2008 Double clutch reliability ?

[Schulmann]

Something really stunning has happened in our Club.
Last Friday we had a parade in dowtown Montreal to celebrate the NASCAR race.
We had about 25 Vipers participating it was spectacular.The parade lasted an hour at a very slow speed. During the first 15 min everything went perfectly. Then I saw some smoke behind me. First I thought that somebody did a burnout on the street. A couple a seconds later the smoke was still there but it got really heavier.

Actually it was a beautifull green Viper whose engine was smoking. First, we thought the guy blow up his engin. Finally we realized that the clutch was burning .... I opened the hood and the firework went on .... It took about 2-3 min before the clutch cooled down. Usually when you abuse the clutch, it smells first before it starts burning. Well we didn't smell anything it started smoking without any notice ...

What is the realiability of these clutchs ? Are they so easy to burn ?

What is the best thing to do when a clutch over heats ? Stop the engin or let it idle ?

The worst thing is that the clutch doesn't seem to be covered by the factory warranty !
The Viper has only 1000mi ...

 

[VIPER GTSR 91]

Hate to hear this is happening now along with the flash issue. I sure would not want to be in Helbigs shoes (the Grail man?) when the darts go flying at the VOI 10 tech session.......

 

[Bobpantax]

Hi Schulmann. Please also post this as a separate thread in the new Grail section. It's a good question for Herb. Thanks.

 

[adamlotus]

cluctches should be covered for 12 months or 12,000 miles and brakes for the same thing for a new car.i have noticed that the clutch in the 08 is not as strong as the 06.

 

[SteveT]

i have noticed that the clutch in the 08 is not as strong as the 06.

Really....anyone have any facts to back this up?

15 minutes at slow speed and the clutch fries, my first guess would be driver error.

 

[mike & juli]

Hi Schulmann. Please also post this as a separate thread in the new Grail section. It's a good question for Herb. Thanks.

Good Point, Bob~! Please do that, Schulmann...I'd actually like to know more about the '08 clutch as well. Warranteed? Good questions for the Grailkeeper....juli

 

[Jeff Monheim]

The double clutch was put in to handel the higher HP, it also has a better feel and lower pedal presure.
I went from an 02 rt/10 to the 08 SSG coupe, it has a completly different feel and is very easy to depress.

 

[Schulmann]

It is difficult to know what went wrong. I didn't see the clutch removed.
The dealer keeps tell "no warranty".

Since the double clutch is able to handle more HP it can also generate more heat by friction.
I am wondering if there is something additional to vent this heat out of the bell-housing.

Maybe there was an oil leak through the engin seal that leaked onto the clutch. The car was smoking white like hell. It was looking like oil burning. This is why we first thought that the guy blow up his engin. Something went really wrong there. Likely the driver triggered it but the mecanial compotants should have been able to handle it.

First of all, when you burn the clutch it smells and it is easy to recognize that it is time to slow down. In addition the clutch should be able to handle more "abuse". Then once the fire stopped the clutch was dead. We had to have the Viper towed to a dealer.

I am just wondering if somebody else had a similar issue. If this is the only clutch issue then lets forget it ...

 

[VIPER R]

Maybe a hydraulic leak at throw-out bearing?

 

[Coloviper]

Someone please explain how the twin disc clutch works. Do the two discs float on one another? Is it possible that it accidentially locked one disc up, the other disc just sat and spun on the other one causing it to burn up?

 

[adamlotus]

after doing a burn out in my 06 and doing one in the 08 i feel the 06 held up stronger less clutch smell.also what is that sound from the belt area when you rev it high like a whinning sound when engine is hot.but overall i love the clutch feel on the 08 and everything else about the 08 bad ass car!!!

 

[Grant]

Sounds like a rear main seal leak to me. Motor oil + clutch is not good.

Someone please explain how the twin disc clutch works. Do the two discs float on one another? Is it possible that it accidentially locked one disc up, the other disc just sat and spun on the other one causing it to burn up?

