Ford Fiesta MPG review Man vs Auto

[EdKiefer]

Originally Posted by bestclimb

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.



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.

right , plus a marine engine you can never get it to lug or bog down as there no direct drive as you in water there always slippage or whatever you want to call it being propeller powered ,engine never gets loaded down at low speeds .
The problem is with small engine if you gear it to high (low final drive) is it just don't have the torque in low rpm to be geared like that . You would get a condition were you be at HW speeds and not allow you to be in high gear until a higher speed for best FE .

[tjts1]

Originally Posted by basslover911

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

The double clutch already does this when you take your foot off the gas unless you're braking.

[comptiger5000]

Part of the auto vs manual gearing difference is also to cater to driver laziness. Most don't want to downshift for every little hill on the highway, so they gear it a little lower for the manual.

[endurance]

Originally Posted by comptiger5000

Part of the auto vs manual gearing difference is also to cater to driver laziness. Most don't want to downshift for every little hill on the highway, so they gear it a little lower for the manual.

That's what I suspect is the primary motivation of car companies. Anyone who test drives one, puts it in fifth or sixth, and steps on the gas and doesn't feel acceleration is going to complain that it's gutless.

[tjts1]

Originally Posted by endurance

That's what I suspect is the primary motivation of car companies. Anyone who test drives one, puts it in fifth or sixth, and steps on the gas and doesn't feel acceleration is going to complain that it's gutless.

Yup. So in the real world the automatic ends up being more efficient.

[rmay635703]

Originally Posted by tjts1

Yup. So in the real world the automatic ends up being more efficient.

Except on my cobalt, most hondas, all geos for example which all do get better with a manual.

[tjts1]

Oh I'm sorry. I didn't realize the title of this thread was 'My Cobalt, Most Hondas, All Geos MPG review Man vs Auto.'. My bad. Please continue.

[rmay635703]

Originally Posted by tjts1

Oh I'm sorry. I didn't realize the title of this thread was 'My Cobalt, Most Hondas, All Geos MPG review Man vs Auto.'. My bad. Please continue.

I would assume if I were to be driving a Fiesta MT that statement would expand to my Fiesta also. Since I've never had an MT of a vehicle ever get worse mileage than an auto of the same vehicle.

But I also don't drive normally either.

[Nevyn]

I've posted the gear ratios multiple times. There's a BIG difference between the 5MT and 6AT - think of one as "sport" and one as "eco."

Fiesta Ratios:

5MT:

1st 3.846
2nd 2.038
3rd 1.281
4th 0.951
5th 0.756
Reverse 3.615
Final drive 4.07 to 1


Optional PowerShift™ 6-speed automatic
1st 3.917
2nd 2.429
3rd 1.436
4th 1.021
5th 0.867
6th 0.702
Reverse 3.507
Final drive 3.895 for gears 1, 2, 5, and 6. 4.353 for gears 3, 4 and R

[comptiger5000]

Typically, the MT will get better mileage around town (with an efficient driver). It's on the highway at steady speed where the gearing difference comes into play.