Gear Changing....

[[TWUBLE]]

ok this is gonna sound real lame... but here goes....
Exactly when do you double clutch (apart from it sounds nicer than normal gear changing) and do you do it on the upshift? or just down shift? and whats granny shifting? is that just normal gear changes?

k that sounds REAL lame but as not owning a performance car before this one i have never had the need to know :/

thanks all

[R33]

It depends on what exactly you are trying to overtake!

Seriously, I am not an expert and I drive like a granny (always employing the granny gearchange ). But I would think you'd double clutch during upshifting because then, the rpm would go down as soon as the upshift is done (unless you have sequential gear box) and to compensate this, you double clutch. While downshifting, the rpm is gonna go up anyway, so there is no necessity for double clutching unless you want to maintain boost at a high level.

Just my 0.02 cents worth!

[[TWUBLE]]

Ahhh k i get ya now... and a granny shift is just a normal gear change right?

[R33]

Not too sure about granny shift though...
Hey, nice car in the avatar. Is that yours? Any plan to soooooouup it up yet?

[[TWUBLE]]

ahhh k kew kewl....
yeah it is my car uhmmm whats your email ill email you a bigger picture of it...

yeah a few plans... GTR Bumper, FMIC, Link Plus, TO4 Turbo, Bosch Motorsports Fuel Pump, Slotted Cross Drilled Brakes, Camber Plates, Strut Braces, Modified Plenum (look like a gtr one), Bigger injectors, hrmmm... yeah thats about all i wanna do to it hehe

[Gonthrax]

Originally posted by [TWUBLE]
ok this is gonna sound real lame... but here goes....
Exactly when do you double clutch (apart from it sounds nicer than normal gear changing) and do you do it on the upshift? or just down shift? and whats granny shifting? is that just normal gear changes?

k that sounds REAL lame but as not owning a performance car before this one i have never had the need to know :/

thanks all

Double Clutching was first used on dogboxes (Gearboxes w/o synchronous mesh) because without it you couln't shift into first while moving at any reasonable speed. Now before I go any further lemme try and find a good cutaway of a tranny.

The green shaft is connected to the clutch disc, which contacts the flywheel(spinning w/engine) when the clutch is out(engaged) The layshaft (red) always spins with the green shaft, so if the clutch is in (disengaged), it will eventually stop spinning. When the tranny is in neutral with the clutch engaged, the green and red shafts spin at the same rate as the engine. The blue (actual gears you hear people talking about) and red gears always mesh, but the blue gears are not attached to the yellow (output) shaft. The blue gears just spin on bearings around the output shaft. The yellow shaft is connected (through other stuff) to your wheels and spins at a rate proportional to that of the wheels. The purple collars are attached to the output (yellow) shaft and spin with it. When you move the gear shift lever, it will cause the dog teeth in the sides of the collar (you've selected) to lock into the sides of the gear and cause the wheels to spin at the same rate as the engine(if the clutch doesn't slip and nothing breaks Generalized flow: Wheels->yellow output shaft->purple collar->blue gear->red gear/shaft->green gear/shaft->clutch disc->flywheel->engine crankshaft.

The above is without synchros. So let's say the green shaft (attached to flywheel) is spinning at 1800RPM when you're in 4th at 35mph. So the leftmost purple collar is pushed to the right and locks 4th gear to the output shaft. Now you want to shift to 1st (where the engine would need to be at 5500RPM). So you push the clutch in and bring it out of 4th, and the green/red shafts slow down because the clutch is disengaged and the blue gears are spinning freely. Now, if you were to push the rightmost collar leftward (into 1st), the red/green shaft would have to be spinning at
5500RPM, and it's probably at about 1500RPM by now. So the purple collar and the blue gear (1st) are spinning at very different rates. Consequently, the dog teeth will not mesh and you'll hear this nasty grating noise. The solution to this(without double-clutching) is synchros. They're cone-shaped protrusions from the gear near the output(yellow) shaft that gradually allow the purple collar to bring the red/green shaft up(or down) to the appropriate speed before the dog teeth lock into the gear. Just FYI, if you try the above scenario, you probably wouldn't even be able to force the shift lever into 1st (probably because the synchro would have to do way too much work, and would probably start to slip). Without double-clutching, I can't really shift into 1st until I'm below 15-20mph, and even then, it fights back.

Double-clutching(what you really wanted to know)....

Here's the steps: (re-using the above scenario, 4th->1st @35mph)

1. In 4th, going 35mph
2. Clutch in, gearshift into neutral
3. Red/green shaft slow down since not connected to
flywheel or wheels
4. Clutch out (engaged)
5. Red/green shaft spin at engine speed
6. Rev engine to 5500RPM (expected speed in 1st)
7. Assuming you're still going about 35mph
8. Blue gears(connected to red shaft) spinning at rate close to
that of the purple collar for 1st gear.
9. Clutch In
10. Gear shift to 1st
9. 1st gear synchro barely has to do work, so tranny slides
smoothly into 1st.
10. Clutch out
11. Going 35mph in 1st with very little bucking, just louder

[Gonthrax]

Oh yea, just a quick disclamer, those figures were given just for ease of explination, Not sure if it would be safe to do without things going Clunk! Soooo do it at a speed you know your safe at ie. get up to that speed in first to see what your revs are going to be at.

[[TWUBLE]]

Thanks man! haha that helps heaps....
but another question is still unanswered... a granny shift... is that just a normal gear change?

[R33]

My mail add. is [email protected]. Mail me some pics....Skylines pics are always welcome
That looks like it's gonna be a wild mod! Yeah...go on and do it....up the boost and whup asses! My car, if you are interested, is at www.ridejudge.com (ride of the month for the moment).

[[TWUBLE]]

sweet as... just sent you a pic of the car

[Gonthrax]

Originally posted by [TWUBLE]
Thanks man! haha that helps heaps....
but another question is still unanswered... a granny shift... is that just a normal gear change?

Ahh a granny shift, it means you shift like my friggin grandma! Slow on the clutch, all the way off the gas when you shift, no poppin the clutch out so it grabs hard, just generaly slow Now this isn't always a bad thing, no need to shift like a bat out of hell most of the time. Just like there is no need to run around at 6,000 RPM runnin full boost when your just going out to get some milk. Well I donno, mby there is need for that

[[TWUBLE]]

damn bro that is a REALLY nice GTR!!!

[[TWUBLE]]

ahahhaha... is there a need for hand brake paralel parking too?? with an entry speed of 40 - 45 k?? (approx 25-30mph)

[Gonthrax]

Originally posted by [TWUBLE]
ahahhaha... is there a need for hand brake paralel parking too?? with an entry speed of 40 - 45 k?? (approx 25-30mph)

haha! Always! Just grab it and slide on in there

[[TWUBLE]]

Originally posted by Gonthrax


haha! Always! Just grab it and slide on in there

Why does my "dirty mind alert" come on when i see that?