3 cylinder cars

[Hockey4mnhs]

How many 3 cylinder cars are made by well known car makers. I know geo makes a 3 cylinder but are there any more well known ones out there?

[SVOboy]

None that I know of. What's geo, by the way?

[omgwtfbyobbq]

Originally Posted by Wikipedia

The straight-3 is the smallest engine in use in modern cars, generally for engine displacements of around 1.0L. Cars in the 'super-mini' class often use them on base models, as do the Japanese Keicars. A straight-3 is also used in the Suzuki Swift, its American cousins: the Geo Metro and the Chevrolet Sprint, the Subaru Justy, the Honda Insight, and also two stroke Saabs (93 - 96). One experimental Saab had two transverse straight-3 engines, the Saab Monster.

The smallest straight-3 engine was the 543 cc Suzuki F5A used in the 1982 Cervo. Smart currently produces a diminutive 799 cc Diesel straight-3, the smallest ever. Most straight-3 engines fall below 1.2 liters, with a 1198 cc Volkswagen unit seen as the largest petrol unit. A 1.8 L (1779 cc) Diesel was produced by Alfa Romeo for their 1984 33 1.8 TD, the largest straight-3 ever produced.

[Sludgy]

I don't know why automakers don't produce boxer-style 2 cylinder engines like the one in the old Citroen 2CV. The engine should be smooth(ish) because the firing order is even, and primary balance is very good. Triples are always unbalanced, and because of it, they sound like a bucket full of lockwashers at full throttle.

A 1 liter boxer twin ought to be capable of producing 80-100 BHP. Subaru already makes boxer engines. They could cut their 4 cylinder engines in half to make a 1.2 liter that would have killer economy in one of their lighter cars like the Impreza. Or, BMW could install one of its motorcycle engines in its 3-series.

[rh77]

Mitsubishi is rumored to provide the U.S. version of the SMART ForTwo with a 1.0L, 3-cyl. gasser.

RH77

[JanGeo]

In line 3 cylinder engines are balanced very well with the 120 degree crank spacings and vibrate very little if at all. My Geo was perfectally smooth. THe BMW Boxer 1 liter in my motorcycle has good balance but a heck of a power pulse and rocks side to side because of the offset crank journals. If you ever rode a K750 triple you would know what smooth is - actually it is too smooth.

[QDM]

I had an 88 Subaru Justy that had a 3 cylinder 1.2L engine, 3 valves per cylinder, with a counter balance shaft. It was smooth running and very zippy. Only thing I didn't like about the engine was the computer controlled carb.

Q

[basjoos]

The Honda Insight is a 3-banger that smooths out the engine vibrations by feeding a "anti-vibration" signal to the electric motor to counteract the vibration impulses coming from the ICE.

[Sludgy]

Originally Posted by JanGeo

In line 3 cylinder engines are balanced very well with the 120 degree crank spacings and vibrate very little if at all. My Geo was perfectally smooth. THe BMW Boxer 1 liter in my motorcycle has good balance but a heck of a power pulse and rocks side to side because of the offset crank journals. If you ever rode a K750 triple you would know what smooth is - actually it is too smooth.

Inline 3 cylinder engines can have 120 degree crank throws for even firing, but their balance is poor caused by a "rocking couple". Triples can use balance shafts to cancel the rocking couple.

Motorcycle inline triples like the K750 feel smoother than big inline twins because twins are incredibly imbalanced. Twins with even firing have massive imbalances caused by both pistons going up and down simultaneously. Boxer twins don't have primary imbalance and are much smoother than inline twins.

Also, consider the effect of the mass of the pistons. 250 cc pistons for a 750 triple have a LOT less reciprocating mass than the pistons for a 1000 boxer twin. Any small-piston engine feels a lot smoother than a large displacement engine.

At any rate, my main point was that a twin cylinder car of equal power to a three cylinder car will have better fuel economy, and the best format for a twin is a boxer twin.

[JanGeo]

Yes but they are harder to build being apposed and tend to puddle oil in the cylinders causing leakage past the rings plus have totally different valve train expansion problems - longer timing chains or belts or require long pushrods for the valves from a centrally located camshaft - longer intake manifolds for each head separate exhost headers etc. High performance boxer BMW motorcycles exhibited crank case stretching under heavy loads under race conditions. It is a great motor but it too has design trade offs.