[Devious2xs]

So I have two heads on my bench. One is a 1050cc Speed Triple head, the other is for my Lotus Elise. It is actually for a 1800cc 2ZZ-GE Toyota/Yamaha engine.

The Yoda head has a few things that would make bike engines very impressive. It has a variable advance/retard mechanism that retards the intake cam as the rpm increases. This makes the cam have very little overlap at low rpm, and more overlap at higher rpm.

THEN at 6200 rpm a second set of lobes on each cam is activated and the engine has a completely new powerband on the cams with more lift and more duration. And the advance/retard actuator works for this set of lobes as well.

This is called VVTL for variable valve timing and lift.

Honda has a system like this on some of their car engines too.

I keep looking at this and thinking about the Triumph 1050cc head next to it. Speed Triple cams for low and mid range use, then Daytona cam lobes for high end. What a bike that would be. Especially if the head flowed a good bit more.

It doesn't look to be all that complicated, and only a few pounds would be gained - but a lot wider powerband would more than make up for the weight.

Something to think about. I know I will be.  ;D

 

[Dobieman]

Kawasaki's new Concours (C14) is based on the ZX14 motor but has VVT. I don't think this bikes on the street yet but the VVT has some people worried. They want to see how it does. While not the same most people relate to Honda's Vtec and unimpressive results on the 800 engine.

 

[Devious2xs]

I am interested to see the results on the Kawasaki.

The problem with the Honda, was they didn't make full use of the V-tec. It was a half-assed attempt, that could have been so much better.

 

[Catahoulabulldog]

yes everything I have read about the VVT isnt very impressive.

 

[Devious2xs]

I will say the VVTL on the engine in my Lotus is very impressive. When the second cam comes in, it comes alive.

It allows very mild tuning down low that makes driving easy. But when you want to let it rev, it pulls hard to 8500 rpm. And you best be ready to shift quickly.

This same idea on a high reving bike would really give it a big improvement at lower rpm.

 

[dr_gallup]

Practically every automotive engine not made in Detroit has VVT. Not so many have variable lift which is harder to do. The results are pretty much universally acclaimed. Even Detroit is catching on. The problem for them is it is hard to do on a cam in block design since there is only one cam for both intake and exhaust. You really need to be able to change the phase of the intake relative to the exhaust The weight and cost penalty is coming down, particularly with the increased computing power in the newer bike ECU's. Plenty of memory & compute power to spare on another actuator. With the more stringent emissions pushing the bikes closer to the cars in terms of technology I think we will be seeing more VVT(L) on bikes. I think the biggest problem is packaging the mechanism without compromising engine width or layout. Can you imagine trying to add it to a Ducati? Much easier on an inline engine.