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Hi Andrew,
Wow, what a choice to face. I'm sure you will get a variety of pro and con view points.
Here are some:
The 20B will produce more power
The 20B installation will weigh approx 60-100 lbs more depending on a lot of factors
The 20B is an older engine model and who knows how long parts will be available. I have seen reports that folks are having problems getting rotor housings for the older engine because all of Mazda's casting capacity is devoted to the Rx-8 Renesis engine - don't know if that is factual, but appears to have some merit.
The Renesis will produce over 200HP in aircraft configuration at sea level
The Renesis is a lighter engine
The Renesis is a new model so parts will be less of a problem
The additional ports (intake/exhaust) could make the induction/exhaust plumbing interesting.
There are other factors as well. How high will you fly? Would turbo normalization be a consideration?
I currently fly an Rv-6A with an older (91 model) 13B. I seldom fly over 10,000 MSL, but I do go in and out of short grass strips. I seldom ever fly at top power or speed (too cheap to burn the gasoline at that rate {:>)
So while I have though many times about turbocharging my engine (have two turbos sitting in the shop), it just doesn't make much since for my type of flying to haul around 50-60lbs more in the nose on each and every flight. In fact, if I did anything it would be to go to the newer Renesis engine and pick up a bit more power for getting out of the short fields with an engine a bit less in weight
Good luck
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda/index.html
----- Original Message ----- From: "Andrew Martin" <andrew@martinag.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, October 01, 2007 1:20 PM
Subject: [FlyRotary] motor decisions!
Hi
I have a 20b and about to start building a plane that is designed for a
IO 360. It has been suggested to me that I should change to a 2 rotor to
save weight. I've gone through the archives but didn't really find any
pro' and con's of 3 or 2 rotors other than the max power available.
The plane will be used almost exclusively for long X-country cruising
once the bugs are worked out and hours flown off.
If my estimated max power required due to VNE is around 200hp, is the
Renesis always the engine of choice or are there advantages to keeping
the 20b, accepting the weight penalty and letting the engine loaf along.
I originally presumed the 20b would be better for me especially when at
my gross weight of 2420 lbs. but now I am unsure, so to change now
rather than later would be easier.
Any help from anyone flying either engine, and points that governed your
engine of choice would be greatly appreciated.
Regards
Andrew Martin
Western Australia
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