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Thread: Rotax vs Lycoming

  1. #1
    Registered User Atomic_Sheep's Avatar
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    Rotax vs Lycoming

    Just a question... I haven't checked out the price for Rotax engines but how does Lycoming make money? The way I see it, O-320 is 2ce as heavy as a Rotax 914 although it does have the extra 35hp which is not a lot considering the weight gain I think. Then there's the price. I'm assuming Rotax are a lot cheaper than the Lycoming (20k for a 280 or something along those lines?) I'm comparing certified vs certified here. But really, I just don't understand why anyone would buy a Lycoming over a Rotax given the specs on paper. Please comment and enlighten my ignorance in this regard.

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    Registered User Mac790's Avatar
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    Re: Rotax vs Lycoming

    Quote Originally Posted by Atomic_Sheep View Post
    I'm assuming Rotax are a lot cheaper than the Lycoming (20k for a 280 or something along those lines?)
    I'm not extremely sure about it, but I've seen Rotax probably 912 or 914 for if I remember correctly 33 or 35 (grand) $, doesn't sound like a lot of cheaper for me .

    Seb
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    TFF
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    Re: Rotax vs Lycoming

    Reliability is the reason. Of the Lycoming engines in our two helicopters, only one, the last one, has not made it to TBO in 8 overhauled engines. The flight school ran one 4000hrs straight; not unheard of with a good rebuild. Also if you have a problem, the engine has a less chance of not stopping even though damaged.. I take care of an Aircam, 2 Rotax 912s; Built with new engines has about 350hrs on them now, and I like them, but they are acting like mid time engines. If they go 700hr without major work I will be suprised. I will say, the high time engines are run almost daly, which is better than letting them sit a bunch.

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    Registered User DarylP's Avatar
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    Re: Rotax vs Lycoming

    Well it has a long record of success, and a true aircraft engine. As far as weight is concerned, I would like to see two complete engines with all parts weighed. I say that because the Rotax does not include the radiator in its weight, at least not in the specs I've seen. The Lycoming has electronic ignition and fuel injection, and I personally won't buy an engine without it. The Rotax you would have to add the FI, from an aftermarket company.

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    Moderator Dana's Avatar
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    Re: Rotax vs Lycoming

    A better comparison would be the O-235 which is (depending on variant) the equivalent in power to the 914. The O-235 is about 40% heaver than the 914 (less if you factor in the 914's cooling system). The Lycoming turns at half the RPM of the 914, making for less noise and increased reliability. The Rotax has a 5 minute limit at its 115HP max, only 100HP continuous. Water cooling adds complexity, as does the gearbox. On the plus side, the 914 can run on autogas with up to 10% ethanol.

    Lycoming now also has the O-233 which is similar to the O-235 but weighs only 200#, making it more competitive with the 914, but it's not yet certificated.

    Finally, all Rotax engines, even the 4-strokes, are tainted in the eyes of many GA pilots and mechanics who want nothing to do with what they perceive as unreliable 2-stroke engines in ultralights.

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    TFF
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    Re: Rotax vs Lycoming

    One thing is owners want to treat the Rotax like a Lycoming; start and go. With the rotax you are to pull the engine through by hand to get the oil back into the sump; one of the owners spins it with the starter thinking it is the same. Dry bearings under load is nice. It is a seasonal plane so it sits a bunch in the winter, he does his start but the engine wont turn, hydraulic lock from sitting for three months of oil leaking through the ring gaps, which is normal, would have found it if he was doing his preflight, but also the engine is small, about the same size as an MG Midget engine, so with its short stroke only takes about 2 oz of oil to jam it. Turn the prop backwards and you have to check if the pushrods fell out. THe Rotax is like a crotch rocket motorcycle, it screams its heart out to make 100hp; where your compact car is loafing making 100hp. The Rotax is built like a motorcycle engine and they Lycoming is built like a Diesel. If it all about light weight you cant beat the Rotax, the Aircam would not be what it is without them, but it is also not a plane that will live as long as a Cub given the same abuse.

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    Registered User DarylP's Avatar
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    Re: Rotax vs Lycoming

    The jugs on the Rotax are not liquid cooled, which is something that I don't understand as it really does not cool effectively then. By that I mean that a typical automotive engine has the jugs integral to the block, and cooling is complete. The Lycoming is a direct drive, which of course means that you are not adding a reduction drive, which I personally like. Less is better.

    As far as price, I bet that if you found a rebuildable lycoming and could do the work yourself, you could build it for a lot less money. Of course that would not be certified unless you were a certified aircraft mechanic.

