cam drive efficiency

[bsfc9]

which type of camshaft drive offers the least parasitic loss; belt, chain, or gear?

 

[ivymike]

is this real parasitic loss (the kind where energy is dissipated), or "tunerland" parasitic loss (aka increased inertia) that you're talking about?

 

[Tmoose]

Unless special measures are taken to achieve minimal lubrication I would expect high speed gears or chain could have churning losses that make their theoretical efficiencies of 95%+ misleadingly high.

So, I'm inclined to bet on on the belt until more info arrives.

But I think the losses in the drive are pretty small compared to the power required to drag cam lobes across surfaces while overcoming hundreds of pounds of spring pressure and inertia.

 

[ivymike]

But I think the losses in the drive are pretty small compared to the power required to drag cam lobes across surfaces while overcoming hundreds of pounds of spring pressure and inertia.

You mean friction power at the cam-follower interfaces?

 

[SUPERKYLE]

There is an SAE paper written by a couple of Roush engineers that has some interesting chain drive data. I don't think it included data from a belt drive. I do know that the engine performance is best with the belt then the chain and the gears were the worst, due to the harshness transmitted through the valvetrain including an impact on spring durability.

Kyle

 

[GregLocock]

Efficiencies I've read over the years:

straight cut gears 99% per pair

chain 98-99% at low speed, much less at high speed

timing belt 90%

The timing belt was being used as the final drive in a solar car, so it may have been running under too high a torque.

Cheers

Greg Locock

 

[crysta1c1ear]

I looked at this a few days ago, and printed myself a copy, and access was free.

Camless Engines
A near future where camshafts don't exist and
performance is revolutionised!
By Dusko Mackoski

http://www.autospeed.co.nz/cms/A_0910/P_2/article.html

...
The valvetrain in a typical internal combustion engine comprises several moving components. Some are rotating and
some are moving in a linear manner. Included Included are poppet valves that are operated by rocker arms or
tappets, with valve springs used to return the valves to their seats. In such a system the parasitic power losses are
major - power is wasted in accelerating and decelerating the components of the valvetrain. Friction of the camshaft,
springs, cam belts, etc also robs us of precious power and worsens fuel economy, not to mention contributing to wear
and tear. The power draw on the crankshaft to operate the conventional valve train is 5 to 10 percent of total power output.
...

Now when I try to check the weblink, they want me to pay to read it.

I guess that's not clear and precise - exactly why I didn't post this earlier. I was expecting a clearcut and knowledgable reply with debate about fine intricacies of it all. Posting it now doesn't seem so bad.