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Old 05-01-2006, 12:37 AM   #51
ACTman
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Good writeup! Some of the text looks familiar. I agree with most of it but not all of it. The main two points I would like to make are:

Torque ratings: We use a dynamic friction coefficent (slipping friction) when calculating torque capacity. This means that the torque capacity we rate our clutches for is less than the breakaway torque capacity (point of slip as you said). Most other companies make general claims for torque capacity or % of increase, etc with little or no testing at all. As a result it is just about impossible to take one manufactuer's ratings and compare them to another. Exedy actually uses two different ratings for theirs, one for road course and one for drag race (I don't know why that matters).

Spring versus solid center discs: You claim that the springs are there to dampen the engagement of the clutch. Not so, at least not like the way you describe it. I think we just have a difference in terminology. The springs bottom out long before they really can do any good to help with a strong engagement such as a drag launch. The main purpose of the springs is to dampen out torsional vibrations from the engine. These vibrations (rotational pulses) if not dampened out, will cause the gears to growl in certain conditions. There are at least four distinct conditions that clutch manufacturers are concerned with tuning the spring center for. They are: acceleration noise, deceleration noise, coast rattle and idle rattle. Yes the clutch has to be engaged for the springs to work but the point of engagement has nothing to do with the springs. I think you were basically saying the same thing, only people get confused because most people think that the springs help to soften the engagement or reduce chatter. Chatter from aggressive friction materials in many cases is worse with a spring center disc so I wanted to clarify this point. The springs do reduce vibrations and shock that can cause noise and premature wear on the disc's splines and the gears. When you eliminate the springs, there is more noise, but the disc is lighter so it is easier on the syncros for faster shifting.

Thank you for the time and effort in explaining this stuff to the readers!

Dirk @ ACT
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Old 05-22-2006, 04:36 PM   #52
jkjersey
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What would be the torque capacity on a 2.2 L subaru oem clutch?
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Old 05-22-2006, 07:58 PM   #53
ACTman
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Quote:
Originally Posted by jkjersey
What would be the torque capacity on a 2.2 L subaru oem clutch?
Maybe I am just subi-ignorant, but what year and model are you talking about so I don't get the wrong specs?
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Old 06-16-2006, 03:17 PM   #54
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Just a quick note - had the CEL issues with an MRT flywheel and Exedy 15802 organic clutch.

Did a reset and sure enough within a day, the CEL's and missfires (plus the magical 20b0 and 20b1 codes) were back and it was pretty consistent.

Used DeltaDash to raise the idle 150RPM and the problem is yet to return.

I have a feeling it's the fact the decel theory is right and that with the standard lower RPM limit around 750rpm is just too low and the ECU does not catch it quick enough when it over shoots the mark.

It would appear that raising the mark means the overshoot does not dip too low.

Usual disclaimer - results might vary yadda yadda but this has worked for me. I do have a VF39 and a bunch of other mods as well.
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Old 06-19-2006, 05:20 PM   #55
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bump for great thread and subscription
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Old 07-19-2006, 09:48 AM   #56
camusSTI04
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so i bought the '04 STI a few months ago with 26k miles on it right?
only mod i found on it was a turbosmart plumback blowback valve..
i put an APS TBE on it and the Cobb AP.. i'm curious because i've never dyno'd it.. what kind of hp am i pushing to the flywheel?

i blew out my clutch, it slips on 3,4,5,6 now. I have it on the driveway because the combination of slippage and my tranny jumping around on shifting has me looking at clutches. I plan to change the MAF too and add a Defi Boost controller..

i have not modified many cars in my day so what do you guys recommend?
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Old 10-24-2006, 04:50 PM   #57
micropro_wright
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Great info on clutch isk & flywheels. Now howabout the pressure plate ????
I plan on installing GT30 turbo & supporting mods, I see many people get 400 Ft-LB at wheels. I have seen many posts where torque in the 350-400 cause the stock STI clutch to slip on the dynos.

I had a Talon with a ACT 2600# clutch presure plate and the pedal pressure was too much for comfortable city driving. Don't want to duplicate this problem with my STI....

Seems to me a Centerforce style pressure plate, where centrifugal forces help increase clamping pressure, combined with the proper clutch disk would be the solution. However i don't see any posts where this pressure plate style is used in the Subie world....
Any input as to why would be much appreciated
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Old 10-24-2006, 09:21 PM   #58
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Why not go to Centerforce's website? Once you go there, you'll see they have exactly zero applications for your car. Have another question? Post a new thread.
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Old 11-06-2006, 12:19 PM   #59
Darth Lefty
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After installing an Exedy Stage 1 clutch and an ACT StreetLite flywheel, I was very happy. Today it threw PO300 and 301, but no other effect. I cleared it, we'll see what happens later.
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Old 11-06-2006, 04:27 PM   #60
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i have an o4 wrx stage 2, and my clutch is starting to slip, i plan on gettting a vf34 setup, if i replace my clutch with the stock one would it hold. also there is a guy selling a Stage 2 Exedy 3 Puck Clutch for 250 with 5k miles on it, is it ok to buy a used clutch, i can go down and cheak it out bc he lives right next to me. i need help finding a clutch that would do the job, where can i get a oem clutch, and how much
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Old 11-13-2006, 01:37 AM   #61
hey1
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When it comes to clutch replacement, I'm the total nOOb. So if I was to replace my clutch. What are the essential parts that I really need to replace? I'm currently looking at the parts list under clutch and I see the following items:

Disc
Flywheel
Pilot bearing
Pressure plate
Release bearing
Release cable
Release fork

What do I need and what don't I need? If someone could answer me, I would greatly appreciate it.
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Old 11-21-2006, 10:23 PM   #62
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I didn't see the info in the FAQ or by searching so here goes a simple question or two.

