[a4anurag]

Originally Posted by mohitk1993

I think you meant something else, but ended up writing this . AFAIK, engine lugging is quite detrimental to the engine's health; you will not just end increasing your car's fuel consumption but could also damage the gears due to the constant slipping.

Sorry. My bad. I just missed a word i.e NOT

"The engine must NOT be lugged at the same time else efficiency drops"

Anurag.

[audioholic]

Originally Posted by smartcat

If you somehow manage to fit the Safari's engine onto a Swift, it should theoretically give you more mileage per litre of diesel than the 1.3 litre engine, on a stretch of say 100 km - because you can get the job done with the engine spinning at much lower RPM.

Here power required for running the swift(Just an example) at say 80kmph will be same whether you use its own engine or shoehorn an 2.2VTT Hence I think FE will be at the most equal, and not greater in the bigger engine unless the gearing is so tall that the engine will be at a very less speed at 80kmph compared to the multijet at the same speed.

Also in either of mine or Smartcats post, we will have to assume that maruti has not made any FE tweaks or so. Both engines running at ideal conditions.

[Raag Sandhu]

Being in Dubai, I have been lucky enough to experince and own some large and small engined cars as well. I felt that the larger engines i.e >4.5 litre V8was a more comfortable engine to work with considering the rpms never going higher than 2500 at decent highway speeds. A smallish, in comparison to the V8s, >1.6 litre I4 engine would rev higher than 3000 in most cases making the 4 cylinder engine give an average of around 9 and the V8s ending up at 6.5 -7. Another reson I felt is the ability of the gearbox to perfectly match with the kind of speed the engine wants to achieve. Well placed ratios definitely help in greater fuel economy alongside other variables. These are my two cents of info!

[fazayal]

There are many parameters which is responsible for Fuel Efficiency.

If we go by ARAI/ICAT mileage of cars available in India we see that many cars with bigger engines have a better mileage compared with cars of smaller engines. Eg. Honda Amaze has better mileage compared to Maruti Swift Dzire, even though Honda's engine is bigger, more powerful and has more torque.

The other important parameters responsible for fuel efficiency are weight of the vehicle, aerodynamics (Swift Dzire has better ARAI mileage than Swift hatchback!), technology used (DOHC gives better mileage than SOHC), engine tuning (some engines are tuned for performance while some are tuned for mileage).

And finally the fuel efficiency depends a lot on the driver and driving conditions. Riding on the clutch, driving in wrong gears, constant braking, unnecessary accelerating, traffic jams, bad roads, adulterated fuel, load in vehicle etc also hamper fuel efficiency.

Hence it is very much possible that a 2 litre, 166 ps Cruze will give better mileage than an 800 cc Alto in some conditions.

[slamnos]

The fuel efficiency depends on parameters like:

Forced Induction/Turbo Charging.
Type of fuel used (Octane Ratings)
No of Cylinders
Newer Technologies used (i-Vtec, CGI, CRDi, Blue Efficiency etc)
Metal alloys used to manufacture the engine block.

But if you are comparing multiple engines with equal number of cylinders, similar technology used, same metal alloy for the engine block, tubrocharged/non-turbocharged and same fuel used, then certainly the engine with bigger CC consumes more fuel.

[Viraat13]

Originally Posted by kaizanfan

I often hear from my friends and read on the net that bigger engines give less mileage. For example a 2 litre engine would give less mileage than an 1.5L engine. Is this absolutely true without considering any other parameters?

There is no way that we can arrive at an absolute figure in this scenario. My 1.6 litre engined Opel Corsa gives me an average of about 6.5 to 7 in crowded conditions, but my 2.2 litre E220 gives me 7.5 in the same kind of traffic. It doesn't make any sense because the larger engine gives a better economy in similar conditions, but out on the highway, the E220 gives 11.5 and the Opel gives about 12. So a 600cc difference is causing the smaller engine to be less economical, if the figures are seen overall. Now to account for the numerous factors and arrive at a percentage in such a scenario is almost impossible.

This, at best is a general rule of thumb. Not accounting for any external factors or states of tune. So, I'd say — No, it is not an absolutely true without considering any other factors.

[LOL_FWD]

Bigger engine, lesser FE and vice versa, is all a concept long gone.
Engine refinement over the years is the reason.
For a simple example take take a G13BB and a 1.0 Ecoboost.
Even though there's a difference of ~300cc a G13BB produces 80bhp @6000 rpm with 103Nm of torque @4500rpm and the ecoboost 123bhp@6000 rpm with a torque of 170 @1400-4500 rpm. Now the same way engines nowadays are made more efficient than they were some years back.
Its the same for FE as well. Can you think of any diesel engines of range say 1L to 2L about roughly 10 years back return about 20~25 kms/litre mileage?
FYI, above figures have been taken from the Maruti suzuki and Ford India websites.

[BackInTheFold]

Originally Posted by kaizanfan

I often hear from my friends and read on the net that bigger engines give less mileage. For example a 2 litre engine would give less mileage than an 1.5L engine. Is this absolutely true without considering any other parameters?

I would like to start a discussion on this topic to learn more about the actual technicals that affects or dictates FE.

Even if engine size is inversely proportional to mileage (FE), could we roughly arrive at the percentage?

Looking forward to some learning.

