New Install UUC Stage III Clutch and Light Flywheel. QUESTIONS! - The Unofficial BMW M5 Messageboard (m5board.com)

Kings MotorSport · 4th November 2004, 08:57

Hey guys looking for some guidance once more,

had the uuc stage III clutch and flywheel installed. a couple of question for anyone that may have this set up or someone that just might know about it.

1. will the chatter dissipate after the break in period? (very loud right now)

2. from a dead stop the car shakes a bit as the clutch is engaging in first (almost the same kind of vibration you get from a vibrating drive shaft) but stop right away and doesn't happen in any other gear. Thoughts?

These two issues aside, the clutch feel great. A signficantly lighter pedal pressure, but you can feel the strength of the clutch. Very quick and precise shifts. First is going to take some getting use to as there is a significantly lower "catch point" but nothing that some practice won't help.

The lighter flywheel is a dream. It feels as if the car may have lost some power in the lower gears but highway sprinting is unreal. The car in 4th gear cruising at ~4000 rpm, stomp on the gas, and watch that rpm meter flyyy.

Assuming the 2 issues above will be resolved, I highly recommend this to any beast owner that's due to replace that P.O.S. Oem clutch. (Mods or no mods)

Guys let me thank you in advance for any info you can provide. As always it is much appreciated.

SC'dKellenersM5 · 4th November 2004, 13:42

Jay,

with the sprung hub design the springs in the hub will need some time to loosen up and therefore you should see a reduction in the noise level of the chatter. It will not however go fully away, but it should get better past about 1000 miles.

As for your vibration statement...all i can say is to ask Rob over at UUC about that...or maybe shadowman as they are the two people that seemingly have the most knowledge of this clutch pkg.

1badm5 · 4th November 2004, 16:04

Jay, congratulations on the new clutch! I got the same setup about 1 month ago and am very happy with the performance. I easily remedied the vibration upon takeoff by raising my rmp's (slightly) to about 1200-1500 when taking-off. If you tried that with the OEM clutch you would obviously "burn" the clutch, but I don't think it is going to have an adverse affect on the Stage III from UUC.

I can't really tell that the "chatter" has diminished much (if any?) during the time I have had the clutch (1 month). I did an "first impressions" as well as a "1-month update" here

Also, if properly installed the "chatter" goes away when you engage the clutch, and when you are in motion. The only time the "chatter" should be audible is when you are at a dead-stop, with your foot "off" the brake. Let us know if this is the case.

I agree with your initial assessment that the clutch is very street-worthy, and would work well with or without mods. I like knowing that I can now do anything I want to with HP upgrades without having to worry about upgrading the clutch.

Robert

Kings MotorSport · 5th November 2004, 01:38

The chatter only occurs when the car is at a dead stop, as for the brakes, i'm not sure if it stops if i press on the brake, i'll have to check it out. I read your write up and I agree the first to second and the second to third shift have become so much easier, it was sometimes a pain with the OEM setup. But I've had some other weird noises today, when the vibration (almost a jerk like not giving enough gas at point of engagement) normally occurs i've had some kind of weird grinding noise almost. I'm going to have it checked out tommorrow. All the UUC guys are at SEMA so they won't be much help until Monday. Will keep you posted.

Thanks

Lscman · 5th November 2004, 02:14

Quote:

Originally Posted by Kings MotorSport

The chatter only occurs when the car is at a dead stop..........

....and I might add, only with the transmission in neutral AND the clutch pedal out. At a dead stop with the clutch pedal depressed (pushed in), rollover noise does not occur, no matter what gear you're in.

Rob Levinson · 7th November 2004, 00:31

We're baa-aaack!

The slight vibration you feel on taking off from a complete stop is a function of the multi-puck design and the material. As it beds in fully, that should smooth out. However, as you may have to do anyway with a lightweight flyhweel, a slight modification of your gas/clutch modulation can eliminate that. I suspect just in the normal course of getting used to it that your engagement style will adjust subconsciously.

The rattle should reduce as well as the sprung-hub springs loosen up. For full effect, it takes 500-1000 miles. Alternately, Amsoil showed us some variations of their ATF specifically to reduce gear rattle. We will be doing some testing over the next feww weeks, I will certainly report to the board if there is any worthwhile development. For M5 results, my own Euro E34 M5 6-speed is the perfect test case; I have experience with many different fluids within that same box, and it has the same general design and rattle characteristics as the box in the E39 M5.

Need4Spd · 7th November 2004, 02:37

Quote:

Alternately, Amsoil showed us some variations of their ATF specifically to reduce gear rattle.

Well, there was quite a bit of debate on this board about a year ago over what oil to use in the M5 Getrag trans. Evidently there is a non-metal part or two inside that will fail in the presence of incompatible oil. The damage is supposedly not evident right away, and in fact the car will shift smoother and quieter. But then..... blam. As a result, some of us that originally went to aftermarket fluids went back to the OEM fluid (which retails for about $28/litre btw, and you need 2 litres to fill the trans in our cars). Others have stuck by their aftermarket fluids and so far, so good but maybe it's just a function of the fact that most of our cars are still relatively new. So, I'll be very interested in seeing some long term testing of alternative oils but I'm not holding my breath. I'm convinced of the benefits of the UUC clutch upgrade enough that I will probably go that route when my clutch wears out but unless I get very good evidence, I'm not changing my fluids just to avoid a small bit of noise.

