Is it possible to convert an ASP.91 from glow to gas, what mods are involved, is it worth the extra expense?

If it is a ring motor it can be converted. To do it right you need a carb adapter, a walbro carb, a cdi ignition system (CH makes good stuff and sells the hall effect adapter and magnet), and a 1/4X32 spark plug. Unless you machine the bottom end for needle bearings you will have to run the oil content at an absolute mininum of 16:1 (more would be safer) to keep from burning up the rod bushings.

On a side note BME sells a coverted SuperTigre 90 that has the needle bearing bottom end and walbro carb. It is setup with CDI and is gasoline ready. It's not cheap but it is a good little engine. Also, the gassers burn a little less than half the amount of fuel that the glow motors do so you can run a smaller tank to compensate for the extra weight of the ignition system.

A abc engine should work also if the oil content of 16-1 or even more of the right kind of oil is used. Is it worth it was you question...the answer is it depends on type of airplane, type of flyling you do, ect. Tell us more of what it is you want to do once you do the conversion. Capt,n

An ABC engine depends on the temperatures developed when running on glow fuel. After breaking an ABC engine in, one should run it on the same factory recommended fuel used for break in; not change nitro contents, as with different nitro contents the engine running temperature changes and this will affect the piston/liner fit. For this reason it is not recommended to run an ABC engine on gasoline, as the operating temperature will be considerably higher, and you will have problems with the piston/liner fit.

Other members have encountered this problem as well, and reported it here in the forum. One should only use a ringed piston type engine when using gasoline or gas/glow mixtures.

AV8TOR

In my post I did not recomend anything...just said it what could be done on around . 60 size ABC engines. I did not recomend Gas/glow in the first place. Just use a good RCexcell ignition and you can run about any fuel you want with correct oil in the mix. Like one guy said...you can run no Nitro at all... but the engine will run like the fuel has nitro in it. Capt,n PS you do not need a specail glow plug either.

Ive seen to many burned down ABC engines that the owner tried to run on gas. Maybe Ok on a test bench, but in a hover scratch one engine

Thanks again Terry!!

AV8TOR

I have seen videos on youtube where pros have had the engine quit in a hover. For one thing that is a good way to overheat a engine. I am sure if a person that set-up a ABC engine on a high wing plane that only needed 1/2 throttle to fly it should work fine. Also a helicopter head could be used in place of regular head if needed. Hey experimenting is the way to find out what can work if done right! Capt,n

Why fuss with something running on the edge. If you want to convert a glow engine to gas, the engine that will give you the fewest problems is a ringed engine.
NOTE: I said fewest problems, not no problems.[&:]
If you want to run an ABC engine on gas, its your nickle.

I think we all under stand that...but if a person already has some exta ABC engines just setting around...its worth a try if done right. No stupid hovering also. Now if a person does not have a engine already...do the ring engine. Most rc people that want to try new ideas, want to use the inventory they already have on hand. Or listen to the nay.sayers and always wonder!!! My 2 cents. Capt,n

Just trying to help the gentleman out so he doesn't end up doing a lot of work reinventing the wheel here. My gas conversions have all run at least 40 degs hotter and some much more than that. (None of my glow to gas conversions run less than roughly 300 degs) An ABC doesn't take too kindly to this type of treatment. One of my gasser conversions runs great but does so around 350 degs and at those temps the ABC will not seal up properly and the superheated gases leaking down beside the piston WILL burn away anything remotely resembling lubrication and in short order our little test engine eats itself. Been there done that and again I was just trying to help out so we don't keep reinventing the wheel and since it is still a free country, for the time being, he is most welcome to experiment till his heart's content.

On a side note, the SuperTigre engines have a bit more cooling fins and they are longer offering more surface area with which to dissipate heat and mine at least seem to run slightly cooler because of that.

What content of castor oil did you have (and oil ratio) in fuel and was this a trainer type of airplane or a Balls to the walls type for hover shows?? Thanks Capt,n

Oil content already stated in first post (don't want to start a flame war so I'll not mention types and brands here) and the rest is purely argumentative ("Balls to the walls type for hover shows"). I'm not interested in the argument kind sir.