Thread: Lugging the Motor
03-29-2010, 08:34 PM #1
Lugging the Motor
I have seen it talked about on here but not 100% sure what it means or what actually happens when it's "lugging". Usually I hear it with the wrong impellor being used and the motor lugs.
Could someone explain this phenomenon and the what happens and how it could ruin an engine.
Sounds like it's extremly important to get the right prop for your application.
03-30-2010, 05:58 AM #2
i think what they mean by "lugging" is when your motor has too much of a load on it, like to big o a prop will "lug" the motor and stress it out,
kinda like, you hook a s-10 to a 22 foot travle trailer and its going to slow the truck way down and put more stress on the motor and drive line..dont ask how i came up with that...
but that is what i get out of it..
03-30-2010, 07:17 AM #3
- Join Date
- Jul 2007
- near Toronto, Canada
Gasoline engines in general, and our PWC 2-stroke engines in particular, are designed to deliver their maximum power in a specific RPM range. For PWC engines, that optimal RPM range is actually rather narrow, and is usually located well within the highest 1,000RPM before the RPM limiter takes effect.
This is especially true for the tuned exhaust pipe engines, since the pipe is tuned for a certain frequency of resonance (essentially a certain narrow RPM band). When the RPM is below the tuned pipe's optimal RPM range, the power enhancing pulses inside the pipe(s) are mis-timed to the exhaust port opening and closing, and they don't work as effectively.
If the impeller pitch is too 'steep' for the available engine power, the engine will not have enough torque to twist the impeller up to the optimal engine RPM. It will deliver significant power at that lower RPM, but not the maximum power the engine is capable of.
The engine is fully loaded, but is operating below optimal RPM. This can result is excess heat being generated, which is not being optimally converted to drive shaft output. The extra heat can burn pistons, waste fuel, and generally adds stress to engine.
You will often see people who are tuning their engine for more power, choose an impeller to start with that is a little less pitch than they expect to be optimal. They prefer to have the engine spinning a little above optimal RPM, rather than below optimal.
High RPM may get them very close to, or even trigger the RPM limiter, but it is less stressful on the engine than having too much impeller load, and lugging the engine with a lower peak RPM at full throttle.
Once the engine tuning is 'close', they can extrapolate from how easily and rapidly the engine reaches for the RPM limiter, how much more impeller pitch the engine can handle.
Increase the impeller pitch, ride again. If the RPM peak matches with the optimal powerband, then that is the correct impeller for that engine.
03-30-2010, 07:36 AM #4
Thanks keith, that clears thing up for me.. The extra heat is what I didnt realize.
03-30-2010, 08:40 AM #5
03-30-2010, 07:48 PM #6
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