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-   -   New 9-speed General Motors transmission boosts fuel economy 2% (https://ecomodder.com/forum/showthread.php/new-9-speed-general-motors-transmission-boosts-fuel-34620.html)

MetroMPG 12-06-2016 01:20 PM

New 9-speed General Motors transmission boosts fuel economy 2%
 
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Some automakers love CVT's (looking at you, Nissan); others (and most auto journalists) don't.

Adding more gears to conventional slushboxes seems to be the way the CVT-haters are headed.

Tasty bits, from the Detroit Free Press:

Quote:

GM spent lots of time refining the gearbox for smooth shifts and to work well with fuel-saving stop-start systems. The transmission has a slightly wider ratio spread than the six speed — 7.6:1 versus 6.0:1 — but gets most of its fuel-efficiency improvement from allowing the engine to run at its most efficient level more of the time. The transmission stayed in ninth gear up to 52% of the time in fuel-economy tests, engineer Scott Kline said.

The transmission is already on 2017 Chevrolet Malibu midsize sedans with 2.0-liter turbocharged engines. It will be available on Chevrolet Cruze compact with diesel engines early in 2017, and on the 2018 Chevrolet Equinox compact SUV later next year.
Full article: 9-speed transmission boosts Chevrolet fuel economy 2%

I've never driven a 9-speed, but have personally heard people complain about the shift quality of the Fiat/Chrysler ones: shift quality and seeming never to get into top gear.

cRiPpLe_rOoStEr 12-06-2016 08:20 PM

Quote:

Originally Posted by MetroMPG (Post 528633)
I've never driven a 9-speed, but have personally heard people complain about the shift quality of the Fiat/Chrysler ones: shift quality and seeming never to get into top gear.

I also never drove any 9-speed, but now the Fiat Toro became available with the same 2.4L Tigershark engine of the US-spec Ram ProMaster City and the 9-speed transmission that was previously only available with the Diesel engine, so I might get a chance to test-drive it.

MetroMPG 12-06-2016 09:33 PM

Let us know what you think.

One complaint from a fuel economy angle was the top gear would only engage under the lightest possible throttle. Which means almost never for most drivers?

ksa8907 12-06-2016 09:36 PM

2% How do you accurately measure that? Im going to guess that will be completely lost in real world driving.

MetroMPG 12-06-2016 10:00 PM

On the dyno, running the EPA test cycles is my guess.

More gears ain't bad if they increase the spread, which they've done in this case. (Lower cruising RPM.)

What bugs me is when they add more gears, but the top ratio is basically unchanged... though maybe that's more of a manual gearbox phenomenon.

jakobnev 12-07-2016 06:03 AM

Personally I prefer 1-2-3-4-5-INFINITY!

LittleBlackDuck 12-07-2016 06:31 AM

Quote:

Originally Posted by jakobnev (Post 528715)
Personally I prefer 1-2-3-4-5-INFINITY!

Nah! Toyota/Lexus hybrid = infinite gears...

Simon

Frank Lee 12-07-2016 08:41 AM

I suppose more gears makes sense if one is engineering for the EPA test, or hilly or urban/suburban stop-n-go stoplight Gran Prix.

As a small-town flat lander, I still like the notion of a three-speed stick, direct drive top "gear" and tall enough final drive to negate the need for overdrive. Because as a percentage of time, accelerating = minute while steady-state highway cruise = vast majority and I don't want any energy being wasted on spinning a bunch of gear sets that aren't doing anything.

MetroMPG 12-07-2016 09:24 AM

^ Do any of the vehicles in your fleet match that description?

Stubby79 12-07-2016 10:34 AM

I've driven an 8-speed, over-sized pickup truck a couple of times. Basically, with my light foot, the engine never changed RPMs after coming up from idle/giving it a bit of gas. It just let the torque converter accelerate the truck, then switched gears before letting the engine spin up any faster. Up and up through the gears at all of 2k rpm, even out on the highway.

Of course, it had plenty enough torque behind it to do that.


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