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Phenomenal Valve Train Article CompCams

By mixxer,
in CRF150F/L, CRF230F/L & CRF250F

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mixxer
mixxer

Momus.... Your pious chest puffing self important bullshit is really pathetic , boring as hell, and not welcome anywhere.... The problem is you personally lack the education and intelligen

mixxer
mixxer

Over the years I have many times over talked about cam ramp rates / shock loads/ seat bounce / my aversion to radical profiles/ valve train snap etc etc.... This article by Comp Cams is a fantas

lanesmatb
lanesmatb

Great link and explanation of variances based on real world loads and rpm on valve train systems.  I think it really illustrates the added problems associated with high RPM engines, especially the cha

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Grand Master

mixxer

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3 hours ago, SteveThe Snakes said:

There is a whole lot to opening and closing ramps and not thrashing your valves and valve gear.

No question....!

We should probably forward that article to WebCams... Grinding off the accel and decel ramps is their first order of business....? 

tick tick tick snappity snap clack clack tick... 

Edited by mixxer
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SteveThe Snakes

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1 minute ago, mixxer said:

You are pretty close...

Let's narrow it down...

All valves have to be small and made of titanium for absolute lowest mass...

5 valve Yamaha’s are. 
 

But I run stainless valves for durability. 
 

There is cam software for designing cams. 
 

These bikes are ripping reliably. 

F0E5BDDA-C125-4B07-A348-7B4C9FE73F9F.png

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lanesmatb

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Great link and explanation of variances based on real world loads and rpm on valve train systems.  I think it really illustrates the added problems associated with high RPM engines, especially the challenges for push rod engines.  I didn't realize the speed changes of the camshaft rpm on multicylinder engines at high rpm, that's insane.

An interesting story on valve float.  Back in the day, there was a WKA sanctioned kart class called "super stock" which allowed open carburetors (methanol) on stock engines.  Big carbs on low lift, low rpm designed engines.  An engine builder in the Carolinas figured a way to grind the opening intake of the cam, which was already highly regulated by rules, to purposely float the valve just enough to artificially increase lift at a given rpm range.  Basically, put a small ramp "bump" in specific area of the opening ramp of the intake.  The package had to be specifically set up for that cam (springs, cam, timing, carb).  For a while, that cam design completely dominated the class.  Damn innovative to use a weakness in the system and making it a strength.

Scott L.

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daled

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4 hours ago, mixxer said:

Plus rotary valves blew up more frequently than land mines?

hummm...   I never seemed to have an issue with any of mine...

But i know that this thread is about a 4 stoke system, so ill stop interjecting...

PS. there is a great book by Prof. Clyde Moon of the kinematics of cam designs, and it covers may types of cams not just lobe and flat follower.  and if some other types would be employed in engine design the kinematic short comings of current designs can be greatly reduced..  but then again that's possible with the free-valve design from Koenigsegg, or even Fiat's multi air system...

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mixxer

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While going to school, I had worked in a shop that sold many brands, including rotax/ bombardier... Rotary valved snowmobiles and watercraft

They grenaded from rotary drive issues so often that they started giving dealers discounts to stock "short block" assemblies , as they called them... Pull off the exhaust and Intake systems... Unhook from drive assembly... yank the motor and drop whole short block in and bolt stuff back on....

stocking short blocks helped salvage some reputation during warranty repair by getting units back to customers faster... and we did short blocks ALL the time... Manager would get nervous if we got below 3 short blocks in stock ??

Rotax... The undisputed king of Zoom and BOOM...

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VortecCPI

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The other thing I recall from the seminars was that the longer the cylinder is "closed" (i.e. tighter LSA) the more "power" (area under the curves) you will achieve all things being equal.  I believe today there are charts and/or formulas to target best LSA for given displacement and valve size?

http://garage.grumpysperformance.com/index.php?threads/how-your-cam-lsa-effects-your-compression-torque-dcr.1070

image.png.b61223b533e8a7ff6ecf1d4bdf52711f.png

 

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