Do I need to use any special type of grease when reassembling the various spline shafts and bearings during a clutch replacement? I've got some left over bearing grease from doing the front wheel bearings on my girlfriends Explorer. Would that be okay?

Also, I bought an Exedy OEM kit from an online retailer. The release bearing was wrapped in packing paper and has more "resistance" than I would have thought. The movement is consistent with no play, the bearing surfaces look new, it just isn't as smooth as I thought it would be. I've never had my hands on a release bearing before and was wondering if this is normal?
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Old 12-08-2006, 12:53 AM   #63
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Quote:
Originally Posted by hey1 View Post
When it comes to clutch replacement, I'm the total nOOb. So if I was to replace my clutch. What are the essential parts that I really need to replace? I'm currently looking at the parts list under clutch and I see the following items:

Disc
Flywheel
Pilot bearing
Pressure plate
Release bearing
Release cable
Release fork

What do I need and what don't I need? If someone could answer me, I would greatly appreciate it.
When you buy a complete clutch it comes with the disk, pressure plate, and the bearings. The flywheel is sold separately but you often find them as a package deal. The fork is a big dumb steel part that doesn't need replacing.

I'm not sure what cable you're talking about.
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Old 12-08-2006, 12:57 AM   #64
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Quote:
Originally Posted by rt4me View Post
I didn't see the info in the FAQ or by searching so here goes a simple question or two.

Do I need to use any special type of grease when reassembling the various spline shafts and bearings during a clutch replacement? I've got some left over bearing grease from doing the front wheel bearings on my girlfriends Explorer. Would that be okay?

Also, I bought an Exedy OEM kit from an online retailer. The release bearing was wrapped in packing paper and has more "resistance" than I would have thought. The movement is consistent with no play, the bearing surfaces look new, it just isn't as smooth as I thought it would be. I've never had my hands on a release bearing before and was wondering if this is normal?
Pretty sure the bearings have grease in them when they arive, that's why they seem sticky. I put moly grease on the spline shaft and the little pads on the fork.
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Old 03-08-2007, 03:08 PM   #65
dkane
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Default Other drawbacks of lightweight flywheel

Overall driveability is much worse than stock and takes a while getting used to. I had one on my car and just thought the sensitivity of the clutch was unbearable. Also, my girlfriend couldn't drive stick and there was no way I could teach her with that flywheel in there. Maybe it's easier for people that keep them in there for more than a month.
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Old 03-24-2007, 08:47 PM   #66
00Maddog
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i'm running the exedy lightweight w/ stage one organic, i think it's one of the best mods i've done. the driveability is ok, no cel even with my gfb underdrive also. The upper rpm's are awesome though, and overall the car feels much faster. the car is a basic stage 2 cobb w/ v6 ra gears.

BUT.... the darned thing is so noisey it drives me nuts. only on decel, but it sounds very much like a ring + pinion problem, just fainter. anyhow there's my input
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Old 05-14-2007, 06:32 PM   #67
colombianwrx
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what are the known symptoms on a bad clutch in a stock '02 WRX? besides slipping. can anyone help? my car feels like it has no horse power at all but revs dont show that the clutch is in fact slipping, that happened recently and is why I'm thinking that the problem with the loss of power may come from the clutch.
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Old 05-14-2007, 09:22 PM   #68
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if, when your foot is completely off the clutch and the car is in gear, you do NOT observe a direct correlation between rpms and vehicle speed then it's a slipping clutch.

if you DO see that no matter what, when rpms go up, vehicle speed rises also--and proportionally--then it's not the clutch.

as to what would cause a car to have a perfectly fine clutch and still be down on power there's a very very long list.
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Old 05-25-2007, 10:12 PM   #69
mintcycles
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That helps...I just roasted my clutch!
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Old 06-13-2007, 12:48 AM   #70
1ockdown
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Thanks for the write up man!
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Old 09-13-2007, 10:02 PM   #71
silverbullet830
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i know it says resurfacing the flywheel is critical. how important is it? my clutch is slipping anytime i get on it. got a spec stg. 1 in today and planning install saturday. how much would it cost to resurface the flywheel and where should i look to find a place that can do it spur of the moment (or at all. what kind of shop). what will happen if i don't? thanks.
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Old 09-14-2007, 06:24 AM   #72
ride5000
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you could get chatter/judder if the surface isn't true.

it's PROBABLY going to be fine, but the thing is... what if it isn't? then you gotta pull it all back apart again! not an attractive alternative.

there aren't many places that resurface flywheels. you need to call around and find out if they do it in the first place, and then ask if they'll do it while you wait.

my preference would be to ask around and see if someone's got a pulled oem flywheel you could get surfaced right away, and then give them yours back when you pull it.
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Old 09-14-2007, 01:02 PM   #73
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good idea. but i'd have to find it today. does anybody know what it cost to have this done? (aproximately)
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Old 09-21-2007, 03:41 AM   #74
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Is there any downside to using the stock pressure plate and say a stage 2 Exedy clutch?
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Old 10-25-2007, 09:08 AM   #75
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Quote:
Originally Posted by Unabomber View Post
Stock clutches should be good for around 250-300 ft/lbs TQ from what I've heard. That means that for MANY users, the stock one is still the ticket.
I'm about to replace my stock clutch, but would it be wise to go ahead and spring for a lighter flywheel while I'm at it? I don't race the car, it's daily-driven (albeit spirited driving is common). I was thinking of the ACT Streetlite flywheel. What do you think?
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