Howard Coleman

iTrader: (6)

"i was just warming up for a 23 psi 3rd gear run as it is a glorious 66 degree day here in wisconsin, maybe the last of the year...

last week i had been out on the same stretch at 48 degrees and the car just went sideways at 3.6 on the 4.6 TPS voltage scale at around 17 psi. sideways at 79 mph. lots of power. cool.

so i dropped my rears another 2 psi to 25 pounds (285/30/18 Toyo TS1s) hoping to pick up some grip especially combined w the warmer road surface.

i guess i did as at 18.7 psi 5600 rpm the rpms took off leaving the car behind.

alcohol is going to change many of the system parameters we run on our cars.

in the case of clutches, if you are running pump-AI, you'd better load up.

i'd be buying stock in the Exedy twin disc Division.

my next move after running 23 psi today was to have been on a dyno. unfortunately that may be put off along w further road testing due to winter lay-up fast approaching. i spoke w Exedy and based on Head Tech USA Kevin Fujioka's comments will probably go w the twin cerametallic which will hold 540 ft pounds of torque at the rear wheels.

howard coleman"




"Why not carbon howard?

You can buy direct out of Japan through www.nengun.com

When I contacted Exedy in Australia they did not want to sell me carbon as they did not have it in stock but did have cerametallic.

My experience of that compound in high end clutch's like Tilton's is its far inferior to Carbon clutches, I mention it in detail in my thread I did on the D-Core. Anyway interested to hear why he recommended that type over carbon version.

Peter"




Since the posts, above, headed off in another direction from my tuning process and the subject is important w regard to AI I thought a separate thread would be of help.

I have mentioned, a few times within the AI Section that the typical rotary hardware utilized might need to change w the addition of AI.

We are heading to a whole ‘nuther power range and will be needing the right clutch...

I did lots of research on the clutch situation a few years back as I was designing my twin TO4 package.

If you make the wrong decision on your clutch you can really learn to hate driving your car. It is a tough engineering task, having enough clamping force to hold 400-500 ft pounds of torque without being on-off, and having pedal pressure that will charley-horse your leg in traffic.

After reviewing all the options I arrived at a comfortable decision: Exedy.

Exedy is the racing R&D division of Daikin. Daikin is a multi billion revenues Japanese company that designs and manufactures OEM clutches for GM, Ford, Mazda, Toyota, Nissan etc etc. needless to say they have the money for R&D. most other clutch companies take the OEM (Daikin) pressure plate covers and add stiffer springs, perhaps a custom clutch disc and a custom flywheel. and don't forget paint

It is of course possible to build a conventional clutch package to hold our engines. The problem is, using the conventional OEM frame, you end up w major pedal pressure, an On-Off actuation, as well as an overstressed throw out arm and perhaps clutch cover deflection.

Exedy offers another set of options all engineered from a clean sheet of paper, or CAD screen…


Exedy starts w a purpose built flywheel from chrome moly steel. Compare the burst strength of chrome moly steel to aluminum. Think of the flywheel as a buzz saw near your feet. Think of what happens force-wise when you launch your car. It is no accident that there are scattershields. I’ll take the steel flywheel thank you.

Exedy, the largest maker of stamped steel clutch covers in the world takes their stamped steel cover and…. throws it in the dumpster.

There are essentially 4 Exedy options ( single cerametallic, single carbon, double cerametallic, double carbon) and they all use a purpose built one of a kind forged aluminum cover and pedestals. By using such a design they can change the leverage on the fingers. More actuating pressure, less pedal pressure. Win win.

The cerametallic material used by Exedy is of patented (by them) design. I opted for the single ceramic ( Exedy Hyper Single). Carbon was not available as an option a couple of years ago.

I have 10,000 miles on it and due to a combination of my 84 pounds per minute of turbos and turning up the boost recently passed the torque limits.

I will need an uprated clutch. My options, as I see them, are the cerametallic twin or the twin carbon.

Both hold the same amount of torque, somewhere just north of 500 ft pounds. I think I am around 450-500 ft pounds tuned out so they both should work. Both offer a degree of slip. The carbon is ahead of the cerametallic w regard to slip.

And it is here where we get to the real meat of the question…

According to Exedy the coefficient of friction for their cerametallic is between .47 and .48 (higher being more grip.) the carbon is between .31 and .48. a stock clutch is between .16 and .33.

