I kep hearing people talking about "floating valves". What does this mean? All I know is it is associated with high RPM's. Oh, and if you want to know why I posted here instead of another forum,w ell I won't go down that road again, lets just say you guys are more helpful[img]i/expressions/face-icon-small-wink.gif[/img]

 

Oh....the floating valve.......I had this ruin my day at an arena cross a few months back.

It's associated with high RPM's just as you said.

To sum it up in plain english,.....the valves can't keep up with the cam.
Once a certain RPM has been achieved, the valve springs aren't strong enough to keep constant pressure on the valve making the valve not to fully close before the cam wants to open it back up.

That's why all high performance cams for "mid-to-top RPM" use require stronger valve springs.

Not sure if I said that in a way that can be understood, but I think you get the picture.

 

This is also why they try to lighten the valvetrain in addition to upgrading the valve springs (i.e. titanium retainers). If you have less inertia to begin it really helps out. Valve springs that have a higher closing force also rob the engine of some power with all other things equal. On some V8 cars with 500# opening force, where you are opening two valves that are opposite sides of the cam can actually cause the cam to twist and alter the timing of the engine

 

Ya like KNOWSALOT said, its when in high Rpm's and your valve spring's arent strong enough to push back up in time and the piston comes up and BOOM.!!!!!

 

To make it sound real simple to understand, the valves are bouncing off the valve seats and opening whenever they please, pretty much.

 

There are some valve actuation systems that get around that hurdle, but neither solution is cheap and easy to modify. One is Ducati's system (can't remember what it is called) and another is the pneumatic actuator (basically infinitely variable cam) as used in Formula-1. I know that there are some other designs (or I suppose "ideas&quot being researched, such as electro-mechanical actuators and rotary valves, but neither is close to production as far as I know.

There is an easy solution to rid yourself of valve float, and that is to get a two-stroke... hehe...

 

<< There is an easy solution to rid yourself of valve float, and that is to get a two-stroke... hehe... >>



Got that right!!!! But I figured I should figure out some of this stuff since my new quad(whenever I get one) will likely be a thumper.

And your statement isnt entirely true... isn't the piston in a 2 stroke also a &quot;valve&quot; and it &quot;floats&quot; on the piston pin and rod, thus a &quot;floating vlave&quot;,lol.

 

ahh grasshopper, you have much to learn.... (just kidding)...

actually, if you want to get technical, the piston never floats at all. Floating implies that there is either no connection or contact, but with a piston there is a constant connection to the crankshaft and therefore no flotation ever occurs. This is the same type of way that the Ducati system works, where the valve is constrained in both directions.

if a piston is floating within the cylinder (in either direction) bad expensive things usually just happened or are about to happen...

 

LOL, I wasn't implying the piston actually &quot;floats&quot;.

I did have a bad case of floating circlip's Saturday though!

 

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