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Old 04-25-2022, 11:37 AM   #1
SuperPete
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Default Slipping ACT Street pro clutch

Hey all,
Just finished my build, 2012 Hatch WRX with fully built forged sti swap motor and transmission.
Motor was stripped down and fully rebuilt by me, all the good stuff, catless, all deletes, FP Green blowing 25lb on E85, smooth running car.
Tuned, watching other cars on youtube having same specs we estimate 500-520WHP
Bran new clutch ACT Street pro with brand new STI flywheel.
After brake in and all I have about 2K mi on this setup, car feels awesome.

ISSUE:

yesterday I was coming back from subaru meet and decided to do 5th and 6th geer pull, I have not done that before, so I punched it in 5th and as soon as boost hits RPM jump and car didn't LOL, I let go, tried same thing again same thing and 6th is same.

1-4 gears no slip, tires spin but no clutch slip.

When I was building car, I looked at the clutch specs and it says 515lb/tq, just now to find out it's crank reading not wheel.
So what now, new clutch?
What you guys think?
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Old 04-25-2022, 11:49 AM   #2
GeoNV
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How much power are you putting down?
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Old 04-25-2022, 12:15 PM   #3
benflynn
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My 1300$ exedy hyper single wouldn’t hold power till I bedded it in. No slip after
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Old 04-25-2022, 12:23 PM   #4
BlackFighter
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Quote:
How much power are you putting down?
He doesn't know how much power he is making because he estimated.

Quote:
515lb/tq, just now to find out it's crank reading not wheel.
515 crank tq is about 430 wheel tq (if my math is correct). So there are a few things I can think off the top of my head.

1) you might be maxing it out, but who knows since we do not have any real numbers.
2) improper clutch break in
3) Clutch paddle needs to be adjusted
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Old 04-25-2022, 01:15 PM   #5
SuperPete
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Quote:
Originally Posted by BlackFighter View Post
He doesn't know how much power he is making because he estimated.



515 crank tq is about 430 wheel tq (if my math is correct). So there are a few things I can think off the top of my head.

1) you might be maxing it out, but who knows since we do not have any real numbers.
2) improper clutch break in
3) Clutch paddle needs to be adjusted
I followed clutch break in from ACT, pretty confident I got that done right.
I will look in to pedal adjustment.
Power estimated, but my tuner who was etuned, he told me based on my mods and logs he seen and him dying similar cars, he says 500-520 wheel.
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Old 04-25-2022, 01:42 PM   #6
SuperPete
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I did looked in to clutch adjustment, my clutch is fine, it starts to grab about 1/3 way away from floor and fully engages half way travel.
I'm good there.
I guess its new clutch for me, hmmmmm
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Old 04-25-2022, 02:29 PM   #7
undyjr
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Ok, I'll ask. Did you clean the flywheel and pressure plate? Were you sparing with the lube on the input shaft and throw out bearing?

I wouldn't give up on your clutch yet. Try putting some more miles on it.
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Old 04-25-2022, 02:37 PM   #8
SuperPete
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I did clean flywheel very well, sprayed with alcohol and wiped with very well, as new they come covered with oil for protection...
installed using gloves so I don't put any grease on it, I did all the work myself as well as engine build and transmission swap, I did lube shaft, don't recall bearing, it was new, I think it was lubed from factory, it was ACT clutch kit...

I need to climb under the car and check out to make sure there is no oil inside the clutch housing, maybe small leak there causing all that.
Also you know that black rubber plug, square one on top of of the transmission housing, I dont have that on, lost it somehow, possibly maybe some oil fumes got in? But my engine very well put together and I dont see any leaks, super clean and well take care of
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Old 04-25-2022, 02:40 PM   #9
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Quote:
Originally Posted by undyjr View Post
Ok, I'll ask. Did you clean the flywheel and pressure plate? Were you sparing with the lube on the input shaft and throw out bearing?

I wouldn't give up on your clutch yet. Try putting some more miles on it.
About more miles, first 500 miles was rough, it was grabbing like crazy, starting from stop was something else, anyway, after 1000 got allot better, manageable, but still little rough at times, something I would expect from new clutch new flywheel.
I did maybe 5 hard launches after tune was done and it smoothed clutch down to almost stock, BUT when in reverse still shakes and grabs hard, backing up in to garage kind of challenge.
Its not my daily, I drive it on the weekend, when weather is nice, this is my toy.
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Old 04-25-2022, 02:40 PM   #10
BlackFighter
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Quote:
Power estimated, but my tuner who was etuned, he told me based on my mods and logs he seen and him dying similar cars, he says 500-520 wheel.
You keep talking about whp, but that does not matter when it comes to tq rating since they are two completely different numbers. As you already know, a clutch is rated by tq, so what tq did your tuner estimated you at? Be careful not to buy the wrong clutch.
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Old 04-25-2022, 03:08 PM   #11
SuperPete
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usually tq should be 20-40lb lower than HP, I would estimate 480-500lb.
I feel like I miscalculated clutch a bit doing the build.
Thats why I am here hoping to get feedback from other members running similar setup and see if they are experiencing same issue, or maybe this clutch has potentially little bit of reserve and can handle more and my issue in something else.
Just trying to figure this out.
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Old 04-25-2022, 04:10 PM   #12
BlackFighter
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Quote:
usually tq should be 20-40lb lower than HP, I would estimate 480-500lb
When it comes to 500whp and all that money spent, me personally I would not estimate anything. I have learned a long time ago, estimating ends up costing more money. Same car with same setup can have completely different numbers, depending on location, weather, tuning, what gas you have in the tank ect... So since you still want to continue to estimate, lets estimate your around 500WTQ. Buy a clutch for 500 WTQ rating or 600 crank tq.

