Discussion in 'Subaru' started by geosnooker2000, Apr 3, 2019.
Some stuff was like 3/32 aluminum diamond plate in the floor, because if you do-do something stupid and "mush" in you don't want the willows poking you in the *. And because it had zero electric it had a nice big handle on the boot cowl to hang onto when it was all gucky and mushy and slippery and ya' know, you wanted to prop the plane. A nice big foot + diameter trim wheel so you could keep you hand up near the throttle incase it was needed, that kinda' stuff.
Excellent source for details on proven auto conversions is the Zenith forum.
Why re-invent the wheel? VW / Corvair / Viking Honda / Aeromomentum All proven auto conversions on multiple aircraft. Many are available with Firewall Forward kits depending on your chosen engine and aircraft.
Put your mouse cursor over the FORUMS tab and select the engine.
FYI - Several cases of replacing VW and Corvair with the 130 HP Viking Honda are on record. The results on take off were impressive. The Viking is on more different planes (Sonex/Van's RV/Zenith/Rans/Just Aircraft/Aventura/KitFox... etc etc) and on several continents. For smaller planes, Viking has a 3 cylinder 90HP model now. See YouTube for more.
This is just engineering of the simplest type. First, the rear end of automotive crankshafts are intended to transmit torque at rpm and tiny axial/radial loads. The axial loads are clutch throwout bearing forces and the radial loads are starter gear reaction forces and due to tolerance level errors in crankshaft to engine shaft alignment. Automatic tranny flex plates are designed the way they are to keep axial loads down. No where did the engine guys at Subaru or anywhere else design the crank for running a propellor. PSRU design must take torque at speed from the crank hub, and isolate or otherwise apply all of the other loads.
PSRU design just starts at sizing shafts and bearings for gear loads and prop forces/moments. Propellor hubs have been standardized, prop shaft sizes/materials are well established. Beyond that you calculate the loads on all of this stuff and design shafts and housings, select bearings based upon loads and speeds and desired lifetime/reliability. When you get to thrust forces, they really are not very big. Gyroscopic precession puts way more stress on a prop shaft. I of the prop times rotation speed of the prop times max combined yaw and pitch rotation speed.
We usually hang the PSRU on the RFOB (rear face of block) for a simple set of reasons - that is the end of the crankshaft for power delivery, and that is the end of the engine block for torque and moment reactions. In cars, big loads and moments get fed back into the bell housing and then the block, and the RFOB is designed for that. Gear train reactions back into the case and then the RFOB are from engine torque times the gear ratio. The RFOB in car engines must do that too - in a front wheel drive car, the total ratio between engine and output shafts is on the order of 16-20, so RFOB will stand the 2-3 times we use in PSRU.
If this stuff makes your head spin, wait until you get into the rest of the topic.
The hard part in PSRU design is torsional resonance of the system. Here is a primer on the topic. https://www.homebuiltairplanes.com/...-and-resonance-basic-theory-and-issues.14215/Once you get into all of this, it can drive resizing of the entire system as well as sizing the isolating elements and driving adjustments in flywheel sizing.
Engineering is part science and part art, but the science part has to be done right. Sounds like maybe you should let other folks do the engineering and then trust that choice.
Turbocharged intercooled Subaru EJ series engines are the light way to a solid 200 hp airplane engine, but kind of heavy for a 140 hp engine. Consult with Ross at SDS and sdsefi.com on this.
Subaru EA-81 series have made some excellent 100 hp aero engines, but 140 seems a stretch for them.
The advice to look at AeroMomentum seems like good advice. I have spent quite a bit of time with the owner, he knows his stuff, he has been developing a good reputation with his turn key engines, and has quite a few flying.
There is another guy selling turnkey engines who has an awful reputation, and I do not know how he can even stay in business... look around the web for good and bad reviews on engine sellers.
Intercoolers - all superchargers compress ambient air and that results in raised inlet air temps to the engine. At even modest boost, that can easily result in destructive issues including preignition and detonation. So, we put in an air-to-air heat exchanger that pulls the temp of the compressed air close to ambient before filling the cylinders with it. Makes for more power too. Even my Chevy Cruze Eco has an intercooler between the the turbo compressor and the intake manifold. The price is you need the manifolding to include a trip to and from the intercooler with its own ducts for its cooling air in and out.
So by-pass a lot of this and go for a new set of problems just use the engine to power a generator and use the generator to power a electric motor. The result will likely be at least for the first generations slightly heavier than a PRSU but look how much safer it is in regards the loads imposed on the crankshaft? Also modern electronics are generally much better than those of our by-gone era's, that is they are reliable and "look ma" no gears. The ratio of engine/generator speed to the motor speed can be established by both the the generator and the motor windings and magnets and is virtually infinite within the practical range of aviation needs. The heavier portion, the engine/generator can be placed in any convenient and logical location on the aircraft and the motor/propeller portion is lighter than a conventional engine and gives more flexibility to were and how it is located.
