So who uses five cylinder engines and why? Do they have a future? DTW asks these questions today. Read on to accumulate wisdom on this subject.
One might be tempted to think of five cylinder engines as being something of a novelty, if they are not a rarity. However, before Audi and Mercedes in the 1970s, Ford experimented with the concept in the 1930s and 1940s but never put anything into production. The heyday of the five has been from the end of the 70s until a few years ago. Not a bad run. The window of opportunity for the five-cylinder now seems to be closing. What opened it?
The reasons one might want to use a five-cylinder engine are much the same as for why one might want a four-cylinder instead of a three. You can add capacity and reduce stress. The in-line five cylinder bridges the capacity gap between 2.0 and 2.5 litres. In this capacity a 4-cylinder can be over-stressed and a V6 or in-line six too costly, thirsty and large. A likely starting point is an engine range based on 4-cylinder units that needs expansion to power larger, heavier vehicles than a firm´s four-cylinder range can cope with. Think of a smallish, middle market firm wanting to
punch above its weight. Our list of applications below show this is the case. Firms with sixes seldom tried fives, but firms with fours sometimes did.
In the same way that we have seen that over-stressed small-capacity 4-cylinder engines (as in VW´s 1.4 TSi) can be problematic, a four-cylinder engine seems to be overworked much beyond 2.5 litres. GM’s Iron Duke of the 1970s and 1980s is one example of an overworked four; Lancia tried to offer a large capacity four-cylinder boxer in the 1976 Gamma without success; and in 1978 Saab tried to avoid adding cylinders by turbo-charging the slant 4 Triumph engine. Respectively, these workarounds resulted in coarseness, lack of prestige and unpredictable power delivery. Add to this litany of try-hards the Citroen solution of turbo-charging a 2400 unit to give coarseneness, thirst and turbo-lag in one fine package.
The quint engine avoids these problems in theory. Furthermore, from the vantage point of considering in-line four cylinders and in-line sixes, an inline five seems like a natural middle point, a transition. In fact, the in-line five might just offer the power of a six but without the torsional rigidity problems of an in-line 6 and bulk of a V6. And a quint can offer the economy of a four but without the need for higher revolutions or too much swept volume. However, in practice a five-cylinder engine has vertical vibrations that need to be dealt with before accessing the advantages of the torque pulses that come every 144 degrees of crank rotation. Counterweights on the crankshaft (at either end) deal with those vertical motions and tuning of the mounts deal with the other, secondary shakes. The end result is an engine that is shorter than an in-line six, and narrower than a four. It can be mounted transversely too. That´s especially good for front-wheel drive cars (middle market brands, step forward).
An early example of the five-cylinder engine is the Mercedes OM617 diesel in 1974. It was economical but deathly slow. Audi claimed a first by installing a quint petrol in a mass produced car in the 1976 Audi 100. Here was an example of a middle-ranking firm trying to build up from a base of fours, as it happens. The 1993 Volvo 850 series was driven by in-line fives of 2.0, 2.3 and 2.4 litres capacity. Sixes didn´t work for them and they needed something better than their tired 2.4 litre four-cylinders used in the 240 series. The 1994 Lancia Kappa went five-ish with 2.0 and 2.5 litre normally-aspirated petrols, along with a turbocharged 2.0. That last one, on paper, seems to offer all the weirdness of a five with the splurgy power-delivery of a turbo. If the 2.4 flat four was like overstretching the four-cylinder concept, a 2.0 turbo charged five seems to cramp the five´s style. The unlamented 1998 Lancia Lybra also came with a five-cylinder engine and this must be the definitive application of the five in a Lancia. Over in the US of Stateside and Japan, Acura-stroke-Honda offered the Vigor saloon with either a 2.0 or a 2.5 five-cylinder five. Yet again: a brand on the make. Acura is Honda´s upmarket marque so adding swept volume the five-pot way fits in with Honda´s start point of mastery of fours. It wasn´t very popular as people went for either the fours or the sixes and so the 2.5 L G25A and 2.0 L G20A engines were discontinued. VW powered various Boras with 5s (mostly for the US, I gather). Finally, Ford used a five-cylinder in the 2005 Focus ST and in some versions of the S-Max. This promised impressive performance but profligate thirst (the S-Max had two tail-pipes in the hotter versions).
Our short catalogue shows a pattern: the five pot engine is ideally suited to front wheel drive, smaller, middle-market marques. The Ford and VW applications are anomalies (and in both cases based on engines developed by other brands).
The future of five looks dim. In 2012 VW and Volvo announced they would discontinue their 5-cylinder engines. The reasons cited involved efficiency (of the engines) and cost (to make). As we have seen in our survey of engines, odd cylinders are in if the count is three. And four cylinder engines are being turbocharged and reduced in volume to satisfy demands for fuel economy. Adding stress, of course, which the five and even larger fours do without.
Here at DTW we tend to favour diversity and the demise of the in-line five simply means a little less colour in the automotive world. I suspect the five-cylinder engine is indeed not a natural format as the four and six are, for reasons of harmonics and symmetry. But the five had what old folks called “character”. I´ve experienced the five cylinder engines in the Lancia Kappa and the Volvo S70 and I quite like the thrum and roar of the units. The engine certainly fitted in with Lancia´s eccentric, Alpine character. And the Volvo´s unit is able to haul their drab slab along uncomplainingly and without stress. A four-pot moving such a car would be working too hard and a V6 would speak against Volvo´s social democratic value. Fives had their uses.