20 valves instead of 16

[pwa]

Yamaha has scrapped their 20 valves design on R1 for many years. Why is this so good on a snowmobile? 2006 was the last year on the R1 but on Sleds they have continued with the 20 valves...

Why?

 

[apexrtxmaniac]

I think I once read that it had to do with the powerband. They were saying that the 20 valve engine's power is much more suitable for a snowmobile clutch. I could be very wrong though.

 

[pwa]

Sounds pretty logical. Thanks...

 

[Essarex]

5 valve heads cost too much to produce as compared to 4 valves. Plus, it is difficult to reliably liquid cool a 5 valve head. I didn't say it couldn't be done, it is just difficult.

With today's advances in multi dimensional mapping and electronic's processing/speed, a 4 valve head can approach the hp of 5 valves, with significantly less cost and more reliability.

Same reason why the overhead cam has not replaced the in block pushrod version.

 

[pwa]

5 valve heads cost too much to produce as compared to 4 valves. Plus, it is difficult to reliably liquid cool a 5 valve head. I didn't say it couldn't be done, it is just difficult.

With today's advances in multi dimensional mapping and electronic's processing/speed, a 4 valve head can approach the hp of 5 valves, with significantly less cost and more reliability.

Same reason why the overhead cam has not replaced the in block pushrod version.

I understand, but why would you not want that in a sled? So for now I'm going with the powerband theory why it still left in the sled and not in the cycle.

 

[Essarex]

Both designs work well with today's technology. So either will work on the snow or on the road. Yamaha chose to focus R&D investment on their bikes with increasing sales, instead of their sleds, in a dying market with a shorter and shorter season each succeeding year.

We will potentially see the 4 valve head in their sleds in the next years, as Yamaha retires that design from their bikes and replaces it with something else, like the dual plane firing motor of last year.