The rigid reciprocating piston assembly is not balanced. Sure, the cams are balanced (they would be even if they weren't counter-rotating), but so is a crankshaft. The pistons in a conventional horizontally opposed engine move opposite each other to balance themselves. There are still third order movements, but they are minor. This Revetec engine design is a vibrating mess. Just watch the videos. Anything not rigidly connected to the stand buzzes like crazy whenever the engine is revved.
The rigid reciprocating piston assembly is heavy. All the reciprocating weight from a conventional engine (pistons & connecting rods) are maintained, but in place of lightweight pins we have heavy roller wheels and bearings. At least, they must be pretty heavy in order to transfer combustive force from the piston assembly to the cams. Also, roller wheels, even with strong bearings are subjected to metal-to-metal contact, and will wear accordingly. In comparison, conventional oilled bearing races are lightweight and extremely durable.
The twin counter-rotating cams push back on the pistons just as much as the pistons push on them (according to basic highschool Newtonian physics). This means that the cam follower on one side is pushed hard in the up direction as it follows the top of one cam lobe, while the follower on the opposite side (at the same piston end) is being pressed downward by the other cam lobe. This must result in some significant torque loading on the piston assembly. What's worse is that the direction of the torque load reverses for each and every stroke. I'm curious to know what provides the resistance to the torque loads.
They claim that a conventional engine doesn't acheive crank efficiency until 60deg ATDC. Maximum crank efficiency is where the crank is being pushed by the connecting rod at a tangent to it's travel. They provide some graphs:

.. but provide no information regarding how their device, which never pushes at a tangent to the travel of the cams, is any better. The graphs have no units and I don't see where the obvious mechanical disadvantage of the follower moving towards the axis (shorter lever arm = reduction in torque) is adequately portrayed by the vague green curve on their graph. At the time during the stroke when the piston pressure is the greatest, the piston has the most mechanical advantage, while it has the lowest mechanical advantage when it has the least piston pressure.
As in most engines, the ultimate limit to the rotational speed is the speed that the pistons travel. The folks at Revetec would like to remind you that by altering the cam profile, the maximum speed of the piston can be customized. What they don't tell you is that by altering the rod:stroke ratio and the stroke of a conventional engine will yeild the same changes in engine speed.
If you watch the video where they claim high revs, you can clearly see and hear that the engine is not revving very high. Why is this? Well, in order to get 3 strokes within one revolution, the engine will need to turn at about 1/3rd the speed of a similarly sized conventional engine (assuming both are limited by the maximum piston speed). You may get 3 times the amount of torque out of the Revetec, but you're only doing it with 1/3rd of the powerband... which brings me up to my last niggle:

I hope you're still reading, because this is a riot...

Revetec lists a portion of the articleTorque and Horsepower - A Primer on their website (CCE Design>>Let's Torque) which reads as follows:

Quote:
The Case For Torque

Now, what does all this mean in carland?

First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.

You don't believe all this?

Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine.


Wow, great! Torque is king! Power is meaningless!

Well, not really. If you read the article in full, you'll see that just the opposite is true.. only that Revetec would like you stop reading there. I wonder why Revetec doesn't want you know the entire story???

The next article (Why is Torque More Important than Horsepower?)refers to how engines with a lower state of tune are better for daily driving. This is true, we all like low end torque for leaving stoplights behind. What Revetec doesn't remind you is that their engine, spinning at 2000rpm is equivalent to your conventional engine spinning 6000rpm. Even though the output shaft is only spinning at 1/3rd the speed, the pistons are still screaming.

I don't see any real-life advantages to this Revetec engine over a conventional crank driven engine, and as long as Revetec isn't willing to provide any real life data they shouldn't be expecting me (or anyone else) to take stock in their company.


KnifeEdge_2K1 If you are so smart and I'm so stupid why am I the only one that ask questions about this SUPER design? It was something else once many years ago that was suposed to replace all engines in the world. What was the name again? hhmmmmmmmmmmmm think it started with a w and I think some asian car brand still use it in a model or two vx5 sa3 or rx7 some thing like that.

kW=kNm/s has nothing with no loss to do.
If the teoretical torque is 100Nm then the teoretical kW is 100Nm x RPM
If the real torque is 98Nm then the real kW is 98Nm x RPM

If you have 3 times the torque and the same hp it means you have mesured the engines under conditions that can not becompared or you runn designs of top and cylinder that can not be compared. If you runn same bore:stroke ratio and use same design of valves top and manifoil. Seams like you guys claim to be engineers and I am a engineer so I expect you to understand this mutch.

Well how mutch is the loss in bearings? annybody know?