Synchromesh and rev-hang

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Re: Synchromesh and rev-hang

Post by Rope-Pusher »

Just shift it as you see fit and let DOG sort out which ones were good and which weren't.
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fa22raptorf22
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Re: Synchromesh and rev-hang

Post by fa22raptorf22 »

theholycow wrote:
fa22raptorf22 wrote:Nahh, you don't want to let the clutch up under power. Thats bad anyway you look at it. Its fine to catch it while the rpm is going up....but not going up under power.
It's not going to go up from gravity. Power's the only way it goes up.

400rpm off is a botched rev match by my standards.
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Re: Synchromesh and rev-hang

Post by theholycow »

fa22raptorf22 wrote:
theholycow wrote:
fa22raptorf22 wrote:Nahh, you don't want to let the clutch up under power. Thats bad anyway you look at it. Its fine to catch it while the rpm is going up....but not going up under power.
It's not going to go up from gravity. Power's the only way it goes up.

400rpm off is a botched rev match by my standards.
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Re: Synchromesh and rev-hang

Post by gizmo »

More off topics posts... should be moved to rants and raves.

While we're at it: isn't inertia an undefined concept from which momentum stems; momentum being resistance to change (which could mean that something that is constantly changing is simply resistant to further change).
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Re: Synchromesh and rev-hang

Post by LHOswald »

how the hell is that off topic?
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Re: Synchromesh and rev-hang

Post by watkins »

Because gizmo is overly literal about thread topics.
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Re: Synchromesh and rev-hang

Post by fa22raptorf22 »

theholycow wrote:Inertia keeps it at the same speed. Inertia won't accelerate your engine.
What happens when you are going up a hill and let off the gas? Do you suddenly halt? Or do you keep moving up the hill?

Same with engine rpm, if you blipped the throttle, even when you let off of it, it will still increase for a second till it settles out and goes back down.

---------

Also, someone above said that their rpm drops too quick to DC an upshift.

Thats bs because a DC'ed upshift takes exactly the same amount of time as an SC.


All you have to do is pull the shifter out of gear without the clutch, and then clutch into the next gear. Problem solved.
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Re: Synchromesh and rev-hang

Post by theholycow »

fa22raptorf22 wrote:What happens when you are going up a hill and let off the gas? Do you suddenly halt? Or do you keep moving up the hill?
Your speed immediately begins slowing. If you're accelerating up the hill and stomp your clutch, your car doesn't keep accelerating from inertia.
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Re: Synchromesh and rev-hang

Post by fa22raptorf22 »

paul34 wrote:Force = mass*acceleration

Acceleration = Force/Mass

No throttle, no fuel, no force (if you're going uphill and no one is pushing you), so no acceleration. Maybe you are refering to dashpot-type behavior where your foot might be off the throttle, but the computer or a mechanical device keeps the throttle open.
Remember, that even though this is true, the rpm keeps going up but at a decreasing rate.

Say your rpm is defined by f(x).

f(x) is increasing, but f'(x) is decreasing, till f'(x) becomes 0, at which point the rpm stops going up and comes down.
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Re: Synchromesh and rev-hang

Post by LHOswald »

fa22raptorf22 wrote:Say your rpm is defined by f(x).

f(x) is increasing, but f'(x) is decreasing, till f'(x) becomes 0, at which point the rpm stops going up and comes down.
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fa22raptorf22
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Re: Synchromesh and rev-hang

Post by fa22raptorf22 »

^^ What???

Do we not understand that something can still increase whilst its rate decreases?
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Re: Synchromesh and rev-hang

Post by LHOswald »

nope. i only got up to geometry :)
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Re: Synchromesh and rev-hang

Post by fa22raptorf22 »

LHOswald wrote:nope. i only got up to geometry :)
:facepalm:

You better be kidding.

Anyway, my point to all this is that rev hang is the result of one or two things.

1) You lifted the throttle but the ecu takes a second to respond and stop adding fuel.
--This is more common with drive-by-wires because you do not have direct linkage to the throttle plate.

2) You lifted the throttle and the engine did respond near instantly, but the rpm continues to increase for a second because you added enough throttle to bring it to a certain rpm, but let up early...So there was enough power to start making the rpm increase, but then it kept increasing, but slowed down as it did.
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Re: Synchromesh and rev-hang

Post by gear323 »

The rev hang or the vw throttle sticking is really bad on new generation Volkswagen cars that have a manual transmission. It is so bad that clutches are wearing out very early. It can also cause accidents in certain situations etc.


There is a petition that you can sign if you have one of the cars with the issue. The petition also has some good info about rev hang and there are links to videos.

Volkswagen 2.0T petition can be found here.

http://www.ipetitions.com/petition/peti ... -rpm-hang/
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Re: Synchromesh and rev-hang

Post by AHTOXA »

Stop. Just stop.
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