Those numbers you posted omen68 are fantastic!!! Great to shove in peoples faces.....provided an argument ever ensues.
We're still slightly on top....

 

who cares how much hp that G35c has, I bought my Z for the looks, and the heritage.. not for how much hp it has.. You can always slap on couple of bolt-ons to surpass that 300hp flywheel mark..

The only car I am waiting for is the Skyline GT-R!

 

that's for the coupe, not the sedan.

 

No, it isn't, at least if you're not a mechanical engineer. Some of us, like vinnay, are on this forum not to impress everyone with what we know, but to learn from those who know stuff we don't. Those who help explain things are much appreciated, and that's most people on this forum, but one of my pet peeves is a post that add nothing to the discussion but to insult a previous poster w/a question, i.e., "You don't know the answer to that already? You must be stupid."

I don't claim to be the brightest bulb in the pack, but I'm not an idiot. I have a doctorate, but not in engineering, and I'm sure that a great many "shade-tree mechanics" w/only a high school education but a lot of intelligence know a lot more about cars than I (and guys like vinnay) do. Some of the brightest engineering types on this forum use atrocious English, but their grammar isn't usually subject to insults (nor should it be), so why are those who admittedly don't know it all about automotive engineering and mechanics flamed?

As for vinnay's legitimate and reasonable question, I was wondering the same thing, and would appreciate an understandable tutorial for the layman from someone who knows exactly what downshift rev matching is in the manumatic context, and what the practical advantages are of the new tranny.

Quite often, generic common sense doesn't help in matters scientific. For example: common sense tells me that SOMETHING'S gotta be matched in the tranny for a shift to take place to begin with, otherwise the gears would grind; isn't rev matching what synchros are for? How can my '04 5AT pull off a downshift at full throttle w/o rev matching (some have posted that you need to let off the throttle a little for a downshift, but I have found mechanical speed to be the limiting factor as to whether the tranny will permit a downshift, not whether the accelerator pedal is fully depressed)?

Thanks in advance for someone willing to help teach those of us who don't know something.

 

I think if your foot is off the gas and you select to downshift the car will blip the throttle then downshift. I wonder if this is the first automatic to feature this.

 

Hypothetical: Lets say youre in 4th gear @ 2500rpms, and youd like to downshift to 3rd. If you WERE to Downshift, it would put you @ 4500rpm (again, this is an example). What the Tranny does is Rev to 4500 prior to the downshift so the downshift itself is more comfortable and much less felt.

this Had BETTER be a flash upgrade for us 03-04-04.5 owners, and if its not, That just SUCKS.

 

Revmatching on a downshift, as above, is when the engine spools up to meet the same shaft speed of the driveshaft/transmission.

Synchros are in a MT to get the gears to mesh quicker, so you don't have to double-clutch (one to N, one into gear). Automatics do not have synchros, or a clucth.

Rev-mathcing is about matching rotational speed, not selecting a gear. When shifting, there is a transition where one side of the engine/driveshaft pairing is spinning faster than the other. The clutch plates (in an MT) allow a smooth transition to make the shafts spin the same speed through friction. Notice, when you slip the clutch, it is a smooth shift, whereas when you pop the clutch, it is more violent--that is the engine shaft speed and the driveshaft speed equalizing. Revmatching (blimping the throttle during a downshift) makes this much smoother, not to mention easier on the clutch plates (less friction and wear).

Now, an automatic works slightly differently and uses fluid and a torque converter instead of a clutch, but its the same principle. See howstuffworks.com for more info on how auto transmissions work. They are much better at explaining (and much smarter) than me.

The torque converter. Notice the usually violent reaction when it does--that is the engine and driveshaft matching speeds. The greater the difference in speed, and the quicker the shift, the more violent the reation. Rev-matching allows this to be much smoother.


THE BOTTOM LINE
In short, revmatching will make for a much smoother downshift. Nothing more, nothing less.

But, this is a huge advantage, especially when you want to downshift as you are entering a turn. A smoother shift will not upset the back end like a violent buck from a "normal" AT will.

 

Very good information. and like I just said, This **** had &%$*&(% BETTER be an Upgrade option for us poor 03-04-04.5 Bastards.

 

I was talking about this with a friend last night, and he mentioned that this sounds a little like SMG (sequential manual gearbox) which would be the BMW equivalent. Anyone wanna take this one on?

 

Thanks lots, Rampant, both for the great answers and the direction to howstuffworks.com website. Exactly the place for non-techie types like me to get a fundamental idea as to, well, how stuff works. Thanks again.

BTW, as a practical matter, I realize after reading the above posts that I HAVE been rev matching by blipping the throttle when downshifting, but only in turns, for the very reason you mentioned, to keep the rear end from getting loose.

Also, would it then be easier on the tranny/drive shaft/rear gear to allow the tranny to downshift on its own when decelerating from 5th to a full stop in manumatic mode, rather than running down through the gears "manually"?