I am considering an engine for my winter project, an 80" T-34B Mentor.

I have to choose between a 2-stroke .61-.91 or 4-stroke .91-1.20.

I have no experience with 4c. How does tuning a 4c compare with a 2c.

Price aside, which is recommended.

thx

If price isn't an issue, there's no question - Go with a 4 stroke.

Some people say 4-strokes require more fussing than a 2-stroke. I can honestly say that I've never seen it.

The 4-stroke will burn much less fuel, make MUCH less mess on your plane, and the sound is worth more than words can say - especially on something like a T-34

I like to use 2-strokes on 40 size planes that require speed, but anything 60 size and over I prefer 4-strokes (For the reasons mentioned)

I agree with MikeB, especiallywhen you are considering the T-34 Mentor. That plane IMO is better suited for the 4 stroke.

DaveB

ww2 .60 sized plane, definitly needs a 4c engine.

You will generally have a little longer break-in with a 4-stroke than a 2-stroke, but that is due to the fact that 4-strokes (OS FL-70 excepted[sm=thumbdown.gif]) are ringed, rather than ABC construction. They also require periodic valve adjustment. In my experience (limited), if properly cared for, 4-strokes are no more finicky than 2-strokes. Definitely worth it.

-Scott

I agree.... 4c are really the way to go for me... I love the
low end grunt..... And the sound!! Valve adjusting is min..

With 2 engines with the exact same displacement, 4 Stroke will let you develop more low end torque but a 2 stroke will usually give you more power to turn larger propellers. That is why you will need a 90 2 stroke or a 120 4 stroke. (My preference is 2 stroke, sorry guys)

If you need the weight in the nose to get it to balance, then by all means, the 4 stroke is the best choice.

Last, is the tuning. Running a 2 or 4 stroke engine rich will cause a decrease in power and a mess on your hands. It is easier to distinguish a rich run 2 stroke than a rich run 4 stroke. When the engines are run lean, the 2 cycle will generate a lot of heat and wear while the 4 stroke will begin to backfire and throw the propeller and spinner. Usually a lean run 4 stroke will not run very long.

On a four stroke, make sure that the prop is not a real tight fit on the prop shaft, ream it out a little if you have to. It should not have to be threaded on the shaft but should just slide into position. Now, if your four stroke kicks back from being too lean, the prop nut will just loosen a little and the prop will freewheel on the motor shaft without getting thrown.

Don't be afraid of four strokes, I shied away from them on my first models because the gurus all said that beginners should stick to the "more user friendly" two strokes. Two strokes indeed are user friendly, in fact, I saw no need to own an electric starter to get them running.

Today I have a couple of four stroke engines and I still don't see a need to own an electric starter. They just aren't that hard to use.

Four stroke advantages; nicer engine sound, excellent and linear throttle response, and you don't have that big ugly exhaust system ruining the appearence of your plane.

Bad points, sometimes it's hard to get them to idle slow enough to not taxi, especially on areobatic planes that have the ability to do almost unlimited verticals. Also, they are actually louder than most people think they are.

The plane just asks for a 4 Stroke. My experience is the 4 stroke will swing more prop than a 2 stroke. 4Strokes also like to be loaded and using a 3 blade prop would really look nice on the plane.

There has been mention of not leaning the engine too much. Also mention of a longer break in period due to the ringed configuration. You will need a tachometer to properly set the 4 stroke. Bring the engine up to high throttle and set it to 200 to 300 RPM less than max after being broken in. Use 300 to 400 RPM less for break in. Most all local fliers are using 20/20 pattern fuel which contains 20% nitro and 20% oil content. The oil content is most critical with a 4 stroke. Most fuels labeled 2 or 4 stroke do not have enough oil content. Low end tork is what is needed for scale planes. This is what gets you off the ground and flying.

My 2cents,

EXCAP232