[Jeroen]

Just to add: Technically speaking, be it a petrol or a diesel turbo charged engine, the turbo is always spooling. Even when your engine just idles the turbo is spinning around!

There is another thread on whether turbo charged engines are more FE then non-TC engines. I've said my piece there. This is slightly different topic of course; under what conditions, do you get the best FE out of a Turbo charged engine. In general, and in this thread, the way I read it when discussing FE we are looking at something like MPG, i.e. what distance we get per unit of volume fuel.

What is being discussed in the last few posts is the most optimum shift point. Which makes the definition of Fuel Efficiency a very different one. Because then we need to look at things such as how much kinetic energy was created per unit of fuel or how much acceleration was created per second or by fuel volume?

You can't really say that shifting at a particular point (RPM) is the most optimum from a FE, without also defining how quickly of slowly you are accelerating. Do you floor the pedal and shift at 2100 RPM, or do you very slowly press the accelerator? This is more your driving style. In general, the driving style has a far more pronounced effect on FE then shifting at a specific RPM. As long as you're shifting within the power band, the actual RPM at which you shift is less relevant and any effects on FE. About shifting near the peak torque, bear in mind that this is also the point where an engine use the most fuel per time unit! So whether that is actually the most FE in terms of fuel per distance unit, remains to be seen.

Also, on some engines extra fuel is injected around this performance point to help cool the combustion chamber and components. So that is never efficient perse. So, again doubtful whether that will also gives you the best FE in terms of fuel over distance.

In summary; the FE (expressed in MPG) is influenced by at least three factors: In descending order of impact, they are;

- Number of accelerations/deceleration on a given distance
(this is the main reason for big difference between city and highway mileage)
- Driving style (i.e. how heavy footed are you on the pedal? How quickly or
slowly do you accelerate each time)
- at what point (RPM) do you shift

There are of course a whole host of other factors that influence FE, some of them have been mentioned already. The above should be seen/read against the discussion around FE and what optimum shift moments are and what it does to FE expressed in fuel per distance.

To put it differently, yes the shift point has some influence, but the other effects (i.e. the first two bullets) have a much larger effect. You control your right foot and actually the number of accelerations/deceleration to some extent you control that as well. A defense driving style gives you much better FE too! Fewer and more gradual accelerations/decelerations though better anticipation!

Jeroen

[auto_enthusiast]

Hi all,

Need some advice from fellow BHPians. Mine is a 2012 figo TDCi done around 29k kms. The car is very well maintained and the services done regularly. Right from the beginning, the car has been giving me a mileage of around 12kmpl(sometimes maybe 13), whereas my friend's figo TDCi done around 73k kms gives a mileage of around 16-17 kmpl in the same driving conditions. I drive in a sedate manner, except for some rare sprints whilst overtaking. The traffic is generally moderate here in surat. I have complained at the A.S.S. but it is of no help. The next service is due in a few days. What could be the problem. Can the gurus pls help.

[wildsdi5530]

It is quite variable. I get 16-19 in bangalore. My brother in law gets 22-26 in his fiesta in tirunelveli. It's probably more a car to car variation. Sprints do reduce mileage.

[saadat1992]

Like wildsdi5530 said, its variable from car to car! Many of my friends' fiestas & figos give diff mileage. That's not the case with Ford alone. My Liva for instance gives me max 11kmpl in city with sedate driving & occasional sprints whereas fellow BHPians are getting somewhere between 16-17kmpl in city!
Point this out to the SA during the service, maybe they can come up with something that might improve the mileage.

[EFF-EIGHT-BEE]

At what rpm do you generally upshift? And what tyre pressure do you maintain? The TDCI engine of Figo has a very narrow efficiency range which is the cause of so much variation between different Figos, one has to drive in that narrow efficiency range in order to get best FE. Figo is happy between 1700-2200rpm, beyond which/below it, the FE reducing very drastically.

[ssjr0498]

Please don't consider this as a personal as I do not know how you drive!

Generally! What I have noticed is that people tend to lug a diesel engine more than a petrol. Simple reason, the diesels have more torque to carry the car through even while lugging whereas the petrol's are unable to do so!

