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Has anyone popped a clutch master cylinder?


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Correct!

 

I've never dealt with one before and had to read up on it. It's a nanny device designed to prevent you from shock-loading the drive train by popping the clutch. It's between the clutch MC and the grommet that heads out to the reservoir.

 

I don't drop my clutch. Therefore all it's really doing is screwing with my pedal feel and potentially eating rather expensive aftermarket components.

 

Hoping to get some pics soon.

 

What would happen if you were to do this delete and then launch the car by dropping the clutch? I can assume "bad things" but an explanation would be useful.

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"Bad things" is basically it. Repercussions are the same as dropping the clutch repeatedly in any car. Broken gears, axles, drive shafts, etc.

 

No different than the risks of sidestepping a cable operated clutch. It does exactly what you tell it to do, whether that was a good idea or not.

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  • 2 weeks later...

Surly,

 

Did you get any 1st gear judder while starting out, on either of your ACT clutches? Did you notice any after the CDV delete?

 

Thanks for any feedback.

 

 

Clutch feels better than ever with the damper deleted and a stainless steel line in its place. The engagement point moved a bit but the feedback is more linear.

 

I would recommend pre-emptively deleting the CDV if you're going with an aftermarket clutch. It appears a metal disc diaphragm inside the valve failed catastrophically. It has a huge crack/crease in it. I forgot to get pictures, I'll try to get some.

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Surly,

 

Did you get any 1st gear judder while starting out, on either of your ACT clutches? Did you notice any after the CDV delete?

 

Thanks for any feedback.

 

Sometimes. X2. Generally controllable with input. I noticed a bit more in the first couple 1st gear starts after the delete. I attribute that to the engagement point moving a fair bit. Not much noise or vibration after I got used to it again.

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  • 2 weeks later...
I know you got a lot going on Surly, and a lot to think about, but you are our front man with NF. :) It sounds like they really know their stuff, so I really hope they can do this for us. I definately want to get rid of that damper, it just complicates the system and as you have shown, it is a weak point prone to failure. The last thing I want is hydraulic fluid squirting all over my interior. :lol:
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Nuke and Fuji are good, knowledgeable, positive people. Seeing how they work with and in the community was already setting me up for the fresh attitude change I just got clubbed over the head with by lgt.com folks.

 

I have little doubt they'd find time for you if you drop them an email. :)

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Looks like it's time for me to chime in. NF Performance used my car as the tester for their clutch valve delete. I was waiting for Nuke to post and then follow-up but I think the guys are very busy and it may be awhile until he gets around to it.

 

I'll give you my impressions the best I can, but understand, I'm not a hardcore car guy-I do not launch ever and I do not flog...much. I've got 65K miles on the OEM clutch and it seems to be holding just fine. For the most part I've been running the Cobb OTS Stage 1/93 oct map for the last 55K miles. Also, as you can see, I don't post. I do read though and I've learned a ton from the members here. Thanks to everyone who takes of their time to post and educate.

 

Prior to Surly reaching out to me I had no idea what a clutch valve delete was or whether it was something I wanted or needed. I knew NF had a great rep. and after talking to Nuke, It seemed like it was something that might be a good thing for us so in it went. The delete itself appeared to be very well made. No need to ask me about the install process because I have no idea what was involved other than it was done by Fuji somewhere under my dash.

 

My biggest concern was that it would make the clutch engagement even more...whats the word I'm looking for? Touchy, finessey- I guess just plain worse covers it best. It didn't. In fact, it seemed to make it better. My son, who learned to drive a manual in this car, felt the same way. I dont know how much of it is placebo effect, or if it is even possible with this particular change, but it seems to engage a little more smoothly in first and second. A bigger sweet spot maybe. If that makes sense. My understanding is that the real benefit of the delete is that the clutch will engage more "purely" during spirited driving. I would say it does. It seems to bite harder when I push it but I do feel like I have to pay a little more attention to my footwork when doing so. I like the change and I think individuals who are more "serious" about their performance, would like it even more.

 

I'll do the best I can to answer questions-just remember who your dealing with :)

 

BTW, the guys at NF Performance are rock solid. They are very experienced, answered a lot of dumb questions and gave me beer while I waited. I will be back.

 

Steve

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Glad to hear that worked out for you! I didn't want to presume since I hadn't heard the final verdict.

 

TBH, I was very reluctant to do the delete even after a fair bit of research suggesting it would have a positive effect on function and feel. I was very cynical.