No, that can't really happen. Both clutch discs sit on the input shaft. Essentially, the setup allows more torque capacity with less overall diameter, and less pedal pressure (which is why the setup might feel "weaker"). Here is a picture of a LSx twin disc: http://www.cranecams.com.au/images/d2 twin disc image (apart).jpg

 

[Viper Specialty]

While I havent seen one of these apart yet, it is possible that the drive plate (the central friction area between the two floater discs) somehow came detached (missed rivet for straps operation?) and by doing so, halved the friction area and torque capacity causing a good bit of slippage. It is also possible the thrashing the day before caused the drive or floaters to warp, resulting in runaway overheating.

 

[Guy]

Here's an exploded photo of a clutch for a *** car:

You must be registered for see images attach

The plates are held in place by the housing along with the spacers and the spline gear. The housing is also part of the flywheel. It is all bolted together to the pressure plate and the whole unit spins. Individual parts inside do not spin.

Drove around a car with a triple plate clutch for a couple of years. It is the definition of an on-off switch, never slipped once though under all sorts of abuse. The twin plates were recommended for 600-700hp and the triple plates for about 1000hp. Quad plate clutches exist now too, however the trend seems to be carbon clutches.. apparently they are more "streetable".

 

[Viper Specialty]

Drove around a car with a triple plate clutch for a couple of years. It is the definition of an on-off switch, never slipped once though under all sorts of abuse. The twin plates were recommended for 600-700hp and the triple plates for about 1000hp. Quad plate clutches exist now too, however the trend seems to be carbon clutches.. apparently they are more "streetable".

Ironic... I have a Triple Plate Carbon on my street car. If set up correctly, it is perfectly streetable with good modulation. We can also make a 4-plate, though as far as I am aware it only comes in a high ratio pressure plate rather than an ultra-high ratio, which is going to make it very on/off switch-like... on top of the decrease in modulation already coming from adding plates alone. Its not easy to overpower even the medium spring 3-plate however, so we havent even found an application for a 4-plate yet, haha.

You must be registered for see images

This picture may help as well. As you can see, in this style of multi-disc clutch, the 4 plates seen on the edge are what is called a "drive" plate. They are attached to the clutch cover [shaped like a donut with slots cut on the outer edge to hold the clutch cover bolt pattern], and by default the flyhweel. Inbetween each of those plates is a set of 3 "floater" plates that are attached via a hub to the input shaft of the transmission. They all engauge and disengauge as a set.

An important thing to note is that in the case of any other clutch but a Tilton which uses 100% carbon drive and floater plates, the metallic plates which hold the friction material can warp under extreme heat. When this happens, the clutch drags creating heat even when depressed. It is a runaway condition as the more heat is introduced, the more it warps, the hotter it gets, the more it drags, etc until it is either allowed to cool, or it cooks the friction material and ruins the clutch.

 

[VENUM INJECTION]

I have the same smell on my 08 when I push it, but this is my first Viper and I know it is driver error in this case, but man it smells for a while after that while I am driving down the road.

 

[SweetRed04]

Someone please explain how the twin disc clutch works. Do the two discs float on one another? Is it possible that it accidentially locked one disc up, the other disc just sat and spun on the other one causing it to burn up?

I didn't really see an explanation on how they actually work so I will give it a shot.

There are two clutch disks and an intermediate separator plate tied to the clutch housing, which is, as in a regular clutch tied to the flywheel. This provides 4 friction surfaces doubling the torque capacity for a given engagement spring force.

The separator plate in a dual setup is typically a relatively thick plate, typically thicker than the triple disk setup's separator plates pictured, that provides a place for the slip energy to be stored giving the clutch more power absorption (the ability to slip under load without overheating the clutch disk facings (which is what burns in a clutch)).

Typically the clutch is designed to take advantage of these characteristics to have a lower release pressure, higher torque capacity, and higher power capacity.

