DLrocket89

Hi all, new here. My name is Dustin, I live in the Rockford IL area. Building the airplane (starting it fairly soonish). Airplane can be seen here: http://www.bearhawkaircraft.com/Bearhawk/BHspecs.php

I'd like to put a rotary on it for a variety of reasons. Weight, power, reliability to name a few. The "typical" airplane engine hasn't changed in since about 1930, a good example is this: http://en.wikipedia.org/wiki/Lycoming_O-540 They have a tendency to blow valves, cranks, crack engine cases, etc.

I'd like a max output of 300HP at about 7000 RPMs on the engine. I have an engine controller (EFI and spark) lined up along with other things to make it airplane ready. My attention now turns to the engine "core". I need a sustained output of about 150 HP with a max of 300HP, and I need it to be able to sustain that 300HP for about 30 seconds straight at a time.

After talking with people on aviation forums, they said that the two main choices are a 2 rotor with a turbo or a 3 rotor without a turbo. If i go with a turbo, it needs to be able to put out max boost for the aforementioned 30 seconds or be at about 1/2 boost for 2+ hours straight. My understanding is that the Mazda turbo won't cut it, a couple of guys almost died finding that out. A "Turbonetics T04" unit apparently seems to work well.


So, a list of questions:

1) I want to have someone build me an engine. Reliability is key, so if they can make enhancements there, that would be awesome. Can anyone recommend to me a good engine builder?

2) Any comments on 2 rotor plus turbo vrs 3 rotor? I'm wondering about weight vrs HP, reliability, cost, complexity, etc...

3) I was hoping to have a variable wastegate so that I could control the amount of boost (if I go with a turbo). What are the options there?

4) Anything else?


Thanks in advance!

Dustin

RotaryRocket88

iTrader: (7)

If you haven't heard of them, Rotary Aviation is a great place to start: http://www.rotaryaviation.com/faq.html#horsepower.

When it comes to building a reliable 13B turbo setup with 300 HP at the flywheel, a small T04b would be a good option. Newer turbo designs will be a lot more efficient than the OEM turbo, which means lower intake temperatures under boost and better airflow. Some commonly used turbos are detailed here: http://www.fc3spro.com/TECH/TURBO/compmap.html.

A 3-rotor (20B) will be harder to find, but NA potential with porting and higher compression rotors should be about on par with a 13B using a small turbo. This will be the more expensive route, but you'll save space without a turbo and intercooler.

DLrocket89

How do those compare in weight? I'll take a slightly more packed system if it can be lighter.

RotaryRocket88

iTrader: (7)

Well, I searched around a bit and found some short block weights:

20B short block: ~270 lbs. (https://www.rx7club.com/20b-forum-95/20b-engine-weight-651221/)
13B short block: ~200 lbs. (https://www.rx7club.com/2nd-generation-specific-1986-1992-17/engine-weight-675202/)

So you've got an extra 70 lbs. from the block, then some additional weight from larger manifolds. You could probably save some weight with a custom intake, but a header with even-length runners can get fairly heavy. So a 13B turbo build should still come out a bit lighter.

Here's another link with 20B info, but it's mostly geared towards a turbo setup: http://fc3spro.com/TECH/SWAP/COSMO/20b.html.

gracer7-rx7

iTrader: (16)

1)
Rotary builders in Il area:
http://www.banzai-racing.com/
http://www.a-spectuning.com/services.htm

Also definedautoworks.com was recommended by a Carlos Lopez for street oriented 3 rotor builds

2) Its a debatable topic. Turbo/Non-Turbo, 13B or 20B. Ported/Non-Ported. A normally aspirated option may be simpler and involve less parts but I'm no expert here. A street ported 3 rotor should hit around the 350 crank HP target easily with good torque and great reliability. For similar power levels on a 2 rotor, you would need aggressive porting (bridge port or peripheral port) which is LOUDER or turbo power which involves a lot more parts - manifold, turbo, wastegate, boost controller, more heat management etc.

3) I don't think there is a variable wastegate, but you can control how much boost you want to run with a boost controller.

DLrocket89

Excellent, thanks!

Looks like either will work, the max installed engine weight on this plane is about 450-500 pounds. I'd love to keep the whole setup to 350lbs or below. That way, I can put the batteries up front and save about 25 pounds on the whole plane by not having to run 30 feet of 2 AWG wire. With too heavy of an engine (up in the 450lb range) you end up needing to put the batteries in back so that your center of gravity is right to make the plane stable.

Mind you, when I say "whole setup", I mean EVERYTHING in front. Engine, prop, radiators, etc.

DLrocket89

That's what I'm talking about then, thanks!


And thanks for the rest of the (non-quoted) input.

FCGURU

rotary avaiation

has some great apex seals

DLrocket89

They're the people who's engine controller and PSRU I'll be using.