Clon3

Hi All,

Sometimes when shifting down 2 gears, I tend to double clutch to minimize syncro wear. I've read numerous methods on how to double clutch and I know exactly how it works. However, there is a step that I seem to do slightly different. When I double clutch for a downshift rev-match, I tend to do the following:

clutch in > shift to N > clutch out > clutch in again > put in gear > Blip throttle > clutch out.

Is it ok to blip the throttle after I clutch in the second time or do I have to blip when my gear in N and clutch out. I tend to be more comfortable doing this way since I can do it much faster. This is how I normally do a revmatch downshift as well.

clutch in > shift in lower gear > blip throttle > clutch out.

I just seem to blip my throttle with my clutch in and wondering if its any different than how it's supposed to be done? Thanks for any help!

Clon3

Mike@Blackline

iTrader: (37)

clutch in > shift in lower gear > blip throttle > clutch out.

if thats how you do it (which is the standard), then when do you do your 'clutch in > shift to N > clutch out > clutch in again > Blip throttle > put in gear > clutch out' method?
that is time consuming, and youre just doing too much

Clon3

Yeah I know double clutching might be overkill, but my main question is when I should be blipping the throttle. Do I put the lever in lower gear first, then blip, or should I be blipping then shifting to lower gear. All this is happening so quickly with the clutch depressed, thats why it's more technical and I was wondering what's the correct way to do it.

Does it matter?

skaterbasist

iTrader: (3)

I don't see how double clutching would minimize wear on the syncros anymore than proper rev-matching.

Mike@Blackline

iTrader: (37)

double clutching, in its original meaning and form, is for transmissions without synchros. for that, you do what you first said; put car into neutral, then did your blip or whatever, and then shifted into the gear.
but obviously the 350Z has a tranny with synchros, so this isnt needed. If you're going from fifth to third for example:
driving in fifth > clutch in, shift into third > blip throttle to get to the matching RPMs needed > release clutch to engage third

no need to do the blipping in neutral

davidv

iTrader: (2)

Canada members get creepy after midnight.

Clon3

Thanks guys.. my first manual car so just trying to get in the right habit of a rev-match downshift. My main question was whether "when blipping the throttle mattered", but I guess it's the same? Some put into lower gear first then blip, and others blip before putting into lower gear. Any preferences?

Cheers!

winchman

The purpose of double clutching is to get the speed of the transmission input shaft to match that of the gear being selected. In order to do that, you have to shift into neutral then release the clutch while you blip the throttle. Next, you depress the clutch before slipping into the next gear. Lastly, you blip the throttle as you release the clutch to rev-match, which reduces wear on the clutch.

Seeing all the threads about problems with pivot ***** and slave cylinders, it sounds like just asking for more trouble.

I'm liking my 5AT more and more.

Jennifer 2

Clon3, ideally you want to bilp the throttle just before releasing the clutch pedal, which should be just milliseconds after moving the shift lever to a lower gear. Think of it as just one smooth operation.

There is a difference between rev-matching and the now obsolete skill of double clutching.

As for rev-matching, consider charging into a corner approaching the limit of tire traction. If you simply let off the throttle and push in the clutch pedal to accomplish a downshift, the engine RPM will have dropped enough so that when you release the clutch pedal, the extra bit of sudden engine braking will upset the car mid corner. If you blip the throttle before releasing the clutch pedal the engine speed will now match the road speed and the transition to the lower gear will be much smoother.

Double clutching harkens back to the days before car and truck transmissions had synchronizers. A double clutching technique was one way to downshift without grinding the gears.

Your great grandpa would push in the clutch pedal on his beloved Hupmobile and shift from third to neutral. At this point with the car coasting along at 20mph the drive shaft would be spinning all the gear halves connected to the transmission’s output shaft. However, with the clutch pedal pushed down the transmission’s input shaft and all the gears connected to it, would stop turning. Leaving the gear lever in the neutral, g-grandpa would release the clutch pedal reconnecting the engine back to the transmission input shaft. Taking careful note of the road speed, g-grandpa would skillfully raise up the engine rpm so that both halves of the gear set would be now spinning at about the same speed. He would now push in the clutch and quickly shift the gear lever down to second gear, effecting a perfect silent shift. This technique used two complete (or double) clutching operations for a shift.

