Powersport Aviation

[gmcjetpilot]

Originally Posted by rv6ejguy

The oil issue is no big deal in the Wankel. Just add your oil prior to fueling. No different than using TCP in a Sube or Lycoming. Just don't forget! (Add to preflight checklist). It's a pretty good Lyc that only burns 1 qt. every 16 hours. The ones I fly are more in the 4-8 hours per qt. The Wankels I have worked use nowhere near this amount of oil.

As discussed previously, Crook and others are reporting fuel flows pretty close to Lycs when aggressively leaned using his ECUs. Crook appears to be a straight shooter but it would be best to verify these claims with a head to head at Van's under controlled conditions.

TCP? Why would I use that? I never have used that and I was a flight instructor in a fleet of 35 plus aircraft, most with Lycoming engines. Lead fowling in a typical (higher compression) O-320/360 today is a non-issue, as long as the pilot leans the engine properly on the ground.

Yes 16 qts an hour, what are you saying I am lying?

Originally Posted by robertahegy

I put 8 quarts in with a new filter on my 0-360. Half a quart (or more) goes in the filter leaving 7.5 (or less) in the sump. I go 25 hrs without having to add. I use about 1 qt in 25. Very little gets on the belly.

Originally Posted by OneTwoSierra

I've put 8 qts in the last 2 oil changes in my 0-320 with oil screen only. The oil drops to 7.5 quarts rather quickly (4 or 5 hours) and then slowly burns another 1/2 qt over the next 20 hours. I'm going to stop wasting that quart and go with 7 and see what she does. I appreciate all the discussion on this topic.

If your Lycoming is burning a qt every 4-8 hrs , you have worn valve guides, rings or both? My twin with 2150hrs used less than 1qt in 8 hrs, which is after 2150 hours. My RV-4 used about 16-18qts/hr. With the new cylinder materials, Nickel-Carbide and thru hardened jugs, oil use has been lowered even more (read above).

Adding oil or any additive is a pain in the backside and you have to do it every time you add gas with the Rotary. I asked Tracy Crook about this. I forgot the oil use but it was significant, like a 3/4qt per fill up, which is about 1qt every 4 hours. Rotary uses more oil than a Lycoming, because it needs oil in the fuel to lube the seals, like a two-stroke engine! I mean it is not big deal and you don't have to be defensive and throw some useless Lycoming number out like a qt in 4 hrs. I mean it is just a fact and you don't have to attack a Lycoming to justify it. It is just the way it is. Every time you fill up you have to break out the bottle of oil to put in the tank. Lycoming might go several fill ups before getting the bottle out. Some are going oil change to oil change with out adding oil to their Lyc. Yes you check it, but that is little effort compared to adding oil. If it is not big deal to you, than great, Mo-power-to-ya. I hate it. I flew Cessna Citations Jets. When uplifting Jet-A I had to add the anti-ice called Prist to the fuel in a little spray-can.

This thread was started to discuss the Powersport, not attack Lycoming with exaggerated claims. When faced with facts like the RVator article I hear excuses and attacks. I can't understand why you have to justify the fact a rotary is thirsty, loud and uses oil. If you have data that is well documented, than just present that with out all the pot shots and defensive attitude. If you want a Wankel get one, but be realistic, it has limitations. Don't be so insecure you feel you must justify your choice in engine by tearing down the prime engine used in most aircraft. Don't justify the limitations of the Wankel, embrace them. There is a reason Mazda is the only one making a rotary engine car. They burn more gas. That fuel burn is justified in a hot sports car and may be an airplane. FACE THE FACTS:

THE ROTARY ENGINE RV-8 IN A FLY OFF AGIANST A LYCOMING POWERED RV-8 BURNED 34% MORE FUEL WITH AN ADVANTAGE OF 3-4 MPH.

I think that is pretty good. However when Tracy wants to race my RV-7 180HP Lyc, 4into1, dual EI, NASA/Lopresti/SamJames style cowl. Bring it. I know power sport engines are modified to make more power than the near Stock 13B Tracy uses. Again go slow, leaned out=Better fuel burn; GO fast, rich=High fuel burn. Apples and Apples. In the end the only way to get efficency is fly high, which applies to the Lycoming or any engine. This is as much or more from aerodynamics of flight and lift/drag relation of the airframe as it has to do anything with the engine.

