mazdaspeed7

I think youre missing something about PP's and reduction drives. 250 hp at 7000 rpm is 187 ft lbs. The 2.85:1 reduction drive turns that into 533 ft lbs at 2450 rpm at the prop. And thats just for one engine.



It doesnt take anything special to make a rotary reliable at 7000 rpm. The problems dont start arising until 8500 rpm and beyond.



PP's have a very high VE(120-130%) at the torque peak. You could run two of Tracy Cooks controllers, provided you treat the engines as two completely seperate engines. But that doesnt mean the engines have to be seperate. You cant link them, nor the stock ecu, but there is no need. There will be no difference from the perspective of the EMS whether you have 2 engines completely seperate, or have the ecc shafts coupled to it makes power as one engine.



All that is somewhat beside the point, as things are very different in the aviation field as far as reliable power goes. You can use a much larger turbo on an aircraft because there is no drivability issues to deal with . The load on the engine is dependent on rpm, nothing else. And it doesnt matter if it takes a second, or even a couple of seconds for a turbo to spool up. As long as the turbo makes full boost by the cruise rpm, it cant be too big. Also, due to the airspeed, smaller radiators and intercoolers will remove much more heat than they would in a car. An IC thats adequate for 200 hp on the ground would cool the charge enough for 400+ hp at aircraft speeds.



That being said, I think you would be best off with a single turbo 13B. You could do a small bridgeport that will make the power you want at 6000 rpm with a nice sized turbo. You dont have to buy a new turbo. Start reading up on compressor maps, and go junkyard shopping for a turbo off a diesel truck. Theres a world of info on just that on the internet. If you want more details on the porting, let me know.

TLT

I knew about the torque at speed for the PP, I just didn't know whether it merited the PP build-up.......all of this is moot though since the retractable gear is playing havoc with space inside the fuselage for twin engines. I'm losing a full 12" of bay-space due to the tires, and the deal with the forward engine sitting adjacent the fuel is really bothersome. I'm going to make one last calculation in X-Plane to confirm the power needed, then I'm off to the turbo boards to see about the diesel's and such; I'd heard about them before. Ironically, I have a Cummin's Dodge. One of the ER nurses I work with has a mild street ported 13B 4-port with:



TO4E 60:1 compressor

.84 A/R divided turbine

HKS manifold

HKS 50mm wastegate

720cc/min primaries

1600cc/min secondaries

big intercooler

fd seals

75psi oil reg



Last dyno run for his rig was 416HP@7,000RPM at the wheels, and supposedly that puts the crank horses at about 480?!



I have already made adjustments for the intercooler size, and planned on keeping the RPM's right at 5252RPM to match the torque to the HP, and Ric suggested that a much smaller wastegate could be used, but I'm still investigating that. I'm still trying to understand the relationship between porting, the turbo's work and the engine's need to breathe under those conditions.......is the porting necessary because the turbo forces the engine to need to breathe & exhaust better? I'm much more a carb/V-8 man than a rotor-head, but I have dedicated myself to learning rotaries since I am convinced they are the aviation wave of the future. Also, what do you think of the practice of using 100psi oil pumps and the pre-mixing of oil into the fuel(aka Tracy's trick on his Otter)? I'd really like to make the power at 5252RPM and use the standard PSRU, but if need be I can go with the higher revving setup and the 2.85:1 PSRU. I have noted so far that during the landing run if the power is over 25%, the ship refuses to slow down, so the maximum boost issue is really only applicable to the take-off sequence(1-2 minutes at most.)

diabolical1

well ... all of this stuff is over my head, but who am i to call another man's dreams impossible or dumb? i live on the other end of that daily and it ain't a nice feeling ...



so here's my input:



1 - research either Audi or companies that modify Audis. i remember reading about a TT that had two 1.8t engines in it. i just can't remember who built it and i'm thousands of miles from my mini-library of car magazines, else i'd look for it for you. maybe you can pursue it until you find out how they did the engine management on that - because both engine were synchronized and controlled by the same e-throttle if i recall correctly.



2 - see if Bob Norwood (or his people) will speak to you. i remember him talking about doing Ferrari Testarossa with two flat-12's, but this was years ago (maybe late 80's). i don't know if he ever went through with it, but from the things that i've seen him create, i'd say you could do a lot worse than talking to him. he's earned my respect and admiration.



good luck with your aircraft project and i hope this helps.

diabolical1

oh yeah ... here



www.bobnorwood.com

TLT

I appreciate the suggestion D1, but it looks as though the space is just not there for the tandem engines. I'm back to powering up my single 13B turbo...FLOL!

mazdaspeed7

Well, theres always a bright side. It will be that much simpler. and cheaper by not having to do everything twice. 500hp in aviation trim is not hard to make reliable. Racing Beat made a 900 hp 3 rotor for an airfcraft. Some info is at the following link.



I believe this link will be a lot of help and interest to you.

TLT

I've been on the ACRE list for over a year, boss, but thanks fer the thought!





Most of their work is mod-specific to standard rotary setups pushing only about 200+HP systems. Only now are they seriously entertaining the idea of a PP and the 2.85:1 PSRU. I don't even think anyone on the list has a 300HP rotary onboard. Tracy is just now converting over to a Renesis.

mazdaspeed7

Well, I tried...



The hp thing is simply because theres not many experimental planes that can take over 200 hp, let alone use it.



I dont have x plane, nor do I really have a lot of time to mess with it. Any chance you could take a screenshot showing the basic design of your plane?

TLT

Actually, they've got experimentals using monstrous V-8's(I think it's a P-51 mock-up)but in my case since I'm using symmetrical foils due to the design, I'm relegated to making this kind of power to offset the lack of low-speed lift. And before you suggest it, yes, the flaps, slats & speedbrakes have all been tried........their not worth the effort.....better to go the way I am and just rig the braking system to stop her at a faster landing speed. I'll send yu a pic when I get some time, bro.