Clutch engagement issue. Possible clutch cylinders upgrade?
 

Lately I've been having a lot of clutch engagement issue. What ive notice was that during cold weather my clutch engages fine, however, if i were to drve for 30 in stop anf go traffic, i will envounter heavy resistance from nutral into a gear and during down shifting. this is true for 1-5 gears at any speed. i also experience heavy resistance when shifting from high gear to nutral, then nutral down shift into a gear. When I encounter heavy resistance, I can slide the gear in by rev matching. Pumping the clutch or double shifting does not help the situation. From time to time I will also experience heavier resistance shifting out of a gear when it's acting up.

I've been reading up the synchro issue, but since I have after market pressure plate (ACT HD portype), I don't know if the problem could due to my master or slave clutch cylinders. I've checked all my hydraulic leak path, they were all dry. I've also check my clutch travel, and it seems to be sufficient.

Someone suggested to me that my clutch could be sticking due to incufficent cylinder pressure because of the increase demand from the aftermarket pressure plate.

Do you guys have any suggestion?

did u change or check your trans fluid? that has a big impact on syncro engadment. i beat on my car all day and it never feels different shifting

What's double shifting ?

Shifting from a gear to neutral and then again from neutral to another gear while engaging and releasing the clutch both times.

"Possible clutch cylinders upgrade"Wft! Dude there is no need to do that. This is a new car; nothing needs to be upgraded unless you really want to turn into race car. I think that you are not rev matching and if you are then complain with Scion/Toyota/Subaru they will fix it.

Not yet. But I will do it during the holidays. I'm looking into bleeding the clutch cylinders. If the problem didn't go away, then I'm looking into changing the trans fluid.

My thinking was that since I've added the new aftermarket pressure plate which adds 50-70% more clamp force. It increase the clutch cylinders work load. Though nothing is leaking at the moment. From my understanding, an underpowered cluth cylinders usually leak if the clamp load of the pressure plate exceeds the max seal load of the cylinders. Since I'm not leaking, it's hard to say its te cylinders fault.

I don't want to bring it in to Subaru until I am sure of my problem is not caused by aftermarket pressure plate. Otherwise they will stick me with void warranty bill.

Sounds like you may have an issue with the engagement of the release sleeve and the clutch cover. It it gets worst when the car warms up, then I would bet that you may have a warped disk or some sort of tolerance issue with one or more of the clutch assembly components. Typically the actual engagement/disengagement has more to do with the hydraulic release mechanism than transmission fluid. Fluid can help the syncros match up easier, but the hydraulic system is what actually disconnects the transmission from the engine (via the clutch).

Thanks for the response. Let me contact ACT perhaps they would like to investigate further.

Since I have a prototype clutch assy. Perhaps they have made adjustment in their production parts.

im at 1200miles and im changing all fluids. factories screw up sometimes and don't put enough oil in trannies.. theres been cases of them having no oil rarely

I had a vehicle that I changed the clutch pp and throw out.....the line from the hydraulic master cylinder couldn't Handle the extra pressure to actuate the racing clutch and the line actually bulged ever so slightly as to not allow the clutch to disengage properly.
Just a thought

okay at the moment im considering a few options.

upgrade the like to SS lines. I think SS lines for STI should work.

meanwhile, i am also looking into upgrading the clutch master cylinder to OE STI cylinders. the stock BRZ/FRS have Nabtesco 11/16. the stock STI 2013 have Nabtesco 11/14. the increase in diameter of the WRX cylinders should be enough to handle any stage 1 pressure plate upgrade.

BTW which brand of SS line did you use?

I have good experience with goodrige SS brake line for bikes. so im leaning in that direction.

I've just finished bleeding both master and slave cylinders. The problem still exist

I believe there is a restriction or delay valve somewhere in the hydraulic system. Finding and removing it may help you out. I wish I had more info on this, but hopefully someone that knows the system will speak up with some advice. Many hydraulic systems have one in place to reduce shock loads to the drivetrain, and they often cause performance minded people a lot of greif.