    I personally would like to see Yamaha enter the market with an engine designed specifically for the LSA market. That of course would mean that the FAA would need make it easier for companies to enter that market. The aircraft industry is so constrained by lawsuits of every stripe though, and that further constrains the ability for any company to build a more up to date engine that is affordable. As the question has been posed, how does an engine company make money, well that is really difficult. But there are other threads on this. Suffice it to say, that if you can afford a plane, and a certified plane, is it not best to stick with a tried and true engine design? At least until something better comes along.

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    Moderator autoreply's Avatar
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    Re: Rotax vs Lycoming

    Good remark by TFF.

    When comparing engines we should not that we are comparing the correct engines. If you compare the 914 (a turbo-normalized engine) with the O-235 that's not really a fair comparison. Since the turbo adds considerable weight, cost and complexity. The 912(S) (80 or 100 hp) on the other hand is (per horsepower) only 60% of the weight of Lycomings/continentals, one of my motivations for 2 light engines instead of 1 heavy one.
    Total installed weight of them is 140 lbs:
    Rotax 912 ULS specifications, performance, weights and documentation

    Cost per horsepower isn't higher as a Lyc/Conti...


    And given the number of those engines flying (many thousands) and their problems (few, except from user abuse) I would trade them anytime for our Lyncosaurs.

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    Registered User DarylP's Avatar
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    Re: Rotax vs Lycoming

    autoreply,
    Yeah they are lighter, and that is the first I have not seen on that spec sheet that included the weight of the radiator weight. It does not factor in the water weight of the cooling system though, but hey...it will still be lighter.
    The new Lycoming, the IO-233-LSA weighs 200 to 210 pounds and the spec sheet (PDF) that I have on it says that it produces max continuous HP 116@2800 RPMs. I am curious how that changes the power to weight. On top of that it is fuel injected, with electronic ignition, with a TBO of 2400 hours.

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    Moderator autoreply's Avatar
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    Re: Rotax vs Lycoming

    Quote Originally Posted by DarylP View Post
    The new Lycoming, the IO-233-LSA weighs 200 to 210 pounds and the spec sheet (PDF) that I have on it says that it produces max continuous HP 116@2800 RPMs.
    There are still some pounds not accounted for, once finished, the total weight is considerably more than that. At least, according to some MLA manufacturers that considered the engine and stated that the IO-233 was 40-50 kg (90-110 lbs) heavier once installed in comparable configuration.
    There's more than just bare engine weight. Smaller engine is less oil weight. Lighter engine is lighter engine mount, lighter starter motor, lighter battery and so on. That really trades of for much more than one'd expect.
    I am curious how that changes the power to weight. On top of that it is fuel injected, with electronic ignition, with a TBO of 2400 hours.
    While the benefit of fuel injection for the Rotax is pretty small (they are more fuel-efficient than most injected engines, including the above mentioned ones), but this can be ordered by 3rd parties, though the engines isn't certified then anymore.

    As for the electronic ignition, it (the Rotax) does have electronic injection right?

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    Registered User Atomic_Sheep's Avatar
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    Re: Rotax vs Lycoming

    Awesome... thanks for the responses, very informative. I suppose this is one of those "if it sounds too good to be true... it is" type things.

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    Registered User Dan Thomas's Avatar
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    Re: Rotax vs Lycoming

    Quote Originally Posted by DarylP View Post
    The jugs on the Rotax are not liquid cooled, which is something that I don't understand as it really does not cool effectively then. By that I mean that a typical automotive engine has the jugs integral to the block, and cooling is complete. \
    The cylinder barrel sees only a small portion of the total rejected heat. The heads are where the higher pressures and temperatures are created. If Rotax had jackets on the barrels, they would (A) add weight for the jackets; (B) add a head gasket to closely machined surfaces, with its attendant risk of leakage, unless they made it a unit with the head, which would require a steel cylinder sleeve in the aluminum barrel; and (C) add plumbing to join the individual cylinder jackets to the system. The total weight could climb significantly, along with the cost, and their advantages over the Lycoming would be diminished.

    Dan

  13. #13
    Registered User DarylP's Avatar
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    Re: Rotax vs Lycoming

    Quote Originally Posted by Dan Thomas View Post
    The cylinder barrel sees only a small portion of the total rejected heat. The heads are where the higher pressures and temperatures are created. If Rotax had jackets on the barrels, they would (A) add weight for the jackets; (B) add a head gasket to closely machined surfaces, with its attendant risk of leakage, unless they made it a unit with the head, which would require a steel cylinder sleeve in the aluminum barrel; and (C) add plumbing to join the individual cylinder jackets to the system. The total weight could climb significantly, along with the cost, and their advantages over the Lycoming would be diminished.

    Dan
    Thanks Dan

  14. #14
    Registered User DarylP's Avatar
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    Re: Rotax vs Lycoming

    Hey...why do I see Soft Starts advertised for the Rotax? I thought they had some kind of soft start in their ignition box. That just keeps the engine from kicking back...right?

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