CDV (clutch delay valve / válvula de retardo del embrague)

Acabo de leer en un foro BMW de los EE.UU.A. que prácticamente todos los BMW tienen instalado de serie en su embrague una pieza que enlentece el tiempo de embrague—no importa la rapidez de acción o la habilidad del conductor.

La pieza en inglés se llama como se lee en el título de este mensaje, CDV (clutch delay valve). El resultado es que, no importa lo que haga el conductor, el tiempo de embrague es lento y por tanto los cambios de marchas, especialmente entre cortas, se alargan y encima se hacen bruscos. Además, el tiempo de vida del embrague se acorta.

Según parece, la sustitución de la CDV por otra similar pero inoperante es fácil y el rendimiento del embrague mejora (podéis ver más detalles en http://www.zeckhausen.com/CDV.htm#CDV by mail). Aparentemente la CDV está instalada para proteger el embrague de conductores inexpertos.

Mis preguntas son:
¿Alguien sabe algo más al respecto?
¿Los BMW vendidos en Europa van también equipados con la CDV? ¿Cómo se llama aquí?
¿Alguno ha cambiado/modificado la CDV aquí? ¿Qué resultado ha conseguido? ¿Hacen el cambio los concesionarios?

Un saludo,

José Luis

 

Yo tambien lo he leido, y flipaba.
A ver si alguien, algun mecanico, aporta algo de info...Es interesante

 

Yo lo de los cambios lentos en marchas cortas si que lo noto, pero ya no se si se debe a esto, o simplemente que no estoy acostumbrado a un recorrido tan largo del embrague.

 

N.p.i......

 

Juer, que de cosas, a ver que se cuentan los que saben...

 

El mio no tiene esa pieza,cambie hace poco el bombin del embrague y no recuerdo ver esa pieza.

 

OÑO, primera noticia, aunque creo que el "retardo" sea (al margen de casi inapreciable) para la busqueda de "comodidad" que otra cosa...a ver Fer con que nos sorpende :roll:

 

Alg de info...que aclara el tema:

Theory of Operation
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The Clutch Delay Valve (CDV) is a one-way restrictor between the clutch slave cylinder and clutch master cylinder, as shown in Figure 1 below. It "delays" the engagement of the clutch, much like old record players used a damped tone-arm to gently lower the needle onto the surface of a record.

Because of this valve, no matter how quickly you lift your foot off the clutch pedal, the clutch engages the flywheel at a constant (slow) rate. In theory, it can save the drive train from shock, were an inexperienced (or teenage) driver to dump the clutch at high RPM. But in practice, all it does is accelerate wear on the clutch and turn experienced drivers into people who, despite 20 years of practice, cannot shift gears smoothly. During parking maneuvers, the delay can be infuriating, causing constant slippage of the clutch. And during hard acceleration, the large amount of clutch slippage can greatly shorten the life of your clutch. During normal, sedate driving, the shift from first into second gear is often jerky, leading passengers to question your skill at driving manual equipped cars. As the driver, you can see your passengers' heads bobbing back and forth during every shift! Yes, in their minds, they are laughing at you.


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Figure 1. Exploded view of 5-Series CDV, slave cylinder, and hydraulic lines
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Interestingly, BMW does not install a clutch delay valve on the E39 M5. The terrible shifting behavior would be unacceptable to these high performance customers. For some reason, BMW does not seem to think the rest of their 3-Series, 5-Series, 6-Series, X3, X5, Z3, Z4 and Z8 customers who shift their own gears will notice. They were very wrong!

Since BMW models have different clutches, they have different clutch delay valves with different valve openings and springs. In order to reduce the odds of a factory worker installing the wrong part on the assembly line, each CDV has a different number of ribs and may even have a different barrel shape. (See Figures 2 & 3 below) The effect on all of these cars is the same. The driving experience is degraded.
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Figure 2. E39 & E60 5-Series and Z8 CDVs with hex-shaped bases
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Figure 3. Z3, Z4/E46 3-Series, E36 3-Series, E46 M3
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The answer, of course, is to replace* the clutch delay valve with a modified valve which has had the interior parts carefully removed. We do not drill these valves. Drilling damages the taper at both ends of the valve. The male tapered end seals against the female taper of the clutch slave cylinder. And the male hydraulic fitting seals against the CDV's tapered seat at the female end. It does not seal via the threads. Drilling a CDV may cause it to leak under pressure and may leave bits of valve material behind, potentially migrating into and damaging the clutch hydraulics.

We have developed a technique for removing the interior valve and spring without damaging the delicate tapered seat at the female end and without touching the taper on the male end. Zeckhausen Racing provides a free service to modify CDVs which are mailed to us. Click here for details. Zeckhausen Racing will also replace your CDV with a modified one at our shop. Nothing else is needed. Just make an appointment and show up with your car.
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