question about AT trans

[sonic370]

Can someone explain to me how or what is the full lockup feature on the 7at
sorry to sound like a newbie

[Vegitto-kun]

Full lockup feature?

Don't really know what you mean but if you mean locking up the gears.

It automatically downshifts around 1000 RPM but it does not automatically upshift. from what I noticed if you hit 7500 RPM the car just cuts all power .

[Jordo!]

Basically it creates a solid connection between motor and trans rather than just fluid coupling... result is greater power transfer.

This is why the AT and MT make about the same power on the dyno (I believe the AT is like ~1-2% less efficient than the MT, which is nothing)

Read more about AT's here Howstuffworks "How Automatic Transmissions Work"

[XwChriswX]

Originally Posted by Jordo!

Basically it creates a solid connection between motor and trans rather than just fluid coupling... result is greater power transfer.

This is why the AT and MT make about the same power on the dyno (I believe the AT is like ~1-2% less efficient than the MT, which is nothing)

Read more about AT's here Howstuffworks "How Automatic Transmissions Work"

I really hope this is not true considering when I was on the Dyno they recorded 248 rwhp (stock baseline) Which means a 25% tranny loss... I really doubt the 6MT has that much. Or perhaps is the issue because they ran the Dyno in 3rd gear... Someone Dyno smart on the 7AT please tell me thats not the gear you dyno it in...?!

[theDreamer]

Originally Posted by XwChriswX

I really hope this is not true considering when I was on the Dyno they recorded 248 rwhp (stock baseline) Which means a 25% tranny loss... I really doubt the 6MT has that much. Or perhaps is the issue because they ran the Dyno in 3rd gear... Someone Dyno smart on the 7AT please tell me thats not the gear you dyno it in...?!

His 1.2% is the difference between a MT and an AT, not from your flywheel HP numbers.
For a AT 7 speed I am unsure of 1:1.

[sonic370]

Originally Posted by Jordo!

Basically it creates a solid connection between motor and trans rather than just fluid coupling... result is greater power transfer.

This is why the AT and MT make about the same power on the dyno (I believe the AT is like ~1-2% less efficient than the MT, which is nothing)

Read more about AT's here Howstuffworks "How Automatic Transmissions Work"

thanks i will

[azn370z]

Originally Posted by Nissan North America
Explaining the benefits of Infiniti’s new transmission

The target: create an automatic transmission with all the best features of a manual transmission. Here’s how Infiniti engineering gives drivers the best of both worlds.


The automatic transmission traditionally represented a compromise. It gave drivers the convenience of smooth, clutchless shifting, but it sacrificed the direct connection, driver control, and enhanced fuel economy of a stick shift.

Infiniti’s new 7-speed automatic transmission, available on 2009 FX35, FX45, G37 Sedan, G37 Coupe, and the upcoming 2009 M35 (rear-wheel-drive), takes the automatic closer than ever before to the feel and operation of a manual transmission.

No More “Slush-Box”

Slippage between the engine and transmission earned early automatics the nickname “slush-boxes.” The hydraulic clutch system for making gear changes could not operate as quickly or directly as a manual transmission’s mechanical clutch.

All modern automatics have a lockup torque converter, which limits slippage by creating a solid mechanical connection between the engine and transmission. For smoother operation over a wider range of operating conditions, newer designs vary the amount of converter lockup (from a 100% solid connection to a partial lockup condition).

Infiniti’s 5- and 7-speed transmissions use a multiple disc torque converter lockup design that allows the unit to “ease” into lockup, minimizing the shudder that can occur in single-disc designs.

While Infiniti is not the first manufacturer to vary the level of torque converter lockup, it has created an extremely wide available lock-up range with the new 7-speed transmission:

With the transmission in Drive, partial lockup is available in 2nd through 7th gears while full lockup occurs in 7th.
With the transmission in manual shift mode, both partial and full lockup are available in 2nd through 7th gears.
Some amount of lockup occurs at all throttle positions and at speeds greater than about 15 mph. The result? Infiniti's 7-speed transmission provides a more direct, solid-feeling connection than drivers typically expect from an automatic transmission.

In manual shift mode, a flick of the 7-speed’s shift lever makes the half-second gear change a reality.

Driver Control

For driving enthusiasts, one of the lures of a manual transmission is the control it gives them to select and maintain the gear they want. Several features of Infiniti’s new automatic transmission directly address this concern.

One of the foremost is manual shift mode. Consider this: for anyone other than a seasoned race driver, it generally takes more than half a second to make a smooth shift with a manual transmission — depress clutch, move shift lever, release clutch, apply throttle.