Exedy recommends a lengthy easy breakin procedure for the carbon clutch and also recommends it be slipped 3 times between 5 and 6000 rpm before hard usage. Notice the wide range of coefficiency of friction… between .31 and .48. so what if it is partially warm, say you are running a road course w some long cooling straights… what do you end up w at the end of the straight as far as the grip range?

I spoke w Kevin Fujioka, head tech guy for Exedy USA. He seemed to favor the cerametallic… slightly more torque, no need to heat issues, approx same life when you take into consideration the wear from the required warm up slippage w carbon, and less money.

I would love to know the real world performance of the carbon series w a 500 plus hp application. I already know the cerametallic and I give it an enthusiastic thumbs up. Rice has written an excellent piece on the twin carbon in his car. ideally i want to know in a 500-600 rwhp application what do you have to do to get it up to temp?

Other options for those not wanting to spend the money might be the Spec 3+, or????

Let’s hear from you.

howard coleman

Howard Coleman

iTrader: (6)

Exedy Hyper Single cerametallic
ZH01SD great in the 350-425 hp range

Exedy Hyper Single Carbon sprung hub anyone using it??????? feedback pls
ZM01SBMC

Exedy Hyper Twin cerametallic sprung hub probably my pick
ZM022SD

Exedy D-Core twin carbon lots of new engineering
ZM022SDMC

Spec line:

stage 2 "465 ft pounds tq" kevlar, sprung disc $499 w/o flywheel

stage 2+ "495 ft pounds tq" carbon-kevlar sprung higher spring pressure pressure plate
$649

stage 3 "518 ft pounds tq" 6 puck sprung metallic $519

stage 3+ "598 ft pounds tq" good daily driver, more slip than stg 3, full faces sprung carbon metallic $669

aluminum flywheel extra... $425.

tq figs and price from co site.

comments from people running various clutches w 400 rwhp and up welcomed.

additions to clutch list welcomed, first-hand user comments especially welcomed.

howard coleman

J-Rat

iTrader: (2)

Lets see:

I have been running the ACT Street Strip XTreme with the full face disk. My hp ratings are 434 at last dyno, and the clutch has survived NUMEROUS 11 sec passes down the 1320.

443 Tq, and 80% increase in clamping force per Manufacturer spec.

I have personally beat the living CRAP out of this clutch, to include lots of happy launches on ET Streets.. They have my vote!

RICE RACING

I run carbon brakes as well and the warm up is not as much as some fear/recommend.... but I explain below.

In the clutch you find *from dead cold* ^ this is the real important bit* that you need some warmth to handle full load and torque from take off, very important in 4WD car where you can apply maximum torque or power initialy.

As soon as you fire the car and have it in gear with foot dperessed on clutch your creating heat ! Enough time (it does not take long!) and the clutch is too hot I have experienced this with Tilton's and other metalic clutches when reversing out of a long dirveway ! you can feel the clutch grow and pedal get shorter on take up.

Once the car, engine/trans are up to operating temp (circuit) there is never going to be a point where you dont have enough heat in the system for it to accept full torque howard.

My practical experience with the Carbon is that it requires NO SLIPPAGE at all after you have driven car for a little while and its up to temp, if your starting it from dead cold then maybe you might need some, but the simple process of engaging gear and reving when in first on launch creates more than enough heat to overcook a normal clutch if your not carefull with it (seen it happen heaps of times).

My expereince of dealing with Exeddy technical people in Australia is that their recommendations were based on what they had in stock and wanted to sell v's what was the best to get. You will kick yourself if you dont buy the carbon unit, metalic is trash in comparison........ so far as life, you cant compare the two of them its a minimum of 10 to 1 in favour of carbon, drivability well I posted about that already. You dont see any serious circuit cars now days without carbon clutches, also they are very popular in Supra world as well (tilton carbon) I would NEVER EVER use anything else, haven pulled down these systems and seen the wear rates and after having driven them personaly.

Howard Coleman

iTrader: (6)

thanks Peter, that's just the info i needed and i did have a suspicion that they were guiding me towards cerametallic and, OBTW, didn't have any carbon in the country.

D core it is.

howard

Howard Coleman

iTrader: (6)

so today J-Rat, one of our AI own makes news on the board!!!

just about 500 rwhp and 400 ft pounds of torque running his T61 off the compressor map with C16 and METHANOL.

