New 9-speed General Motors transmission boosts fuel economy 2%

[Frank Lee]

Not quite. I suppose the closest is the Escort diesel with 4-speed m/t. In the '80s the Ford eco-trans was the 4-sp more than the 5.

Back in the day I had a few Chevys with 3-on-the-trees; plenty good.

[cRiPpLe_rOoStEr]

Even though the city where my mom lives is quite hilly, I still believe a 4-speed transmission with a direct-drive top gear and a wider gear spread and a higher differential would be better than the stock 5-speed fitted in her Toyota Etios. Anyway, considering that more gears end up increasing the manufacturing cost while the Etios is supposed to be a no-frills model, it did surprise me that the updated versions got a 6-speed manual even though the recently released automatic ones still rely on a 4-speed transmission.

[LittleBlackDuck]

Originally Posted by Frank Lee

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.

Nope. The more gears, the more time the engine spends in its most efficient load / speed band. This allows for tuning the engine to be more efficient over a narrower band of revs, better using things like resonant tuning of inlet and exhaust. This is part of how the Toyota / Lexus hybrid piston engines are optimised.

Simon

[Frank Lee]

Nope. As noted my usage is mainly cruise.

[Gasoline Fumes]

I could use a few more gears. I have a CRX HF trans. It takes a lot of clutch to get my Wagon going, especially starting up a hill. And I want a taller final gear. 2000 RPM feels too high at 65 MPH!

[LittleBlackDuck]

Originally Posted by Frank Lee

Nope. As noted my usage is mainly cruise.

Even at cruise I doubt you will hold exactly the same speeed forever. Couple this with hills and a CVT can add to the overall efficiency. Adding in the extra speeds will always have a gain - it may be small but it will be there.

When not at cruise the gains will be bigger.

Simon

[kafer65]

Originally Posted by Gasoline Fumes

2000 RPM feels too high at 65 MPH!

Yeah! I've got 6 and still feel like I need a much shallower final drive ratio to get the rpms down at highway speed. I definitely need the first three about where they are at full beans and light load shifting. I tend to skip shift after that. I guess a 5 spd with the last two for low and really low rpm highway I believe I could be getting 42 mpg at 65 mph if I could get the rpms down at least 500 rpm.

[Frank Lee]

Direct Drive or Overdrive? Direct Drive or Overdrive?

Yes, direct drive makes the most sense for some of us.

[oldtamiyaphile]

Originally Posted by LittleBlackDuck

Even at cruise I doubt you will hold exactly the same speeed forever. Couple this with hills and a CVT can add to the overall efficiency. Adding in the extra speeds will always have a gain - it may be small but it will be there.

When not at cruise the gains will be bigger.

Simon

It's not that simple of course.

Some GM V8's force you to shift 1-4-5-6 in an effort to improve economy - sixth is never used in official tests (at least the NEDC has never been updated to account for six speed manuals). In essence, a Corvette on the NEDC is a three speed.

Skip shifting is a valid Eco driving technique. I skip shifted (1-3-5) my Renault Kangoo in 100% city use (20mph average speed) and scored a best ever tank of 75% over NEDC. Skip shifting increases average engine load which beats 1-2% gains on official test cycles.

[cRiPpLe_rOoStEr]

I didn't skip-shifted so frequently because it's an eliminatory fault in the Brazilian driving tests, and because much of the cars I drove had low-output 1.0L engines. And since I usually drive accompanied by either my dad or my mom (I don't tend to drive so frequently when I'm in my hometown), they would freak out.

Originally Posted by LittleBlackDuck

The more gears, the more time the engine spends in its most efficient load / speed band. This allows for tuning the engine to be more efficient over a narrower band of revs, better using things like resonant tuning of inlet and exhaust. This is part of how the Toyota / Lexus hybrid piston engines are optimised.

Priuses and other hybrids from Toyota and Lexus actually don't even have a transmission at all, relying on the constant torque of the electric motor to emulate the behavior of a CVT.