The only negatives are cost (more parts) and the need to have enough pressure plate travel to provide adequate release clearance for the two disks, typically double. This is relatively easy, for hydraulic clutches needing at most size changes in the master and slave cylinders or with linkage revisions for mechanical clutches.

Typical automotive automatics (planetary types) use wet multidisk clutches and brakes to achieve their gear changes.

If you really wanted the best setup, a wet multidisk clutch would be virtually bulletproof!!

They are used on motorcycles and explains how liter sized street bikes can run repeated high 9 low 10 1/4 miles without toasting clutches. They'd roast them if they used dry clutches, Ducati's don't hold up to abuse as well for those who think of them....

 

[Boxer12]

Ferrari has been using twin plate clutches for years, and everyone knows they are burned out easily in high TQ applications (ie., Testarossa/TR), but I think its a matter of driver technique more than clutch. They are easy to slip, even just resting your foot on the clutch, which puts very minor pressure on the hydrolic release. Keep your foot off the clutch and make clean shifts (not slipping it). Don't let the valet park your car, or newbie's (eg., journalists) drive it. It should last a long time that way.

 

[Viper Specialty]

Ferrari has been using twin plate clutches for years, and everyone knows they are burned out easily in high TQ applications (ie., Testarossa/TR), but I think its a matter of driver technique more than clutch. They are easy to slip, even just resting your foot on the clutch, which puts very minor pressure on the hydrolic release. Keep your foot off the clutch and make clean shifts (not slipping it). Don't let the valet park your car, or newbie's (eg., journalists) drive it. It should last a long time that way.

It all comes down to clutch technology and dollars. Ferrari likely uses regular organic facings as their cars dont produce enough torque to really need anything more. while organics feel great on the street, they are also the easiest facing to have exceed its thermal limit.

With newer technology, they could for example use a Carbon Clutch, retain the torque capacity or increase it drastically, remove the heat related problems (Carbon clutch discs quite litterally cannot overheat) and develope it to modulate just as well. The problem is cost.... not that it should be a factor in cars costing that much.

 

[Viper Specialty]

The separator plate in a dual setup is typically a relatively thick plate, typically thicker than the triple disk setup's separator plates pictured, that provides a place for the slip energy to be stored giving the clutch more power absorption (the ability to slip under load without overheating the clutch disk facings (which is what burns in a clutch)).

Typically the clutch is designed to take advantage of these characteristics to have a lower release pressure, higher torque capacity, and higher power capacity.

-At least in the case of a Tilton Carbon, the central drive plate need not be thicker for heat capacity, they are already immune to overheating/warpage of discs. The only components that can "overheat" are the pressure plate (if using Alum version) and spring.

-Another added bonus of multi-plate is that you can decrease the diameter of the clutch lowering is mass moment of inertia, while at the same time still adding surface area and torque capacity. This makes a huge difference, especially for the input shaft and floater disks which must be sped up and slowed down by the synchros during a shift.

 

[Guy]

Dan, sorry to hijack the thread, but it's turning out to be very informative. Read the review of the Tilton carbon multi-plate clutches on your site, and saw the mention of flywheels; light vs heavy. Is a light flywheel that bad on Street car? Perhaps is it dangerous because it is much thinner?

 

[Grant]

Dan, one thing I've always wondered is, why aren't Kevlar clutches ever OE? In my experience they are extremely long-wearing, and hold just as or more power than organic materials. I'm told they are easy to glaze over and ruin if they are overheated, but (again, in my experience) that doesn't happen without some serious power and drag slicks.

 

[SweetRed04]

-At least in the case of a Tilton Carbon, the central drive plate need not be thicker for heat capacity, they are already immune to overheating/warpage of discs. The only components that can "overheat" are the pressure plate (if using Alum version) and spring.


-Another added bonus of multi-plate is that you can decrease the diameter of the clutch lowering is mass moment of inertia, while at the same time still adding surface area and torque capacity. This makes a huge difference, especially for the input shaft and floater disks which must be sped up and slowed down by the synchros during a shift.

