Clutch for the STi

So if anyone was following along in the build/run thread, I believe I spectacularily blew up the clutch at PFR. 'Twas a sad day.

Anyways, I don't know much about clutches. What I do know is it always seems that people go WAY OVERKILL for the amount of power they make.

The car came with a Bully Clutch (Canadian company) "stage 3 awesome kevlar deal" something or other. While I like supporting local companies, I don't like it when their shit ruins a rally for me

ACT is a well known and respected company all around. I want to use their HDSS disc with the HD pressure plate. They "say" it's "good for" some absurd amount of torque (~550lbft) and advertise it as their street clutch. I've driven a STi before with this clutch in it, and it seems fine.

So, uh, do I just buy it? Or are there any other suggestions from the peanut gallery? I'm kind of confused here because I don't have an opinion on this besides a a "4 puck EXTREME-REDBULL ENHANCED FORGED STEEL CLUTCH!" seems a bit excessive for my slow car. I would prefer to only do this once for the next year

I thought Red Bull and flour mixed together could get a clutch to last another 5,000 miles!

Some guys at the LeMons race last weekend riveted brake pads to their destroyed clutch disk so they could continue.

That's all I've got.

---

Andrew Steere
Lyndeborough, NH
KB1PJY

I'm surprised some put and recommended a Kevlar disc in there! Kevlar is great for longevity, but but very easily overheated, and then "cooked" and doesn't come back. Pretty easy to cook a clutch in a rally car: get stuck in a ditch/snowbank, load the thing onto the trailer, etc.

I'm a fan on "pucked" clutch discs, and i'm running a 6 puck disc. A pucked disc will disipate heat better than a full faced disc, which is a good thing. The engagment will be less "progressive" and more on/off, but honestly that's all we ever need.

ACT makes good stuff, i'd probably be looking at the XTG6 over the HD66 if it was me.

Exedy has a history of supporting Rally Competitors, so i'd think they would be worth a look as well.

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Chris

You "believe" you destroyed the clutch?

If you are replacing the clutch, what do you plan to do with the flywheel? Is it a stocker, or something else. Subaru flywheels don't like being turned, at least in my experience. They are heat treated, and once resurfaced, they are never the same.

I would second the suggestion for a pucked clutch. It should hold up better, and you dont need awesome streetability anyway.

I loved the 6 puck carbon disk I had in my S14.

Also, look at hub designs. I have seen street clutches launch all their hub springs into never never land when subjected to rally beatings.

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I Seppanen, Car #240

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Ian S
You "believe" you destroyed the clutch?

All evidence points towards it, besides actually pulling the transmission and seeing. Which is the plan for this weekend. I mean, if it's the transmission itself that is hooped, well, good thing I know where and what to use (and how much it'll cost!)

I don't think I've ever saw a 6 speed STi transmission blow up besides for when Pat was using a synchro box.

Thanks for the info Chris, that's the kind of knowledge you just don't really find on a place like NASIOC. The more you know... (and the 6 puck is cheaper to boot!)

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HiTempguy

All evidence points towards it, besides actually pulling the transmission and seeing. Which is the plan for this weekend. I mean, if it's the transmission itself that is hooped, well, good thing I know where and what to use (and how much it'll cost!)

I don't think I've ever saw a 6 speed STi transmission blow up besides for when Pat was using a synchro box.

I was just curious as to symptoms. I have seen the clutches fail in many different ways, and understanding the failure is something I always like to take into account when building a new setup.

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I Seppanen, Car #240

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Ian S
I was just curious as to symptoms. I have seen the clutches fail in many different ways, and understanding the failure is something I always like to take into account when building a new setup.

A bit of backstory:

My lights (as chronicled elsewhere) arrived at the hotel on the day of recce. As I was already behind, I suggested my crew cheif take the rally car to Canadian Tire to get a rivet gun/rivets to assemble the pods/lights. Unfortunately, in my rush, I didn't explain to him how to drive the car as it it quite tempermental. He slipped the clutch enough to get the flywheel and disc to stick together. This typically happens when a high amount of heat (lots of slipping) is introduced, and then the car quickly shutoff. The disc and flywheel then "fuse" together.

