what limits an engines ability to rev?

[GasX]

Originally posted by: Turin39789


Rev limiters?

I am amazed it took this long...

 

[Vic]

Originally posted by: Mwilding

Originally posted by: Turin39789
Rev limiters?

I am amazed it took this long...

Rev limiters are there to protect the engine from over-revving past its design limit, and not the actual reason why the engine couldn't otherwise rev higher. Rev limiters are really a function of electronic ignitions too. Back in the old points-and-condensor days, the "rev limiter" was when the points couldn't work fast enough to provide decent spark.

 

[GasX]

Originally posted by: Vic

Originally posted by: Mwilding

Originally posted by: Turin39789
Rev limiters?

I am amazed it took this long...

Rev limiters are there to protect the engine from over-revving past its design limit, and not the actual reason why the engine couldn't otherwise rev higher. Rev limiters are really a function of electronic ignitions too. Back in the old points-and-condensor days, the "rev limiter" was when the points couldn't work fast enough to provide decent spark.

Why you are wrong.

 

[Vic]

 

[Motorheader]

It all comes down to harmonics, balancing, and efficiency.

Wankel Engine

 

[Vic]

Originally posted by: Motorheader
It all comes down to harmonics, balancing, and efficiency.

Wankel Engine

A Wankel rotary is hardly the pinnacle of efficiency. If anything, high-revving is inefficient. Note the low-revving diesel engine -- now that's efficiency.

 

[Howard]

Originally posted by: Motorheader
It all comes down to harmonics, balancing, and efficiency.

Wankel Engine

Not sure what harmonics has to do with anything, but plenty of I4 engines redline higher than I6 engines.

What about efficiency? What's it got to do with anythign?

 

[Motorheader]

Originally posted by: Howard

Originally posted by: Motorheader
It all comes down to harmonics, balancing, and efficiency.

Wankel Engine

Not sure what harmonics has to do with anything, but plenty of I4 engines redline higher than I6 engines.

What about efficiency? What's it got to do with anythign?

Hehe. I only pointed to the Wankel since is revered for it's ability to rev high due to balance and harmonics. Every engine has been harmonically balanced in some way - whether weights are added to the flywheel like a car tire, or the crankshaft is ground in a way that has the same effect as adding weight to a tire.

Have you ever rode in a car whose tires are out of balance? As the speed goes up so does the shaking/vibration (harmonics). Now imagine this happening in a piston engine.

As far as efficiency, if the materials are lighter and just as strong or stronger, the engine has to do less "work" to get the same amount of useful energy out of the energy supplied. It can rev higher and produce more useful power.

Take a 4 Cylinder from a 75 Vega and a 2005 Camry - which would be more efficient? And what about those Cadillacs that had 8 Cylinder Engines but would run on 6 or 4 cylinders depending on the driving conditions.

 

[Nyati13]

Originally posted by: Motorheader

Hehe. I only pointed to the Wankel since is revered for it's ability to rev high due to balance and harmonics. Every engine has been harmonically balanced in some way - whether weights are added to the flywheel like a car tire, or the crankshaft is ground in a way that has the same effect as adding weight to a tire.

The Wankel can rev very high, because it doesn't use reciprocating pistons, it uses rotors.

 

[Howard]

Originally posted by: Motorheader

Originally posted by: Howard

Originally posted by: Motorheader
It all comes down to harmonics, balancing, and efficiency.

Wankel Engine

Not sure what harmonics has to do with anything, but plenty of I4 engines redline higher than I6 engines.

What about efficiency? What's it got to do with anythign?

Hehe. I only pointed to the Wankel since is revered for it's ability to rev high due to balance and harmonics. Every engine has been harmonically balanced in some way

Yes, but is there not a point when the moving parts are fully balanced? What can you do after that?

As far as efficiency, if the materials are lighter and just as strong or stronger, the engine has to do less "work" to get the same amount of useful energy out of the energy supplied. It can rev higher and produce more useful power.

The thermal efficiency of an engine is the ratio of the energy of the fuel input to the work you get out of it, but it is hardly related to higher maximum RPMs. Look at any modern turbodiesel, for example. The thermal efficiency is significantly higher than a comparable gasoline engine, while its redline is probably lower than 6000RPM. Conversely, take any modern 20kRPM F1 engine. Mileage is probably in the single-digit range.

Take a 4 Cylinder from a 75 Vega and a 2005 Camry - which would be more efficient?

I assume your point is that you get better mileage out of a smoother-running engine? Sure, but that's irrelevant.

And what about those Cadillacs that had 8 Cylinder Engines but would run on 6 or 4 cylinders depending on the driving conditions.

 

[SSSnail]

Energy.

That and a sense of reliable power producing mechanism.

 

[grrl]

I asked the same question a while ago. Check out this thread