Point 1: If designed right, the separator plates just need to be thick enough!!

Point 2: Exactly right!

I'd also add since you have pointed this out, that the less clutch inertia the better the car will accelerate, the same effect as a lightened flywheel.

 

[Viper Specialty]

Dan, sorry to hijack the thread, but it's turning out to be very informative. Read the review of the Tilton carbon multi-plate clutches on your site, and saw the mention of flywheels; light vs heavy. Is a light flywheel that bad on Street car? Perhaps is it dangerous because it is much thinner?

That depends what you consider "light".

The Tilton clutch and flywheel in the light configuration is far too light for street use. The system in its light version only has FIFTEEEN PERCENT of the mass inertia of the OEM setup. Imagine trying to drive your car with less than half of a Honda 4-****** flywheel. A lightweight flywheel coupled to a regular clutch in a Viper still retains 80% of the mass inertia, which is within the acceptable limits to retain driveability. For the street, you can lose mass up to a point, but them you will start running into other problems. Taking off the "excess" is a good move- but keep trimming and you'll be sorry.

The thickness of the flywheel from a safety standpoint is irrellevant. most Automatic Transmissions use flexplates far thinner than any flywheel for any clutch.

 

[Viper Specialty]

Dan, one thing I've always wondered is, why aren't Kevlar clutches ever OE? In my experience they are extremely long-wearing, and hold just as or more power than organic materials. I'm told they are easy to glaze over and ruin if they are overheated, but (again, in my experience) that doesn't happen without some serious power and drag slicks.

Kevlar is less resistant to overheating from slipping the clutch during normal use. As you know, some people arent exactly clutch artists. The organic is more suited and more forgiving to those who ride the clutch half the time for no reason.

 

[Fast1]

I haven't had any problems with my clutch, however I do know a few people that have had dual disc clutches that have warned me against trying to get "smooth" engagement. Some people will try for a smooth shift and end up slipping the clutch on every shift through casual driving. Like most everything else on a Viper, the clutch was built for performance, and does not like to be slipped. It really has a better engagement when you are pedal down than the '06, but around town and through the parking lot it is a bit jerky. Just keep your shifts clean and crisp and you won't have a problem.

 

[Guy]

That depends what you consider "light".

The Tilton clutch and flywheel in the light configuration is far too light for street use. The system in its light version only has FIFTEEEN PERCENT of the mass inertia of the OEM setup. Imagine trying to drive your car with less than half of a Honda 4-****** flywheel. A lightweight flywheel coupled to a regular clutch in a Viper still retains 80% of the mass inertia, which is within the acceptable limits to retain driveability. For the street, you can lose mass up to a point, but them you will start running into other problems. Taking off the "excess" is a good move- but keep trimming and you'll be sorry.

Thanks for the detailed answer Dan, however, could you elaborate more on the "other problems"? I know that light flywheels allow engines to spool down very quickly too and this could be a problem on slower upshifts.. Or are you talking about problems when getting the car moving from a stop (say heavy traffic)?

I heard once that if the crank pulley and the crank are of a certain weight, the flywheel/clutch assembly must also somewhat balance the whole equation out, otherwise the engine may develop some problems.. Not sure if this is a correct statement, if it is perhaps the length of a crank and differences in pressures exerted by the crank on certain bearings may have something to do with it? How about lightening the whole assembly?

Once again, thanks for all your answers!

 

[Viper Specialty]

Thanks for the detailed answer Dan, however, could you elaborate more on the "other problems"? I know that light flywheels allow engines to spool down very quickly too and this could be a problem on slower upshifts.. Or are you talking about problems when getting the car moving from a stop (say heavy traffic)?

I heard once that if the crank pulley and the crank are of a certain weight, the flywheel/clutch assembly must also somewhat balance the whole equation out, otherwise the engine may develop some problems.. Not sure if this is a correct statement, if it is perhaps the length of a crank and differences in pressures exerted by the crank on certain bearings may have something to do with it? How about lightening the whole assembly?

