ACTman

iTrader: (5)

OK, I have a bit more time so I will try and explain further. First let's clarify what chatter is. Chatter is when the clutch ocillates from engaged to disengaged as the engine winds up and bounces back in it's mounts.

Looking back on auto history chatter became a problem back when engines started using rubber mounts to reduce vibration (not torsional vibration). Naturally they wanted to keep the flexible mounts. The fix for chatter was to place cushioning between the linings of the disc so that the pressure plate can gradually sqeeze the disc. But cushioning does not have the desired affect if the coefficient of friction is too high as it is with puck discs (it's been tried).

With higher friction (to hold higher torque) as what is used on race discs, the clutch tends to chatter. Now if you use totally solid mounts, as many race cars do, there is no chatter at all, no matter how aggressive the friction material. This is because there is no wind up affect. The clutch has no opportunity to ocillate from engaged to disenaged.

This brings up my point. Just like flexible mounts allow for this wind up affect, the springs in the center of a disc allow for more wind up affect. It is just from the other end of the engine. So chatter tends to increase by using springs, not decrease. Just like chatter goes away when solid mounts are used, chatter reduces when a solid disc is used.

The springs are there to reduce torsional vibrations. The frequency of these vibrations is much more rapid (a few times per revolution) than the frequency of chatter which is maybe a few times per second. Torsional vibrations (rotational pulses) you usually can't feel, but it makes noise by rattling gears, such as the decel noise, idle rattle, etc. I don't know if I explained this adequately, but hopefully you get the idea.

elhalisf

iTrader: (171)

If an evo driver switches to a lightened flywheel, and shifts the same way, he will add wear to the syncros.
what I mean is that in an evo with a regular flywheel, the rpm's drop down at a certain rate, and for a person shifting normally, the syncros really don’t work too hard since the output and input gears are at that point where their speeds are almost matched.
a person can actually clutchless shifting EASILY without grinding the gears. ( i know i am gonna get flamed for this, lol). now popping it out of the gears without a clutch might hurt it a bit, but you can go from a low gear to a high gear by just holding it lightly against the high gear, and it will shift right in. this is what people try to do when rev matching.
now a person with a lightened flywheel, the rpms will drop faster forcing the syncros to work harder or all the time.
now, of course, a person who rev matchs his car when shifting wont have this disadvantage.
This is the reason why I said a lightened flywheel will wear out the syncros faster. ACTman, please tell me if my theory is wrong.

ACTman

iTrader: (5)

Let the flames begin. Just kidding. You reasoning is correct, but I think your assumptions are incorrect. I know that when I had to shift a car without a clutch (clutch cable broke on old car), I had to shift pretty slow to allow time for the rpms to drop enough to rev match the next gear. This is also true on other cars when I was playing around to see if I could shift without the clutch. Now if I had to wait longer for the rpms to drop than I normally would if I used the clutch, then it stands to reason that a lighter flywheel which helps the rpms drop faster should be easier on the syncros, not harder. I don't have an EVO so I can't tell you if the rpms drop faster than it takes to shift normally (as in spirited driving), but that is my experience on other cars.

Let's test it. Everyone, go out there and shift your EVO without the clutch as fast as you can and time it... Well, maybe that isn't a good idea!

x838nwy

I see your point(s) and they are very valid. But I am curious and may be you can help me out. I was under the impression that the juddering of the clutch on street cars (to which i will limit this discussion) comes from the stick-slip characteristic of the friction material. Assuming that the engine puts out enough torque, so we're not confusing this with stalling it, as you raise the clutch pedal, the clutch begins to engage with the flywheel. The increase in power transfer is not going to be smooth, i.e. the amount the clutch plate 'grabs' the flywheel does not increase smoothly. There is usually a point where the material switches from slipping to sticking that you get strange things going on.

When the material alternates between slipping and sticking, you get torque pulses and the sprung plate is there to damp this out so whatever torsional vibration goes on at the clutch face does not get transmitted to the transmission and to smooth out the torque.

With a race setup, you're not so worried about this, cos when you go, you go and don't have to worry about the granny in a fiesta in front who hasn't noticed the lights so it won't be so much of a problem.

