Topic: Question on Spec Stage 3 Clutch

[Steelmesh]

I don't know too much about the reason for the slave cylinder spacer, I know it brings the engagement point near the end of clutch pedal (where that last amount of clutch pedal movement will engage). 

I am mentally trying to work this out maybe it makes sense to someone else, but I am speculating warning:

No Spacer
Foot off Pedal |----------------engaged*****| Pedal to Floor

With Spacer
Foot off Pedal |--engaged***************| Pedal to Floor

Where - means engaged, and * means the slave cylinder has lifted pressure off the clutch plates aka disengaged.  With this diagram and if it is true, since the 'With Spacer' has more ***, does this mean it is physically lifting more pressure off the clutch plates?

[MattM]

I wouldn't think it's more pressure just allowing the throw out bearing to reach further.

That said, I adjusted the master cylinder out towards the back of the car one turn and it has seemed to get rid of the clutch drag....Now it the damn clutch would hold all the time I would be set.  I'll keep breaking it in and hopefully it will come around...

[Steelmesh]

I tried several time to re-bleed the system, including using vacuum pumps or connecting the hose from intake manifold to create vacuum.
Almost unnoticeable improvement.

What I have found is, it isn't the vacuum that bleeds the system, it is the change from vacuum to atmospheric pressure back to vacuum over and over that bleeds the system.  Holding a vacuum is ineffective with my experiences bleeding the kappa clutch system.

[MattM]

Steelmesh....Just so you know...the adjustable master cylinder I purchased from Performance Autowerks does the same thing with regard to make the clutch engage more towards the top of the clutch pedal movement as opposed to the floor. 

I have the slave spacer that came with the Spec Clutch kit (thinner than PAWs) and that coupled with the adjustable clutch master cylinder really does fix the issues with regard to engagement.  It's just a matter of having it engage correctly as opposed to still putting that pressure on the plate when not engage or having the clutch drag because it doesn't fully separate when the clutch pedal is engaged.

[Robotech]

Steelmesh....Just so you know...the adjustable master cylinder I purchased from Performance Autowerks does the same thing with regard to make the clutch engage more towards the top of the clutch pedal movement as opposed to the floor. 

I have the slave spacer that came with the Spec Clutch kit (thinner than PAWs) and that coupled with the adjustable clutch master cylinder really does fix the issues with regard to engagement.  It's just a matter of having it engage correctly as opposed to still putting that pressure on the plate when not engage or having the clutch drag because it doesn't fully separate when the clutch pedal is engaged.

I got the opportunity to talk to Centerforce clutches (they use to make a clutch for our car) about our slave cylinder since they make a long travel version of our slave cylinder. Without going into specifics (because frankly I can't remember them all and even trying to process them all made my head hurt) the slave cylinder's travel is very critical.

I took a stock Kappa Slave to have them look at it so we could see if it was similar to theirs (looks identical since their product is for GM applications) and to explain the difference. Looking at our slave they mentioned the throw was very short.  Theirs was about three to four times the travel of our stock unit. They then went on to explain what each part of the system does.

The spacer behind the slave cylinder sets the bearing deeper into the clutch. Thus the slave now will push further in to fully disengage the clutch but will not travel back out as far to re-engage the clutch. The Slave must also account for clutch wear and thus still be able to come back out far enough as the clutch wears to maintain engagement. The overall distance the slave travels and the distance it is fully out are both critical.

The Master Cylinder is completely different. No matter how you adjust the master cylinder, it has NO affect on how far the slave travels or, if when at full extension, the clutch is completely disengaged. Only the travel (and depth) of the slave can determine that. The adjustable master cylinder only allows you to adjust WHERE in the pedal's travel the slave reaches full disengagement.

Needless to say it was a very enlightening conversation.

As for my 2.4 with the stage 3 clutch, I noticed there was an issue shifting from 2nd to 3rd during WOT "quick shifts" when I first installed the clutch with the spacer.  Clutch engagement was right off the floor. It was so bad, I wound up breaking my trans. The molded aluminum guides in the trans that guided the shift lever internally physically broke from me trying to get it into gear. When the new trans went it, I got the adjustable master and had it set so that clutch engagement happened about half way through pedal travel and not right by the floor. My theory is that before, when I would try to quickly shift, I wasn't hitting the area of pedal travel that was where the clutch was fully disengaged and thus "ramming" the shift lever into the gears. With the adjustable master on the new trans, this problem is gone.

Thus with the adjustable master cylinder, I've set the point at which the slave fully disengages the clutch further from the floor so during high speed shifting moments, I'm quicker to get the clutch fully disengaged in the pedal's travel and not trying to change gears when the clutch is still partially engaged like before.

[Steelmesh]

Thanks for sharing the insight on this. 

My take away (correct if wrong) in regards to the spacer: the spacer makes ensures full disengagement, but there is a risk it is not fully engaging the clutch and clutch wear can impact this dynamic. 

I can probably move the clutch pedal down 1-2" and the clutch will disengaged, so the reality with my car (Spec 3, Spec AL FW, werks slave spacer) matches this explanation.  I got the car with an Exedy Stage 2, that required about 0.5-1" pedal travel to disengage, a bit less than the Spec 3 now.  The exedy was about near end of life when I changed it, but it was pretty much holding the at least 300 ftlbs of wheel trq doing something like a 4th gear WOT pull.  With 2-3 gear WOT pulls I suspected some slip...my point is that the spacer with a worn Exedy didn't reduce the clutch performance significantly, as I was at or above rated torque for the Exedy.

[MattM]

You're right it doesn't necessarily effect how long the throw is, but it does control the amount of fluid pumping to the slave.  If enough fluid isn't pumped then the slave won't fully disengage the clutch which is what causes clutch drag.  Here is a pretty good explanation of it:

https://www.jackstransmissions.com/pages/clutch-drag-kills-synchros

Here is the video explaining it....

[MattM]

Interesting update! So I got on it today....1st 2nd then into 3rd and it started doing that wierd "slipping" thing i've described only this time it kept doing it so I just rode it out to see what would happen....I'm glad I did because the check engine light started flashing and come to find out I had a WOT miss in cylinder 3. Now I'm not going to say definitively that it was a miss the whole time, but interestingly when it did this.... after the miss was gone the rpms shot up by 500 rpms where they should have been and the car starting pulling again. It perfectly mimicked what I thought would have been a slipping clutch. Not only that from what I understand most of the time when you have weak spark it's going to show itself in third, fourth, and fifth gear low rpms when the boost starts shooting up and blows spark out. I can't believe I didn't notice this from the get go because I've had this issue before.

The other funny thing is that I went to two step colder plugs than the 2008 stockers because I was getting knock according to my datalogs. I switched to Sheetz 93 octane fuel and haven't seen that knock forever so I'm thinking that its making much more power and the tune has acclimated to the fuel. I'm going to put one step hotter plugs in tomorrow and see what happens. I'm assuming I have fouled plugs but it was too dark out to check so I'll definately look tommorow. I honestly hope this is what it is! It would be so great!

[MattM]

Just wanted to update everyone here.  I finally said screw it and bought another Spec Stage 3 six puck but with a Spec flywheel in June of this year.  I got through break in and the clutch has held up perfectly.  It has NEVER had that 500rpm slip in 2nd through 5th from 2500rpms and flooring liek the first clutch setup did. 

Im really impressed with the holding power of this thing!  It's been great and it's not too harsh at all!

[Critterman]

Good to hear