Ford Fiesta MPG review Man vs Auto

[EdKiefer]

Originally Posted by basjoos

The Chevy Cruze comes with a either a 6 speed manual or a 6 speed dual clutch automatic, both with the same gear ratios and the manual gets 4 mpg better city and 1 mpg better highway mileage. From your description above, the dual clutch automatic goes into 6 gear engine braking whenever you let up on the throttle rather than the no drag freewheel that's available with just the touch of the clutch pedal on the manual. And with freewheel easily tapped, it is a lot easier to hypermile your way to even greater mileages than the EPA stickers would show. They've sold a lot of manual Cruzes overseas, so it must be enjoyable to drive.

I have very tall gears on my manual Honda Civic CX and manual Ford F150 and have no problems or frustration driving them.

Acording to Chevy site the Cruze LS (1.8L ) 6 speed manual gets 26/36mpg and the Cruze LT, LTZ with 6 speed DC auto gets 24/36 but have turbo 1.4L engines with fatter TQ #'s

[basjoos]

That mileage comparison isn't valid since the two cars being compared have a different transmission and engine. The EPA mileage figures I saw were 26/36 mpg with the base 1.8-liter four-cylinder and a 6 speed manual and 22/35 mpg for the same engine with the 6 speed automatic.

[endurance]

So if there's no torque converter and no transmission oil pump in the auto, why couldn't you turn the engine off in neutral? I thought the reason you couldn't/shouldn't turn off the engine in an auto was because it stopped the flow of oil in the transmission, thus, you had an unlubricated driveshaft end of the transmission.

I'm not claiming you can, I'm just curious if I understand correctly.

BTW, this is the first American-made car that has piqued my interest in the last 20+ years (since I sold my hotrod). Not to say I haven't owned a half-dozen Chevy/GMC pick ups and Blazers in that time, but they were tools of necessity rather than something that actually interested me.

[ShadeTreeMech]

I agree that Detroit has mad a lot of uninteresting vehicles for many years. Thankfully Ford seems to be doing a good job of improving the quality and value of their vehicles.

Bassjoos did make an excellent point about the differing gear ratios. The tallest overdrive gear ratio I've ever owned was in an automatic; for the life of me I can't understand why car makers can't put taller gears into manuals as stock. I know the 6 speed in the Corvette has a ridiculous overdrive (.50 to 1 IIRC) which allows the Corvette to get amazing fuel economy on the highway when cruising, as in around 30 mpg!

[d0sitmatr]

Originally Posted by ShadeTreeMech

I agree that Detroit has mad a lot of uninteresting vehicles for many years. Thankfully Ford seems to be doing a good job of improving the quality and value of their vehicles.

Bassjoos did make an excellent point about the differing gear ratios. The tallest overdrive gear ratio I've ever owned was in an automatic; for the life of me I can't understand why car makers can't put taller gears into manuals as stock. I know the 6 speed in the Corvette has a ridiculous overdrive (.50 to 1 IIRC) which allows the Corvette to get amazing fuel economy on the highway when cruising, as in around 30 mpg!

most likely as with an auto if it starts to bog on you, the trans downshifts, with a manual, you could end up damaging the engine if you refuse to downshift.
thats the best reason I can come up with.

[skyl4rk]

Originally Posted by euromodder

BTW the Fiesta Econetic (diesel) version, is rated for 3.7 L/100km or 63.6 mpg US in the Euro cycle !

Aargh rub it in!

[Leadfoot]

Originally Posted by d0sitmatr

most likely as with an auto if it starts to bog on you, the trans downshifts, with a manual, you could end up damaging the engine if you refuse to downshift.
thats the best reason I can come up with.

If they built it with special piston rings and cylinders as they do marine engines, then you could bog that motor down all day. I believe marine engines also use special bearings.

[rmay635703]

Originally Posted by Leadfoot

If they built it with special piston rings and cylinders as they do marine engines, then you could bog that motor down all day. I believe marine engines also use special bearings.

Modern engines like my cobalt 2.2 won't bog like antiques because the computer doesn't allow it, I have driven off from 500rpms with rather minor bog, it just doesn't take off efficiently doing that.

I find it odd my 5sp cobalt is rated higher than the 6sp cruise, should have put in a double overdrive instead of short shifter me thinks.

[bestclimb]

Originally Posted by d0sitmatr

most likely as with an auto if it starts to bog on you, the trans downshifts, with a manual, you could end up damaging the engine if you refuse to downshift.
thats the best reason I can come up with.

Someone would have to be pretty brain dead to not understand what the engine is telling you long before you can do any damage. I can do the same thing <20mph in 5th in most cars.

Originally Posted by Leadfoot

If they built it with special piston rings and cylinders as they do marine engines, then you could bog that motor down all day. I believe marine engines also use special bearings.

Not so much. A marine engine is built to run at a higher power setting for long durations. As in 80% load at 3500 rpm. They use heavier duty bearings, better internal oiling, and increased cooling to deal with the higher internal temperatures and higher average stresses that they are submitted to continuously.

The bogging and chugging you get when you lug an engine is due to the spark happening before top dead center, and with lower speed the piston is not far enough past top dead center when the pressure of the expanding fuel charge is increasing. So instead of adding a push down the burning fuel charge puts a stopping pressure on the piston and the momentum of the engine and previous combustion in other cylinders forces the "lugged" cylinder over the top and down.

This increase in resistance coupled with low oil pressure (because the engine driven oil pump is not turning very fast) causes the rod bearings to squish all the oil out and the bearing surfaces come into contact.

A marine engine with better bearings can withstand this for longer (though it would not likely be subjected to this as water is a viscous medium to transmit power to rather than a tire/road interface) but it is still bad for it.

[basslover911]

Originally Posted by endurance

So if there's no torque converter and no transmission oil pump in the auto, why couldn't you turn the engine off in neutral? I thought the reason you couldn't/shouldn't turn off the engine in an auto was because it stopped the flow of oil in the transmission, thus, you had an unlubricated driveshaft end of the transmission.

I'm not claiming you can, I'm just curious if I understand correctly.

I want to know this too... or if you can just pop it in neutral (since in this case it would be "true" netural)