Sport Pilot Talk

I was curious, does fuel injection solve any of the previous worries over the ULS (besides emissions, carb icing, etc)? Also, I read that mogas is limited to 10% ethonol. Is the ethonol issue any less critical now that we can have fuel injection in the iS?

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According to the Rotax Operating Fluids service instruction, the injected engine is approved for "up to 10% ethanol".

Mainly the concerns over ethanol. I assumed that the rubber were the same or similar (and likewise, similarly susceptible to 10% ethanol), but I wasn't sure if there were anything new that would make ethanol less of an issue.

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IFlyRC wrote:I was curious, does fuel injection solve any of the previous worries over the ULS (besides emissions, carb icing, etc)? Also, I read that mogas is limited to 10% ethonol. Is the ethonol issue any less critical now that we can have fuel injection in the iS?

I'm wondering where you heard about those "worries". I fly behind a 912ULS, burn mogas with 10% ethanol, and don't have any of them.

I sure wish these rumors would dry up and go away about ethanol worries. Rotax has approved 10% ethanol and the engine doesn't care. Rotax only recommends 10% ethanol because that is all they personally tested at the factory. Rotax can not nor do they have the time to test everything that comes down the line for the engine WORLDWIDE. When you think Rotax just don't think USA. Parts on the engine are just fine with ethanol. There are a few million run hours worldwide with ethanol without any issues. Places in South America use up to 23% and a couple of engines have been torn down and they show absolutely no ill effects. Rotax recommends staying away from 100LL which is far more damaging over the long haul. Ethanol isn't an issue in the majority of humid climates. First it could absorb a fair amount of water and it would still burn through the engine. Second the fuel in the wings isn't openly exposed to the air except for the tank vent which is quite small. Since auto fuel starts to off gas at anything above -45F then in temps above zero it is off gassing which is produces venting out that tiny vent. It would take forever to absorb enough moisture through that vent to affect the engine running. Any introduction of humid air moisture through that vent would be extremely negligible compared to fuel volume.

You could get some water in the fuel if you leave your plane outside in the rain. This problem would depend on several other factors coming into play as to how much you might get. Again if it is a small enough amount to the fuel volume you may never know the difference.

A few years ago I got tired of hearing about ethanol and water absorption scary tales that weren't backed up by science , but just hearsay. I'm a retired Fire department HazMat tech. We have put water in and on fuel at times and do all kinds of test. To prove a point I put ethanol auto fuel in my lawn mower, then poured a measured amount of water in. Then started and ran the mower. I can remember many years ago back in the late 50's & 60's we used to spray small amounts of water right down the carb throat to help clean cylinders and plugs.

Everything has to be put in perspective and it isn't a one size fits all scenario.

10% ethanol auto fuel in the Rotax 912UL, ULS and the 912is engine is just fine to use and far better than 100LL.

roger lee wrote:10% ethanol auto fuel in the Rotax 912UL, ULS and the 912is engine is just fine to use and far better than 100LL.

Great write up, Roger. Thanks. I wish airframe manufactures would build their fuel systems to the engine's specs.

Merlinspop wrote: I wish airframe manufactures would build their fuel systems to the engine's specs.

So do I, but a bigger issue is: I wish the airframe manufacturers would actually test their fuel system components, to determine whether they are ethanol-compatible, rather than just outright prohibiting it. (A few have; just not enough.)

roger lee wrote: I can remember many years ago back in the late 50's & 60's we used to spray small amounts of water right down the carb throat to help clean cylinders and plugs.

Drag racers sometimes use fine mist water injection on supercharged and turbocharged engines to cool the air charge instead of or in addition to intercoolers. Low cost, big power gains, no damage to the engine.

drseti wrote:

Merlinspop wrote: I wish airframe manufactures would build their fuel systems to the engine's specs.

So do I, but a bigger issue is: I wish the airframe manufacturers would actually test their fuel system components, to determine whether they are ethanol-compatible, rather than just outright prohibiting it. (A few have; just not enough.)

I know this won't work for you Paul, but one could turn an S-LSA to E-LSA and do all the testing they wanted to, replacing any components that show accelerated aging from ethanol exposure with ethanol-resistant parts.

Andy -- think that would be a little beyond my risk profile for a SportStar since it has a wet wing. Ethanol deteriorating a fuel tank is one thing, eating through a wing is a little more problematic

I concur, Dave.

dstclair wrote:Andy -- think that would be a little beyond my risk profile for a SportStar since it has a wet wing. Ethanol deteriorating a fuel tank is one thing, eating through a wing is a little more problematic

Agreed you'd have to have some risk tolerance...but if you really inspected the wing tanks with a flashlight and checked for leaks every flight, the risk is minimized. After all, we don't expect a single flight with ethanol to destroy your tank lining...it would take continued exposure. Of course, you'd want to be checking your fuel filter and gascolator very often too for particles indicating some fuel system components deteriorating.

My only point is somebody sufficiently motivated could do the testing the factory did not. And who knows, you might find no ill effects!

MrMorden wrote:

dstclair wrote:Andy -- think that would be a little beyond my risk profile for a SportStar since it has a wet wing. Ethanol deteriorating a fuel tank is one thing, eating through a wing is a little more problematic

Agreed you'd have to have some risk tolerance...but if you really inspected the wing tanks with a flashlight and checked for leaks every flight, the risk is minimized. After all, we don't expect a single flight with ethanol to destroy your tank lining...it would take continued exposure. Of course, you'd want to be checking your fuel filter and gascolator very often too for particles indicating some fuel system components deteriorating.

My only point is somebody sufficiently motivated could do the testing the factory did not. And who knows, you might find no ill effects!

Don't argue that it could be tested but you're missing a little detail -- there is no fuel tank. The WING is the fuel tank and inspecting the entire interior of the wing is not as simple as scoping a tank.