Subaru hydraulic clutch time..., Need help from the gurus! Options

[Chris H.]

Hey all,

I'm at the point where the hydraulic clutch setup needs to be mapped out for my Subie conversion. The donor trans is from a 2006 WRX with a 13/16 slave cylinder. Initial reaction is to buy a 13/16 generic (wildwood or CNC) master cylinder so they match and give a “factory” clutch feel but after some internet searches it seems that pedal travel is also a factor and might mean a different size would be better. I’ve seen some GREAT hydraulic clutch threads but could not find one for the Subie trans setup.

I’d assume the pedal throw is probably similar but could be wrong. BIGKAT is using a 3/4 and mentioned he might rather have a 5/8. His trans likely has a ¾ slave.

Any insight or thoughts on this? You don't have to be right! Brainstorming is great too. (IMG:style_emoticons/default/biggrin.gif)

[andys]

Knowing the Subie slave travel (in order to calculate the volume) is generally a safe approach, though what you really need to know is how much travel is required by the slave to dis-engage the clutch. Also, I suspect the subie slave is forward sprung, meaning that the slave has an internal spring that keeps the piston in its most forward position at all times and keeps the TOB in constant contact with the PP fingers. With this type of slave arrangement, the volume of fluid required to dis-engage the clutch is kept to a minimum. So my advice would be to determine if the Subie slave is internally sprung forward first, followed by how much travel of the TOB/PP fingers is required to dis-engage the clutch in order to get the correct fluid volume required. Some of the travel to dis-engage is dependent on the clutch configuration (I'm not familiar with Subie stuff), but the travel requirements for a clutch disc that has a Marcel spring design will be different than one that is a puck design or bronze/ceramic design. My appologies if I've done nothing but added to the confusion :-}

When I was configuring my clutch system designed around QuarterMaster comonents (not for a Subie), they were able to provide me with all the tech info I could have ever hoped for.

Andys