The Radial Valve theorygreenspun.com : LUSENET : MV Agusta F4 : One Thread
Anyone have an explanation on how these things differ from "regular" valves? The answers I get from dealers are just hype/buzzwords/jargon.
-- ben kifle (email@example.com), March 10, 2003
Good Questions. I would like to know myself. Thanks
-- Scott K (firstname.lastname@example.org), March 10, 2003.
Simple explanation of the Radial Valve theory: Cylinder head is the area of the engine where the air and fuel introduced into the cylinder, compressed, burnt (via spark) and exhaust sent via the valves, and the amount of which is determined by the lift and duration of the camshaft profiles.
OK.... in a normal cylinder head, the valves (this example is 4 valve at 2 imtake and 2 exhaust), are similar to an early automotive layout where the valves are SITUATED in the cylinder head in STRAIGHT fashion.The inherent design flaw is where the valves would be too close to the cylinder wall and/or the piston (therefore requiring "flycut" pistons when running high lift agressive camshafts. So not only was the design limited, but left little room for the proper flame propogation or complete burn and exit of exhaust gases. Example: The first semi radial valve was the Canted Valve Cylinder head introduced Cosworth Ford, and then adopted by Chevolet in the 18 Degree valve Angled cylinder head in racing engines which needed very special valvetrain.
So..... at the risk of sounding like a professor here- the Radial Valve head is designed to promote better combustion, allowing more agressive cams and profiles, an advanced valvetrain that allows a higher revving engine without valve "float" and more FREE area around the valves to allow for a scavenging effect as well an advanced valvetrain layout that has less restrictions.
Thanks, and hope I was of some help.
-- Giorgio C (email@example.com), March 10, 2003.
The radial valve layout does not actually refer to a difference in the valves themselves, but the way they are positioned in the cylinder head. This arrangement allows improved port size and shape, valve included angle, and improved combustion chamber shape. It may also contribute to better cooling. The main benefits are better breathing and better combustion efficiency, leading to better power output. This is extremely important in a short-stroke engine design, because there is very little stroke length to draw-in the intake mixture, or to push-out the exhaust gases. So breathing capability is paramount. As we know, the MV engine is the shortest stroke 750cc 4- stroke motorcycle engine ever made. This short stroke contributes to the high-revving abilities of this engine, and in a design like this, revs mean power. At nearly 14000rpm there is an extremely short time for the mixture to enter the engine, so the flow rate must be maximized. The radial valve layout is an effective way to maximize the flow, and improve the efficiency of the combustion by better chamber shape so that the fuel can be efficiently transformed into power at the high revs that are seen in this engine. With short- stroke designs, there is little inertial mixture flow to aid in the induction of the mixture beyond the BDC point of the stroke. Even with longer duration of the cam profiles, it hasn't enough time to keep drawing much after BDC. So it all must flow in on the initial draw of the descending piston. Anything that can be done to improve this initial mixture flow will do alot to help the power output. Having the added benefit of better chamber shape, with less valve area being shrouded by the chamber walls and cylinder walls gives us the second benefit of getting the best burn out of the additional mixture that has been inducted into the cylinders. Then the radial layout of the exhaust valves has a similar effect in getting the exhaust gases out of the cylinder. I am not certain, but I believe this was first done in some Ferrari F1 engines.
-- Tom Lyons (firstname.lastname@example.org), March 10, 2003.
Georgio C is an idiot. His answer is that of a 7 year old, and is as bad as the buzzword hype he got from dealers. Why such an answer was ever posted I dont know.
-- Steve Kimpo (email@example.com), March 17, 2004.
I would be interested in hearing the individual who posted that last answer give his explanation of the Radial Valve theory.
-- My Full Name (firstname.lastname@example.org), June 04, 2004.