Brand new clutch slipping under boost.
 

Hey guys. So it was a pretty unfortunate day :sigh:


Clutch started slipping under boost today, first noticed it while I was on the highway, just cruising along in 6th sitting at around 3k rpms. Went to pass someone, only gave it about 1/2 throttle and noticed some minor slippage (rpms went roughly 300 above what they should of been and came back down when I let off the throttle.) I tested this a few times just to be sure I wasn't crazy or something but it definitely seems to be slipping slightly only under boost.


I have a South Bend Stage 3 Daily clutch with seriously like 1.5k miles on it.. it's basically brand new. I don't see how a brand new $800 clutch that was properly broken in (drove roughly 750 city miles before even going boosted) could be slipping already. Installation was done properly, no excessive grease or anything. All surfaces were thoroughly cleaned with brake cleaner prior to install. Brand new OEM flywheel installed along with the clutch.



I don't beat my car at all. This clutch has seen redline twice and that was only for tuning purposes. Only running 10 PSI so the boost isn't anything crazy, this clutch is rated for more then enough of the power going to it.


Basically I'm trying to see if I have any options prior to contacting South Bend and having to rip my tranny off again.. could this possibly be a slave cyclinder (clutch not completely disengaging) or something with the pedal? (roughly 1 inch free play before bite) Faulty clutch..? I'm more leaning towards the clutch itself though because I have no issues driving normally, it just starts to slip slightly only under boost.


Rip...

Did you adjust your clutch pedal after the install or is it still stock setting?

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I have not adjusted the pedal at all. Still at the stock setting to my knowledge.

Worth a try but if it's slipping from damage then it may be too late for the pedal adjustment. I had to adjust mine to get it comfortable.

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Are you sure it's slipping? Can you replicate it in other gears? 6th and under 3k is kinda lugging the engine a bit. Tune related?

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Pretty sure. I start building boost right around 3k, and I was able to replicate it earlier in like 3rd and 4th (although it was slight, didn’t seem to be the same extreme as it was on the highway.)

I’ve felt clutch slippage before and that is just what it feels like off the bat. Once I start getting decent boost, the rpms will shoot up a bit almost as if I was revving it, and drop back down a few hundred rpms if I instantly let off. I do not have any smells of a burning clutch or anything though, could it be something turbo related like overboost or something? I’ve been driving manuals for years but only been driving boosted for like a month.

You might be on to something with overboost? Did a shop do the install or you do it yourself? What power and torque are you making at the wheels ballpark?

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I did the install myself but I was pretty meticulous. Remote tuned at the moment so I don’t have a dyno number but I’d say roughly 300-325 whp on 10 PSI + E85. Gonna have to test it out again and keep an eye on the boost, just don’t have a dedicated boost gauge yet. (Currently using OBD + Torque app on an android head unit)

This would honestly make more sense if it turned out to be the case over the clutch, but I’ve never really experienced overboost so I’m not sure how similar they would feel compare to each other.

Can you capture a log and send to your tuner? The stage 3 daily can handle 400tq at the flywheel. So if your running 10psi on e85 you should have plenty of headroom... You are tuned on ecutek? Your running on waste gate pressure only or do you have ebc?

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Yep tuned on Ecutek. I’ll do a log tomorrow and keep an eye on the boost.. no EBCS so it’s wastegate pressure. If it’s indeed overboost I imagine I’ll have to do some adjusting on the wastegate actuator arm I believe.

I am betting your on the right track... Not saying for sure as I have a supercharger on my twin. Also running a southbend clutch stage 2 with no issues. They are just slightly modified excedy clutches.

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Brand new clutch slipping under boost.
 

I ran the same clutch for a bit, my issue was when on track and shifting at redline the clutch pedal would stay at the floor. Tried bleeding clutch fluid and also replacing the slave cylinder and didn’t resolve.

Pulled out the southbend and replaced with OS Giken and have had no issues at all. I’m running 13psi on E85 w/ Harrop supercharger around 330whp and clutch holds easily.

The southbend looked like the pressure plate was applying uneven pressure by the wear on the clutch when we removed.




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Any updates on this? I'm interested in the South Bend Stage 2 Daily for boost @ 10 PSI as well but I'm only running it on 93 pump gas.

You should be fine... Turbo or SC. Daily stage 2 is rated for 315 at the crank and I am sure that's conservative a bit. So at 10 psi you will be hitting 250wtq max would be my guess

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