: Clutch Grabbing



spearfish25
07-04-13, 10:12 AM
All you manual guys, please weigh in on this.

When I start from a complete stop, I notice a lot of clutch grabbing/chattering. So pulling away from a stop I can feel jerking throughout the car and hear some chatter from the center console. The slower I start off, the more noticeable it is. If I jump off the line there's no issue because the clutch is rapidly engaged. I've had three manual cars before this and never a clutch issue. The service manager said this was typical of Vs but he'd 'adjust it'. Looking at my Helm service manual, they need to pull the trans and inspect the clutch disc.

Thoughts? Any of you guys have clutch grab/chatter on take off? No problems whatsoever once I'm rolling.

VMoose
07-04-13, 10:28 AM
To get a smooth start on level ground, I use no throttle and just let the clutch out slowly. I get smooth acceleration like this. Moderate hills, I add a little gas.

JFJr
07-04-13, 10:38 AM
I can make mine do that if I'm a little lazy with the throttle. If I lead clutch engagement in 1st with a little rpm, everything is smooth.

Jud

Random84
07-04-13, 11:04 AM
I can make mine do that if I'm a little lazy with the throttle. If I lead clutch engagement in 1st with a little rpm, everything is smooth.

Jud

+1

You need to give it more gas - the engine RPM will drop as the clutch engages, so you want to give it more than you think it needs.

spearfish25
07-04-13, 11:38 AM
It just seems like she needs a LOT of throttle to get rolling. My previous cars would just need 1000 to 1500 rpm for a nice smooth engagement from a stop. I'm getting the chatter if I'm under 2k rpm and still can't be slow with releasing the clutch.

It's not engine bogging either. It's a chatter sound from the transmission tunnel under the nav, so clearly at the clutch/flywheel interface.

F'ing annoying. Starting off at 2k rpm feels like I'm going to be wearing the clutch prematurely.

JFJr
07-04-13, 11:50 AM
It just seems like she needs a LOT of throttle to get rolling. My previous cars would just need 1000 to 1500 rpm for a nice smooth engagement from a stop. I'm getting the chatter if I'm under 2k rpm and still can't be slow with releasing the clutch.

It's not engine bogging either. It's a chatter sound from the transmission tunnel under the nav, so clearly at the clutch/flywheel interface.

F'ing annoying. Starting off at 2k rpm feels like I'm going to be wearing the clutch prematurely.

Next time I'm in the car, I'll check the tach to see how much throttle I actually use to smooth out the launches. It's a feel thing with me and I usually don't pay any attention to that when starting in 1st. BTW, I've even launched it in 3rd (the other 1st) by mistake, but it needed a lot more rpm. Ha haa!

Jud

spearfish25
07-04-13, 12:13 PM
Next time I'm in the car, I'll check the tach to see how much throttle I actually use to smooth out the launches. It's a feel thing with me and I usually don't pay any attention to that when starting in 1st.

Thanks, I'd appreciate it. The only reason I looked at my RPM is because it was shuddering when I'd start off with my normal 'feel' from my previous manual cars. None of them took over 1500 rpm to get a smooth start. But then again, none of them were 556hp with heavy clutches.

Random84
07-04-13, 12:28 PM
I just came back - I go anywhere from 1500 to 1800 RPM for a "normal" engagement, during a typical start, with RPM's dropping to an even 1,000 once the clutch fully engages; no chatter. Anything less than that and I tend to get chatter.


It may have something to do with getting 4400 pounds moving.

spearfish25
07-04-13, 01:35 PM
The weight could definitely be part of it. Guess I can't complain if the car WANTS me to drive it like I stole it :).

JFJr
07-04-13, 01:55 PM
It appears that between 900 and 1200 rpm is what I use a fraction of a second before I start to release the clutch pedal. Idle is around 650. What is really excellent is the harmony of the shifter, clutch and throttle, and the butter smoothness of the downshifts when revs are matched, even going from 6th directly to 4th. I don't heel and toe but I plan to teach myself just for the fun of it.

Jud

Random84
07-04-13, 02:16 PM
Well, perhaps the rate of acceleration (from a dead stop) will vary for each of us, as well as the actual length of time it takes to "feather" the clutch in to full engagement... which may also effect the RPM preferred?

I'm right around 1500+ as stated, but I'm no Stig either and I have zero regard for the riding comfort of my passengers. :D

spearfish25
07-04-13, 02:58 PM
I was going to say, this car is a gem for rev-match and heel-toe downshifting. Initially I thought the pedals (brake and accel) were poorly positioned but under mod-hard braking they're nicely aligned. The engine revs nice and freely and it's a pleasure to heel-toe rev match downshift. Just these god damn standing starts are pissing me off. Guess I'll try some extra throttle when I get the car back.

Xaqtly
07-04-13, 11:58 PM
It may have something to do with getting 4400 pounds moving.

Ding ding ding! You get clutch chatter when using mild throttle input while engaging the clutch because it's trying to break 4400 lbs worth of inertia. There's not a lot that can be done about that. I've found there are two solutions, both of which have already been mentioned here.

1. Use more throttle, like 1500 RPM.
2. Don't use the throttle at all, and simply let the clutch out slowly. This takes a little more time but there's no chatter this way either, and it is easier on your clutch disc.

cdog533
07-05-13, 10:02 AM
More throttle, and slip the piss out of it! Smooth as silk.

Random84
07-05-13, 10:18 AM
2. Don't use the throttle at all, and simply let the clutch out slowly. This takes a little more time but there's no chatter this way either, and it is easier on your clutch disc.

How is a long engagement (intentional slip) better for the clutch? If anything, a shorter engagement time/less slip is "better" for the clutch, but results in a more abrupt gear change and that lurching feel for your passengers.