YIPPIE for J-RAT

which gets me back to how are we going to hold 400 ft pounds of torque which we are all going to be making w alcohol/water.

to sharpen the discussion i spoke w a tech guy at ACT today.

ACT, a very legitimate factor in the aftermarket clutch space, really doesn't have a product for the street driven 400 ft pound rx7.

all ACT torque ratings are at the FLYWHEEL.

J-Rat's 400 ft pounds is at the rear wheels so we gross it up by 1.15.... or 460 ft pounds. then ACT recommends another 10% so we end up needing, using ACT's parlance, a clutch rated by ACT at 506 foot pounds.

the ACT Extreme w a sprung 6 puck (sprung intro'd 8 months ago) holds 577 but is not recommended for street. the Heavy Duty w the similar disc rated at 514 and is also not recommended for the street.

the ACT Tech guy, Daryl, stated that the springs in the clutch disc do not effect the engagement shock, rather they soak up noise and vibration. they will not, as some would like to believe, save your trans or rear end.

ACT will be releasing the next generation of clutches (multi disc, carbon, carbon) next year but is not planning anything for the rotary initially as they consider it a modest volume product. retail on the carbon multidisc was est'd around $3300. gulp.

and yet when we consider clutches to hold our soon to be uprated power engines (AI) it might be wise to consider the cost of running something like the puck/hi pressure pressure plate options... the cost in blown transmissions/rear ends due to harsh engagement. in addition, they are just adequate to hold our motors and decline as far as capacity quickly w wear.

i considered all this a couple of years ago when i looked at the options and went w the Exedy Hyper Single. not much has changed hardwarewise. un/fortunately my engine has outgrown the clutch (Hyper Single rated @ 465 tq at the flywheel) and after a re-look at my options i conclude it again comes down to 2 Exedy options. the twin cerametallic and the twin carbon.

Exedy rates the twin cerametallic at 705 rw torque for road racing and 610 rw torque for drag racing. that translates into 600 rw torque R-R and 518 D-R. the carbon rates at 4% less than cerametallic. while carbon is more expensive it will last longer and is lighter in the disc area for quicker, smoother shifts.

a key to the twin disc is more frictional area so less need for skyhigh clamping force... for instance the Exedy Hyper single uses a 2655 lb clamping force while the twins use a 2430 pound spring rate. yet the twins hold approx 50% more torque!!

there are other companies/options available, but most look sort of like the ACT product and may not convey the engineering that ACT is able to deliver based on it's leadership position in aftermarket conventional design clutches. i see some much higher torque figures quoted by some but wonder if they are actually able to suspend various physical laws to deliver...

as 07 unfolds more and more of us are going to be making on the upside of 400 ft pounds of torque at the rear wheels. it is going to present lots of challenges as to hardware and clutches might be one of the most important issues.

any input welcomed.

howard coleman

RICE RACING

IF you want the best engineering in a conventional sized clutch (7.25")

Then Tilton Engineering is the ultimate, I have their 3 plate carbon carbon unit wich is certified and dyno tested to 1750Nm of torque (thats about 1800HP on a rotary !) It requires you to make you own flywheel. Cost is all relative, when you buy this clutch you get 3 for the price of one, then when its worn you send it back to the factory and for minimal charge it comes back like new !

Tilton are the leaders in Carbon Carbon technology all else are pretenders realy, Tilton introduced the first carbon clutches in 1000bhp GP cars in 1987. The only thing is for a FD you need to engineer your own set up, For a Supra you can buy a kit for about 5k USD.

I'll save mine for a rainy day Till then the cheapo Exeddy Carbon twin is more than enough & its a simple bolt in solution.

SACHS is another top shelf brand but you will pay 10k for a clutch set up through them that equals what the Tilton can do.

BNA_ELLIS

I have decided on the spec line stage 3+ rated to 598ft/lbs torque. This is a streetable clutch with a sprung hub, Ill probably go with the act 13lb flywheel as I suffer chronic rev drops on the drag strip with the hks one which is I think 8 or 9lbs. I do know the later style hks twin plate clutches called the gmax don't hold as much torque as the older hks ones. I rev to 9krpm so don't think a stock flywheel will hold out at that rpm without blowing up.