Lets have a Cross country side by side fly off between Tracy's RV-4 and a RV-4 with Lycoming. Than we can see who is burning more fuel. Even a Lycoming with fuel injection can run lean of peak and get real low fuel burn, at the expense of speed. Again, lets o this. ANY RV-4's pilots with a IO-320 out there want to do this? I say IO-320 because Tracy's RV-4 is as fast as a fast 160HP Lyc powered RV, however a IO360 would work to. Tracy raced in the 160hp class lastat Sun-in-fun but claims it makes 180hp?

Fuel burn? Facts, how fast was Tracy going in this super lean mode. I have flown my RV-4 to 17,500 and got fuel burn down below 5.25gal/hr and still had TAS of +165MPH (that was a O320 150HP Lyc). When you open up a Wankel (race mode) it will drink fuel at a higher rate. I like how you ignore the RVator article and divert the rhetoric to Tracy and his ECI can go into super lean mode. Look Apples and Apples. You want power you burn gas. Wankel will burn more than the equivalent piston Lycoming producing the same thrust. Deal with it. You can mitigate this weakness but you can't eliminate it. You want to dream of super efficient super Lean mode go ahead. Accept it or continue to be delusional. People don't fly "Super Lean". Tracy's own test on a new rotary engine produce eye watering fuel burns (17gal/hr) or something like that. Again the experts agree that the physics of combustion in a rotary engine has inherent inefficiencies. I know I am blaspheming on the alter of rotary, but it is true.

As far as noise, prove a turbo makes the rotary quite. Facts, numbers, test. I don't care I love engine noise, including a rotary. Again from the RVator:

DURING THE RV-8 FLY OFF THE ROTARY POWERED RV-8 GOT THE ATTENTION OF THE AIRPORT AUTHORITIES!

G

[Rotary10-RV]

Originally Posted by rv6ejguy

Not possible to have 6000 on takeoff with a fixed pitch prop and have much less than 7000-8000 in cruise flight. To have 6000 in cruise, I'd guess that you'd be closer to 4000-4500 rpm static on the ground at WOT.

Problem with most auto engines including rotaries is that power peaks are usually developed at 5000-7500 rpm. You can't develop rated power at 1000-3500 rpm below power peak plus a FP prop is partially stalled at low airspeeds leading to poor acceleration and thrust. With a Lyc, power and torque peaks occur at almost the same rpm and are very flat so a FP prop works pretty well on a light aircraft like an RV.

Yes, it does seem that Tracy is getting pretty decent fuel flows compared to the Powersport guys.

6EJGuy,
Tracy is flying with a newer version of his PSRU with a 2.82:1 reduction ratio. Take off is at 75-7800 rpm and cruise about 4800. (I don't remember what his static RPM was.) Don't be as concerned with those high RPM numbers as the rotary doesn't suffer at higher R's as piston engines do. In fact Mazda did stress studies when preparing to build it's '91 LeMans winner and found that at 6000 RPM the net bearing load was zero. (due to various balance factors) Tracy is swinging a 79" prop if I remember correctly and on his first flight wasn't ready for the torque reaction and P factor when he firewalled the engine and almost ended up in the weeds to the left of the runway! The rotary does have a wide RPM range and I'm sure a C/S prop is the way to go. I like Tracy, but if you want to run a C/S Mistral's Psru may be the way to go for you. Expensive at around $6500 bucks, but comes equiped for driving a prop govenor and a second alternator. The unit is a purpose built planetary with a 2.82:1 reduction drive using spur gears designed for the power output. A great looking magnesium casting as well. I'm glad they will sell to experimental builders. Unless Tracy goes C/S I will use the Mistral unit on my RV-10.
As an aside, Mistral will also sell you a "engine forward" package with the PSRU, C/S prop, and governor at a "reduced" overall price. (I didn't ask) They have been very honest at promoting the rotary though and it's probably worth a look.
Bill Jepson

[cjensen]

Hey George,

I hope those last couple of paragraph's weren't directed at me and my comments. I have never boasted about low fuel burn of a rotary. I know Tracy was running super lean, and I was just making mention of the low burn he achieved for that particular trip. I am not that concerned with fuel flow rates, and if my power comes at the expense of higher burn rates, so be it. I can accept that. There's no question whatsoever in my mind that the rotary is thirsty. I'm not going to use one in an effort to conserve fuel. And I will never attack lycomings, or the clones. I've said it before, and will say it again, they are great engines, and I have no problem with them. I've had two previously, and they were almost perfect in performance, and just about 100% dispatch reliable. If I ever go back to certified airplanes, a lycoming will power it again.

