This may be a stupid question but how do different engines with the same displacement seem to be more or less powerful than their counterparts i.e. os .46ax to os .46la.

Thanks</p>

the os .46 la is a bushing engine that isnt ported very aggressivly (ports are the holes that allow fuel/air/exhaust to enter and leave the engine, the larger the ports the more powerful the engine...to a point)
now the ax.46 has ball bearings which help reduce friction and it has larger ports so its more powerful

thats about as simple as i can put it, i can get much more complex if you want an indepth explination

It is as JJ explained it.
Also, the carburetor design makes a difference.

The two main ideas behind higher performance engines are:
1) Improvement of the "breathing" and air-fuel mixing, which leads to more air-fuel mix into the combustion chamber to produce a more powerful combustion.
2) Reduction of the internal friction among the parts.

The trade-in is a more expensive-complex-heavier engine: better materials, more precise machinning, higher number and complexity of parts.

It's no different than cars. You can have a car manufacturer making 2 engines with the same displacement and even many parts in common but one has different cylinder heads, camshaft(s), induction system, fuel system, compression ratio, etc. and one makes more power and at different RPM ranges.

You may even find RC engines that are similar displacements from different manufacturers but one might make a lot of high RPM power while the other does better at lower RPM and spins a different prop. All have their place and advantages for certain applications.

And some manufacturers just lie!

There can also be differences in porting and metallurgy. The only way to know for sure which engine is more 'powerful' is to run them on a test stand with the same fuel, prop and glow plug and measure the rpm. With quality engine manufacturer's you generally get what you pay for (I know some won't agree with that).

A manufacturer lie about its product?[X(] Oh, no. Seriously, I recently got a notice in the mail about a class action law suit against many, if not all, lawn mower manufacturers misrepresenting (lying about) the horse power of their products. Seems like I'm eligible for a $75.00 refund bacause I recently bought a lawn tractor built by a manufacturer who was included in the law suit.

The claimed horsepower by the manufacturers is a fairy tale. Better to check the tach readings forum and see what people are getting in the real world with real setups.

All good answers. I have a Thunder Tiger Pro-46 I swapped a Perry carbureator onto for the original and got 2,000 more RPM out of the same prop size.

It is also possible to cripple individual engines permanently by sucking grit and scouring the sleeve or by running overly lean; or just improperly breaking them in.