Also, when you don't use the throttle for this intentional slipping - in reality you're really just letting the ECM accommodate for additional engine load over by opening up the throttle for you; you just don't see a rise in RPM on the guage. However, there is still more air/fuel/timing coming in to actually get enough power to move the car. The only difference is you're doing it at 800 RPM with a much longer engagement, and giving the ECM enough time to do the adjustments for you.

Smooth, perhaps - but I am skeptical of it actually being better for the clutch. Honestly, when I do get chatter, it's usually because I'm trying (and failing) to get 1st gear under 1200RPM due to lack of power.

My vote remains "1500 RPM." :D

Now, who's with me on complaining about the rather stiff return spring on the third pedal? Holy cow, my left calf muscle has never had so much definition!

jb_bgg
07-05-13, 03:08 PM
You may be releasing the clutch too slowly. On level ground don't even need throttle, just a smooth quick release (half a second or so.) Up a grade, maybe a steady 1000rpm until fully engaged...

Mr. Hyde
07-05-13, 04:21 PM
My 2008 C6Z did the exact same thing. I learned to live with it.

JFJr
07-05-13, 07:18 PM
BTW, the V2 clutch is far superior to the "sticky" clutch on the last Porsche Boxster I drove. I've never driven an underpowered stick shift econobox, so I haven't been "spoiled."

Jud

spearfish25
07-05-13, 07:29 PM
Less definitely isn't 'more' in my case. Letting out the clutch without throttle will stall.

JFJr
07-05-13, 07:51 PM
Less definitely isn't 'more' in my case. Letting out the clutch without throttle will stall.

I discovered it in a parking garage; it's spooky and in the old days would lead to bucking and eventual stall. Well, we all have to get used to that and auto rev, for the future. As long as we can turn off some of this electronic crap, it's fine (except DOD which is totally overkill, stupid and made for a Buick).

Jud

sybersport
07-06-13, 02:27 AM
I have the exact same issue - but it hasn't proven to be a problem. She can still get herself down the track pretty quick (12.3!)

spearfish25
07-06-13, 10:28 PM
Dealer claims its normal and should be better now that they 'topped off' the clutch reservoir. Please.

I guess I'll live with it for now. When it fails I'll at least have it documented already.

JFJr
07-06-13, 10:46 PM
Dealer claims its normal and should be better now that they 'topped off' the clutch reservoir. Please.

I guess I'll live with it for now. When it fails I'll at least have it documented already.

I've had my clutch fluid replaced twice under the normal maintenance schedule and it made no difference in clutch operation, but I really don't have a problem with it. Hopefully, your dealer wasn't selling you unnecessary maintenance.

Jud

Xaqtly
07-07-13, 02:46 AM
How is a long engagement (intentional slip) better for the clutch?

Because it's much lower RPM, therefore there is less friction between the clutch disc and the flywheel, therefore extending the life of your clutch. Higher RPM means a higher rotational difference between the disc and the flywheel, which generates more friction, more heat and the loss of more clutch disc material. So while doing it the low and slow way may take longer, it's actually easier on your clutch disc due to lower friction due to lower rotational speed. And in fact I believe it grabs sooner too, because if the engine is lugging then the clutch disc is already attached to the flywheel and there is no friction being generated.

spearfish25
07-07-13, 08:53 AM
I've had my clutch fluid replaced twice under the normal maintenance schedule and it made no difference in clutch operation, but I really don't have a problem with it. Hopefully, your dealer wasn't selling you unnecessary maintenance.

Jud

Yeah, no worries. I do all my car maintenance myself unless there are big issues or warranty work is necessary. So things like bleeding the clutch, I'd never ever pay a dealer for.

cdog533
07-08-13, 11:49 AM
Because it's much lower RPM, therefore there is less friction between the clutch disc and the flywheel, therefore extending the life of your clutch. Higher RPM means a higher rotational difference between the disc and the flywheel, which generates more friction, more heat and the loss of more clutch disc material. So while doing it the low and slow way may take longer, it's actually easier on your clutch disc due to lower friction due to lower rotational speed. And in fact I believe it grabs sooner too, because if the engine is lugging then the clutch disc is already attached to the flywheel and there is no friction being generated. I'm not sure lugging it is the best approach. I like a nice slow engagement from like 2,000 rpms. This is smooth, prevents lurching, and does not drop you super low into the torque curve like a 750 rpm launch does.

spearfish25
07-08-13, 12:25 PM
Well, 1500rpm definitely helps. It also seems better now that my whining rear diff has been replaced by the dealer. It's now perfectly quiet.

Xaqtly
07-08-13, 01:32 PM
Yeah higher RPM engagements are smooth, but like I said, it's more wear and tear on your clutch disc. I tried it a few times yesterday and I found I can avoid the chatter at 1100-1200 RPM, so 2000 probably isn't necessary. OTOH I also have a pulley, intake and a tune so I may be making a bit more torque at that RPM, not sure about that. Anyway ideally you always want to rev match when downshifting to minimize clutch disc wear, and starting from a stop you want to do it at as low an RPM as you can while still avoiding the chatter so you can have a smooth start while minimizing clutch disc wear. The idea is just to keep the rotational speed differential to a minimum when mating the disc to the flywheel, to preserve the clutch disc.

JFJr
07-08-13, 01:53 PM
Yeah higher RPM engagements are smooth, but like I said, it's more wear and tear on your clutch disc. I tried it a few times yesterday and I found I can avoid the chatter at 1100-1200 RPM, so 2000 probably isn't necessary.

That's my sweet spot, too, and my car is bone stock.

Jud