Now, this depends entirely on clutch design and how you match the various parameters and matrials, but without the sprung centre, surely this judder will be transmitted straight to the gearbox? I'd say that it would be best to use this plate to damp out this (low freq) vibration and use the clutch interface to damp out the power pulses (high freq) from the engine?

I'm not being a smart ar$e, and I know for a fact that you know a heck of a lot more about clutch stuff than I do, but I am truly curious and would like to be educated.

p.s. the link to your homepage on your profile is borken. It points to https://www.evolutionm.net/forums/ww...ncedclutch.com instead of www.advancedclutch.com

ACTman

iTrader: (5)

The stick/slip characteristic of the material is not really the problem. I think you are missing the most important part of my explanation. By having everything solid, the clutch is not able to alternate from slip to stick and the transition is smooth as a result.

Maybe it will help to have an example. We use a 10 second Camaro (drag car) for testing clutches. We have adapted a few different clutches to this car for testing because it has enough torque and is reliable enough to put the parts through the paces. Anyway, when we put the most aggressive of clutches in this car, it takes off glass smooth. On the typical street car with rubber mounts, many of these clutches would chatter like mad, but since the Camaro has totally solid mounts, they don't. Movement in the mounts (or spring center) will add to the tendancy to chatter. If you have a clutch that doesn't want to chatter such as the typical street clutch, then spring centers or rubber mounts are no problem.

x838nwy

What I am getting at is that the stick-slip happens anyway regardless of whether or not you allow for movement. It's a property of the interface. And when you engage the clutch when there's a difference in rpm it's going to happen to some extent.

However, from what you've said it looks like the compliance of the various bits are tuned to damp out other vibrations can in fact make this chatter worse. This would make sense as the rubber engine mounts are designed to remove engine vibrations (in the region of 20-100Hz or something like that) while chatter would probably be nearer single figure Hz. God knows what the combination of sprung centre and rubber engine mounts resonate at, but if they're in the wrong places, it can be like having really softly sprung centre which may be near resonance at the chatter freq. Without the flexible bits, the vibration from chatter would not be amplified by this resonance and thus should die out realtively quickly.

Have you had any experience of anyone running solid centres on an evo with stock engine mounts? Would be interesting to know how that goes....

threepointsix

This mount is supposed to help alot on our street cars low speed throttle transitions... interesting to note from the previous posts it will help with high friction clutch driveability also...

Mine is on a brown UPS truck . .
http://lancershop.com/customer/produ...0&cat=8&page=1

ACTman

iTrader: (5)

[QUOTE=threepointsix]Mine is on a brown UPS truck . .
[url="http://lancershop.com/customer/product.php?[/QUOTE]I bet it performs better on the EVO than it does on the UPS truck.

ACTman

iTrader: (5)

We don't sell a lot of the race setups to EVO owners since there are not too many that need them. I am not sure what mounts are used, but Turbotrix uses the solid center disc on their race car and has sold quite a few to customers. I am sure other shops that have sold them could chime in as well if they are listening.

What sometimes confuses people is when they compare our puck clutch with someone elses or from their experience from one car to another. If you are going to make a comparison of solid to spring center puck discs, it should be done on the same car, with the same pressure plate, and with the same disc manufacturer.

ACTman

iTrader: (5)

I got your email but my reply bounced back on me. I tried to eliminate the attachement (small photos of flywheels) but it still was rejected. Please advise.

x838nwy

I rekon Exedy _clutches_ are one of the best you can get. But they're a lot of money and I'm talking from experience only with the carbon stuff, not the racing stuff. Heard only one report from a guy using the d-core who says its great, but he drives a civic so he almost doesn't need a clutch anyway I have no idea why he decided to spend all that cash on the thing (it dynoed at 289hp at something like 8000rpm woo hoo!!!). That's with Motec and god knows what else in it.

Having said that the flywheel in the picture looks a bit shoddy to me. Looks like they just took a drill to the stock one and then balanced it after. Then again, you don't see it much when you're using it.

Surely it would be more cost effective if you do your clutch and flywheel at the same time? By the general concensus here it doen't look like you are in a urgent need of a flywheel, so why not wait?