No hard feelings, man.

[Rotary10-RV]

Fuel burn? Facts, how fast was Tracy going in this super lean mode. I have flown my RV-4 to 17,500 and got fuel burn down below 5.25gal/hr. When you open up a Wankel (race mode) it will drink fuel at a higher rate. I like how you ignore the RVator article and divert the rhetoric to Tracy says his ECI can go into super lean mode. Look Apples and Apples. You want power you burn gas. Wankel will bun more. You want supper efficient and you claim a super Lean mode is more efficient than another type of engine
Accept it or continue to be delusional. People don't fly "Super Lean". Tracy's own test on the new engine produce eye watering fuel burns. Again the experts agree that the physics of combustion in a rotary engine has inherent inefficiencies. I know I am blaspheme on the alter of rotary, but it is true.[/quote]

George,
I will NOT insult LYC's, but you should know the the rotary using more fuel at the same MAX and CRUISE output is a MYTH not a fact. Early rotaries were truly gas hogs in around town driving in auto use. They had thermal reactors (read afterburners) to get the HC smog levels down. The use of FI and improved intakes and exhaust technology has provided a much more efficient engine. In '91 running the rotary powered prototype to a overall win at Le Mans Mazda finished with the MOST fuel remaining of all the prototypes! There are many factors which go into this, but the engine was shown to be at least as efficient as any of the pistons running. You are going to use a similar amount of fuel in the rotary to produce a given HP level as a Lyc will. As to the oil thing, THIS IS A NON ISSUE, if you don't want to add to the fuel tanks RUN THE STOCK SYSTEM. The oil consumed isn't even close to typical LYC oil consumption. This isn't an insult just a fact. Throughout rotary development the amount of oil injected has continually gone down, with the newest RX-8 engine using the least of all.
Bill Jepson

[cjensen]

Hey Bill,

Those were the numbers I was referring to, but it seems like dragging names into threads can cause problems. Anyway, thanks for posting that. You are right about the high RPM contentness in the rotary.

What a lot of people don't realize (but many do) is that the rotary turning 6000 rpm is the rpm at the eccentric shaft. The rotors are only turning 2000 rpm. The e-shaft is a solid piece of balanced metal turing a very small radius. This has probably been posted here before, but I can't remember.

The Mistral is another outstanding package, and I am hot on that one too! There PSRU is the perfect solution, being able to use a hydraulic C/S prop. Pricey though, even more so than Powersport. Does anyone know if there FWF package comes with an engine mount?

[cjensen]

I listened to the RV-8's fly at OSH, and didn't think they were obtrusive. Louder than a 180-200 horse lyc, yes, but I didn't think they were any louder than a 210, Bonanza, or Viking taking off. It's just a different sound to me, and it's pretty cool sounding, and I was right next to the runway at the approach end.

Maybe it's just me, but I think they sound good!

[gmcjetpilot]

Originally Posted by cjensen

Hey George,I hope those last couple of paragraph's weren't directed at me and my comments. No hard feelings, man.

Oh no sir, I am laughing and appreciate your comments. I just have to keep Mr/ RV6EJGUY in line. All in good fun of course.

I would like to see more side-by-side fly-offs so we can cut thru the emotion of bull. I don't care what the out come is, and would love an alternative to come out head and shoulders above, but this is the real world. I would love the Subi, Rotary, Lycoming to go head to head and really get the facts. We have some data and I think most of the pros and cons are on the table with some noise and smoke clouds. I like to cut thru the noise and smoke.

Cheers George.

[Rotary10-RV]

Originally Posted by cjensen

Hey Bill,

Those were the numbers I was referring to, but it seems like dragging names into threads can cause problems. Anyway, thanks for posting that. You are right about the high RPM contentness in the rotary.

What a lot of people don't realize (but many do) is that the rotary turning 6000 rpm is the rpm at the eccentric shaft. The rotors are only turning 2000 rpm. The e-shaft is a solid piece of balanced metal turing a very small radius. This has probably been posted here before, but I can't remember.

The Mistral is another outstanding package, and I am hot on that one too! There PSRU is the perfect solution, being able to use a hydraulic C/S prop. Pricey though, even more so than Powersport. Does anyone know if there FWF package comes with an engine mount?