Please understand, that though it is good to shift to higher gears as quickly as possible, the common mistake that we do when we read the above line is that shifting to a "higher gear as early as possible" does not mean driving in 5th gear at say 40kmph! Or likewise!

Driving sedately does not guarantee you good mileage!

The idea to get good mileage out of your car is to "accelerate slowly", shift at the most "optimum" rpm (pref in the meat of the torque band), never lug and then decelerate as gradually as possible.

Also,all of us need to remember that "mileage" is "inversely proportional" to the "pressing of the accelerator pedal"

[honeybee]

As suggested abive, do check the tyre pressure. Also if possible, switch cars with your friend and see if that makes any difference.

[auto_enthusiast]

Originally Posted by wildsdi5530

It is quite variable. I get 16-19 in bangalore. My brother in law gets 22-26 in his fiesta in tirunelveli. It's probably more a car to car variation. Sprints do reduce mileage.

Originally Posted by saadat1992

Like wildsdi5530 said, its variable from car to car! Many of my friends' fiestas & figos give diff mileage. That's not the case with Ford alone. My Liva for instance gives me max 11kmpl in city with sedate driving & occasional sprints whereas fellow BHPians are getting somewhere between 16-17kmpl in city!
Point this out to the SA during the service, maybe they can come up with something that might improve the mileage.

Agreed to your point that it varies from car to car but every thing being the same(all the components of the car, the driving conditions, etc), I personally feel that it should not vary that much. Even fellow BHPians here are getting in the range of 15-18 kmpl. Have complained it at the A.S.S., but there's not much they could do.

Originally Posted by EFF-EIGHT-BEE

At what rpm do you generally upshift? And what tyre pressure do you maintain? The TDCI engine of Figo has a very narrow efficiency range which is the cause of so much variation between different Figos, one has to drive in that narrow efficiency range in order to get best FE. Figo is happy between 1700-2200rpm, beyond which/below it, the FE reducing very drastically.

I generally upshift in the range of 2000-2400 RPM. Tyre pressure is always 32 psi.

Originally Posted by ssjr0498

Please don't consider this as a personal as I do not know how you drive!

Generally! What I have noticed is that people tend to lug a diesel engine more than a petrol. Simple reason, the diesels have more torque to carry the car through even while lugging whereas the petrol's are unable to do so!

Please understand, that though it is good to shift to higher gears as quickly as possible, the common mistake that we do when we read the above line is that shifting to a "higher gear as early as possible" does not mean driving in 5th gear at say 40kmph! Or likewise!

Driving sedately does not guarantee you good mileage!

The idea to get good mileage out of your car is to "accelerate slowly", shift at the most "optimum" rpm (pref in the meat of the torque band), never lug and then decelerate as gradually as possible.

Also,all of us need to remember that "mileage" is "inversely proportional" to the "pressing of the accelerator pedal"

I know what you mean to say regarding lugging of the engine, but as stated above, I upshift in the range of 2000-2400 RPM. Also, previously I had A Fiat Uno D with me for close to 10+ years and therefore I'm very well versed with diesel engines. With regards to driving characterstics, my Uno D gave me a mileage of 15+ in Mumbai traffic with 100% A.C.

Originally Posted by honeybee

As suggested abive, do check the tyre pressure. Also if possible, switch cars with your friend and see if that makes any difference.

Good suggestion though, but i have even switched the car with my friend's car, results being more or less the same.

[ramzsys]

How are you measuring fuel efficiency?

If indeed it is giving low FE, then get a ELM327 and use torque app and find engine load at idling- it must be 20% without AC, ~35% with AC.

Checking the diesel lines for leaks is also suggested; also better to check how wheels spinning freely after jacking up the car.

[ObsessedByFIAT]

I too had a Figo TDCi Titanium for exactly 2 years and 40K on odo. Always and each time I got atleast 20 kmpl. A few things I religiously followed and still do:
(You might already be doing some or all of these already, but doesn't hurt sharing!)
1. Do not upshift in haste to be in over drive. Diesel engines need more time to reach that "crusing" speed.
2. Maintain tyre pressure based on how much the car is going to carry. If my memory serves me right for single occupancy it is 28 PSI, whereas with a full house and luggage it is 32 psi.
3. Anticipate stops/slow moving traffic. Engine breaking does help in getting better out of your car.
4. maintain a comfortable speed where you just have to open the throttle sufficient enough to keep the momentum going. Keeping the engine always on boil has negative effects on efficiency.
5. Keep the car clean inside and outside. Especially outside. Reduces air friction.