Throw the idea of batteries in the trash! Except the generally 1 or 2 normally used to start the engine and run normal engine and aircraft needs which are charged by the engines normal alternator system.
Just wire the engine/generator straight to the motor/propeller 1 to 1. Engine spins faster propeller spins faster, engine spins slower propeller spins slower. Propeller speed is directly tied to the engine throttle.
Also Personally I'd look to "rv6ejguy" he has been running a Subaru setup an average of 26hrs a year for 16 years, I'd be happy with a setup like that.
All of the four auto conversions that I referenced have excellent records. Those were... VW / Corvair / Viking Honda / Aeromomentum Suzuki
Depending on your aircraft, mission, etc any of these will serve.
Based on real world installations on the Zenith engine forum pages, including ease of installation and customer support, for "turn-key" engines both Viking and Aeromomentum have been very well received.
Aeromomentum comes out of AirBoat applications which match aircraft continuous high rpm use. Viking has over 500 engines sold and a long record of improving their product via fuel system design, electrical design, installation support videos, etc.
Dozens of good comments on record for both companies. These two companies have different philosophies about what makes a "good" engine. Both are fuel injected engines, ECU controlled. Either would be a good choice.
Check out the Zenith forum for each of these engines. Affordable. Reliable. Good support. Why reinvent the wheel with a Subaru and have all the fuss and bother to get things right?
I would be really careful about doing business with Jan Eggenfellner and Viking. There have been a lot of folks pissed with Eggenfellner and both of his companies...
I used to think that way, until one day I realized that some of the people I thought were smarter that I... were not.
I check most everything now.
Just to let you know, I have a masters in Architecture, which included 3 semesters of structural engineering, including wood, steel, and concrete (surprisingly, concrete was the most complicated). So I have a pretty good grasp of the engineering process. I am just moving into a new realm, and am feeling my way around to figure things out. I'm not saying I'm gonna design my own PSRU or 5th bearing. What I AM SAYING is, I want to learn enough to make an informed decision on my powerplant choice, the components I choose, the makers of said components, etc.
Funny you should mention that, I was just checking out Zenith last night.
I feel like I am swerving away from Subaru and into the path of Corvair. Mainly because I agree with one comment one gentleman on Youtube made which made all kinds of sense. Why risk one more point of failure (water cooled vs. air cooled) when you don't have to. But I still need roughly 140Hp or better, so I'm not completely sold if Corvair can satisfy my mission (that being, 4 place, cross country, 250lbs+/- luggage, 150Kts or better cruise).
Air cooled is generally going to be lighter all parts and pieces. Air cooled is generally going to require more pilot interaction all parts and pieces.
Air cooled is generally a misnomer, as many so called air cooled engines derive much if not most of there cooling from oil, of course the oil is cooled by air ultimately but liquid cooled engines, the liquid is cooled by air ultimately also so moot point.
Air cooled is less forgiving of idiots. Idiot in, cracked cylinders and cases out. So if you want to text while driving, air cooled may not be for you.
Liquid cooled is generally heavier, more mass = less prone to idiots.
If you want to get up to altitude and go to sleep between texts till you get to your descent point Liquid cooled with an ECU is more for you, if you plan to stay alert and keep the phone turned off unless you turn it on to get information pertaining to your flight, and you learn proper procedures for operation of an air cooled engine … .
If this is really your mission then you are in the heart of Lycoming territory. Look for a low time 320/360 off a wind damaged Skyhawk or Cherokee, add EFI/ignition and be done with it. Compared to an auto conversion you will be ahead financially, your reliability risk drops a bunch and you will be flying YEARS earlier.
The real problem is that you can not evaluate the whole design except by seeing if ALL of the customers have been happy, or how many are particularly unhappy. I am a retired transmission engineer, with considerable expertise on this topic, and I do not dare pronounce a product acceptable from their spec sheets and sale documents. I judge products I am buying based on how well they have been working in the field. For a powerplant, I want to know how many are flying and how the service history has been running. PSRU's are particularly tricky as they are vibration isolator, load isolator, gear box, and prop mount all rolled into one. One little detail not completely right, and you are in a glider, maybe on fire, maybe with critical parts busted by flying pieces of the engine, prop, or gearbox, maybe shaking the engine right out of its mountings... One little detail can sink the whole ship.
The Corvair won't make 140hp unless turboed or fitted with a gearbox to get the rpms up and then it would be too heavy as well.
