It seems that there are few good choices for single plate clutches. Sure for the street, they are great, but for drag racing and road racing with high HP I do not see many good choices. Can anyone chime in on the drawbacks and benifits of a twin disk clutch like the Exedy Twin. Carbon is out of the budget! Thanks

I am surprised that nobody chimed in yet. I will try and give an honest (but bias) opinion.

There are always tradeoffs to a design which I will try and explain. By design twin disc of equal size and clamp load will hold twice as much torque. But there are reasons why cars don't come with twin disc clutches. The problems are that you have twice as many discs spinning (increases inertia and air gap requirements), space restrictions, and challenges with floater design.

Generally it is best to compromise a little of the diameter of the discs to reduce the inertia which is what Exedy and many others do. The Exedy, Cusco, ATS, RPS, Tilton floater is a loose design which means it is going to make noise. Balance of the clutch assembly is affected by the loose heavy floater being able to shift around, even by only a few thousanths and there has to be some freeplay in the floater to allow for heat expansion. If the floater is made lighter and thinner, then heat damage is a concern since it is heated from both sides. Eventually that hammering of the floater is going to wear the posts. None of this should be too much of a concern on a race car if that is going to acheive the performance and reliability you require but those are the tradeoffs.

Warning: Shameless plug to follow
ACT HDR6: For about $500, you can get our HD pressure plate and a 6 puck which is proven to take a lot of abuse an win drag races on high powered cars. It is that "keep it simple, stupid" design. Yeah, it's not pretty or fancy, no bells and whistles, but it doesn't have the tradeoffs that occur when you have a floater. Turbo Trix has been the quickest EVO for quite some time running this setup, running as fast as 9.7 in the 1/4. It can take a beating. It is reliable, rebuildable, and heck, at that price, it's replaceable.
ACT HDG6: You may want our spring centered puck (available soon) for high powered road race cars.
ACT HDSS: I am not trying to downplay our street clutch which has also proven itself very effective on cars that compete on the weekend and still driven daily. For up to 450 ftlbs of torque (rated at 497) it works gooood IMO.
(Shameless plug over)

If you think it takes $1500 or more to get a clutch that will win drag races, we can raise our price just for you. Just let me know what you are willing to spend, or better yet, send a credit card number or signed blank check. ; )

See this recent poll for what others think:
https://www.evolutionm.net/forums/sh...d.php?t=126768

Dirk....question for you

I have your clutch in my evo with the street disc.....my car is currently making 351 at the wheels but i am in the process of installing a 50 trim turbo with methanol injection. I am shooting for about 500 whp....

my question to you is....will the clutch hold the power the car is making...and if not....are there any suggestions you can make for a future clutch that will hold that kind of power without including the 6-puck disc. I know that disc will hold the power...but i want something a little more street friendly to drive.....

thanks

I don't want to highjack the thread with ACT question and answer so please email me at dstarksen@advancedclutch.com. We are releasing an Xtreme version of our pressure plate. Coupled to the street disc however it's going to pose more adjustment to the pedal and more pedal effort but it will be streetable and yet hold big power.

More on topic: As I mentioned before, there are always tradeoffs. At some point you have to decide if the car is going to be a race car or street car, or the tradeoffs are going to limit you either on the street or on the track. A lot has to do with intended use, driving style and vehicle setup.

What tradeoffs can you live with?
Higher $$$?
Torque capacity?
Stiff pedal?
Harsh engagment?
Shorter clutch life?
Slower shifts?
Weight?
More inertia?
Transmission wear?
More maintainance?
lower heat tolerance?
vague pedal feel?
Noise (floater rattle, gear growl)?

I think there are other clutches out there besides ours that are well-suited for particular applications. But don't compare apples with lemons. The problem is getting honest information about what the benefits and tradeoffs are for each clutch. I am sorry I don't have more answers, but I am a much better engineer than salesman.

what about locking out of 2nd gear at over 7000 rpm?

^ I had my act hdss installed and the next day the engagement did not feel right....certain lock up and such. After playing with the height of the pedal (to adjust it, it feels so awkward and hurts my head!) i did not get the lock up...ok, maybe 1 in 15 times

Off Topic: Dirk, do you think you guys would have a meet up at ACT kinda like the HKS folks did for the Evo's last month? That would be awsome!

I have the Brand-new Exedy twin metallic Heavy Duty, love it so far, 1,500 miles. grips like crazy, very quiet. am updating as I go along on my other thread.

Oh yeah, Dirk is a very good man who knows his stuff. It depends on what you want to pay, and for what application you will MOST use the car. research alot on this one!

That would be ceul! We did an open house one time when IDRC had an event at LACR. I would love to do something like that again. I am not sure who to get a hold of to help organize it. I think I will mention the idea to a few other folks and see what we can do. I mean we are right in between LACR and Willow Springs so we can sure make it more interesting than just looking at clutches. Hummmm.

There is a huge recent thread on this, most of it useless speculation, but you can read through it at https://www.evolutionm.net/forums/sh...d.php?t=156995
Don't miss this link I posted with my current thoughts regarding this topic:
http://www.advancedclutch.com/EVO_Shifting.pdf