FastestBusaAround

I have the Mantic 9000 Dual disc. I just replaced the stock clutch with this setup, but am having nightmare issues trying to get around the ultra light flywheel issues

When releasing the clutch in 1st from a dead stop, once the engine has warmed up somewhat, the car shudders badly until the car starts to roll. It's not as bad in reverse; in fact it's almost imperceptible.

Doug at ECS mentioned increasing the airflow in the 1st and 2nd gear air tables, which we did and it's a bit better, but nowhere near acceptable.

At least it isn't stalling now, but it shudders badly going into 1st.

Now, if the engine is cold and is running in enriched mode, there's no issue at all. This only happens once the engine warms up.

If I start the car from cold, and idle it without touching the clutch, it will do the same thing once the car has warmed up, so it doesn't seem to be a mechanical issue to me.

I haven't heard of anyone else having this issue -

Any thoughts?

I'm running a YSI putting down over 975 WHP

inspector12

I find on real aggressive clutches in the past, I bring the RPM up a little and let the clutch engagement bring the RPM's down with it and usually the car is moving enough that it was pretty smooth. worth trying I guess. GL!

Pekka_Perkeles

As it is not doing it when cold, it is very probable a tune issue.

Adding Base Running Airflow, as suggested by Doug is a good start. Note that there's an ECT multiplier for Base Running Airflow, which may explain why the situation is better when the engine is cold. I would increase values, (until you'll notice rpms hanging) and see if it solves the issue.

Check (log) the advance / idle advance at cold, as well as hot. You may have gone past MBT, which is not a good thing when trying to maximize torque around idle rpms.

FastestBusaAround

So we are thinking -

Unreal

Mine doesn't do that, runs great.

Dealripper

Never had any issues with mine. Hope you get it sorted out.

walhan_qtr

same with mine. I don't have that issue. same with 3-4 I have driven too.

FastestBusaAround

We did some tuning - more timing on bottom and a bit more airflow. It mitigates the effect somewhat, but it's still got a shuddering issue most of the time, in 1st. When clutching in reverse, it's not there. Definitely NOT the same as the stock clutch. I wonder if it's defective...

Pitufina

I thought you posted on another thread that you went with a super LW flywheel? I would start looking at that. They have their pros and cons.

Unreal

Could be that. I have the normal flywheel. I would expect some issues going lighter.

Turbo2L

If you went with the super light flywheel I'd hedge my bet there. The stock assembly weighs around 55lbs and the 9000 HD with standard issue flywheel is around 36lbs. That's a huge difference in rotational mass. When you get too light, you pay the price in drive ability and idle quality (even more so with larger cams).

Hope you get it sorted. I went with the standard weight and should have the car back before the end of July.

Detoxx03

The clutch disk themselves are already light so going with a lightweight flywheel isn't needed. That combined with no experience driving a lighter clutch is your issue. I have the steel flywheel and heavy duty pressure plate. Obviously lighter than the stock clutch and even lighter than the garbage LS9R setup I had. Drive great and handles the power.

Pitufina

I just went and found the thread: http://forums.corvetteforum.com/c6-f...installed.html
I was right, you did have an ultra lightweight flywheel installed. That in my opinion is the cause of your issues. You took away the engine rotational inertia. I've always read over and over from pros why not to do it.

realcanuk

Steve,

I would agree that the lightweight flywheel is causing the issue and I know that my Seth always steers people away from that. Then again, if Doug or Chris says it can be tuned out, then I guess it can. You just need to figure out exactly how with some trial and error I suppose.

needcheese

I have this clutch with the flywheel that comes with it installed. I have had the clutch removed and reinstalled due to engine rebuild. I think I had about the same problem you did when I installed the clutch the first time. The person doing the rebuild on my engine asked my a unique question I never thought about when I installed it the first time. He asked when installing the clutch pad plates, do you install them facing each other or stagger? he suggested installing with the clutch pads clamping directly apart from each other and not staggered. I hope I am explaining that you understand. This provides a better clamping force. With it installed it installed this way now, the clutch works great in 1st and reverse.. I barely hear any noise from the clutch when it is in neutral. it is very quiet. The first time around I did have the LG G6x3 cam installed. I now have a slightly smaller cam.

FastestBusaAround

Yes, it is the ultra-light flywheel, as was recommended by Chris @ECS. So, we did some airflow /timing tuning under 1600 RPM to help - then screwed with it for a few days and it's probably at about 80-85% of the stock feel now.

Unlike my other cars, the Z06 has this stupid tuning that aides the engine from stalling when engaging the clutch at too low an RPM - and I've never liked that. It is much to aggressive now that I have less mass in that flywheel. It's gets accentuated with this setup and we're working to eliminate or scale it down that - if possible. This clutch has caused me to relearn clutch engagement in this car.

It's also calmed down a bit due to break-in, so I am thinking with more tuning and more mileage, it should get to the point where it engages in 1st as good as or better than the stock clutch.

FastestBusaAround

I just reread your post - so, you had the same issue as me, but when he reversed the plates, it went away? To be clearer, the issue you had was that the car would shudder bad when releasing the clutch into 1st?

FastestBusaAround

Lot of trial and a lot more error - LOL. We have made a lot of headway on the clutch issues though.

Now I have to deal with a new one - engine temps (your pet peeve) and my A/C shutting down due to that. Part of the monster we created with the clutch mods - was adding more timing to 1st under 1600 RPM, which from what I was explained, has some carry-over into the other gears. I think that the added timing (20 degrees) is adding a bit to my engine heat issue. In 94 ambient temps, in stop and go traffic, with more stop/ idle than go, I saw it hit 238 last week. Needless to say, my A/C is cutting out at 220 or so...so the more I fix, the more **** I create. I was going to drive the car to NYC on Sunday, but decided against it, because of the heat issues. Good thing too; it was 95-98 there and I was in Manhattan, stuck in stagnant traffic. She would have puked and died 400 miles from home. I would have overheated and died too. My trusty Duramax dually doesn't get over 186 no matter what, and the AC runs ice cold in 100+ ambient temps.

camirocz

Had an rxt in my 07 z06 and an aluminum flywheel and off the line i had to release the clutch at a slightly higher rpm than with the stock clutch or i would get the same shuddering you re getting.Took a few days to get use to it then i was fine with it.

FastestBusaAround

Problem is that the shuddering is far more pronounced at higher RPM, in my car anyway. I'm more successful at lower RPM with eliminating the shuddering...