valve float
#11
10-05-2013, 03:00 PM
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Valve bounce is peculiar to set ups that use only a single valve spring, the valves float due to harmonics in the spring and on motors that use twin valve springs of different rates you don't get valve bounce as much, if at all.
You also don't get it on formula 1 cars that use pneumatic valves.
You also don't get it on formula 1 cars that use pneumatic valves.
#12
10-05-2013, 03:21 PM
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The lifter remains in contact with the cam (that would be very bad if it didn't, lol). It's the valve that doesn't close fully and contact the valve seat when it should, allowing compression to escape through the partially opened valve, and effectively reducing power. It is just as it sounds, the valve is "floating" above the valve seat surface during this event, never fully closing until you back off the revs and the lifter bleeds off the excess pressure. Think of it as a "mechanical rev limiter" if you will.
http://en.wikipedia.org/wiki/Valve_float
#13
10-05-2013, 04:04 PM
Valve float is an adverse condition which occurs when the poppet valves on an internal combustion engine valvetrain do not remain in contact with the camshaft lobe during the valve closure phase of the cam lobe profile. This reduces engine efficiency and performance and potentially increases engine emissions.
Valve float - Wikipedia, the free encyclopedia
Valve float - Wikipedia, the free encyclopedia
BTW, I don't think it's a good idea to do this on a regular basis, sounds abusive on parts!
#14
10-05-2013, 04:15 PM
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#15
10-05-2013, 04:25 PM
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Floating valves can do a lot of damage when they come in contact with a piston.
Motor goes clunk.
#18
10-05-2013, 08:46 PM
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I used the Wikipedia reference and just because it's on Wikipedia doesn't make it wrong ... Valve Float, Valve Loft and Valve Bounce .... Three Different Scenarios!
Valve Float is an adverse condition which occurs when the poppet valves on an internal combustion engine valvetrain do not remain in contact with the camshaft lobe during the valve closure phase of the cam lobe profile. This reduces engine efficiency and performance and potentially increases engine emissions.
Valve Loft is intentionally using a controlled valve float to increase lift and duration of the valve open cycle. In some motorsports there are rules that limit camshaft lift; therefore, provoking this type of exploitation. Properly optimizing the system avoids undue stresses to the camshaft lobes and tappets.
Valve Bounce is a related condition where the valve does not stay seated, due to the combined effects of the valve's inertia and resonance of metallic valve springs that reduce the closing force, and allow the valve to re-open partially.
Valve Float is an adverse condition which occurs when the poppet valves on an internal combustion engine valvetrain do not remain in contact with the camshaft lobe during the valve closure phase of the cam lobe profile. This reduces engine efficiency and performance and potentially increases engine emissions.
Valve Loft is intentionally using a controlled valve float to increase lift and duration of the valve open cycle. In some motorsports there are rules that limit camshaft lift; therefore, provoking this type of exploitation. Properly optimizing the system avoids undue stresses to the camshaft lobes and tappets.
Valve Bounce is a related condition where the valve does not stay seated, due to the combined effects of the valve's inertia and resonance of metallic valve springs that reduce the closing force, and allow the valve to re-open partially.
#20
10-05-2013, 09:06 PM
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