavy on fuel?  In this case would I be better to convert it to a single rotor engine and run at a higher speed to reduce the fuel usage.  I have had nothing to do with rotary engines before so things that may be obvious to you experts are not so to me.  Any input is greatly appreciated.

Col Dale

It depends on your intake runner length. The best BSFC always occurs at peak torque which is the
same as peak Volumetric Efficiency (VE). This is the same for piston or for rotary.

To cruise efficiently at 4000 the intake runner length  should have to be about 3  feet long.


Paul Lamar

The Rotary Engine News Letter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
You Tube http://tinyurl.com/beqqxas
Copyright 1998-2015 All world wide rights reserved.