 

When I picked it up I was kind of pissy to begin with having just received my compression results. Accordingly, I was ULTRA critical during the inaugural valve-deleted test drive... It felt really good. Only complaint so far is the engagement point is a little further up the pedal than I'd prefer. Purely a driving style nitpick and something I can work with later... perhaps while installing STi pedals. :D

 

I dont know how much of it is placebo effect, or if it is even possible with this particular change, but it seems to engage a little more smoothly in first and second. A bigger sweet spot maybe. If that makes sense. My understanding is that the real benefit of the delete is that the clutch will engage more "purely" during spirited driving. I would say it does

 

No placebo. I don't think the sweet spot feels bigger, it's just consistent now. It is always, always, always in exactly the same place, requiring the same pressure and responding the same way. It's not "harsh" like I was worried about. Moreso firm and consistent. It offers solid positive feedback on exactly what's going on with the clutch pressure plate & disc at all times

 

With the CDV in place I noticed the engagement point would move around and surprise me now and then. It felt vague in comparison.

 

 

Here's my preschool understanding of how the valve works. Fuji, keep me honest here:

 

Basically it's a hydraulic-pressure-actuated diaphragm sitting on top of an extra little reservoir that you are forced to fill before the fluid pulse is allowed to be fully transmitted from master to the slave. It comes into play when you let the clutch out fast enough to build enough hydraulic pressure to actuate the diaphragm/valve. It does nothing if the pressure is insufficient to move the diaphragm. Fluid will flow right by it.

 

Say there are [masterCCs] cc's worth of fluid pushed from the master cylinder. Also say the CDV can hold [cdvCCs] cc's worth of fluid.

 

With no valve, exactly [masterCCs] worth of fluid is required to actuate the slave. You have a 1:1 correlation at all times.

 

With the valve in place, at "full pressure" the diaphragm actuates and requires you to fill an extra reservoir. So now you have to move [masterCCs] + [cdvCCs] worth of fluid before the slave sees the full pulse. Moving more fluid is going to require more pedal travel. Exactly how much more will depend on how much pressure was applied to the CDV. More pedal travel means your engagement point just changed, dynamically... and you got crappy feedback about the whole process.

 

 

Edit: Sidenote - Most of the vibration I thought was from the clutch is probably a power steering issue. I think there is a bubble in the lines. If that ends up being an issue I'll spin up yet another "Surly broke more #$%&" thread.

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I notice the engagement point moving around too. It catches me off guard and suprises me sometimes. When it happens, it makes me think for just a split second that something is wrong in the drivetrain or with the way the motor is running.

 

I think getting rid of the CDV will be a welcome thing.

 

Thanks for all your info Steve and Surly. And Steve, it is really great to hear from you and thanks for the test fit!

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No placebo. I don't think the sweet spot feels bigger, it's just consistent now. It is always, always, always in exactly the same place, requiring the same pressure and responding the same way. It's not "harsh" like I was worried about. Moreso firm and consistent. It offers solid positive feedback on exactly what's going on with the clutch pressure plate & disc at all times

 

This is a much better way to describe the change. I think I was misinterpreting that "hold my breath a bit when engaging" feeling I sometimes got with the old set-up and the consistency of the new engagement point as a bigger sweet spot. The consistency makes for a more pleasurable/easier to drive car that I mistook for a larger sweet spot.

 

Thanks for the explanation on how the valve works. Good to know.

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  • 6 months later...
  • 1 month later...
  • 1 year later...
^are there differences between the 4th and 5th gen master cylinders? or are they the same?

 

I don't know, but I really want to know. And I reaaallllly really want to make my way through the "how to [clutch damper] delete" thread to see if the 4th gen has a similar 'fix'.

 

...Damn theres a lot of pages -_-

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I don't know, but I really want to know. And I reaaallllly really want to make my way through the "how to [clutch damper] delete" thread to see if the 4th gen has a similar 'fix'.

 

...Damn theres a lot of pages -_-

 

 

 

There are 2 dampers on the 5th Gen, one in the hard line between the MC and slave cylinder. You will see the page from the service manual in that thread, probably on page 1. Based on this pic from the Subaru parts diagram for 05, your slave cylinder does not have one, only 07+.

 

http://parts.subaru.com/images/parts/subaru/fullsize/B13_10001101.png

 

 

Below is a page taken from the factory service manual for your '05. You do not have an in-line damper like the 5th gen, but rather a damper on the clutch master cylinder (red arrow). This is very similar to the WRX and STI damper and I am pretty certain I have seen damper delete threads for this style damper on IWSTI, NASIOC and I-Club. The green arrow shows where the slave cylinder damper would be if you had one, but as shown on the parts diagram above, the 4th gens have 2 different style slave cylinders, 05-06 and 07-09.

 

Good luck with this. :)

 

454875744_2005clutchsystem.thumb.jpg.86f311ebca76ce1bc2eb6b15d9025c40.jpg

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  • 1 year later...

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