look dude I really dont know why you are trying to get under ppeople skin. Anyways so you think that b/c the car was in its 1 year of production in the STATES, that when my clutch went out w/NO mods, or launching actually nothing other than babying the car for the first 1500 miles that i owned it. Mitsu was right to screw me and make me drop another 1200 dollars right after i spent 32000. Ok then you are a bad karma person and that will return to you have a good day and i wont bother to speak to you again

 

I have 13k miles on my car still on the original clutch with no problems at all

 

well i had to replace mine around 9-10,000 and the new one is going to have to be changed before i put any more horsepower in the car, now i got 23,000 miles on the car, every day driver

 

ACTman, can you help please? - I have the EVO VII RSII in the UK with Xtreme's XT330 mods raising power to around 320 flywheel hp (no chipping, just 3" Haywood & Scott exhaust, HKS induction filter and boost control rod adjustment).

At under 9K I too have clutch slip. (At peak torque in 5th gear 3 days ago & getting rapidly worse). I have NEVER launched and always waited for full clutch engagement before flooring it. I had an Impreza Turbo and the clutch lasted to 72K! So I KNOW it isn't me. I've never had judder.

I have followed this thread from the beginning. What are the conclusions?

ACTman - You confirmed sufficient clamping pressure, especially on the EVO 7, good quality materials and construction, clutch line restrictor could cause some wear when launching (but I don't think the UK EVO 7 has it).

You and all the pics seemed initially to suggest a too low melting point for the Resin bonding.

What is your best thought with over a year to consider? Is it almost solely the friction material?

 

Update:

Approaching 36,000 miles, stock clutch, no problems.

 

Good God man,

Does Pizza Hut pay your miles???

(:

 

I made it....21k and still going strong.

 

Mine lasted for 25K miles... I did not make it through the few launches I did without paying the price ............... Anyway, I'm getting a new EXEDY twin disk installed so I hope my problems will be over at least clutch-wise

 

I thought i would add, that my car has 11,000miles and the tranny is going out fast on it...I cant engage 2nd gear half the time and fifth gear has been grinding for a while now...sooo...im guessing mitsu isnt going to touch my car if i take it in or will they???....

 

Thanks ACTMAN for your very detailed reply to me. I've now removed the clutch and replaced it with an AP Racing clutch. Can anyone help to work out just what happened to the old one?

The flywheel was fine with no wear or damage. The friction plate was worn but not worn out. It had a rivet sink of 29 thou and 33 thou on the pressure plate side and flywheel respectively. The manual says that it needs replacing if the sink goes below 12 thou.

The pressure plate showed all the wear with large scoops about 1/2 inch wide and 1 1/2 inch long spaced at regular intervals round the inner circumference (see pics below)




Notice that one side has less damage than the other, in fact you can still see the majority of the original machining of the surface.



and this is the friction plate -



Why the scoops? I've never launched or abused it.
If it had been high rev launches it would have been continuous all round, wouldn't it? The direction of the smearing over of the metal at the ends of the scoops shows the disc was slipping while driving forward, not on overrun while changing down through the gears.

Why are the scoops at regular intervals like it's been bouncing? Is the pressure plate metal way to soft? Has it been clamping unevenly?

Has anyone got any ideas?
Thanks for any comments.

 

Defector,

These are sings of an overlly burnt clutch. Probably slipping for some time. Surface on the flywheel is probably warped, hence the heat spots on the press. plate (scoops you described).

Either you have defect in the clutch system ( clutch master, clutch slave , line ect.) or you've been slipping the clutch too long upon take off.
Or.... you just really messed up bad launching.

BTW....I've seen this sort of damage before when my friend miss-shifted into 2nd and burnt his clutch on his Evo 8.... it only takes one bad slip.

 

i dont drive nuts so my clutch is still intact

 

Thanks for the comments. I only noticed any slipping less than 2 weeks before it was replaced, and even then I was gentle after the first noticeable slippage. The flywheel was completely OK, with no discoloring, overheating or distortion, but then it is a much higher mass than the cover. I have never abnormally slipped it on take off either.

My thoughts are (just my guessing and trying to understand) that it is as a result of breakaway at max torque causing oscillation. The pressure ring is driven through 3 tri-leaf flat springs attached to the cover. The driving force (say 330 ft lbs torque on my car, or around 800 lbs force at 5.2" radius where they are) puts these 3 in tension.

Because this spring is at a slight angle to the direction of rotation, the component of the tension force in this leaf link perpendicular to the surface of the disc will be tending to pull the pressure plate off. The angle this leaf is on my clutch would mean that the static clamping force of around 2460 lbs would be reduced by around 100lbs to about 2360 lbs at max torque.

When you get breakaway, the tension in this leaf will drop suddenly to zero and this would cause the diaphragm spring to release and swing in the other direction, so causing the clamping force to RISE momentarily to 100 lbs over static clamping force. That is, to 2560 lbs. This would be enough to cause the plate to grip again for an instant. This oscillation would be repeated over and over causing the periodic scooping damage. Does this sound reasonable?

If this is the case then it clearly isn't abuse that is causing these fairly common failures, but rather that some clutches aren't gripping as evenly all round the clutch ring as they should be. This would make breakaway more likely to happen at max load than they are designed for.

The questions are then - do other prematurely failed clutches show this scooping damage? Is it more pronounced on one diagonal than the other? Is this pressure plate made from soft metal? I would expect it to be hard if it is cast.

 

That's quite a theory about the "scooping", but I don't think that is the case. First of all, the variation in machining from how the casting was tooled will cause the wear to usually be more pronounced in three places. It is very common for the casting to slightly bow when it is clamped in the jaws of the lathe and it may show up later. Not only that but the casting is thicker and will absorb more heat in certain areas. I don't think it has to do with the torque strap (leaf). The "scooping" you are referring to are made from hot spots from the clutch slipping. These hot spots may be slight or very severe. Yours are somewhere in between in my estimation. Typically they end up as low spots when the clutch cools down. My thought is that when the clutch is overheating in these areas the metal expands toward the disc and therefore gets even more wear, and it continues until the clutch is able to cool and the area retracts. The next time you overheat the clutch you will make new spots since the old ones are now low spots and will not contact. This is not a quick oscilation, but a slower time after time heating and cooling.

Your disc also shows some pretty good heat as well. The friction surface does not apear to be smooth and polished, but rough, like the resin melted out of the material. When it is rough like this from overheating, the disc will hold more power until it is lapped in again (as long as it has had the chance to cool down), but it sacrifices material each time it is overheated.

Because the geometry of the EVO 7 is different from the EVO 8, the pressure plate doesn't have as broad of working range. This may account for it slipping earlier than it's disc wear limits. On the EVO 8 the pressure plate will give good clamping force (probably still not enough) all the way until the disc wears down and the pressure plate bottoms out on the limiters. Then without warning it starts to slip like crazy.

 

im at 16000 and it slips just a little on release. if your gonna make a car like the evo you need to have a strong clutch. f mitsu and their warranty dept. acura replaced an engine and trans under warranty when my buddy had a supercharger \AND nitrous. toyota did the same on my buddies tranny. mitsu and subaru are gonna scare away customers