2017 3A92 engine with roller cam.

[Daox]

I would imagine roller on the cam vs roller on the lifter has several advantages and disadvangates. These are the ones I see:

Advantages
1) It is cheaper to make. Roller cam allows the use of the existing head. I'd think roller lifters require additional height.
2) Less mass as Old Mech mentioned. This means you can use lighter springs, so even lower power loss through the cam drive.


Disadvantages
1) Limitations in cam lobe design due to the tip needing to be a radius vs a variable profile.

[cyclopathic]

There is also a design which uses rollers on rockers.

The other disadvantage of roller on the cam is limited MPG improvement, and not that much reduction in wear.One can only wonder if Teflon coating tapets would have been a cheaper and better solution.

I am willing to bet that HP improvement comes from higher lift due to roller height, not reduced losses.

[Daox]

It definitely would be interesting to see a dyno graph comparing the two engines to see exactly how the effects changed things. As 3dplane said, it was a lot more than just a cam change.

[Eggman]

One can only wonder if Teflon coating tapets would have been a cheaper and better solution.

Slick 50 is all the old engines need!

I am willing to bet that HP improvement comes from higher lift due to roller height, not reduced losses.

I thought that is what MIVEC was for.

[cyclopathic]

Slick 50 is all the old engines need!

I thought that is what MIVEC was for.

Slick 50 is only good for clogging oil filter.

One of the advantages of rollers is reduced valve train wear. This allows camshaft profiles with higher rate of change and higher lift. Could be used with or without MiVEC.

[Eggman]

But why change the cam profile when this can be manipulated, during operation, using MIVEC? Seems to me this feature is already built in.

Are you saying that Mitsubishi has altered the effective cam profile, or only that it is possible?

[cyclopathic]

I don't know, but suspect it is likely the case.

MiVEC can adjust timing and lift within designed range, but not the cam profile. Profile is chosen for engine performance but also for durability, so they cannot go too crazy or engine will not last long enough.

[Eggman]

Wouldn't electric valves be pretty cool? I remember reading about them some time ago, but haven't heard much since. I always thought that if engineers could ever solve that puzzle, it would open a big door toward efficiency gains. Imagine - no further need for a throttle plate.

[91cavgt]

Wouldn't electric valves be pretty cool? I remember reading about them some time ago, but haven't heard much since. I always thought that if engineers could ever solve that puzzle, it would open a big door toward efficiency gains. Imagine - no further need for a throttle plate.

That was BMW that came up with that. Infinitely variable valve lift, timing, and duration! It would do away with the throttle body which would enhance power and efficiency. The big problem they had is making them last for thousands of miles while not adding a significant expense to the car. It has been a few years since I last read about it so they may have gotten it to work now.

[cyclopathic]

Wouldn't electric valves be pretty cool? I remember reading about them some time ago, but haven't heard much since. I always thought that if engineers could ever solve that puzzle, it would open a big door toward efficiency gains. Imagine - no further need for a throttle plate.

Pneumatic valves have better track record in terms of durability, but they still too expensive. Mitsubishi design makes sense as it doesn't require redesigning head for higher tapets, and most of wear happens at the leading edge of the tip, so it should reduce parasitic loss..

Now if roller cam is only fitted to CVT transmission that would mean that it is interchangeable with non-roller, right?