It's always fun to read people racing from their keyboard. We don't often talk or post much about what we do but maybe I can shed some light on this Exedy, ACT, RPS clutch discussion. Here is our history; I mention it so that you can understand what we look for in a product. My company is an engineering house for the 4g63 platform. Our client base consists of major players in the Mitsubishi Racing world. Every part we design, engineer, manufacture has a specific purpose. If a flaw is found in the Mitsubishi 4g63 platform we design something to fix it. We are not like most shops that will make parts for no reason. We make parts to achieve certain engineering results. We are picky and we strive for perfection in all that we do. That being said, I purchased Exedy twice for our company Evo 8 test platform. Do I run Exedy? No. As funny as it sounds, I like the feel of a soft clutch. I like the feel of a clutch that slips a little as it engages. I believe it helps keep a predictable chassis attitude of the race car. I didn't see being achieved with any of the Exedy product offering. The reality is that copper/ceramic is a brutal material. Its friction coefficient is aggressive when cold and falls off when it over heats. What does this mean? This means that when you want to drive the car soft, the clutch has its highest horse power holding potential. This makes stop/go in town driving a PITA. I believe a car is meant to be driven and not parked. I didn't want any harsh clutch when I wanted to drive the car soft. Knowing what carbon based technology is, I watched the development of various manufactures carbon offerings. I looked at the Exedy Semi Carbon unit. I almost purchased one until peers that we have in the market told me how noise it was. I then was looking at the Tilton unit but again it is real noise. I ended up purchasing the RPS. When I received one of the first ones available we looked at it like an engineer would. RPS was doing many things correct. We worked through a few minor issues. Right now I believe RPS is on their 5th rev of their Evo 8 carbon product and now that it is mature, it is simply an amazing clutch. Imagine having a clutch that when driving in stop/go traffic is near stock drivability, but when you get into some spirited driving and the clutch temp comes up, it holds horse power just like the biggest toughest race clutch you have ever run. This thing is the holy grail of clutches. It plays both worlds nearly perfect. This can only be achieved with a friction material that changes its friction coefficient as the temperature changes. It takes carbon/carbon to do this. Carbon/Steel can not because the steel pulls the heat out of the carbon making it slip and not hold even stock power until it’s temp comes up. I mentioned I hate noise clutches. This RPS Evo8 unit is very quiet. It does not sound like a box of rocks like many multi plate units that are available in this market. Yes you are right, this is an expensive clutch, but I have to say without any reservation that this is the finest clutch solution that I have seen for this platform. I normally don't put on a sales hat, but I would hate to see some one overlook the RPS twin disk carbon/carbon because of the typical mis-information that can be found on the internet. I would and do recommend this solution to my most discerning clients.

Sincerely

Quinn Whipple
Innovative Development, L.L.C.
Concept Racing
www.crco.com

 

Have you tried the Exedy Twin Carbon or Triple Carbon ? I feel the same stock like smooth engagment - BUT - they are also super light and quick shifting due the the 100% carbon technology. Also - have you driven the carbon / carbon Tilton - I know someone who has one on a 1st Gen DSM and they report stock like engagment as well.

I have nothing against the RPS design - however - it seems like the heavy metal disks they attach the carbon to will be very heavy and slow down the shifting ?

 

I would like to see where people rank the Cusco clutch, and I know others would too. I know it is made by Exedy, but this clutch was available to the Evo community, back when Exedy USA was not offering a carbon/carbon clutch yet and the HKS was much cheaper than it is now. I was really hoping this clutch was gonna be the last one I ever bought and just have to rebuild it when necessary, but just recently seeing Martin of AMS say the Exedy twin carbon was not holding his power levels and had to switch to the tripple carbon has changed my thinking. Originally my next mod was a complete built 2.3 stroker with intake manifold and t/b, but now I have to budget in a new clutch like the Exedy triple at around half the cost of the engine build. Oh well, you have to pay to play, and I will always live by that moto.

 

BTW - I love the HKS unit - its one of my personal favorites but aparrently the pricing structure took it right out of contention. The HKS unit draws big props from me for its secure throw out or release baring attachment method

 

But what about the torque capacity of the Cusco? Personally I would put it in between the original exedy twin and the exedy twin c/c. I remember doing a little research on it a year ago after Martin from AMS tuned my car and raved about the feel of the Cusco compared to the original Exedy they had in the shop car before they went to the Exedy c/c and then the Exedy c/c/c. In my limited research I came to find out that the Cusco was a Carbon Metallic material and the Exedy c/c was actual carbon, if I am wrong please correct me. Now I am not so upset that I didn't wait for the Exedy c/c to come out when I purchased the Cusco as the Exedy c/c can't hold the power levels I plan to attain. Not so sure the Cusco can hold the power I have now, but time will tell.