crispeed

I personally would never use any clutches that come out of Japan again. They are good quality but they are way over rated as to horsepower holding capabilities.
OsGiken is probably the worst rated of all. Those things slipp after little use with medium power levels. The Excedy twin disc much superior design to anything else from Japan but in the high horsepower department meaning 550rwhp/450rwtq plus they too start to show their weak points also. I've seen a couple break the retaining clip for the throw out bearing. That seemed to be a problem they had with all the high strength pull type clutches. The EVO guys were the first victim of that problem. I believed they have solved the problem as of late.
Their carbon technology is not up to par with RPS or Tilton.
When it comes to carbon technology there is only one choice in manufacturer for me and that's Tilton. Tilton has the highest power/temperature operating ratings and also from my experience are the easiest to drive.
ACT offers the best bang for the buck for a street/strip car. They can hold a lot of power and I've tested them to over 600rwhp/500rwtq on street applications using drag radials. If anyone is worried about breaking driveline parts in a street car then you have to adujust your shifting/driving technique. If you attempt to rip out the shifter on every change then it's obvious you're not making power.

Howard Coleman

iTrader: (6)

thanks for your post...

above all, i appreciate opinion from (all) people who have actually done what they are talking about.

it might be one thing to throw race gas at a dyno run w some alcohol and have the clutch make it thru the session and another to run lots of methanol on the street, along with some track days and still have a functional high hp clutch. i have a sneaking suspicion that as flywheels get scored and discs do likewise torque capabilities significantly change.

hmmmm

howard coleman

crispeed

It's also amazing how many people rate stuff based only on a dyno run. Fuel pumps and clutches fall into that bracket often.

Howard Coleman

iTrader: (6)

continuing my sleuthing around in the clutch patch...

Modified Magazine arrived today and had an unsual amount of content probably due to SEMA.

two items jumped out of the magazine at me clutchwise.

the most interesting being an ad, first time for me, from Carbonetics.

as serious carbon clutches are at the top of my list i visited their site: Carbonetic.net. it appears to be a serious effort. they list single and twins for the FC and the FD.

clamp pressure for the FD single is either 2860 or 3520.
the double is 2420 and 3520. that compares to the Exedy Hyper Single at 2655 and the double at 2205.

i will call them tomorrow and report back.

the other interesting item was a Spec ad showing a multidisc. i had a second conversation w Spec (supposedly the top tech guy this time) yesterday about their rotary offerings and engineering. he basically said run the 3+ and i'd be happy. he was less forthcoming on details like clamp rate and how they came up w 595 ft pounds of torque (flywheel). he made no mention of multidisc products? i don't feel interested enough after 2 calls to them to call back.

anyone know anything re Carbonetic?

howard coleman

VGT

ATS used to be Carbonetic, and on Carbonetic's website, it used to read as such.
ATS made a triple plate carbon rated @ 1400bhp (unknown torque rating) for the FD, but it appears that Carbonetic only offers the twin for the FD and rates it at 800bhp. Perhaps, a call to Carbonetic might clear things up, or the company in Japan (ATS) might still offer the carbon triple for the FD.

see
http://www.carbonetic.net/match/usa_mazda.html

and
http://www.a-t-s-usa.com/ats-product...%20mazda.shtml

Silly HP ratings (where are the torque metrics!)
http://www.a-t-s-usa.com/ats-product...ch-table.shtml

FDNewbie

iTrader: (10)

Hey Howard

I'll tell ya first off, I do NOT have first-hand experience w/ such a setup YET, but I will soon. So I'm curious to see how your experiences go, and I'll be sure to post up mine as time progresses.

I spoke w/ Kevin Fujioka too, as well as Mike O'Neil, the Managing Engineer of Tilton Engineering, Inc. I have to say that based on BOTH expert advice AND real world experience from a few very high hp guys I know, I think carbon clutches are the way to go w/o a doubt - especially if your car sees ANY street use. Resistance to heat, durability, rebuild cost, and ease of engagement come to mind as reasons

While I know this isn't what you said Howard, he's comparing apples to oranges. If he was comparing Tilton's ceramic to the Exedy ceramic, THAT would be fair. But little does he know that Tilton has carbon-carbon clutches too

So the question remains...I haven't seen any good enough reasons yet

+1

You're almost right Rice Racing. Tilton's 7.25" clutch can be used with the Fidanza flywheel made for that size Tilton clutch. Ask me how I know

I think that's pretty much a good way to sum it up.