Chad,
The Mistral rotary comes with a custom built rear cover that attaches to the standard Dynafocal mount. They will also supply mounts for a bed (Conti) style mount. Their prices are higher on everything as they are certifing the rotary, as opposed to just suppling parts. Certified engines are great, but they have their problems too, witness the extension of the Lyc cranckshaft recall to new 4 cylinders as well. ANY engine has pluses and minuses. I believe the rotary makes a excellent aircraft package. Powersport has a nice package, but it is not without flaw. Powersport has had money problems as well that have prevented a lot of additional product development, hope they can get their problems ironed out. Alternate engines are best used by those who have enough engineering expertise to contribute to the design process. If you have any doubt put in a standard aero engine. On the other hand developing your engine package can have the same rewards as building your own aircraft. You MAY produce something that works better than the standard. The converse is also true so always be sure to use the best possible parts and systems throughout. It's your tail on the line!
Bill Jepson

[cobra]

All internal combustion engines TARGET approximately the same air to fuel mixture, ideally somewhere around 14:1. Lean mixtures generate a lot more more heat than rich ones do, particuarly so at high power levels; the actual mixture used ends up being a compromise. Water cooled engines should be able to run slightly leaner than air cooled engines, because heat breaks down lubricating fluids and we have to regulate piston/head temps.

From what Ive gathered, the rotaries (and probably most of the auto conversion fuel-injected motors run safely/leaner compared to carburated motors- because their mixture is automatically optpimised by sensors and computers, not by "feel" as most of the old-school Lycs, etc.

However, the conventional aircraft engines run at about 1/2 the automotive conversions' rpm, which likely burns less volume than an a smaller automotive motor running at a faster speed. It is a matter of large displacement x rpm/2 x fuel concentration with the Lycs vs smaller displacement x rpm x concentration with the rotary. The rotaries fire on each rotation of the crankshaft, the 4-cycle engines on every other rotation. Im guessing the displacement of the Lycs is the 320/360 cu/in listed in the engine series??? The rotaries have 1.3 liter displacement.

All in all, actual fuel burn rates are pretty close from what Ive seen reported, with the older rotaries slightly higher, and less efficient, due to the rounded constantly-changing shape of their combustion chamber. The newer Mazda Renesis designs have a better design that looks to be more efficient at low rpms than the older motors were. There is also the issue of the geared reduction units- there are always efficiency losses thru a tranny and propeller.

The sound issue is also a push- noise generation depends on the individual exhaust systems being compared. Tracy's muffled engine is quieter than most of the Lycs on the flight line. With straight pipes, the rotaries are probably worse- exhaust is hotter (more energy to dissipate) and has a higher pitch (more like a snarl than a roar).

The oil burn rate in the rotary is much less than the 2-cycle motor we all love/hate-- not a big deal. The oil loss rate is unnoticable when the burned oil is pulled from the crankcase. I feel the best solution is to use a separate oil tank to provide 2-clcyle oil to the rotor lubricating pump, and use a synthetic oil in the crankcase. Mixing oil with fuel is another common racing alternative that works well, generaly requiring a few ounces of 2-cycle oil per 5 gallons fuel added to the tanks. I dont like the potential of detonation, fuel/oil separation under extreme conditions, or problems with the oil mixing completely with the fuel in the tanks under that scenario.

[gmcjetpilot]

Originally Posted by Rotary10-RV

There are many factors that go into this, but the engine was shown to be at least as efficient as any of the pistons running. You are going to use a similar amount of fuel in the rotary to produce a given HP level as a Lyc will. As to the oil thing, THIS IS A NON-ISSUE, if you don't want to add to the fuel tanks RUN THE STOCK SYSTEM. The oil consumed isn't even close to typical LYC oil consumption. This isn't an insult just a fact. Throughout rotary development the amount of oil injected has continually gone down, with the newest RX-8 engine using the least of all.
Bill Jepson

Ok that is good. I would like to see that. I am not saying in some operating condition the Wankel can approach the efficency of a piston engine, but lest have some side-by-side fly offs. There it is in black and white in the RVator. OK. So now we should have Tracy do a fly off using his equipment.

As far as oil, I agree it is a moot point with Av gas costing an avg of $3.23 a gal. However I got it from the horse?s mouth, Tracy and the oil burn, or should say use, was high. I don't recall but it was the better part of a qt to each tank of gas. Really no lie, 16-18 hours per qt is not an unrealistic amount for a Lycoming. So what is the real world oil use of a Rotary engine?

Cheers George