Gunrun

so when I am in 3rd and go to 2nd so I can hear the exhaust the tac will go to like 3000 rpm or higher and jerk the car? I thought rev matching a avoids that? If the car jerks forward like it does I was told it is bad for the car? Remember I have an A8 and of course this is using the paddles so it jerks forward and slows down the car.

Foosh

This is a thread about the auto rev matching feature in the M7. I can't figure out why A8 people are jumping in here. What the A8 does is irrelevant to this discussion.

pdiddy972

Thanks, Nissan!

pdiddy972

Why wouldn't it? My 2013 370Z with 7-speed automatic had it.

JerryU

Rev match reduces wear on the clutch disk. If you don't you're asking a slipping clutch disk to increase the engine speed to match the car speed when you chanage to a lower gear, i.e. when making a turn to another road.

Been driving only standard shifts as my DD for over 50 years. Good at heel toe at higher rpm's when driving aggressively. Have done that where the peddles were not laid out to accommodate as they are in a Vette.

However at low rpm's it's harder to modulate the throttle to get a perfect match. Here is an example. I live off of a 65 mph 4 lane divided highway and turn into our 25 mph road. It starts as a narrow single lane around a 70 foot diameter circle with a fountain. Traveling at 5th gear at 1500 rpm I need to be in 3rd at 3000 rpm after the turn. I put it directly in that gear before making the turn. In my C6 and modified S10 truck I used heel-toe and got a perfect half the time! Rev match does that perfectly every time.

When on the Interstate in 7th and leaving on an off ramp, same issue. Need to go from ~1300 rpm in 7th to ~2800 direct drive in 4th. Just shift there directly. A perfect rev match makes it very smooth. Note the shiftier springs are set for that 7th to 4th shift, just pull back lightly and the springs bring it to 4th. It's also good for passing 18 wheelers to limit exposure to their flying rocks! The C7 has an interesting feature. After a 7th to 4th shift to pass an 18 wheeler quickly etc, when you shift back directly to 7th, if on cruise control it will reengage automatically. No need to push a resume button. Never had a standard shift that did not disengage cruise control when the clutch was depressed.

I find it most useful for normal driving, especially having 3 overdrives where there is no need to row through all the gears when downshifting. Best thing since syncromesh!

pdiddy972

Well you're wrong; 370Zs have had rev-matching on both manual and torque converter auto trannies for a long time. Here's a video demonstrating it quite clearly.

Stangslayer

You are confusing Marketing Hype with reality! Unless you disconnect the transmission from the engine as in manual transmissions or DCT automatic transmissions there is no rev match due to the fact the engine and transmission are always connected. Don't confuse "blipping" the throttle with synchronization. That's why Nissan automatics can't hold a candle to DCT's in performance.

rbartick

My 2014 Infiniti also offers Rev Match with a standard 7-speed auto. It might be marketing hype, but it does work. With that being said I have no idea if the C7 offers this. My C7Z is an M7.

Woodson

Yes. Anybody that says they can get it perfect every time at low RPM's and under light braking is either a professional race car driver or is lying.

pdiddy972

It does disconnect the transmission (how do you think autos put the tranny in neutral if they're unable to disconnect the transmission?). You can clearly see in the video (and I know from driving it for over 3 years) that when you drop from, say 3rd to 2nd, the RPMs spike to the correct RPM before it engages 2nd. And the vehicle speed is not altered in the slightest, nor is the chassis upset. How could what you say be true and that occur if not for rev matching?

JerryU

Doubt even Mario Andretti could do it consistently at lower rpm's! He is used to doing it at high rpm's

Mashing the throttle with the side of your foot when your going to be near redline when you engage the clutch is one thing, a little bit off would be hard to detect. Shifting from 1200 rpm in 5th to 2800 rpm in 3rd when making a turn is much more difficult, as you note. Even if your brain could define the exact rpm, modulating the throttle exactly is difficult. Getting a perfect match manually will not happen every time. Rev Match does!

pdiddy972

? The thread is titled "Rev Matching" and nowhere in the first post does the OP even indicate whether he's referring to an auto or a manual, so why would that be derailing?

Foosh

Because anyone who reads the OPs initial post (quoted above), could only reasonably infer that he's referring to the M7, which is described on the window sticker, on the paddles, and elsewhere as w/ [auto] rev matching.

The A8 is not so described, and the paddles perform a different function.

Stangslayer

You obviously don't understand how a torque converter works.

pdiddy972

Well then explain how to reconcile your statement that in the auto the transmission is always directly linked to the engine, and the fact that, at least in the 370Z's case, it can and does blip the throttle/RPM before entering a lower gear without altering the car's speed or upsetting the chassis?

Stangslayer

Why don't you read up on how torque converters work, then you will not only LEARN something, but will understand about fluid dynamics?

JerryU

Ah yes, Fluid Mechanics 101!
How a Torque Converter Works: http://auto.howstuffworks.com/auto-p...-converter.htm

First paragraph: "But cars with an automatic transmission have no clutch that disconnects the transmission from the engine. Instead, they use an amazing device called a torque converter.

pdiddy972

^^^

Now maybe Stangslayer can explain why this means what the 370Z automatic is doing doesn't count as rev-matching (when it most certainly appears to, in every way that matters).