I used to fly 2 stoke 46 sized models
I planning on moving to 3d flying using a larger model (60-90 size)
i wonder weather should i buy 4 stoke engine like os91
or stay with the 2 ones

as i saw through the forum many people (but not all) recommends the four stoke.
so is it really the right choice ?

by the way why those toc fliers with their huge models uses 2
stoke engines

thanks

First of all, the TOC planes are powered with gas engines not glow engines.

The four stroke engine can offer a more instanious power control at medium high throttle settings than a 2 stroke. This is needed in 3D flying. 4 strokes have a lot of torque. But to utilize it for 3D you need a light weight prop.

Enjoy,

Jim

isn't the the difference between 2 and 4 stroke still exist even if the engine is gas powered ?

why not to use 4 stroke gas engine ?

4 stroke gas engines have not caught on yet. There have been a few around like the Honda and the Ryobi but they were not powerful and light enough for anything but just flying around. They had close to 2 cubic inches displacement.

Also there have been a very few glow four stroke engines converted over the spark ignition and gas but it's not very common.

When you get above 2 cubic inch displacement, the cost of glow fuel begins to really enter into the picture. Also the larger 2 cycle glow engines like the big Super Tiger 3200 and 4500 usually have to use a different glow fuel than what you would use in your .46 engine.

Four stroke glow engines have been around for close to 30 years but only in the recent years, have they been refined enough to be used in fun fly. It took a lot of refineement to get to where we are today.

The more powerful gas engines used in the TOC planes cost more than a $1000 each. They have been very refined over the years.

Perhaps, in the future with a refinement of materials like in NANO technology, a TOC plane will have a four stroke gas engine?

Enjoy,

Jim

The technology to make TOC sized four-stroke engines with enough horsepower and lightweight has been around for a long time. I just don't think that the manufacturers have been convinced that people were willing to pay for them.

Frankly, I can't see much of an advantage anyway. At least not enough to justify the extra weight.

When you have a 3:1 or better power-to-weight ratio, the number of strokes it takes for a combustion cycle doesn't matter. When they start them up, they pick the chubbiest guy they can find to hold it down. 90+lb of thrust in a 32lb plane... Outrageous to the extreme. Really, what would be the advantage of a 100+cc 4-stroke gas engine in a TOC plane? It's more complicated, heavier, etc..