Differences: Feathering and Dumping the clutch?

What is feathering the clutch, and dumping the clutch? What are the main differences between feathering and dumping the clutch and what are the advantages/disadvantages of each?

(I already searched, came up with nothing. I know there's a few questions here... heh..><)
 
5,071
What does farting and dumping have to do with cars?

..


Dumping the clutch is when you release the pedal as fast as you can. It can never be good, It puts much stress on the clutch and the transmission.
 
5,071
:)

About feathering, found this on some site:

Slipping the clutch is slipping the clutch. The engine rpms are turning
faster than the transmission input shaft and the clutch is partially engaged.

Feathering the clutch (feathering *anything*) is about reacting to feedback.
It's slipping the clutch *just* enough to keep the engine revs from dropping
but not to induce wheelspin, while simultaneously holding
the revs up. There's no formula that'll tell you how
to feather. It's something you simply have to practice.

Try this. (not going for ultimate launch here, just how to feather clutch)
Rev the engine up to 3000 rpms, let the clutch up to the point that
it *just* barely touches, then back off a quarter inch or so so you're not engaged.
That's where you should be sitting at the line. When the light
goes (practice at a stop light) start letting the clutch out slowly,
and simultaneously hold the revs steady at 3k rpms until the
clutch is fully engaged.
Do it again, but faster on the clutch.. again keeping the revs *exactly*
at 3k with the gas, while letting the clutch out as smoothly but as quickly as
possible.

Eventually, 1 of 2 things will happen. Either the revs will drop (in
which case the feedback tells you to apply more throttle), or the tires
will spin (telling you, you're letting the clutch out too fast). The "feathering"
part is you balancing the throttle and clutch to keep the revs steady
and the tires *right* on the edge of slipping. You actually want about 10-15%
wheelspin for maximum acceleration on street tires, and you'll only get there with
practice. Once you've got the first 3k rpms down your speed should
be high enough that the clutch should be fully engaged and then all
you've got to concentrate on is the gas, *feathering* it if you've
still got enough torque through the midrange to simply break the
tires loose at WOT. You may be able to let the revs rise a bit
as the clutch gets closer to fully engaged.

Some people find the powerband of their cars too obnoxious, in that
they'll just spin the tires at the middle/top of first gear, so they'll actually
feather the clutch all the way up to 5k rpms or so. That's really hard
on the clutch, but gives them the ultimate control over how
fast the car accelerates because they can hold the revs high, while
controlling the power entirely with the clutch, which reacts
much faster than the throttle. If you let the revs rise at the same
time that you feather the clutch, you can keep the speed differential
a little under control thus not smoking the clutch in one fell swoop.
A lot of the best FWD drag racers use that technique.
It also means you don't have to worry as much about holding
the revs at any one point. You just manage wheelspin
with the clutch, while rolling on the throttle at a constant rate.

My car (S/C VR6) is pretty peaky. If I pop the clutch at 2k rpms
at this elevation (mile high), my car will be parked at the 60 foot mark.
3-3.5k, I might get lucky.. kind of a 50/50 chance of spin versus bog
depending on whether they decide to glue me to the track with
that sticky crap. 4k.. spin spin spin.. So to get a good launch I
*have* to feather the clutch, and hold it on the
edge of wheelspin.

Same on the street, although in some ways I find the street
more consistent in that I'll almost never bog. I can dump it at 2k
and get a little wheelspin and go. The track is
so grippy that's not possible.

BTW, it's interesting to note that none of the definitions of the word "feather"
really apply to this technique, yet it's not the only context in which it's used to
mean the same thing. Using feedback to control a mechanical
device to acheive an "edge" effect.. (on the edge of too much).
Only thing even remotely related I can find is "feathering the oars" or "feathering a propeller"
which both mean to turn the blade edge on to the fluid flow, thus
reducing its resistance.
 

Duke

Keep 'em separated
Staff Emeritus
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United States
Midlantic Area
GTP_Duke
Dumping the clutch creates a rough launch that stresses the driveline components. If you don't have great traction it leads to a burnout; if you have great traction and a lot of horsepower it can lead to broken halfshafts, universals/CVs, motormounts, etc. It's really only used for racing, and then only if you are confident in your traction.