Hi David,
By slowing down the fluid it makes you take more time to change gear and so takes strain from the drive train, but it also makes gear changing gratey if you don't give it time, especially when cold. I do not race the said car nor change that quickly usually, so I can't imagine I put any strain on the box, but I find now everything is a lot smoother.
I cannot imagine that any race car would ever have one fitted, but see it as a device to save BMW from coughing up on warranty issues with boy racers.
This is from Wikipedia and explains:
A
clutch delay valve is an automotive component added to the clutch system of an automobile to standardize clutch engagement speed. Its purpose is to engage the
drive train of an automobile without introducing shock to the drive train components by engaging too quickly. By preventing drive train shock, CDVs also prevent an automobile's balance from being upset, which aids in handling characteristics.
Clutch delay valves operate on the principle that engagement only needs to occur at a certain rate to be efficient and that engaging at a quicker rate can damage the drive train components of an automobile. Engaging the drive train to the engine too quickly can damage
drive train parts, including the
transmission,
differential,
half shafts,
axles, and
CV joints. Engaging the drive train too slowly can damage the clutch friction disc and cause clutch slippage.
Clutch delay valves operate as one-way restrictor valves that limit the volume of fluid that can move through the lines in a given time. This ensures a steady quick and firm engagement without being too fast for the drive train to handle since clutches can quickly disengage but re-engagement is damped. The clutch delay valve slows clutch engagement and was intended to reduce drivetrain shock in the event that an inexperienced driver quickly engaged the clutch at higher revs.