IMHO Howard (also to answer your PM), the Exedy D-Core is the way to go, hands down. And I'll be looking forward to hearing from you re: your expeirence w/ it. I'm confident you'll be VERY happy I, on the other hand, unfortunately CANNOT use an Exedy clutch. My tranny uses an 18-tooth spline input shaft, and Kevin Fujioka flat out told me not only do they not make such a spline pattern for their clutches, but they're so overwhelmed w/ development projects that it would take over a YEAR if they did (by some stretch) agree to custom make one for me. So I'm def. going to be going w/ Tilton (unless some unforseeable problems arise). Tilton can essentially custom-make ANYTHING for your application

My $0.02,
~Ramy

Howard Coleman

iTrader: (6)

i would really like this thread to be THE clutch thread so thanks all for your contributions and anyone out there making north of 400 rw i would love to hear what you use and what you know about rotary clutch packages.

a half an hour ago i took my Hyper Single apart and as i thought it is in excellent condition. no overheat marks anywhere, cerametallic probably very close to full depth even after 10,000 miles. i am sure it will find a good home thru the classifieds... i just simply have outgrown it torquewise.

at the moment it looks like i will either run an Exedy D core carbon, or a Carbonetic twin carbon or an Exedy twin cerametallic.

i like the pick-up on the cerametallic and i don't see any wear. the Exedy cerametallic is an Exedy patented material so i really don't know if it should be compared to other like materials. i do know how it came out of my car after 10,000 miles and it was perfect. i like the fact it holds all it's rated torque no matter the temperature. i am primarily a road racer so i am pretty easy (very easy) on clutches. i just need more torque capacity...

Carbonetic looks interesting w their matrix material. there is a thread on the EVO forum re the twin Carbonetic which seems to be running fine after 1000 miles... but it is a 350 rw situation.

let's hear more re what you know about clutches as we are going to be needing them.

howard coleman

FDNewbie

iTrader: (10)

Just a suggestion then. How about moving the thread out of the AI subforum? I'm under the impression that AI is referring to water or alcohol injection etc. Wouldn't this thread be better situated/located in the general "Rotary Performance" subforum?

~Ramy

Howard Coleman

iTrader: (6)

Ramy that's a reasonable idea however this section, as i envision it, should cover everything relating to AI.

AI lis literally a new paradigm as to FD performance.

as such, i see turbo selection, fuel (pump) system changes, ignition requirements, certainly tuning from all aspects all changing due to AI. i would like it all under one roof. one stop shopping.

clutch packages// because we are all going to make more torque/horsepower more of the time. alot more.

so yes, a clutch thread could certainly be under Single Turbo but i prefer it here to better help AI peeps anticipate their needs and know, for example, that my Exedy Hyper Single was great at one bar but when alcohol was added needs to be upgraded.

howard coleman

FDNewbie

iTrader: (10)

Gotcha

J-Rat

iTrader: (2)

LOL, I just saw this.. thanks Howard. Actually, I am still on denatured alcohol. Havent even upgraded to Meth yet.

Far as the clutch goes, I have a 4 puck in the garage waiting to go it, but I might just take the car out to the track on the existing clutch just to see how it holds up..

Howard Coleman

iTrader: (6)

i received the following (edited) PM and thought it would be worthwhile to address it on the "AI clutch thread...."

"Exedy clutch link, and a few questions.

What was there shipping time? And did they package the item correctly for shipping?

Also I have a question if you have the time, I am thinking for me the dual carbon is better, because I would like the best streetability out of it possible, and the loss of your hyper single seems a little concerning.

I am running a GT35R and going AI in the future.

Wondering if I should get the carbon or the cerametallic IYO, now that you have had some time on it? I have not read any reports of what the warm up window is for the carbon in terms of whether it will hold its temperature or will it cool down during use for daily driving making it infeasible for daily duties.

I have not been able to find a definitive argument on whether a carbon or cerametallic is better for a daily driving application in terms of holding ability when temperature is a factor.

Do you have any opinions or information on this question?"

of course you aren't going to find anything "definitive" here but.

i have a couple thousand (07) miles on my Exedy Twin Cerametallic. PN ZM022SD.

of all the mods that i threw at the car this winter the clutch is the most invisible. i
almost never think about it. probably because of it having 2205 pounds of springs versus the Hyper Single w 2650 of spring pressure. of course it makes up for less spring pressure w much more friction surface.

the Hyper Single chattered just a bit (only) in reverse... the double does not. also, i remember them talking about some rattling noise associated w double discs... i have zero rattles.

i did the first half of my dyno program sunday... idle, tip-in and tuning to one bar. about 20 runs. not tuned out at all even at one bar i made 425 and 353 ft pounds of torque.

