Radial valves - MVAgusta.net
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post #1 of 26 (permalink) Old 11-23-2007, 03:28 AM Thread Starter
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Radial valves

O.K. folks, not being ignorant regarding engines and their operation,the purpose and relationship of various engine components, but can someone describe to me "radial valves" and the difference from a conventional valve.
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post #2 of 26 (permalink) Old 11-23-2007, 05:26 AM
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I will try to answer but forgive my english with is not so good (I am french).

As I know, radial valves are convergering to the same point therefore conventional valves are parallel two by two (exhaust and inlet on each side of the cylinder).
So conventional valves use a roof cylinder head and radial valve use a spherical cylinder head which is better for fuel burning.
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post #3 of 26 (permalink) Old 11-23-2007, 07:16 AM
Hi, i'm not an expert but take a look at my avatar and also the picture below and you might be able to visualise it a bit better.
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post #4 of 26 (permalink) Old 11-23-2007, 07:42 AM
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It refers to the shape of the inside of the cylinder head. Ideally, it's shaped like a sphere, which is why sometimes you hear it referred to as "hemispherical" (eg "Hemi").

The other more common shape to the cylinder head is sometimes called "pentroof", which is shapped like the roof of a house, with 2 flat sides and the valves are parallel. Take a sheet of paper, fold it in half and then stand it on the table so it forms a triangle with the table (not sure if I'm making sense).

The MV has it's valves arranged along the surface of the "sphere", so there are no parallel lines.

Not sure what advantage it really has, nobody on MotoGP is using it (well can't say for sure, but probably not). It requires some funky setup. The MV has sloped valve lobes, which I think is a first on any engine? Honda got away with it in dirt bikes by using forked rockers which were bent to accomodate the radial valve layout.

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post #5 of 26 (permalink) Old 11-23-2007, 07:46 AM
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Radial Valves......this is a common misconception........the words are in italian....which directly translates to "radio valves".....which means the factory worker gets to listen to the radio while he machines the valves.

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post #6 of 26 (permalink) Old 11-23-2007, 08:11 AM
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"Radial Valves" is a description of the angle of the valves in the head. The purpose is to reduce the amount of bend in the port in order to create less restriction in the port thereby increasing the port's flow capability. The larger the included angle between the valve stems the better the intake and exhaust flow. The angle has a practical limitation though due to the limits of the design of the valve train. Ideally the port should have no bend but rather be a straight shot from the throttle body/manifold and the exhaust port to the head of the valve. This gets limited though by available space for everything around the throttle bodies to fit within reason. It's a compromise.

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post #7 of 26 (permalink) Old 11-23-2007, 03:11 PM
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The farther away from the cylinder wall the head of the valve gets as it opens, the better it will flow. A radial configuration is a little better than the conventional setup because the valve is moving towards the center of the cylinder in two axes, not just one.

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post #8 of 26 (permalink) Old 11-23-2007, 03:35 PM
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Yehaw! I have a Hemi!

I found this on Google:

The Radial Valve theory

Last edited by Allan Gibbs; 11-23-2007 at 03:42 PM.
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post #9 of 26 (permalink) Old 11-23-2007, 04:18 PM
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Originally Posted by triple
O.K. folks, not being ignorant regarding engines and their operation,the purpose and relationship of various engine components, but can someone describe to me "radial valves" and the difference from a conventional valve.
It originated from a Ferrarri F1 engine of about 15 years ago, as noisysilmotoman says his avatar gives you a good idea,

advantages? The sticker looks good! in this modern day and age I would say very little if none at all, if it was that good all the Moto GP teams would use it, a bit like a 5 valve per cylinder R1--just a gimmick.

Disadvantages? very hard to make, hard to get anyone to make you replacement cams, also difficult to get a valve guide replacement I would think unless you can find a real good machine shop.

(This reply has not been checked for punctuation, grammar, or spelling mistakes and is devoid of any big long cleverwords or condescending manner)

MV's all gone now, still have a soft spot for MV's, waiting for MV to tick all my boxes again.
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post #10 of 26 (permalink) Old 11-23-2007, 05:57 PM Thread Starter
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Well then fellas, if thats all thats entailed in "radial Valves" then you will have to accept that the majority of vehicles produced these days with 3 or more valves per cylinder will have a radial layout.

Sounds then, thats its more of a sales pitch than anything else.

I do like lewdog998 reply though.
where I work we are not allowed radial valves for safety reasons..........................''
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