Hello,

Have a Sig LT-40 with an OS 40 LA.

Sometimes in the high grass it seems underpowered taking off.

Was looking at the OS 46 LA. Would this engine provide more takeoff power? Also, what would the fuel comsumption be?

Thanks in advance.

i would personally get a higher performance 40-50 size motor. supertigre g-51 is a nice priced motor, and puts out a lot of power with good fuel economy. its what i used in my trainer and would make it go straight up and take off in about 15 feet tops. i orginally had a os .40la in my trainer and the g-51 put out a LOT more power and made flying a lot more fun. You could also go with the 46ax which is comparable to the g-51 but a little more pricey. the .46la wont put out that much more power than the .40la and weighs more. just my opinnion.

GF,

Before spending money on a new engine, try a few different props. Go for a biggest diameter prop that still allows the engine to do about 12K static (suggestions: APC 11x4, 11.5 x 4, Bolly 10.5x6).

A guy at our field has an OS FP .40 (about the same power as your engine) in his 65" trainer. It flies really well with a Bolly 10.5 x 6 prop.

The .46LA will help. But a GOOD .40 like the Super Tigre, OS FX, or TT Pro will help even more. Don't get me wrong, there's nothing wrong with the LA, it's just not a powerhouse engine. Before you buy a new engine, though, try a 10-4 or 10-5 prop on the one you have.

Dr.1

I do not know what wheel size you are using going to a 3 or 3 1/2 inch may help ( sort of bush plane type) I do this with myVMAR apache 2s with a irvine 40 diesel flying off a rough grass field, and oher consideration putting a diesel head on the LA 40 i t turns into a bear when converted thse are excellant engines but to go from mild to great on diesel martin

I do not know what wheel size you are using going to a 3 or 3 1/2 inch may help ( sort of bush plane type) I do this with myVMAR apache 2s with a irvine 40 diesel flying off a rough grass field, and oher consideration putting a diesel head on the LA 40 i t turns into a bear when converted thse are excellant engines but to go from mild to great on diesel running a 12x5 or 12x6 will give you the thrust to get it uo martin

With the larger tires and wheels 3 - 3 1/2 and a 10x4 MAS prop. This will save buying a new engine for now.

What prop are you using now? I agree with experimenting with props first, but I think 10 x 4 is too small to be efficient on that engine--the 11 x 4 suggestion sounds more like it to me. I've seen LT-40s at our club fly well with the 40 LA which is about the same power as the FP.

I found my 40 FP did very well on an 11 x 5 on a trainer and 10 x 5 on a much smaller Dynaflite Mustang. The LT-40 is a big, light trainer and my first try would be to go down a notch in pitch and keep the 11 inch diameter.

If I were buying an engine for it from the start it would be a TT 36 Pro, or something like it. It's light (same as the OS 40 FP) but plenty powerful even on 11 inch props, and Radical RC sells them for about 65 bucks--I think it might a better choice than the 46 LA for a similar price. But try different props first--good learning experience and might solve your problem. Jim

Most of the post state that the motor is not a powerhouse. Actually a misconception as the motor has plenty of power but the carb is woefully small. This is done intentionally, probably to guarentee good fuel delivery. If you want more power from the motor you need to find one with a bigger choke area that will fit the motor. Also be advised that it does not have boost ports so it really is not a Schnurle in the strict sense of the word. It is more a loop scavenged motor with moderate power and excellent fuel consumption characteristics.

The 40 LA is not a powerhouse at all. Many feel it is best served as a paperweight or to help balance out larger planes. It does run as well as any other OS. Seems like a lost engine in not finding the right plane to install it on (whatever that may be). Super Tigers would be a better direction.