Jrtrebor: “trouts2 - I agree, Bumping up the RPM on these engines does seem to be the only difference I've been able to find that explains the increase in HP.”
I’ve been curious about the hp ratings on similar engines for years. Very puzzling.
SO:
Looking for feedback on hp production to see if I have things right.
Relative mostly to 4-7hp HSK and R*Tec two stroke engines with varying hp ratings.
It’s looking like they get their hp boost from rpm changes but I’m wondering about the mix of a few things like gas, muffler and throughput.
What effects will various things have questions like the following scenarios:
CARB/GAS MODS:
If more gas is added but the governor fixed at 3600 no change in hp will happen or if any extremely slight. The added gas with the same air will make the engine run a little faster but being governor limited won’t make much difference. Possibly it could make a bit more powerful chamber explosion and add some torque when running up to rpm 3600 max but being governor limited at 3600 no significant change in hp.
A carb change or bowl nut change without upping the governor will not do much. T/F?
BETTER ASPERATION:
Similar to gas. If the intake or exhaust flow are improved the combustions will be more efficient the engine could see a very modest improvement in torque because of the improved combustions and the engine will spin up faster and more efficiently to 3600. If still governor limited the intake or especially exhaust change will only get you to 3600 in a better and efficient way with a tiny improvement in torque or hp due to governor limit.
MUFFLER CHANGE:
Same as better asperation. Thinking here of just a slightly better muffler not a “tuned pipes” type change.
Real hp changes would happen for the following while still 3600 limited:
Larger bore, long stroke, tighter head, port change i.e. all pretty big physical changes.
Generally speaking no real change in hp will take place on an engine without big part mods.
Most changes without changing the governor to allow faster spinning will have only insignificant effects on hp or torque.
Given a well built engine with wide latitude in aspiration and gas flow, governor changes will easily bump hp. I’m now thinking the HSK850 and R*Tec are engines with wide latitude. Borat, you ran your engine to rpm max and it made me wonder if gas might have been the limit like if you go there then gave it slight choke it might have spun a bit higher. ?? It’s looking like all along from 4-7 hp for the HSK850 and 4-6.5 for the R*Tec that only governor changes were responsible for the walking up of hp. At least that's what I've been thinking until JRT posted his crank differences.
