RSMike

iTrader: (1)

Gearbox shifting issues.
There seem to be a lot of information out there, but nothing really super concrete or anything with back to back tests being conducted. Mostly anecdotal information.

Things that I think contribute to shifting issues:

1) Balance shaft removal. Increases vibration and resonance problems.
2) Going from 2.0 to 2.3 stroker engine. Makes the vibration worse.
3) Each clutch design is different. ORC (Ogura Racing Clutch) is the best clutch i've personally used, the shift performance is amazing. I've only noticed some resistance to shifting when on the track after 3+ laps and everything is really hot. I'm guessing the gearbox gets hot and tolerances change.
4) clutch diameter - I haven't had good results with large diameter (more than 200mm) clutch plates. The bigger plates will wobble more than smaller plates.
5) Central hub versus splines plates. The ORC uses a central hub like the exedy triple plate. It gives another degree of movement and freedom. I think this is a big benefit rather than having the input shaft splines hard mounted into the clutch plate. Also it's more surface area to protect the input shaft splines life.
6) Clutch floater plates and assembly balancing. Not many companies balance the individual floater or clutch plates. I think this is also why the ORC clutch shifts so good, they are all individually balanced.

I think the clutch plates will whip or wobble at high rpm. This wobble causes the clutch plates to touch the floater plates which then puts drive into the gearbox, even with the clutch pedal depressed. This is where the clutch drag test comes into play.

The Evo doesn't use a spigot bearing either. I have checked the input shaft movement and it's only 0.03mm which is more than likely just the ball bearing clearances. Jack's does have an tapered bearing option which would reduce this movement. But 0.03mm is only just over 1 thou (0.001") which is not much at all.
The issue with a spigot bearing or tapered bearings is the input shaft to crankshaft alignment needs to be perfect.
So if you're line boring the mains tunnel for your mains bearings, that will likely move the crankshaft up. Yes it will be a small amount, but you dont need to be out by much to cause problems.

Thoughts?
Anyone done any testing before?

Ayoustin

iTrader: (2)

Most clutch lockout issues stem from the pedal being out of adjustment (aka not getting enough stroke on the slave for full disengagement).

Multiplate clutches need more attention than singles. I have seen cases with multiplates dragging because the floater was sticking on the posts that it rides on. This used to be a common issue with Exedy units, not sure if it still is. Also, singles will get most people by, shifting only really becomes an issue if you're revving to 8500-9k+ on a single disc.

Balance shafts have no impact on torsional vibrations. An aftermarket crankshaft balancer helps reduce torsional vibes, which will make an impact on vibration related shifting issues. Having the rotating assembly properly balanced makes a good amount of difference here too.

Wouldn't waste my time converting the input shaft to a tapered roller bearing IMO.

RSMike

iTrader: (1)

What makes you say this?

I've tried a clutch drag test with a triple plate I was having problems with.
It starts to rattle at around 40% clutch pedal stroke.
Tested at 50%, 75% and 100% clutch pedal stroke, and all of those had drag (car moves with clutch depressed)

mitsuatb

iTrader: (6)

I don't have an answer just a thought. Crank walk could change the relationship between the slave and the throw out bearing. With a pull clutch the effective travel of the slave will be reduced. Many people who have this problem are pushing things pretty hard and might get accelerated thrust bearing wear. You make a number other good observations.

RSMike

iTrader: (1)

Thank you sir!
Every time I change/remove the oil pan, I check the thrust movement.
It's been 0.10mm (4 thou) for a while now, and hasn't been moving at all.
I must have taken the oil pan off 20 times now with the Infinite Evo testing and development!

Dallas J

iTrader: (1)

I've always felt it was related to either clutch wobble or clutch drag on a single side.

When the clutch PP is pulled only one side separates and the disc needs to separate from the flywheel. Any little bit of stiction here will add some amount of drag to the shift.

I always detail the splines on the trans and pressure plate with a triangle file just to make sure theres no built up burr. Then wipe the input shaft on trans with molylube. Only a very small layer left but better than leaving dry.

Side note, been curious about the Ogura clutch and how it holds up to moderate launches. My Exedy was good all the way up till I launched it and warped the small plate. Been like that for a while now, but need to find a better solution that can tolerate a ProSolo.

RSMike

iTrader: (1)

Yup agreed on the stiction of the floater plate on the posts or basket.
The plate balance will have an effect on this also, as if they are out of balance they will want to stick also.
With the ORC plates being individually balanced, it seems to work well.

Moderate launches seems to be OK. I've got customer's here in NZ using them for Targa with lots of standing starts at the beginning of stages.
The floater plates will eventually warp with enough heat.
The old unit I just put back into my car has a small amount of warp, but doesn't seem to effect the driveability or disengagement.

mitsuatb

iTrader: (6)

Devin Nemelia (Sp?) Youtube just had a mysterious failure of the new ACT twin on a high HP STi. No oblivious cause but clutch was dragging hard. That clutch acts like a motor cycle clutch with a large internal hub and the floaters and disks keyed to and moving on that. But unlike a MC clutch it is not running in oil. I wonder if the disks / floaters were jamming on the hub. No way to grease those contacts like the central small spline on the single disk or Exedy twin design.