4 cylinder engine RPM
Trevor and I both have new 4 cylinder engines.Last night we were talking about what seems to be fairly high RPM people are running the 4 cylinder engines at.
With 2 cylinder engines it seems the larger they get the slower the RPM. Now!! As Trevor and I were talking perhaps these 4 cylinder 200+ cc engines perhaps should be running RPM numbers similar to a 100cc twin instead of lower RPM like a 210cc twin? :confused: Has anyone got any input on this? :oha: I know we can ask the manufacturers, but this is more fun :yes: Jack |
Re: 4 cylinder engine RPM
Hi Jack, in the 4 cylinder bike race engines I used to build years ago higher RPM's is where the power is and with the 2 cylinder high cc engines it's the opposite, low RPM's as you stated is correct.
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Re: 4 cylinder engine RPM
Yeah Ed, that's what we're thinking too. At first I was thinking I'd like to prop it under 6000 RPM, but after some thought perhaps it would run hotter at the lower RPM and not as crisp a throttle response.
I see veryone else is propping for 6200 and above so I guess I'll do the same.Makes sense when a person thinks about it a bit :) |
Re: 4 cylinder engine RPM
Your right, loading an engine under the power band will give you excessive heat and cylinder wear due to wash. If only you could have the engine on a slip mount where you have it hooked up to a tension meter and then do spool ups to full throttle with different props to see at what RPM's the props fall off at and loose there pulling power to determine the optimum prop and RPM range. Does this make sense or did I word it wrong?
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Re: 4 cylinder engine RPM
It's more a matter of engine design than whether it's a 2-stroke or 4-stroke. If a 4-stroke engine is over-square it will likely spin faster than the same displacement designed undersquare. A full-scale 360 ci, air cooled, Lycoming engine redlines at less than 3000RPM while a 3 liter Formula 1 engine can rev 20,000 rpm.
...............and then there's the fueling issue. Best power seems to come on at or near peak EGT, while best economy is somewhat lean of peak. But Ottertok is right... you don't want to lug it. |
Re: 4 cylinder engine RPM
It's worded OK for me ED...But what's a slip mount :?: :) Cool word for a test stand????;)
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Re: 4 cylinder engine RPM
Hey Ed
Do you mean a dynamometer? Engine dyno. That would be cool. A mini dyno able to load the engine. |
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