Look into southband. That is the clutch I'm choosing for my build and many people say good things about them.
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Old 04-25-2022, 04:17 PM   #13
benflynn
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Quote:
Originally Posted by BlackFighter View Post
You keep talking about whp, but that does not matter when it comes to tq rating since they are two completely different numbers. As you already know, a clutch is rated by tq, so what tq did your tuner estimated you at? Be careful not to buy the wrong clutch.
HP and Tq are two ways of saying the same thing. X hp at x rpm is always y tq, and other way around
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Old 04-25-2022, 04:25 PM   #14
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My clutch said it could gain 50% holding capacity with proper break in
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Old 04-25-2022, 04:26 PM   #15
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Quote:
Originally Posted by benflynn View Post
HP and Tq are two ways of saying the same thing. X hp at x rpm is always y tq, and other way around
Except that you can make 500whp with 350wtq or 500whp with 550wtq... clutch requirements for both are different.

So no, they aren't saying the same thing. If he had his car on the dyno to tune it the tuner would have found it slipping at peak torque under proper load and flattened his torque curve that it wouldnt be a full hit and his problem would have dissapeared.

this is the reason on the 1-4 run it doesnt slip, because he never actually makes peak torque, but when he does a pull from a lower rpm in a high gear he develops enough load at lower rpm/peak torque to exceed the torque rating.
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Old 04-25-2022, 04:30 PM   #16
benflynn
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It’s an equation, no special circumstances
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Old 04-25-2022, 04:31 PM   #17
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Quote:
Originally Posted by benflynn View Post
My 1300$ exedy hyper single wouldn’t hold power till I bedded it in. No slip after
how did you like this clutch? I feel like I make the wrong choice and should have tried this one
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Old 04-25-2022, 04:33 PM   #18
benflynn
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Quote:
Originally Posted by blurred View Post
Except that you can make 500whp with 350wtq or 500whp with 550wtq... clutch requirements for both are different.

So no, they aren't saying the same thing. If he had his car on the dyno to tune it the tuner would have found it slipping at peak torque under proper load and flattened his torque curve that it wouldnt be a full hit and his problem would have dissapeared.

this is the reason on the 1-4 run it doesnt slip, because he never actually makes peak torque, but when he does a pull from a lower rpm in a high gear he develops enough load at lower rpm/peak torque to exceed the torque rating.
In reality much more goes into it, like gearing, like planned use, like flywheel or all rotating mass, heat capacity and on from there. It dosnt slip in 4th os because of gear ratio, might never slip in a 4.44 5mt but a 3.90 6mt puts more load on the clutch.

As much as unabomber would like tq to be the only factor, it’s not.
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Old 04-25-2022, 04:35 PM   #19
benflynn
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Quote:
Originally Posted by blurred View Post
how did you like this clutch? I feel like I make the wrong choice and should have tried this one
It holds fine, it’s a dance to take off or reverse. Bite point never seems to be in the same place twice. I quickly got use to it, but I’ll be getting the twin version next time. I did go through a 300$ disc pretty quick, second one has lasted longer.
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Old 04-25-2022, 08:38 PM   #20
Unabomber
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1. On a list of good ideas, going WOT in 5th or 6th gear is up there with invading Russia in winter. Full stop to that now or ever.
2. You buy clutches based on torque. People think I'm crazy for saying this. Call ACT or South Bend or Exedy and fact check me. Maybe I'm lying.

You bought the wrong clutch, one that won't hold your torque. Inhale this through the nose and out the mouth. You stepped on the rake and there's nothing you can do now other than baby it until you get the funds/time to get the right clutch which is one that is rated for your torque. And every high power clutch sucks to drive in reverse, so that's normal due to the ratio in reverse.

I'm a fan of South Bend myself and there's nothing wrong with calling the horse's mouth and telling them your car and your torque and listening to their recommendation. Call the big three above and see which one of them talks to you in person within 15 minutes.
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