Ford Fiesta trannys

[Sludgy]

The Ford Fiesta 6 speed automatics are rated at 38 (or 40 in "SFE) trim) hwy mpg, but the manual tranny models are 37. This is the first time I remember slushboxes with better mpg. Anybody know why?

[Jay2TheRescue]

I've noticed that with a few of the new model cars coming out, the auto is often within 1 or 2 MPG of the manual, and sometimes its better. I've also noticed that in some model cars, the manual is only available on the sport model with the biggest engine, and gets far worse mileage than the base model with an automatic.

[theholycow]

It's becoming more common and I think it will soon be universal.

New automatics have more and better ratios, better control of the torque converter clutch, better computer programming, etc. They also get all of the R&D money so they get better materials, better attention to friction loss, etc.

Too many manual transmissions seem to be missing a real highway gear.

Additionally, being able to program it for the EPA fuel economy test has got to be an advantage over letting EPA procedure or a driver's judgement be in control of gear choice during the test.

I think hypermilers will continue to get better fuel economy from manuals than automatics.

[Jay2TheRescue]

Originally Posted by theholycow

I think hypermilers will continue to get better fuel economy from manuals than automatics.

It just means you have to work harder

[kamesama980]

From my knowledge of how companies work and how I'd do it if I were them and didn't care about the minority that like manuals...

not enough people want manuals to make it worthwhile except to reduce complaints. Less money coming in because of them means no R&D and no new transmissions. no new trannies means no new gear ratios. on the other side of the office, the autos are getting redesigned every few years because 98% of cars sold have them. lower highway gears, more efficient converters, etc (as mentioned above). People are stupid and can't downshift or don't want to rev the engine up to pass someone so the manual's highest gear is usually positioned to be pretty low whereas the auto can revmatch 2-3 gear downshifts perfectly and you just accelerate smoothly. so you end up with the auto turning 1400 rpm at 65 like a 6 speed f-body and the manuals doing 2300 so you can accelerate w/o downshifting, killing your mpgs.

I'm waiting for warm weather and a long break to swap the new transmission into my cressida for the same reason. automatic OD was .705:1, current 5-speed has .86:1 and gets the same mpgs. the manual I'm replacing it with is the one I wanted originally with a .78:1 5th (and the one I have is on it's way out)
At 60mph:
auto: 2100 rpm
W58: 2300
W57: 2600

oh yea, and I can drive around town at 30 mph in 5th at 1100 rpm. OD is very much a passing gear for me.

[theholycow]

Originally Posted by kamesama980

oh yea, and I can drive around town at 30 mph in 5th at 1100 rpm. OD is very much a passing gear for me.

Word...my VW was just like that. 3000RPM on the highway when 1800 would have been much more efficient (and heaven forbid I'd have to downshift to pass while climbing a hill!).

[Jay2TheRescue]

I wonder what the gear ratios for the manual tranny in the Chevy Cruze ECO model coming out in January are? I wonder if the ratios are optimized for economy on that manual. I'm curious to at least test drive one.

[trollbait]

Automatic also covers several systems beyond the standard automatic transmission people think of. Slushbox may not even apply to some of them. The US Smart is a manual that is just automated. The Fiesta uses a dual clutch tranny. The clutches might even be dry, as opposed to the wet ones in the VW DSG.

[bobc455]

Lockup torque converters are a major part of what has brought AT efficiency up in a major way, almost as efficient as a manual. Doesn't surprise me that you could surpass the efficiency of a manual with some changes (i.e. taller final drive ratio or whatever).

-BC

[GasSavers_Erik]

Even with a locking torque converter, an auto trans will still have have the extra drag of running a pump to maintain 80-100 psi of fluid pressure to keep the clutch packs from slipping.

If the gear ratios were identical, the manual trans ought to outperform the auto out on the highway.