The “Three Litre” Ka

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ar manufacturers have been designing, and in some cases, building, cars designed to use just three litres of fuel for every hundred kilometres (hence the “three litre Ka,” which sadly does not indicate the engine capacity!). Before everybody reaches for their calculator to try to work out what three litres per hundred kilometres is in metric terms, it’s 94·2 mpg.

Volkswagen have sold a number of “three litre” Lupos, these feature a 1·2 litre, 60 PS, three-cylinder turbodiesel mounted in a pared down Lupo bodyshell, with expensive magnesium alloy panels, thinner glass, thinner suspension components and low grip, low rolling resistance tyres. I’m pleased to report that VAG lose money on each one sold.

So how would I amend the Ka’s design to achieve this target?

First, a brief discussion over how I’m going to improve the Ka’s efficiency. There are many factors that determine the fuel efficiency of a given car: weight, aerodynamics, frictional losses and engine efficiency. I can improve the Ka’s design in all of these respects, but I also still want the car to be enjoyable to drive. This is not something that would have bothered the VAG engineers, because all Lupo models bar the GTI are about as much fun to drive as eating a cockroach sandwich. The Lupo’s drawbacks include the cramped accommodation, presumptuous VW badge and the fact you need the car handling skills of a pre-war works Auto Union driver to get on top of those tyres, the jerky Tiptronic gearbox and the dent-prone, thin-as-fag-paper body panels. It also looks like a startled teenage lad just caught in his parent’s bed with an equally startled young lady.

Weight

In the context of modern small cars, Ford’s baby isn’t exactly portly with a kerb weight of 900kg, but there’s a lot of room for improvement. I could take the Lotus approach of throwing everything not essential to the car into the bin, but I’d like to treat the driver and occupants a bit better than this. We’re going to keep the luxuries such as air conditioning, electric windows, central locking and a CD player.

But what we are going to do is use a high-tech aluminium alloy body, and plastic-derived panels. Yes, I know that these panels will be very costly to replace if you’re ever involved in an accident, but they are extremely lightweight and they’ll never rust.

We’ll substitute lightweight parts wherever possible - including the wheels, suspension, brakes, air conditioning, even the engine hoses, the fuel tank and the seats.

The net result is a kerb weight (with full fluid levels) down by over 200 kg, to 675 kg.

A lower weight makes an important difference at low speeds, since the heavier the car, the more power is needed to change speed. It also endows the Ka with much perkier performance than would otherwise be expected from a car so tilted towards low fuel consumption.

Aerodynamics

The standard Ka has a Cd of 0.36 - not bad for the class, but not brilliant. We need to improve the aerodynamics, but without reducing or compromising any other aspects of the car - and that means high speed stability, engine and brake cooling, air conditioning performance. It will also mean some modifications to the bodywork, fixtures and fittings, much in the same vein as Volkswagen did for the Lupo.

First up, some modifications to the front upper and lower grills. I’ll replace the conventional upper grill with three rows of slats (fast becoming the normal technique). At low speeds, sufficient air enters the engine bay to provide adequate cooling, but at higher speeds, the slats push some of the air over and around the nose, and not into the engine bay - the insides of an engine bay are not aerodynamic! However, we do need a flow of air into the engine bay for cooling purposes. However, because at higher speeds, the flow of air into the engine bay is reduced from the normal Ka, we’ll use two bonnet vents to help draw air out of the engine bay (and as such, improve the flow of air).

Note that I did consider an active slat mechanism was considered, but dropped, since the tangible benefits were negligible and the complexities of the system would have increased weight.

For the lower grill, we will mount the intercooler and oil cooler in the centre, behind a conventional grill with a large mesh, and then smooth and blank off the sides, so as to shift the airflow to the sides of the Ka.

Ford’s wing mirrors will be replaced with rather more aerodynamic versions, closer to the side of the car.

We’ll add a spoiler to the top of the hatchback to reduce turbulence.

The “three litre” Ka will also benefit from lowered suspension, which will reduce the effective frontal area.

We’re going to continue using 165 width tyres, and the “three litre” Ka will use 165/60/14 low rolling resistance tyres, however we’re going to mount small splitters immediately in front of the front wheels, and spats over the rear wheelarches to reduce turbulence (and we’ll ignore any comments from other car drivers, heh). This Ka will use very expensive, lightweight alloy wheels, with flush valve covers. The light alloy wheels give the Ka a light unsprung weight.

Accessory Systems

Ford’s hydraulic power system is excellent in all respects, bar the power-sapping. We’ll replace it with an electric system with much greater efficiency.

When used, the air conditioning system will naturally make an impact on the efficiency of the engine, but wherever possible, more modern, lightweight and low friction components have been used.

Engine & Drivetrain

My apologies for all fans of the Endura-E, but this is one of the first items to go into the bin. Instead, we’re going to use a modified variant of the TDCi / HDi turbodiesel engine, a joint development between Ford and the PSA Group. Except whereas the TDCi engine in the Fiesta is 1·4 litres in capacity, and has four cylinders running eight valves, we’re basically going to lop one cylinder off the sixteen valve version, and make ourselves a new 1.05 litre, three cylinder, twelve valve donk. Using a small capacity, three cylinder engine is beneficial in many respects - the fewer the cylinders, the fewer moving parts, and therefore the less loss through friction. To capitalise on these benefits, we’re going to revise the engine components to reduce frictional losses.

Naturally, this engine will feature an intercooled variable turbine vane turbocharger, extremely high pressure direct fuel injection, and sophisticated engine control electronics with a tilt towards minimising fuel consumption and exhaust emissions. Power and torque outputs will be in the region of 60 PS and 160 Nm of torque, and with a near-flat torque curve from 1,600 rpm until over 3,500 rpm.

Whereas the Volkswagen Lupo uses a semi-automatic gearbox, with pre-programmed economy modes, we’re going to stick with a conventional, traditional five speed manual transmission, a clutch pedal, and with deliberately tall gearing to give the Ka a fifth gear ratio of approximately 27 mph / 1,000 rpm.

The driveshafts and associated mechanical systems are engineered to reduce friction wherever possible

The end result is an engine that is up to 65% more efficient that the eight valve 1·4 TDCi / HDi engine. Performance will be in the region of a 0 - 62 acceleration time of approximately 13 seconds and a maximum speed of approximately 105 mph - slightly quicker than the original Endura-E engined Ka.