By the fifties cars had adopted synchromesh devices (pioneered by Porsche) to handle the job of getting the speed of both sides of the gear set synchronized for smooth silent shifts. This still didn’t prevent great grandpa from yelling at his dimwitted son (your grandpa) for abusing the transmission in his beloved 1954 DeSoto.

In keeping with family tradition your grandpa probably yelled at his son (your dad). If your father ever finds himself too busy to reprimand you, please tell him that we here at the forum are always available to fill in.

Clon3

Thanks for the clear explanation Jenn. So during a double clutch operation, does it matter when you blip throttle? Can you blip just right before you release the couch the 2nd time or does it have to be in neutral with the clutch out?

Was wondering when the tranny input shaft speed takes affect.

winchman

It has to be blipped while the transmission is in neutral with the clutch engaged (pedal up).

0jiggy0

iTrader: (13)

Jennifers post is excellent and amusing. Every other post is ****ing stupid and useless. Damn canucks.

Clon3

Thanks, this was the main answer I was looking for. I didn't know there was a difference between:

1. Reving engine with clutch in.
2. Reving engine in neutral with clutch out.

winchman

Keep in mind that you don't need to have the clutch pedal all the way up when you blip the throttle. Since you're only transferring enough power to spin the input shaft, halfway up will probably get you enough engagement.

Trendkill

Whoa whoa whoa! This guy needs to learn how to drive a manual!!!!!
It's not cuz he's a hoser!
Damn Yanks.....

Jennifer 2

Clon3, the tools you need to learn about all this rev matching stuff are already in your Z, it’s the tach and speedometer.

When I was a young kid, my dad, who was a mechanic, had an ancient old 1963 Chevy convertible 327/4-speed. Well beyond heel & toe rev matching and double clutching, dad could also shift most of the gears in the Chevy without using Mr. Clutch pedal! He was a genius at knowing what engine rpm would match with what gear at any and every road speed. When I turned 16, Dad bought me an old MGB and to my horror and dismay he would also click it through the gears without using the clutch.

I was happy to have a cool little convertible to tool around in and wasn’t into any circus tricks with the shifting. However, I did learn to make the third to fourth shift naked & natural without the protection of the clutch pedal.

From experience I knew the exact engine rpm the MG made in forth gear at 30 mph. When in third gear I would accelerate up 30 and then when letting off the gas pedal I’d give it a little bump in order create a momentary bit of slack in the drive train. This allowed me to nudge the shift lever into neutral without much effort at all (no use of the clutch), and simply throttling the engine to the abovementioned rpm allowed a perfect smooth clutch-less shift into fourth.

If you want to try a little experiment get your Z rolling along at about 25 mph on a slight down grade. Shift into fifth gear (which being a one-to-one ratio) will be the easiest one to fool with. Take note of the exact rpm on the tach in fifth gear at 25mph. Now using the clutch, place the shift lever into neutral. Your only difficult job, is to now bring the engine back up to the magic rpm that matches 25mph, and this time without the use of the clutch, push the shift leaver back into fifth. Because the relevant gears are now spinning at the same speed the synchromesh will not have to do any work at all. It will be a revelation; it will be the smoothest most effortless shift you will have ever made in your Z. If you apply what you learn about rev matching to all your shifting (when using the clutch) the synchros in the transmission will last forever, as they will not have to do any work at all.

By the way, what part of Vancouver are you located in; I’m your neighbor just over the bridge in West Vancouver. Next Thursday is girl’s night out in Kitsilano, with the expected hot weather I’ll be driving over in my 350Z roadster with the top down. If you stop by, you could buy us all a drink.

Clon3

Hey Jenn,

Thanks again for the clear explanation. I am pretty familiar with downshift revmatch already and almost get it perfect everytime. Again, my main question was regarding whether blipping the throttle after putting the lever into gear was the same as blipping prior and I think I've found my answer.

I'm from the Burnaby area myself. Hopefully we'll meet up sometime.

Cheers!

Trendkill

Aww you two!!!!

BrazenZ

If I didn't know better I would think that some of our Canadian brethen are taking shifting tips from Vin Diesel in 1st "Fast and Furious". Guys it just a movie!

BonesZ33

iTrader: (2)

why