Once again, thanks for all your answers!

The most apparent problem is going to be getting moving from a stop, yes. However, a side affect of this is also MUCH shorter clutch life. I am talking an extreme reduction, likely 75% loss or more unless you are one hell of a clutch artist.

Another major problem is going to be the PCM response rate issue. A lighter flywheel is going to have a much faster RPM decay, especially when coming to a stop. If the PCM cannot adapt fast enough, it is going to stall on you. This can be tuned out, but its a pain in the butt sometimes.

As to your other question, I have never heard anything of the type for an internally balanced engine? Perhaps someone is confusing externally balanced engines with internally? We have run heavy flywheels on heavy cranks, light flywheels on heavy cranks, heavy flywheels on light cranks... you name it. You can lighten the whole assembly, but whether or not you want to do that depends much on your goals. For a street car, there isnt much point in most cases to lighten- you want strength and longevity, not a flash-in-the-pan fast-shifting race car.

 

[Grant]

The most apparent problem is going to be getting moving from a stop, yes. However, a side affect of this is also MUCH shorter clutch life. I am talking an extreme reduction, likely 75% loss or more unless you are one hell of a clutch artist.

How do the carbon-carbon friction materials wear compared to organic? I'm wondering if their wear rates make up for this problem at all. And is this really an issue on an engine with as much rotational inertia as a Viper's?

After I removed my first (heavily abused) Kevlar clutch from a car and still saw hatch marks on the pressure plate surface, I was sold on Kevlar as a long-lasting and low-cost friction material. I hate changing clutches.

 

[Viper Specialty]

How do the carbon-carbon friction materials wear compared to organic? I'm wondering if their wear rates make up for this problem at all. And is this really an issue on an engine with as much rotational inertia as a Viper's?

After I removed my first (heavily abused) Kevlar clutch from a car and still saw hatch marks on the pressure plate surface, I was sold on Kevlar as a long-lasting and low-cost friction material. I hate changing clutches.

Carbon friction surfaces wear at a much slower rate than any other type of friction material. For example, the "wear interval" of a Tilton Carbon is .025". To give you an idea, that is roughly the thickness of about 8 sheets of paper. That much clutch material will get you through 7-10K miles of street driving. Roughly 1-2 wear intervals is equivalent to other high power clutch lifespans. For the sake of argument, we'll say that 2 wear intervals equals roughly the lifespan of a Kevlar/Organic/Metallic facings under heavy use- which usually contain about 1/8-3/16 wearable material. Again, for the sake of argument, we'll say its only 1/8". Even in this example purposely estimated on the low side, the Carbon clutch wears 60% slower than the other friction materials. A 3-Plate Carbon has about 1/4" of total wearable material, even if you dont "push-it"... which you can in almost all cases. If you want to run the numbers... you will quickly see what kind of a total lifespan that can equate to with a half decent driver. However, this kind of a characteristic will NOT make up for using a super-light flywheel on the street. I cannot emphasize enough how much slipping you really have to do to get the car moving from a stop with said flywheel. Once moving, you are fine and its pretty much on par with anything else- but I would be very surprised to hit 2000 miles per interval [<1/4 normal] with that flywheel on the street because of all the stop and go. If you dont mind servicing your clutch pressure plate with your oil changes, then it could work.... haha.

The hatch marks on the pressure plate is only an indicator of the hardness of the kevlar facing and its inability to score the steel. It is not an indicator on lifespan or torque capacity. A similar example would be EBC Red Brake Pads- they are rotor friendly [Non-Metallic], so they wear the steel very slowly. However, the pad is consumed at a more rapid pace because it is the only surface wearing, and is a sacraficial consumable. The coefficient of friction may be the same as a metallic pad, but there is a different item that is wearing at a different rate than its counterpart.