I read the "numbers quoted" by various users -then sometimes wonder how anyone new to this stuff,can make heads or tails of the apparant wide differences.
One guy quotes 8000 plus on a 50 size engine with a tiny prop, another quotes on a smaller engine using a big prop!
Weights are quoted differently ,etc..
Some guys think one must use a noisy exhaust spigot as a "standard" -inferring that a tuned or quiet can is cheating or misleading.
Weights for motormounts are quoted - when no motormount is used ((woops!).
Here is something else to add to the confusion.
In testing various tuned cans -and quiet only cans-I can get an engine to really pull (7600 on 20x10 Zinger Pro)but fall flat on it's face with the 24x10 (not a misprint)Mejzlic--5200 rpm
But if I switch to a different type can -I can get 5900 on the same prop!
On the J&A mufflers I get typically (and that is how you really have to look at it) 6200-plus or minus a hundred, on a 22x10 Zinger Pro.
That seems about the norm with others using similar engines
Going back to a can -set for the load range desired - I get close to 7000 on MenzS 22x8 -which is a pretty hefty load.
This is also a very quiet setup.
My own ratings for engines is based on the total weight of the package (engine/exhaust)and how well it will slug really big props -as that is the most quiet setup.
A new entry on the scene is the ZDZ rear exhaust engine - this engine does not require any mount -and the exhaust can run straight back under the wing on some designs - directly into a quiet can.
I scratch design most of my personal models so this very light package will be my selection for a 11 lb FAI legal design.
It will be close on weight - but possible .
We have tried 1.4 gasoline engines - specifically, the RCS1.40 on a can and it works great - but total weight of the plane must be under 9 lbs to get truly competitive performance.
Hope this confuses everyone ---