Valvetrain

mag2555 · Post by **mag2555** » Mon May 16, 2022 6:04 pm

Whatever happened to the Desmodromic type of valvetrain?

Walter R. Malik · Post by **Walter R. Malik** » Mon May 16, 2022 7:16 pm

mag2555 wrote: ↑Mon May 16, 2022 6:04 pm Whatever happened to the Desmodromic type of valvetrain?

Probably, COST ...

englertracing · Post by **englertracing** » Mon May 16, 2022 7:35 pm

The fact that honda revved 4 strokes with valve springs to 21,000rpm in the 60s should be a clue to their usefulness.

PackardV8 · Post by **PackardV8** » Mon May 16, 2022 7:45 pm

Improved camshaft lobe design
Improved valve spring materials
Lighter, better quality valves
Four and five valve heads.

Geoff2 · Post by **Geoff2** » Tue May 17, 2022 3:12 am

Don't Ducati still use it?

PSA · Post by **PSA** » Tue May 17, 2022 5:44 am

Ducati still use it. Maybe less useful with 4 valves these days.

shoe · Post by **shoe** » Tue May 17, 2022 8:22 am

Ducati still uses it with success.
The MotoGP bikes are consistently at the top of the top speed charts.

The advantage over pneumatic springs appears to be small but with greater complexity. Ducati is invested the other manufacturers are able get similar to same power without it

Having worked on them for years the frictional losses are negligible. Not sure how they compare at 16000+ rpm.

The early Desmo valvetrains came about when valve springs were not very reliable at high RPM. (Mercedes as I recall)

Post by **CamKing** » Tue May 17, 2022 11:11 am

The biggest issue was material expansion from heat.
On a normal valvetrain, as the engine gets hot, the lash opens up, so we design a lash ramp to deal with it.
Think about what it does on a desmo system.

Don Terrill’s Speed-Talk

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