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Clutch pressure change on acceleration?  

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scotched
(@scotched)
Trusted Member

I swear I'm not imagining this.

Occasionally, when I'm accelerating on the freeway (with my left foot resting on the clutch) it feel like the clutch pressure drops for a few seconds.  My left foot (on the clutch) moves about an inch down on it's own weight with no added force.

Is there any science to what's going on here?

The only thing I can say about my clutch setup is that it's not OEM.  Southbend Stage 1 clutch and Competition Clutch Lightweight Flywheel both with about 30k on them.  I haven't changed clutch fluid.

scottsmods.com

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Posted : July 28, 2020 5:40 pm
marsrock7
(@marsrock7)
Reputable Member

Then take your foot off of the clutch pedal? 🤷‍♂️ 

I'm all seriousness thou, why is your foot resting on the pedal? 

I can't think of any simple reason why clutch pressure should change with acceleration, engine speed or vehicle speed. 

I have Southbend Stage 2 with the CC LW flywheel.... For about 12k now. Can't say I've ever felt anything like this, but I don't rest my foot on the pedal either... If I'm driving hard I will float my left foot, keeping contact with the pedal but no pressure. Otherwise my left foot is on the dead pedal. 

30k over how many years? Sounds long enough to warrant some new clutch fluid. Hopefully it's not an issue with the pressure plate or clutch springs, but if it were, I don't see why the problem would only present itself during acceleration.

 

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Posted : July 28, 2020 11:53 pm
dev and neomr2 liked
dev
 dev
(@dev)
Just a member. Moderator

I agree. Old clutch fluid will do weird things with the clutch behavior once it gets heat in it.  At one time I use to use performance brake fluid for the clutch and within 6 months to a year it would have issues. The solution is to stick with DOT 3 Toyota fluid and I haven't had an issue. 

 

 

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Posted : July 29, 2020 1:01 pm
scotched
(@scotched)
Trusted Member

@marsrock7

It's probably been 4 years since I've touched it.

Guess I'll change the fluid.  It would be magical if it somehow solved my shifting problems.

scottsmods.com

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Posted : July 29, 2020 9:29 pm
marsrock7
(@marsrock7)
Reputable Member

Hopefully some fresh fluid will be the remedy. Even if not, there is sure to be a difference. 4 years is plenty long for any brake fluid. I usually flush brake/clutch fluid after 2 years if it hasn't been done otherwise. The difference is always more significant than I expect.

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Posted : July 29, 2020 11:36 pm
scotched
(@scotched)
Trusted Member

@marsrock7

Does your Southbend Stage 1 feel lighter than or as light as stock?  Has the feeling changed since you've had it?

I have a c60 and a Stage 2 (street) sitting in my closet.

scottsmods.com

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Posted : July 30, 2020 2:17 am
marsrock7
(@marsrock7)
Reputable Member

@scotched

I have Southbend stage 2 in with my 2zz swap. I honestly can't remember stock since the 1zz only lasted a couple hundred miles before dying. Had an exedy stage 2 with 2zz for a while and that pedal was pretty heavy. Southbend stage 2 is way more comfortable and feels like a stock clutch at the pedal to me. I'm very happy with how it feels. The lightness of the clutch pedal matches the lightness of the car as a whole in my opinion.

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Posted : July 30, 2020 1:03 pm
haloruler64
(@haloruler64)
Honorable Member

FWIW I have a Southbend Stage 2 Daily on my 1ZZ. Same pedal pressure as a stock clutch, maybe even a hair less.

2000 Toyota MR2 Spyder, 2017 Lexus CT200h F Sport

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Posted : July 30, 2020 6:45 pm
marsrock7 liked
marsrock7
(@marsrock7)
Reputable Member

...well, and here I was just complimenting my southbend stage 2 daily.... And it's gone and broken itself. So very disappointed. I just put a c65 gearbox in about 1000 miles ago. And only 11.5k (checked my records) on the kit. More details in the clutch rant thread I'll be posting shortly...

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Posted : August 2, 2020 10:51 pm
dev
 dev
(@dev)
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Posted by: @marsrock7

...well, and here I was just complimenting my southbend stage 2 daily.... And it's gone and broken itself. So very disappointed. I just put a c65 gearbox in about 1000 miles ago. And only 11.5k (checked my records) on the kit. More details in the clutch rant thread I'll be posting shortly...

Sorry to hear. Just curious, did you grease the splines with moly paste.  

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Posted : August 2, 2020 10:59 pm
marsrock7
(@marsrock7)
Reputable Member

@dev Yes I greased splines as well as all of the clutch fork contact points. I use Honda's ultra high-temp urea grease. It is what they call for in their bell housings and I paid quite a bit for the little tub I have so I use it for all near-unreachable lubrication needs.

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Posted : August 3, 2020 12:27 am
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