Why do some engines take longer to spin out and some spin up quickly?

(2010-05-30 20:20:59)

1. jaymax173 Says: Short stroke engines rev up quickly and usually rev quite high. They usually make their power at high RPM's and generally need to be kept 'wound up'. Long stroke engines rev up slower, make their power at lower RPM's, and work at lower speeds (diesels).

2. Harry Says: Some other factors are:
Internal resistance, a engine with larger journals and rod bearings will take longer because the friction face is increased. The total mass of the reciprocating parts, pistons, rods and amount of weight in the crankshaft counter balances.
External resistance, accessories and factors external the engine. The weight of the flywheel, brakes disks/drums on the driven axles, to mention a few.

3. Old Man Dirt Says: When internal reciprocating is heavy along with long stroke, short rods big heavy clutch and flywheel, small ports, small carburetor the motor will rev up slower.

An engine with a light, short stroke crankshaft, light long rods, light short skirt pistons, small diameter light flywheel and clutch, high compression, large diameter light valves, long duration high lift camshaft, wider lobe center, bigger carburetor or throttle body and a bigger diameter dual exhaust system will allow a motor to REV up quickly.