i will be back on the dyno in two weeks and will be running my setup to the max and will report back. since my twins should be able to make 88 pounds per minute, which is GT42 territory, i do expect to test the clutch.

as to the "where" to buy it. given it is relatively expensive i did look around. Rice Racing suggested Nengun.com. i came close to buying it from them. i believe the price is around $1075 but air shipping adds another $200+. if you had a couple of months i think that would be a good place as surface shipping is as cheap as it is slow.

i needed it pronto so decided to call Rotary Performance (RX7.com) and paid a friendly $1475. other outlets were around that neighborhood but i have had a lot of good dealings w RP.

as to carbon or cerametallic... if you are talking carbon/metal which almost everything but Tilton is, you are talking a huge varience in frictional coefficient. from .39 to .48 depending on temperature.

that means that the carbon will slip when driving around town somewhat better than cerametallic but if you are making power nearer the limit of the clutch temperature could be a factor.

Crispeed has posted that it is wise to be a bit skeptical as to published torque capacities... Exedy rates the carbon clutch about 10% less torque than the cerametallic BTW.

here it depends a bit on your setup. my whole point w AI is that it allows you to do, sorry Corky, "Maximum Boost" anytime. when you hit your GT35 w alcohol you will see a bunch more torque. that's how i lost my Hyper Single.

the single is rated around 400 ft pounds and the double around 600+ ft pounds.

my summary is... love the cerametallic double. i don't see a need for any further drive-ability that would lead me to carbon.

clutch case closed for me.

howard coleman

RICE RACING

I just updated to a tripple plate carbon Exeddy of the HD variety, 90 day custom order as they need to fit it into production schedule though.

1100+Nm V's 670Nm for the D-Core I had previously.

Went for this as I will have much more power this time around and Its lighter flywheel combination, love the drivability of carbon, and the low wear, sold my old D-Core twin for same money I payed for it after 2 years of use and the clutch looked 90% of new condition unit despite some heavy use on lauch control testing.

rotarypower101

iTrader: (1)

Hey Rice, can you give a short synopsis on the carbons ability to be a street clutch with the temperature issue as a focal point for arguments sake.

Since you have first hand experience with it, can you comment on how the carbon reacts to a “stop and go” daily driving environment? And your opinion as to if the carbon would be a good choice for this application over the cerametallic?

How long does it take for the clutch to “cool off” to a noticeable change in torque capacity? Is the clutch really only going to be at or near its torque capacity say if autoxing, or would it be OK to use in say a backroads “enthusiastic” driving environment? Really would like to get a feel for what the window of practical and sensible usability is for the carbon?

It sounds like from what Howard is saying that perhaps there is no practical advantage choosing the carbon over the cerametallic for a street application, for what I can assume the fact that the cerametallic is always ready as compared to the carbon which does have a lag time or warm up period.

What would be your advice on this issue if the price is not taken into consideration between the two materials? Would you recommend the cerametallic over the carbon for a street use application taking into consideration the warm up period(s)?


I also want to say thank you to both Rice and Howard for their wealth of knowledge and their willingness to share their hard earned information. There are many of us very grateful for your time and effort put into this place and other associated forums that help us learn and make better choices.

A sincere Thank You!

RICE RACING

I am kind of retyping stuff said before but here goes.

My metalic clutch experience has been with the Tilton range (rally specification), my experience of these V's carbon (tilton, Exeddy) is that you cant compare the two for function... you can probably only comment after you have tried both?

Onto operation of carbon.
Never ever had a problem cold with the D-Core personaly, heating up after 5 consecutive GP styled starts (5500rpm) slipping to 5k engagement in first gear, the clutch STILL functions absolutley perfectly and is NOT harsh at all and is for all purposes the exact same as drving it cold, it NEVER becomes as poor as a metalic type clutch. In my experience its double as good for drivability.
WEAR: Carbon lasts in my experience 5 times longer at minimum than metalic but more so than that it can be used as intended (slip it) try and slip any metalic be it a Exedy, Tilton, AP (all of which I have used) and they will fial badly usualy by cracking the floater disks or distorting them badly ! not only that the pick up point of the clutch chages greatly with temperature increases, which happens very quickly in metalic clutches.
If you want more cold torque capacity? then go the 3 disk Exeddy like I have now, its cold capacity is so far in excess of any power you will generate on a 2 rotor road car that it will never be a factor, If it is (you need over 1100Nm or 1200Nm in HD form) then buy a Tilton 3 disk full carbon, I have one of them as a spare and its dynod cold to 1790 Nm !!!!!! and is on the spec sheet in the delivery documentation.

