[sreenivass]

I have changed my driving habits recently. I was using early shifts earlier for city drive like 1st gear 10-15 kmph, 2nd gear 30 Kmph, 4th - 40 kmph, 5th - 50 kmph.

Now I shift from 1, 2,3, 4 at: 20, 35, 45, 55 kmph. I definitely enjoy the improved pull (which I always did on highways), also seems like I am going to get better KMPL. Some how I can not understand the principle behind.

Is it like power delivery is more efficient at higher RPMs (also torque) causing better FE ? I was always thinking one should drive at minimum required pull/ torque (RPMs).

I am already past 140 KMs with less than a quarter tank consumed, hope its not fuel gauge playing games.

[anupmathur]

Originally Posted by sreenivass

Is it like power delivery is more efficient at higher RPMs (also torque) causing better FE ?

Exactly! There is a 'bowl shaped' curve for most engines' 'specific fuel consumption'. This figure is best when the engine is driven at the lower parts of the bowl (the most fuel efficient range) - too low an rpm for a given load OR too high an rpm both cause the FE to be poor.

[sreenivass]

Originally Posted by anupmathur

Exactly! There is a 'bowl shaped' curve for most engines' 'specific fuel consumption'. This figure is best when the engine is driven at the lower parts of the bowl (the most fuel efficient range) - too low an rpm for a given load OR too high an rpm both cause the FE to be poor.

The manufacturers seem to recommend early shifts in city traffic. May be we are expected to add that feel factor to decide what speed/ RPM is early for a gear.

[anupmathur]

Originally Posted by sreenivass

The manufacturers seem to recommend early shifts in city traffic.

Most of the Operating Instructions give only one table for gearshifts wrt rpm. However a lot of people tend to shift up too early under the mistaken notion that that will give better FE.
An engine in too high a gear for a certain load might manage to pull but is in an 'uneconomical' part of the operating range.
Yes, it would be good to judge by the sound. Try to develop a sense for where the engine sounds 'happy' or is 'singing'! Engines actually almost 'talk' to you.

[vasudeva]

FE decreases rapidly once speeds exceed 90-100 kmph. Peak FE is achieved at speeds of 35-60 mph (corresponding to speeds of 55-95 kmph). Here is the link:

Tips to improve your Gas Mileage

[ajrage]

i personally hv tried this and if the skoda octavia tdi 1.9 digital meter showing litres/100km is right then with the aircon on and at about a speed of 80-90 kmph i have sufficiently reached a mark of 4.5L/100km max. and and avg of about 5.5 to 6.5L/100km depending upon my mood lolz..

[gemithomas]

Turbo Sam could you please get me the torque chart for the FIAT 1.6 engine. I've been searching for it for some time now.

[sreenivass]

Originally Posted by gemithomas

Turbo Sam could you please get me the torque chart for the FIAT 1.6 engine. I've been searching for it for some time now.

There is a couple of them on the web. You could get links from palio users group india. Its a scanned copy of original manual. Its too big to mail or distribution may not be adviced.

Search fiat use pages for fiat marea workshop manual.

[sreenivass]

Here it goes, I am assuming 1596 16v (called 2000 Range torque is same as the one in Petra, Siena and Palio)

[img=http://img249.imageshack.us/img249/1924/62038282dg5.th.jpg]

[gemithomas]

thanks a lot sreenivass. I guess this is the same one on the Adventure.

Turbosam seeing this chart where do you think the spots would be for best performance and the best F.E

[TURBOSAM]

hi ,
there are two 1.6 engines 1580<siena,weekend> and 1596<pallio,petra,adv,stile> the 1596 engine has flat torque curve fron 2k to 3 k <around 123 Nm >where as old 1580 has steadily rising torque curve from 115 Nm to 138 Nm >
old engine has near perfect torque curve rising from 1500 to 6500 which has very slow drop 5000 onwards. power is 98 bhp
new engine torque flattens from 2.5-3 then rises dramatically from 3-4 k
ideally the old engine has more potential to give better milage.<hough marginally>
old engine has 4-2-1 exhaust system.
new engine has 4-1 ex manifold
ENGINE IS MOST EFFICIENT AS PUMP AS WELL AS HEAT EXCHANGER AT THE PEAK TORQUT RPM.
so in short engine will be producing max mechanical work in given amount of fuel<thats max volumetric eff and max chemically efficient range >
but when we talk about max kmpl terms- MINIMUM SAFE RPM WITH TALLEST RATIO WILL GIVE U MAX KMPL
U DRIVE AT 80 - 100 UL GET god milage.<got @ 16-18 in adv in a/c .

[TURBOSAM]

this dashara was suppose to go to pilgrimage to kolhapur and some other places tried 40 psi air in tyres<max recomanded 44 psi @ 350kgs>,radiator partially blocked<except the fan area>wheel alignment 00 when fully loaded, a/c from the begining .
driving only for milage<@80-90 kmph max possible distence on great quadrangle highway from pune to kolhapur .with family <240 kgs of total weight including stepney, tool kit ,excluding 3-4 tank of fuel.
i got 21kmpl in palio IN A/C

[gemithomas]

Originally Posted by TURBOSAM

old engine has 4-2-1 exhaust system.
new engine has 4-1 ex manifold

Does this add/negate the mileage figures or performance in terms of pickup/power delivery

Originally Posted by TURBOSAM

but when we talk about max kmpl terms- MINIMUM SAFE RPM WITH TALLEST RATIO WILL GIVE U MAX KMPL
U DRIVE AT 80 - 100 UL GET god milage.<got @ 16-18 in adv in a/c .

Does that mean below the 2200rpm mark just before the torque curve flattens for some time?

Or should it be at this flat spot where the power keeps increading but the torque remains more or less constant?

Just confused about the TALLEST RATIO aspect!!

[chetanhanda]

Originally Posted by gemithomas

Does this add/negate the mileage figures or performance in terms of pickup/power delivery

Does that mean below the 2200rpm mark just before the torque curve flattens for some time?

Or should it be at this flat spot where the power keeps increading but the torque remains more or less constant?

Just confused about the TALLEST RATIO aspect!!

To get best mileage u need to drive with the lowest rpm in the tallest gear possible.

I dont know why everyone is searching for torque curves ? You dont need to see a torque curve chart in order to understand when to shift gear for best mileage... Just see how low you can allow the speed to drop without stressing the engine, after a few minutes of experimenting u get the feel of the engine as to how low the gearing will allow u to go.

Even if u are driving the car for the 1st time - shift to 4th and leave the throttle, let the revs drops, then try to see how comfortably the engine picks up with mild throttle just enough to keep the car cruising along... then just stick to that throttle input.

For long flat stretches/freeways try it with your overdrive and for city try with everything apart from overdrive.simple.

You need minimum the torque if u want max mileage, in terms of gear ..think of it as higher/taller gears with lowest rpm give best mileage..

[anupmathur]

Originally Posted by chetanhanda

To get best mileage u need to drive with the lowest rpm in the tallest gear possible.

Very difficult for a lay person to decide.
Too many people are driving at too low rpms in too high a gear and getting bad FE figures. The engine is being operated in it's 'inefficient' range from the FE viewpoint/specific fuel consumption viewpoint. Solution? For the Average Joe: the middle path, courtesy Gautam Buddha!