I have never driven an Evo with a HKS multi-plate clutch, but I wouldn't want to if it is anything like the HKS triple available for the Supra.

 

I have had both the exedy and the cusco twins on my car - I could not tell any difference between the two in operation other than the cooler blue color of the cusco twin. The material is different but in practice the feel and function seemed identical to me

The HKS clutches come in TWO flavors - the PRO unit which is unsprung racng clutch and is a nightmare to drive on - which is no doubt the one you sampled, and the other MAX style which is a sprung unit more suited to road use.

The spung unit retails for $1999 which is a really exgagerated price and IMHO prices it right out of contention when compared to the superior exedy units which have street prices significantly lower than the HKS units

In the begining HKS was selling for $1200 per unit which was a fair price but then they raised the price to crazy levels

Also - the HKS unit CAN NOT stand up to serious HIGH WHP applications - its a unit more suited to under 350 whp applications

Out of th 450 evos I have tuned and driven only 2 or 3 had the HKS units

 

The Exedy twin carbon is Carbon/Steel.
***Remainder of the coments retacted***

 

I can assert that the unit which Mr. Switzer "obtained" was a very early production unit which did not have the new style upgraded pressure plate. I used that same unit to go 10.9 in the 1/4 mile and over a hundred drag passes. All it needed was to be slightly warmed up and then it held all the power I could throw at it. Giving a clutch a slight warm up before you beat on it is a minor consession for the other benfits it provides. With the new style pressure plate there is no warm up needed and the cutch holds up to 450 whp with no warm up needed.

As for noise - I think most people will agree that as light rattle when the clutch is depressed is a non issue on a racng clutch - a minor nusiance and something that most twins do. Ironically - my triple makes even less noise when depressed.

People need to understand that the stock cluches are the most "easy" to use and "normal" feeling. As you start to head towards the more exotic carbon units - they don't work just like a stock unit. They are not computer designed for a specific car to balance out drivetarin noises. They are made for sport and performance use and people who complain about a slight rattle on a clutch which can hold 600 tq are not being realistic.

Mr. Whiple - BTW - how much power does your Evo make ?

I would suggest that you have Mr. Switzer contact Exedy to recieve the new style upgraded pressure plate which will solve his cold holding issues

 

Your triple makes less noise than your double because a pressure plate has a fixed amount of release, when you spread that across your 3 plates the total distance is less making the total assembly tighter

I believe that you can ask for a clutch to hold 600-700#'s of torque and still have it be stock clutch quiet. People that listen to my 2 plate RPS can't believe how quiet it is. It is as quiet as my stocker that we removed from the car.

As far as the current horse power level of our company car... It hasn't been dynoed in it's current configuration. This time of year the car is normally apart (winter time) for research. I put it back to gather to drive while my truck is getting fixed by the dealer. When the truck is done, the evo will get taken back apart to receive the remainder of it's winter updates. I don't know how some of these new internal parts will work. They are fresh designs that have to be tested. As you know with product development, some fresh parts are hits and some are duds. These new parts are founded on solid engineering, but what looks good on paper, and what works correct in a car are different things. I will say that the car makes good solid power but no paper dyno numbers to back it up. We scheduled our AWD dyno time during the month of May when we are on our next trip back east. As you know every dyno is a bit different. This is why we are traveling to a dyno that has other reference data that we wish to compare our data against.

 

good luck with your car - sounds interesting !

 

why do people care about chatter? the stock clutch sounds like dancing tin cans at every stoplight... if it's a little worse it's why the big deal? it's not like it wasn't there to begin with...

 

Sounds like you have a problem if your car is making noise like that, Every stock clutch I've heard has been real quiet.

Chris

 

How many miles are currently on your RPS?

Chris

 

My clutch doesnt make ANY noise at all, except when the throw out acts up...but it shuts up when i actually push the clutch in...and really though, who cares about the chatter, anyone who'd put a chattering clutch probably can't hear it anyway

 

uhm... i leave my car in neutral when i'm at a light... so i don't think my clutch is broken... btw... is it bad to leave a car in neutral without depressing the clutch... i heard something about the throw out bearing not being lubricated but i might have the context all wrong.