Ok,Which engine has more power.? Which engine is more suited to pattern flying,Which engine for more speed,What effect does longer stroke mean? Which is better engine?

Engine A.
Weight: 385g
Displacement: 8.65cc
Bore: 23.7mm
Stroke: 19.6mm
Power Output: 1.82PS@17,000
Practical RPM: 2,000-17,000

Engine B
Weight: 404g (524g w/silencer
Displacement: 8.933CC (0.545 cu.in)
Bore: 23.0
Stroke: 21.5mm
Power Output: 1.75PS @ 16000RPM
Practical RPM: 2000-17000

Engine B should turn larger props due its displacement advantage and its longer stroke but not a given. Engine B may not win the HP rating but should handily win in the Flying Power department.

ok, thanks for some input

engine A for more speed
engine B for better tractability, though still not very good at that.

hi, what gives it the edge for speed?

They look like they are nearly the same, how do you guys know these engines from those specs?

Where are the boost, transfer, exhaust, and crank numbers in degrees? What is the C.R.?

Hi!
Come on guys! From the data given you can't draw any conclusion at all. Those engines are so near identical it's impossible to say what is most suitable for speed and what is for pattern flying.

ok,
engine B is a os55ax

engine A is irvine53(now made by os)