But in manual shift mode, a flick of the 7-speed’s shift lever (or available steering-column-mounted paddle shifters) makes that half-second gear change a reality.

For smoother downshifting, Downshift Rev Matching (DRM) mimics the heel-and-toe maneuver used by skilled drivers during manual transmission downshifts.

The 7-speed design targets both performance and fuel efficiency.


The 7-speed includes other features first seen on Infiniti 5-speeds, including:

Adaptive Shift Control, which enhances gear selection by using a lateral acceleration sensor to detect changes in the road (such as hills and turns).
Drive Sport Mode (DSM), which allows the driver to select a more aggressive shift pattern (automatic up- and downshifting at higher rpm).
Combined, these features allow any driver to enjoy quick, smooth shifts and gear choices that are appropriate to both the road and their desired driving style — some of the enthusiast’s main reasons for choosing a manual.

Enhancing Economy

Automatic transmission vehicles typically suffer a small penalty in fuel economy estimates when compared to their manual transmission counterparts. Infiniti’s 7-speed design targets not only performance, but also enhanced fuel economy:

The wide range of torque converter lockup operation maximizes engine efficiency (less power is wasted as slippage).
In previous 5-speeds, only 5th gear provided an overdrive ratio. Now both 6th and 7th gears are overdrive ratios, allowing the engine to operate at lower rpm during a broader range of highway speeds.
Owners may not understand the penalties they have paid in the past for the convenience of an automatic transmission. But whether drivers want “hands on” or “hands off” control, Infiniti’s new transmission will provide a satisfying driving experience.

[cossie1600]

Ferrari and BMW's SMG are faster than a normal driver shifting a manual......

I drove an auto on my test drive, the unit is not anything special.

[Zsteve]

DSG is really nice, I had it on my Audi and it was a blast and super fast. I even got a chip for it to make it even faster.

[Jordo!]

Originally Posted by theDreamer

His 1.2% is the difference between a MT and an AT, not from your flywheel HP numbers.
For a AT 7 speed I am unsure of 1:1.

Exactly -- and those < 250 numbers must have been from a Mustang Dyno.

On the Website that Shall not be Named, it was a difference of 5 whp and 2 lbft of wtq between the MT and AT. That's pretty inconsequential

5th gear is 1:1, but I've been told to dyno in 4th... in 3rd gear there is some sort of a limiter, so not a good idea to dyno in 3rd.

EDIT: Yep.

On a superflow dyno (they dyno very low!)*
6MT = 261 whp and 212 lb/ft wtq
7AT = 256 whp 210 lb/ft wtq

Assuming 332 bhp
6MT drivetrain loss = ~21.5%
7AT drivetrain loss = ~22.75%

That's pretty awesome, especially considering the 7AT generally performs a little better in track tests of straight line acceleration.

I believe dynojet numbers on here for both transmissions will corroborate with that, although both will be in the 270's for whp.

EDIT: Going by dynojet numbers, I'd say drivetrain losses are between 16.5% and 17.5%, with no clear evidence of a difference between the 7AT and 6MT.

For sake of argument, assume the estimated 1%-2% difference at the most is probably about right, but curiously I only see any evidence of that difference in the midrange rather than at peak.
__________________________________________________

*Regarding which kinds of dynamometers skew realtively high or low, see further here:

http://www.newcelica.org/forums/show...56&postcount=1

and here: http://www.turbomagazine.com/tech/03...ash/index.html

[JACKPAC]

Originally Posted by cossie1600

Ferrari and BMW's SMG are faster than a normal driver shifting a manual......

I drove an auto on my test drive, the unit is not anything special.

Although not as fast a a DCT, the 7AT is also faster than you can shift manually. I found it not as quick as the BMW, but actually found it more responsive than the Audi DC.

[Z eliminator]

You dyno the car in 4th as you will hit the speed limiter in 5th.

[Jordo!]

Originally Posted by Z eliminator

You dyno the car in 4th as you will hit the speed limiter in 5th.

Ah, cool -- thanks for confirming that

Say, while your here, what did you put down again stock and what kind of Dyno?

We don't have an offical dyno database on here do we...? If not, we should see if AK will create one.

[jetguy]

good info on the 7at !!! thats one high-tech auto!

[Vegitto-kun]

Those half second shift are only when the oil is hot.

when I just started driving it and the oil is cold sometimes it changes quite sluggish

but damn it is quick on the track.

I have driven with my parents's GT-R before and that AT isnt that much faster.

and 2nd to 3rd is ******* harsh and I love it.