Luckily, after going a bit crazy, Andre from SwapShop (he is da bes, in case you didn't know) said it was a simple fix, just had to break them lose by romping on it real good. Clutch felt fine afterwards.

For fear of the clutch not being in good shape, I took to launching sans-launch control on Friday. Saturday morning, being a new day and the clutch feeling peachy-keen, I did start to use launch control again (there were TV cameras DAMMIT!) 2nd stage of the day, about 1km in, I went to grab 3rd from 4th. Got out of 3rd, grinded the crap out of the 4th gear synchro, tried to grab 5th, managed to pop it in, then bogged in a L3, grabbed 3rd (which was there), but no drive.

Finally came to a halt. All of the gears are there, but there is no forward drive. Grinding sounds coming from the drivetrain with or without the clutch pedal pushed in.

One theory presented to me is that by pushing the clutch in when the flywheel and disc were stuck together damaged the pressure plate. Another is that the clutch disc blew apart after being overheated badly. Both seem extremely plausible. I also pray it is, because a $3500 STi close ratio box will put me out for the rest of this season.

Been very impessed with southbend clutches (as opposed to Spec) was un impressed with the spec clutch. Wore early, and was noisy with an aluminum flywheel until it warmed up.

Have loved the clutches from clutchnet in my DD's. Good price, no premature wear, not squealy, and I haven't had one slip. I overdo my clutches. I figure if I want to be a retard with the car on occasion I don't wan't the clutch to be the piece to give up as it's the hardest to change. If there is a reason not to do this, I'd love to hear it as I can't come up with one. Clutch in my dd s4 is a southbend stage 3 with complimenting PP and is a bit stiff for traffic, but if I want to do a launch control aided start on the way to church I've got no qualms doing so. Rally car got a clutchnet job that I haven't tried out yet.

I've also had a couple of buddies weld their spec clutches to the flywheel in their street cars. Won't be going back there.

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fiasco
I thought Red Bull and flour mixed together could get a clutch to last another 5,000 miles!

Some guys at the LeMons race last weekend riveted brake pads to their destroyed clutch disk so they could continue.

That's all I've got.

A can of Coke will get you home too

Have ACT clutches - "street kevlar" and "heavy duty".

The kevlar clutch does not like a lot of slipping - overheats easily, clutch action goes away, and the material frays away from the disc. Bad bad.

The HD clutch on the other hand has an unsprung disk (bad bad) but the pucks basically last forever no matter how much they're slipped. I think the pressure plate sucks, it has way too much internal leverage to make the pedal feel light, at the expense of requiring FULL pedal stroke to disengage.

What I'm getting at is screw fancy fiber clutches, no matter what they are made of they are still fiber/resin and you can cook the resin out with slippign and then the fibers disappear. Get a puck clutch, but get one with a sprung hub.

---

Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Quote
Pete
Have ACT clutches - "street kevlar" and "heavy duty".

The kevlar clutch does not like a lot of slipping - overheats easily, clutch action goes away, and the material frays away from the disc. Bad bad.

The HD clutch on the other hand has an unsprung disk (bad bad) but the pucks basically last forever no matter how much they're slipped. I think the pressure plate sucks, it has way too much internal leverage to make the pedal feel light, at the expense of requiring FULL pedal stroke to disengage.

What I'm getting at is screw fancy fiber clutches, no matter what they are made of they are still fiber/resin and you can cook the resin out with slippign and then the fibers disappear. Get a puck clutch, but get one with a sprung hub.

Plus Juan.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
HiTempguy
A bit of backstory:

My lights (as chronicled elsewhere) arrived at the hotel on the day of recce. As I was already behind, I suggested my crew cheif take the rally car to Canadian Tire to get a rivet gun/rivets to assemble the pods/lights. Unfortunately, in my rush, I didn't explain to him how to drive the car as it it quite tempermental. He slipped the clutch enough to get the flywheel and disc to stick together. This typically happens when a high amount of heat (lots of slipping) is introduced, and then the car quickly shutoff. The disc and flywheel then "fuse" together.

Luckily, after going a bit crazy, Andre from SwapShop (he is da bes, in case you didn't know) said it was a simple fix, just had to break them lose by romping on it real good. Clutch felt fine afterwards.