If even after following the above basic things does not help, I would suggest taking it up with Service center guys.

HTH!

[auto_enthusiast]

Originally Posted by ramzsys

How are you measuring fuel efficiency?

If indeed it is giving low FE, then get a ELM327 and use torque app and find engine load at idling- it must be 20% without AC, ~35% with AC.

Checking the diesel lines for leaks is also suggested; also better to check how wheels spinning freely after jacking up the car.

I calculate it using tankful to tankful method. Can you pls elaborate what is ELM327 and suggest a good torque app. Will definitely check for leakage in diesel lines during the scheduled service.
With respect to the wheel spinning freely, I haven't noticed any bearing noise even at triple digit speeds.

Originally Posted by ObsessedByFIAT

I too had a Figo TDCi Titanium for exactly 2 years and 40K on odo. Always and each time I got atleast 20 kmpl. A few things I religiously followed and still do:
(You might already be doing some or all of these already, but doesn't hurt sharing!)
1. Do not upshift in haste to be in over drive. Diesel engines need more time to reach that "crusing" speed.
2. Maintain tyre pressure based on how much the car is going to carry. If my memory serves me right for single occupancy it is 28 PSI, whereas with a full house and luggage it is 32 psi.
3. Anticipate stops/slow moving traffic. Engine breaking does help in getting better out of your car.
4. maintain a comfortable speed where you just have to open the throttle sufficient enough to keep the momentum going. Keeping the engine always on boil has negative effects on efficiency.
5. Keep the car clean inside and outside. Especially outside. Reduces air friction.

If even after following the above basic things does not help, I would suggest taking it up with Service center guys.

HTH!

Noted. Thanks for the advice.

[ramzsys]

Originally Posted by auto_enthusiast

I calculate it using tankful to tankful method. Can you pls elaborate what is ELM327 and suggest a good torque app. Will definitely check for leakage in diesel lines during the scheduled service.
With respect to the wheel spinning freely, I haven't noticed any bearing noise even at triple digit speeds.

This thread will give you the details: http://www.team-bhp.com/forum/techni...dian-cars.html

And torque is available as both paid and free in android market.

The parameters that you need to monitor is engine temperature and engine load. Instant and average FE can also be monitored.

About the wheels spinning freely- it was to rule out any brake jamming.

[auto_enthusiast]

Originally Posted by ramzsys

This thread will give you the details: http://www.team-bhp.com/forum/techni...dian-cars.html

And torque is available as both paid and free in android market.

The parameters that you need to monitor is engine temperature and engine load. Instant and average FE can also be monitored.

About the wheels spinning freely- it was to rule out any brake jamming.

Even though the obd-onboard-diagnostics may help, it proves out to be a costly proposition. Any other way of diagnosing the cause.

[humyum]

Hey, That indeed is a low mileage for a diesel car and I know Surat, its not particular choke o block Mumbai town side type crowded with traffic.

32 PSI seems at about right when it comes to tyre pressure.

Since it's giving you this much mileage right from the start, I would be 99% be blaming the driving style for it because say when you got the car new, the air filter would be spanking clean, the intercooler too, clutch would be new, wheel bearings would be new, alignment would be right, so the only thing I can think of is the driving style. Hey, I don't mean to judge here, I am far from a perfect driver, but just giving the probable causes.

How about this ? Try shifting in city at around 2000 rpm tops, U don't need the pickup in slow city life. Of course, the Figo has a brilliant low end in diesel cars, so this would not lead to any lugging when u shift at 2000 rpm to another gear too.

Try this for the next tank and see what improves.

[ramzsys]

Originally Posted by auto_enthusiast

Even though the obd-onboard-diagnostics may help, it proves out to be a costly proposition. Any other way of diagnosing the cause.

http://www.youtube.com/watch?v=TBVdF_odrDQ

I don't know if fuel flow is displayed-it is displayed as FL i think- you can count it by comparing with another car.

You can monitor the exact coolant temperature also- both this may give an idea about what is happening/differing from your friend's figo.