Keith97M3turbo · 7th November 2004, 20:33

please ,please, don't start the fluid 'thing' again.
N4S , if you've never had a aluminum flywheel'd car you don't know about the noise, when you go to the alum. flywheel any noise is louder than the stock you had, some loud and some fairly acceptable . It depends on each individual box. So the noise becomes annoying and you want to make it quieter asap. If there is no pure evidence of fluids ,and it is all here say they say from opinions from users to product sellers to engineers , you WILL try to make it as quiet as you can, or just live with it. Most would try the fluid change I'll bet! I did, 3 times in the m3 (97 turbo,alum. fly'd with euro 6SPD)

Rob, can you make a note to post back after testing the Amsoil, the rattle is just like I had in the M3, I knew there would be some noise as to be expected but this loud in a M5 not cool. I think the box was quieter with the R/P than with the Redline.

HBRAMSTEDT · 7th November 2004, 20:57

Here is one person who confirms what I have said. The lightened flywheel feels weaker at launch. He says it feels like it lost power in the lower gears with the lightened flywheel. I am not sure if that is a technically correct expression, but it is not reassuring. The lightened flywheel S2 I drove felt absolutely weak on the upshift to 2nd, and it would drop about 300 revs. versus stock on the upshift. That absolutely has to cost time in a street race. The S2 was clearly quicker in gear than my stock M5 though. The S2 was reluctant to break loose in 1st gear starts. It didn't seem as eager as my stock M5 from the drop. It pulled harder afterward though. This was partly due to the huge dip in the torque curve (versus stock) at low to mid r.p.m.s that I have seen in S2 dyno. pulls posted on this board.

Dinan is not the untouchable engineering firm that is claimed. They are innovators and the quality is sound, but their engineering is NOT the absolute best. Look at the Z8 frame debacle, the poor visible contruction of their M5 header, the dip in the S2 power curve, and other stuff. Dinan is good, but highly overrated.

Rob Levinson · 7th November 2004, 22:35

Quote:

Originally Posted by HBRAMSTEDT

Here is one person who confirms what I have said. The lightened flywheel feels weaker at launch. He says it feels like it lost power in the lower gears with the lightened flywheel. I am not sure if that is a technically correct expression, but it is not reassuring. The lightened flywheel S2 I drove felt absolutely weak on the upshift to 2nd, and it would drop about 300 revs. versus stock on the upshift. That absolutely has to cost time in a street race. The S2 was clearly quicker in gear than my stock M5 though. The S2 was reluctant to break loose in 1st gear starts. It didn't seem as eager as my stock M5 from the drop. It pulled harder afterward though. This was partly due to the huge dip in the torque curve (versus stock) at low to mid r.p.m.s that I have seen in S2 dyno. pulls posted on this board.

I'll try to give an explanation, but I will preface it with the statement that none of it must be taken out of context or glossed over. If appropriate attention is not given to all that I write below, then none of it should be read.

When you install a lightweigth flywheel, there is no torque loss from the engine. Period, end of story, verify it on a dyno.

A flywheel, by it's very nature, is an energy storage device. It's purpose is to either absorb excess energy from the engine, or average out the energy being put into the transmission, when an imperfect rpm vs. gear/wheelspeed clutch engagement happens.

The energy is stored in it's mass. When you rev your engine, energy is used to move that heavy flywheel... energy that is not put to the wheels. The mass of the flywheel stores that energy by it's motion.

Thus, a lighter flywheel requires less energy to be moved, allowing more of the net total force produced by the engine to go to the wheels, making the car quicker. The mathematics of this are covered on our website here:
http://www.uucmotorwerks.com/flywhee...heel_works.htm

But the important question is then, how does this jibe with "real world" experience?

Those who say their car feels quicker with a heavy flywheel are revving the motor above the correct gear/wheelspeed amount, and "dumping" the clutch. The heavy flywheel stored energy, and then transferred it to the transmission/wheels. Technically, during this engagement, the stored energy plus the engine input energy is more than the engine makes alone. The critical thing to realize is that this only holds true during the period of clutch engagement and is a "false torque" sensation.

That "false torque" sensation tricks human perception into thinking the car has more power, when the torque measurement of such an engagement style shows that the "false torque" jump up is immediately followed by a sub-normal torque dip as the heavy flywheel requires more energy input to re-accelerate than the lightweight alternative.

An example of this is quite clear in a dyno graph. This section shows a torque curve, specifically the initial clutch engagement at 2000rpm and up to 3500rpm.

The "false torque" effect of the green line clutch dump is obvious; during, and only during the clutch engagement up to 2500rpm, is the energy that the flywheel has stored being transferred to the drivetrain. After 2500rpm, it uses even more energy to re-accelerate. Contrast this with the red line smooth engagement which has more torque at the wheels everywhere above 2500rpm.

Even though that graph is showing two successive runs on the same car, the point regarding the "false torque" effect of the heavy OE flywheel is exactly the same.

So you see, this is the reason why a lightweight flywheel car will walk away from a heavy flywheel car every time, regardless of how the initial clutch dump may "feel" stronger with the heavy flywheel.

- Rob