For fear of the clutch not being in good shape, I took to launching sans-launch control on Friday. Saturday morning, being a new day and the clutch feeling peachy-keen, I did start to use launch control again (there were TV cameras DAMMIT!) 2nd stage of the day, about 1km in, I went to grab 3rd from 4th. Got out of 3rd, grinded the crap out of the 4th gear synchro, tried to grab 5th, managed to pop it in, then bogged in a L3, grabbed 3rd (which was there), but no drive.

Finally came to a halt. All of the gears are there, but there is no forward drive. Grinding sounds coming from the drivetrain with or without the clutch pedal pushed in.

One theory presented to me is that by pushing the clutch in when the flywheel and disc were stuck together damaged the pressure plate. Another is that the clutch disc blew apart after being overheated badly. Both seem extremely plausible. I also pray it is, because a $3500 STi close ratio box will put me out for the rest of this season.

Huh. My first thought would have been the slave cylinder, but it is just as possible that the pressure plate gave up the ghost. Odd that it would fail in such a way, I would have put a lot more money on the clutch starting to slip due to damage to the friction material.

Having it fail so suddenly seams strange to me. I'm very interested to see exactly what, and how it failed. Its always neat to see pictures of truly nuked clutches.

Quote
Pete
Have ACT clutches - "street kevlar" and "heavy duty".

The kevlar clutch does not like a lot of slipping - overheats easily, clutch action goes away, and the material frays away from the disc. Bad bad.

The HD clutch on the other hand has an unsprung disk (bad bad) but the pucks basically last forever no matter how much they're slipped. I think the pressure plate sucks, it has way too much internal leverage to make the pedal feel light, at the expense of requiring FULL pedal stroke to disengage.

What I'm getting at is screw fancy fiber clutches, no matter what they are made of they are still fiber/resin and you can cook the resin out with slippign and then the fibers disappear. Get a puck clutch, but get one with a sprung hub.

+2

For an AWD car, a pucked clutch is the way to go, no question. Slip it till the cows come home and you'll be fine as long as you dont cook the flywheel or pressure plate too badly. The feel will suck, and street driving will be less then awesome, but hey, its a race car.

I run a full face Spec clutch in the S13, but its 2wd, and not immensely powerful. I wanted something a bit softer so if I wanted to refrain from upsetting the car when using the clutch I could. I can still kick it if needed though. 3 events in, and no complaints.

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I Seppanen, Car #240

bear in mind that Spec does not change the diaphragm spring, so any increase in torque capacity comes from the disc.
Personally I want more clamp and to get that you have to change the spring.

With more clamp pressure then I can use an organic disc and still have nice easy engagement, and modulation when I want like pulling ahead one car length every minute at a start control.

It's not like most of us have serious Horse Powerz.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham
With more clamp pressure then I can use an organic disc and still have nice easy engagement, and modulation when I want like pulling ahead one car length every minute at a start control.

It's not like most of us have serious Horse Powerz.

That's why I was interested in the ACT HD clutch. More clamping pressure, and a nice easy to modulate disc.I'd be extremely surprised if my car made 250whp and 350wtq. That's stock STi clutch territory for holding power requirements (minus the launch control launches).

Looks like it's coming down between ACT SB4-HDG6 or a Exedy 15951 HD (Paul Eklunds recommendation). I don't want to do the XTG6 as it is simply overkill for my application. The HD pressure plate already provides 40% more clamp.

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HiTempguy

Quote
john vanlandingham
With more clamp pressure then I can use an organic disc and still have nice easy engagement, and modulation when I want like pulling ahead one car length every minute at a start control.

It's not like most of us have serious Horse Powerz.

That's why I was interested in the ACT HD clutch. More clamping pressure, and a nice easy to modulate disc.I'd be extremely surprised if my car made 250whp and 350wtq. That's stock STi clutch territory for holding power requirements (minus the launch control launches).

Looks like it's coming down between ACT SB4-HDG6 or a Exedy 15951 HD (Paul Eklunds recommendation). I don't want to do the XTG6 as it is simply overkill for my application. The HD pressure plate already provides 40% more clamp.

Kiddo, how'd you know there's increased clamp?
Gotta read all the ad copy and propaganda really carefully. Many places just paint stock covers yellow or red or whatever.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.