I will NEVER use any type of metalic clutch again after my expereince with various vendors carbon/metalic or full carbon options, in real life the reduced wear and increased drivability hot and cold is many times greater than their conservative lower end claims, they literaly are worth their weight in gold.

I like carbon so much I use it in my RC 1/8th car and even in this small scale Carbon shoes exhibit massive tollerance to heat build up, have linear engagement characteristics and last so long its stupid while also NOT destroying the other mating parts either.

Cost for the 3 plate HD version of the Exeddy with flywheel is about $2700 Aus ($3500 retail?), its not cheap but again for how much longer these things last and how good they are and the reduction of rotational inertia they are worth every single penny..... oh and NOTHING changes gear as smooth as a carbon clutch NOTHING, especialy noticable after a clutch slip fast take off, a metalic clutch will grow and as a result wont disengage as fast and as a result in practice they dont allow gear changing as fast as a carbon unit can.

Alot of this stuff and forums in general is all down to individuals enthusiam for their own products you must remember, I try to be as neutral as possible and as a result am only passing to you my experience of running both techonologies. I will not run any type of metalic clutch after using a carbon one personlay.

p.s. my carbon was daily stop & go and it was/is totaly perfect, much more so than a metalic type ever can or will be.

Howard Coleman

iTrader: (6)

i don't take issue w anything Rice says about carbon as i have never used carbon.

i do feel that 3000 miles on my Exedy Hyper Single cerametallic entitles me to draw conclusions that might be helpful to some...

it was a very good clutch until i exceeded it's torque capacity... around 400 ft pounds at the rear wheels. no shift problems.

when i sold it i checked w Exedy as to the disc thickness and it was new at 4.6 MM. my disc measured 4.58 MM after two seasons, around 3000 miles of fairly hard driving... (no actual road racing or drag racing but lots of full power runs.)

there was no evidence of burn marks on the flywheel surface etc.

i am not trying to promote cerametallic over carbon. i am just stating that i have been very happy w both my clutch packages and don't mind saving a significant amount of money in the process.

perhaps carbon lasts longer but my cerametallic showed little wear. carbon discs are significantly lighter but i have had no shift hangups to date. carbon clutches do engage easier but i have been happy w that aspect of my cerametallics.

i do have a suspicion that all cerametallics aren't the same. Exedy is a subsidiary of Daikin, a multi billion dollar annual revenues drivetrain supplier to the OEM market. Exedy is the R&D/Racing division. consequently, their cerametallic compound is patented. comparing their disc to a metallic road race disc, for example, would be apples and oranges.

the sole reason for my update post was to state that versus the Exedy Hyper Single my Exedy double has less pedal pressure, smoother engagement and none of the dreaded double disc rattle.

beyond that is carbon and i have no knowledge and will defer to those that do.


hc

RICE RACING

Further to back up howards wear rate, my Rally spec Tilton metalic (thick puck style v's sparyed on thin disk road race version) had little wear on the disks after 20 000km road and a some track use. BUT I never dared slip the clutch much at all.

Simple test of how bad they are in general is a long reversing manouver, where you have the clutch engaged for say a minute or more slowly leting it out then back in till you get out of a drive way, this combined with the drag between the disk and drive plates will result in the metalic thick pucks expanding quite alot to the point that you will ahve a very large difference in the take up point of the clutch , the same thing happens when you slip the clutch (easy to overheat and expand the drive disks) and is why gear changing can be very bad.

If you dont overheat the metalic clutch they can be fine though as mine was for a long time. I realy do love the carbon though, for it can be abused and used to its designed limits *sliping* and this is the secret to them and a fast take off (if thats what your into) its much faster to clutch slip than to wheel slip when you dont have the required torque at zero to very low vehicle speed. The biggest benifit of the carbon is it allows you to do this (apart from other benifits) and thats why I love all of the one I used to date

I fully recommend them to anyone, and have never come across any operational problems... If your realy keen look up some of the feedback from other vehicle users such as Mitsubishi EVO's that are the biggest end users of 3 disk carbon Exeddy's and you will see lots more testimonials and alternate opinions giving heaps of detail for any questions you may have?