3 Cylinder Cars - Real World Fuel Consumption

[NHB]

3 cylinder engine has so many advantages ovat 4 four cylinder, that I see the 3 cylinder population growing in the near future. I would like to add short block to Eckys list. Short block and crank shaf are inherently stiff which allows low weight. Short block leaves also more space for automatic transmission. Also electric motor in hybrid applications needs some space. Transverse layout doesn't have too much space available.

That Top Speed mag article is mostly about diesel engines. Small diesel engines inherently produce a lot of NOx-emissions, which is a huge problem in modern post Dieselgate world.

Ford's 3 cylinder has been around a long time. The engine seems to be quite sensitive to load. In some tests it has very low consumption, but sometimes the consumption is not impressive at all. It seems that consumption raises a lot when the load is raised. Lately one Finnish magazine tested Ford Ecosport. In low speeds consumption was low, but at high speeds the consumtion was much more than what one would expect. VW's much younger 3 cylinder seems to be much better. Lately Ford introduced the new updated version of the engine. Let's see how much they have improved things. At least cylinder deactivation sounds exciting in a 3 cylinder engine.

[cRiPpLe_rOoStEr]

Originally Posted by NHB

3 cylinder engine has so many advantages ovat 4 four cylinder, that I see the 3 cylinder population growing in the near future.

It did surprise me that even here in Brazil, with a quite conservative market for subcompact cars, 3-cyls in the 1.0L range became more popular since 2012. IIRC by now GM is the only major automaker that doesn't offer a 3-cyl 1.0L engine in Brazil. OTOH it did surprise me that Fiat recently released a 3-cyl that still relies on the 2-valve per cylinder layout while the other contenders now feature 4-valve per cylinder.

[ProDigit]

It all depends on the load.
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.
The weight savings of the smaller engine only apply when there's a lot of acceleration going on. Yet even then, the engine needs to rev higher to get similar acceleration, as the load (percentage wise) is higher on a smaller engine (still needs to push 4 tires, driver, passenger, luggage, body, gearbox).

Smaller engine means lower HP, lower speed, lower weight, and also means you can tune the car. Smaller engine compartment, smaller brakes, smaller wheels....

Nothing affects mpg, as final gear ratio.
2 identical cars, one with a direct drive as final gear, and one as an overdrive, the one with overdrive will do better in mpg.
Which is why the Smart for two has such a low mpg, because it revs quite high in final gear.

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..

The best mpg, you get from an as small engine as possible, tuned to the lowest rpm range possible, at the speed most frequently ridden.
A turbo charged, ecotec car makes most sense for occasional acceleration, but mostly continuous speeds (eg:highway speeds of up to 55mph). The turbo is just there for the acceleration phase, after which the engine reaches it's desired speed. At that speed, the rpm should be lower than needed for the turbo to be triggered, to essentially ride at a lower overall compression ratio than a NA engine, which is less efficient... But more efficient than riding with turbo working...

Also, compared to a larger size engine, a turbo during acceleration phase, negates the fuel gains of the smaller engine size idling at a stoplight.
So ecotec engines make no sense in start-stop traffic.
They neither make sense at the point of saturation (where the turbo robs the engine of hp at high rpm).
And neither at a constant speed, where the engine will run at a lower psi, and efficiency, than the same engine without turbo.

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)

[JMB#7]

It will be interesting to see if the Elio makes production yet this year (or ever). Does a 3 cylinder Cyclo-Car qualify for this list? "It is projected to achieve up to 84 mpg-US (2.8 l/100 km) on the highway and up to 49 in the city". Search Elio specifications for more detail. "Fuel-injected, SOHC gas-powered, Variable Valve Lift, 3 cyl., .9 liter, liquid-cooled, automotive engine"

[sidecar]

I just wonder how a 3 cylinder Kubota would go

[Quasiff]

Regarding exhaust pulses, I expect a turbo messes up any benefit one might gain from balancing pulses.
Maybe we'll see a revival of direct drive supercharging on small engines, with variable boost to allow efficient running on different fuels, such as E85, gasoline, methanol.

[stoatwblr]

It should be noted that due to ownership of various brands, the same engines crop up in deferent "makes"

Renault==Dacia and engines are shared with Nissan.
Volkswagon == seat == skoda (and several other brands)
peugeot == citroen (and in some cases == toyota too. The Aygo/C1/106 are all built on the same production line)


Mitsubishi, Ford, Hyundai and Suzuki tend to be more independent.

Apart from the vehicle mass, how a car's driven (especially turbos) has a huge effect on its economy.

The idea of these wee engines is that they're operating at higher efficiency but the moment the turbo (and in some cases supercharger) spins up to give a power boost that efficiency falls away a bit.

Revvy little 3cyl engines tend to lend themselves to peppy driving with heavy use of the brakes (which is where energy gets dumped). It can be difficult to restrain this, but small engine economy is extremely sensitive to driving style.

[Quasiff]

Originally Posted by stoatwblr

It should be noted that due to ownership of various brands, the same engines crop up in deferent "makes"

Mitsubishi, Ford, Hyundai and Suzuki tend to be more independent.

.

Re diesels, Ford use PSA (Peugeot/Citroen) engines in some cars and Suzuki use at least one Fiat diesel. Hyundai and Kia are the same company, so use the same engines. I read some years ago that Hyundai was doing development work for Mercedes and Mitsubishi on some diesel technology. Hard to know who is doing what for whom. And what the end product ends up with can be modified by the ECU program anyway.

[cr45]

Originally Posted by ProDigit

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..

I drove citroen 2 cv's and citroen Dyane's as my daily driver for quite a number of years. These were all built in the last 10 years of the production run and all had the 602 cc version of the engine.

One thing I learned early on was that it was just about impossible to get 60 mpg imperial. Typically I would get 52 to 56 mpg imperial with there being hardly any variation between driving easy or hard.

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.

A modern 3 cylinder car such as the mitsubishi mirage with double the engine capacity will comfortably average 65 mpg imperial yet is some 40% heavier.

[BikeHelmet]

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

I'm in Canada and drive a 98 Ford Escort.

We have highways here that are 110km/hr, or about 70 miles per hour. The terrain is hilly, so you'll be going up or down a hill for 30-60 seconds quite often. If you speed to 120km/hr, you can hit greens on most of the stoplights. Nearest Walmart or Costco is 30 mins away, so if you go shopping you'll be tossing lots in your hatch to make best use of the trip.

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. My car is around 1300 kg once you sit down in it with your stuff, and cruises nicely on the highway at up to 120km/hr. Gets about 29-30mpg highway, and 34-36mpg if driving slower. (~90km/hr) When converting to L/100km, that's shockingly close to these numbers despite the vehicle's age.

I think to see an upgrade, I'll have to go EV or HEV.