There have been some very learned explanations to your query. The summary, to which I too subscribe, is that this old rule of thumb no longer holds true. To the various examples given, I'll add my own. My 2l Laura DSG gives me more kmpl than my 1.2l i10, ignoring the whole diesel/petrol angle

[audioholic]

Originally Posted by LOL_FWD

Bigger engine, lesser FE and vice versa, is all a concept long gone.
Can you think of any diesel engines of range say 1L to 2L about roughly 10 years back return about 20~25 kms/litre mileage? .

Except that good mileage and good performance cant be achieved at the same time in todays engines. If the Ecoboost is utilised to its full potential or even close to full potential, I bet it wouldn't give FE anywhere close to an old school 1L engine. Just that we can achieve a balance between the two.

[Viraat13]

Originally Posted by LOL_FWD

Can you think of any diesel engines of range say 1L to 2L about roughly 10 years back return about 20~25 kms/litre mileage?

The first generation old Octavia that we got here in India did do about 20 or 25 km/litre back in the day. That was around '03, I guess.

But your point does hold true.

[k_nitin_r]

Originally Posted by Raag Sandhu

Being in Dubai, I have been lucky enough to experince and own some large and small engined cars as well.

Vehicles in Dubai defy the naive size-efficiency relationship too. The Chevrolet Spark has a 1.0 litre 4-cylinder engine and it takes 5.5 litres of fuel to travel 100 km. The Spark has a 4-speed automatic transmission, can do a 0-100 km/hr in 17 seconds, has a top speed of 140 km/hr, and the engine has an output of 67 hp.

On the other hand, we have the BMW 1-series. The base model comes with a 1.6 litre 4-cylinder engine, but it has a 6-speed automatic transmission, the exact same fuel consumption rating as the Chevrolet Spark, a 0-100 km/hr in 9 seconds, and a top speed of 210 km/hr. The engine of the BMW 1-series produces an output of 136 hp, which is over twice that of the Spark's engine. In terms of pricing, the BMW 1-series costs over thrice as much as the Chevrolet Spark.

Now, Lexus has the CT 200h hybrid with a 1.8 litre engine and it has an even lower fuel consumption than either the Chevrolet Spark or the BMW 1-series but costs more than both vehicles. It comes with a CVT transmission, has a fuel consumption of 4 litres for 100 km, can do a 0-100 km/hr in over 10 seconds, has a top speed of 180 km/hr, and has a power output of 134 hp.

[Vkrm_Rghvn]

Originally Posted by kaizanfan

I often hear from my friends and read on the net that bigger engines give less mileage. For example a 2 litre engine would give less mileage than an 1.5L engine. Is this absolutely true without considering any other parameters?

I would like to start a discussion on this topic to learn more about the actual technicals that affects or dictates FE.

Even if engine size is inversely proportional to mileage (FE), could we roughly arrive at the percentage?

Looking forward to some learning.

Hello kaizanfan, to simply put I would say its all down to the power to weight ratio. Classic example being the K10 series engine from Suzuki is mounted on the A-Star, Wagon R, and Alto K10. The lightest is the Alto, followed by the AStar and then the Wagon R. Lesser fuel is required to overcome the friction because other components are lighter and hence the work done is less by the engine which in turn consumes less fuel (energy) to complete the task.
All in all it does not matter whether you have a 2l or a7.5 l engine in your vehicle. If the power to weight ratios are comparable, then the fuel consumption will be similar, otherwise the higher power to weight ratio vehicle will have a slight advantage.
Another example in the case of Diesel engines would be for trucks. Now the truck manufacturers do not have a huge portfolio of engines foe different GVW ranges. Now say for tonnage capacity from 7.5tonnes to 16tonnes capacity, the manufacturers use one engine across this range(because for GVW>3.5tonnes it's only engine certification required for emission clearance). Hence the 7.5 or the 9tonne vehicle has a slight advantage of fuel consumption over the 16tonner because of the power to weight ratio.
I hope this throws some light to your discussion and helps you.

Regards,

Vikram Raghavan

[trtraj]

Originally Posted by Vkrm_Rghvn

to simply put I would say its all down to the power to weight ratio. higher power to weight ratio vehicle will have a slight advantage.

I second Vikram's point. Similarly taking consideration of our National engine which is running on Swift, Ritz, Dzire, Ertiga, SX4, Punto, Linea

This is also proportional to the engine tune (read bhp) and the Aero Dynamics which makes difference.

IMHO a Punto is giving more mileage with respect to its 90bhp engine with more than 150 kg comparing swift with 75bhp and lesser body weight !!

The dynamics would give more efficiency and which matches the difference in the body weight !!

But as you mentioned about the size the overall wallet factor is bigger the engine bigger the hole

[SPIKE ARRESTOR]

Guys, for a rough estimate, use brake specific fuel consumption values. Gives a fairly good idea of how "efficient" an engine is.

bsfc = fuel consumed in g/kWh
May be some manufacturers data will help in getting there.

Spike

[Vkrm_Rghvn]

Originally Posted by SPIKE ARRESTOR

Guys, for a rough estimate, use brake specific fuel consumption values. Gives a fairly good idea of how "efficient" an engine is.

bsfc = fuel consumed in g/kWh
May be some manufacturers data will help in getting there.

Spike

Hey spike,
I think you just summed it up.
For Engine its the bsfc
For vehicle its the power to weight ratio and the drivability calibration (sporty or sedate style)