To replace the Rotax, you need an engine around 200 pounds complete. You're looking maybe at a G13 Suzuki, Subaru EA81 or maybe a Honda Fit and all would have to be turboed to get that power and have similar altitude performance to the Rotax. You'd have to pay close attention to the accessory and gearbox weights on all of these.
I think you need to design the airplane first and then accept what engine it will need to work. Airplane numbers are always fudged to look good.
The Tsi, if you put four people in it and 250 lb of bags, which is probably impossible to keep in CG, you would have 65 lb left for fuel. That’s 11 gallons instead of the 45 it can hold. Full of fuel, you can carry three people and the bags. The speed they are advertising is true airspeed at 9500. It a 130 kt airplane; that is what shows on the airspeed gauge. Because of less air friction the plane will go faster the higher it goes. The climb they state is one person and half fuel; that’s the standard. Full, I bet 500 ft a min is being generous.
It is working on 140 turbo and what that is doing is allowing is not loosing power at altitude like a natural aspirated Lycoming would. That’s the only reason 140 hp is working. It will stink taking off but at 10000 ft it will be making what a 200 hp non turbo engine does. It just has to make it the hard way. Bill Clapp is doing a turbo Corvair, but I don’t know how hard he is pushing it.
My bet is if you want the load you dream of, you need 200 hp engine. If you are really going to travel with 4 often, the plane will be 15% bigger than you are thinking it should be.
some of us started out much like you....knowing some and not knowing lots more.....it is a tough crowd here......but it is a great hobby, do not get too discouraged......There are successful auto conversions out there, and a world of air-frame choices, along with the boring stock aircraft engines. You will figure something out.
I did that. An EJ22 into a Glastar, using an RAF redrive. Not my airplane; someone else's. In the end he could have had a nice Lycoming for less money, and I didn't even charge for the work I did. It's a LOT OF WORK and it's not cheap. Nothing about aviation is cheap. I had to build a prototype mount from inexpensive steel tube, and then a tacked-together 4130 mount that I had welded by some TIG experts. My welding experience is mostly stick and MIG. That mount had 17 pieces of tubing in it in order to reach around the engine and grab it at its business end. Way more complicated than a Lyc's Dynafocal mount. The engine needed mounting points machined, welded and installed, and I MIGged those. Same with the mufflers, of which I built SEVEN iterations, trying to get effective silencing in a really tight spot. Cooling required the building of a plenum for the radiator. The fuel and ignition and electrical systems....oh, dear. A pile of work.
It is going to be hard to fly four people reasonably fast (true 235+) at altitude (18,000ft max) with less than 180hp at altitude. I think. If you spend some time (I have) reducing successful designs power/speed/wing area/aspect ratio and weight to what you want to accomplish. Approximately 175mph indicated (at any altitude) will give you approximately 235mph true airspeed at 17thousand to 18thousand feet. 140hp is close enough in general terms, you might make it work, but you have your work cut out in the myriad details to make it happen. You are going to have to have a powerful boost system. If it did not have a waste gate it would cause the 140hp engine to have around 290hp at sea level at wide open throttle (WOT) (it would likely blow up first) you'll not likely get that much boost (so kiss the 290hp goodbye) 20% to 25% is more sane, so maybe if the waste gate stuck shut you could get around 175hp (remember we want the engine to stay together with people we care about in the plane). But with a waste gate dumping excess pressure you'll have just the 140hp the engine is designed to take. Now most of us reduce power after take-off to around 83% of take-off power so in the neighborhood of 115hp on your engine and that is what we would climb with up to cruise. You'll want to cruise between 60% and 75% rated power so between 85hp and 105hp for the 140hp rated engine. Because you have boost (lucky you) you had 175hp available at sea level and loosing about 3% available power for each 1,000ft you'll have left at 17,000ft 49% of that 175hp so 49% x 175hp = 85.75hp, hurray just enough to cruise the engine properly. But wait we need 140hp to go fast … oops.
I have followed the Viking Honda almost since inception. "Lot of Folks" is just not the fact.
Go to the Viking Forum or the Viking specific Zenith Forum and you will find the opposite. One guy messed with the ECU and blamed the factory everywhere he could get an audience. All this is just left over from Jan's Subaru problems. Get over it.
Seems some people just cannot move forward. All about the Viking Honda conversion is ready and available on the internet. Do the research instead of just making such comments to discourage people.
The Viking is a solid and proven engine, outstanding work to improve over time. Check and see what those hundreds of delighted customers have to say. They tell the fact.
Impossible to say that those hundreds of builders have failed to do their due diligence and are just befooled. Follow the engine and you will read First Flight posts and watch the videos year after year. Viking ships out multiple engines every week all over the US and the world. Time to move on.
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