3 Cylinder Cars - Real World Fuel Consumption

[Ecky]

Originally Posted by BikeHelmet

What I learned from this thread: Get the proper engine size for where and how you drive.

Truth. Different sized engines are more efficient at producing different amounts of power, there is no "one size fits all".

[Joe of Loath]

The latest Skoda Octavia (VW Jetta ish) comes with a 1L turbo engine as an option.

That's a 1400kg car with a 1L engine. Apparently it even drives OK too, although I dread to think what the emissions are.

But what do I know, I drive a pre-DPF VW diesel and an 80s Volvo.

[NHB]

Originally Posted by ProDigit

It all depends on the load.
A 2CV with twin boxer engine supposedly got twice the mpg of current econo-cars (80mpg vs 40mpg on modern economy cars), all thanks to it's 350-500cc twin cylinder equipped with a large overdrive. The thing could only do 45mph..

Turbo engines have a very narrow rpm range where they are functional.
NA engines are more fuel efficient, especially with direct injection. A 1 liter engine usually is geared to work well in city traffic of 35mph, but are less efficient than a larger engine at higher speeds (say, a constant 60 mph)

I just checked a test of our local car mag from year 1970. Citroen 2 CV had a fuel consumption of 33 mpg @ constant 62 mph and 50 mpg @ constant 31 mph. This tiny death capsule consumes 20-35 percent more fuel than a new VW Golf 1.0 TSI.

I really don't understand what do you mean when you say, that turbo engines have a narrow functional RPM range. They deliver plenty of useful torque on very wide rpm range. These modern 3 cylinder engines with turbo are also more fuel efficient in low and high speeds than any other engines except some hybrids. I'm just reading a test where VW Golf 1.0 TSI costumed 33.3 mpg @ constant 72 mph. Not bad for a compact car which never are too aerodynamic.

[NHB]

Originally Posted by cr45

The cars only had 4 gears and top gear was most certainly not an overdrive. It was however just right for the car, having only 29 bhp to play with.

There does appear to be a myth that 2CV's had fantastic fuel economy but in reality they had quite modest fuel economy considering the light weight - 600 kg - and small engine capacity.

The engine of a 1970 2CV runs 5400 rpm @ 60 mph.

Also in my country a lot of people want to believe, that old cars have mystical fuel saving powers.

[NHB]

Originally Posted by BikeHelmet

I have a feeling that most 3 cyl cars would be at far too high of an RPM here. I've heard from people that drive them that they wear out or break down quickly - probably because of how they are driven rather than the technology itself.

This is not the current situation. Modern 3 cylinder engines deliver plenty of torque beginning from 1500 rpm. They don't need high rpms for normal driving. Usually 1500-2500 rpm range is enough for normal driving.

[roosterk0031]

Normal driving is very hard to define. In the US I speculate most 3 cyl turbos (Fords) are running with boost most of the time a 3000+ rpm. Under boost means rich = bad mpg = bad emmisions. A 2.0 NA can do better under what I consider normal US driving conditions because it stays closed loop.

[cRiPpLe_rOoStEr]

Originally Posted by ProDigit

The engine revving at 4 k rpm, 3 cylinder has a similar load as a same single cylinder size, 4 cylinder revving at 3k rpm, similar mpg results.

Considering that those 3-cyls usually have a larger stroke proportionally to the bore, they perform better at lower RPM, thus leading to the expected fuel savings.

[NHB]

Originally Posted by roosterk0031

Normal driving is very hard to define. In the US I speculate most 3 cyl turbos (Fords) are running with boost most of the time a 3000+ rpm. Under boost means rich = bad mpg = bad emmisions. A 2.0 NA can do better under what I consider normal US driving conditions because it stays closed loop.

For example 3 cylinder VW Golf runs 85-90 mph @ 3000 rpm. Is this the speed you drive most of the time? What 2.0 NA would be more fuel efficient than this VW engine? A modern 3 cylinder with integrated exhaust manifold is not going to need rich mixture too often.

[NHB]

Originally Posted by cRiPpLe_rOoStEr

Considering that those 3-cyls usually have a larger stroke proportionally to the bore, they perform better at lower RPM, thus leading to the expected fuel savings.

Bore/stroke ratio has very little to do with this. You should thank turbos, cams and compression ratio for torque at lower RPM. I'm surprised how often people think, that these 3 cylinder engines will run at high RPM when in reality they don't need high revs in normal driving. Downsizing comes with down downspeeding.

[cRiPpLe_rOoStEr]

The longer stroke-to-bore actually is one of the reasons that lead those 3-bangers to have a better low-end responsiveness. At least in my country they're still more restricted to entry-level subcompacts while forced induction is the exception, not the rule.