Overview: Aston Martin Cygnet and Toyota iQ

Aston Martin’s city car, the Cygnet, is due on sale in 2011. Mechanically and structurally, the Cygnet is a Toyota iQ; that much we know already. Aston Martin has now confirmed that it has no intention of making any significant engineering changes to the Toyota product, so the Cygnet will be defined externally by its new nose and other, less major, styling revisions. The most important change, though, will be the car’s refitted interior.

One way or another, the Cygnet is a curiosity. Despite wearing an Aston Martin badge, it offers no performance advantage over the Toyota version. And although Toyota’s engineering standards may well be high, the iQ is not a particularly advanced car in any respect: perhaps its most remarkable feature is that the 1.3-litre 1NR-FE petrol engine used in the Aston version (as well as the more upmarket Toyota derivatives) is equipped with variable valve timing for both intake and exhaust camshafts. This does not make it a remarkable engine though, and its outputs of 97PS and 123Nm are hardly startling. Worthy of note is that the pistons feature carbon ceramide as a friction-reducing measure. The engine is fitted as standard with a stop-start system, for which a 0.4s restart time is quoted.

Aston Martin Cygnet (pre-production).

Despite its modest dimensions, the iQ has scooped a five-star NCAP safety rating.

It’s perhaps not for us to say, but the question of snobbery arises. Aston Martin is talking about the Cygnet as a ‘bespoke tender for a luxury yacht’ — a city car for owners of ‘real’ Astons — and there’s no doubt that customers will have a lot of say over the trim and equipment that go into their cars. But everyone will know it’s really a Toyota. It will never be easy to tell, even with hindsight, whether snobbery has affected the Cygnet’s success, because few would admit to being swayed by such things.

Description

Toyota’s iQ is a straightforward three-door hatchback. At under three metres in overall length, it offers accommodation for three adults and a child with the front passenger seat slid some way forward.

The Toyota’s body is a steel monocoque, featuring multiple load-paths at the front to help the short nose absorb crash energy. To this end, the engine is mounted slightly behind the front axle line, with the final drive ahead of the gearbox. This also clearly shifts the centre of gravity back a little. A very compact, flat fuel tank is mounted under the passenger floor, leaving the space beneath the rear seats for stowage. The tank’s 32l capacity is adequate for a town car.

Toyota has sought to endow this very short car with decent straight-line stability by giving the McPherson front suspension a lot of caster — 8.3° — and by minimising roll-steer at the back; here, the wheels are located by trailing arms mounted on a shared torsion beam, with the dampers angled towards the rear to reduce load-space intrusion. A proportionately wide track also helps: despite being roughly 800mm shorter overall than a Yaris, the iQ’s track is 10mm wider at the front and identical at the rear. Toyota also talks of reducing the torsional stiffness of the steering arms in the interest of straight-line stability: because of the substantial caster, distortion of the suspension bushes and steering arms under lateral loads will result in the outside front wheel toeing out during cornering, increasing perceived understeer and making the car feel less twitchy.

(Real understeer is the situation in which the slip angle of the front wheels is greater than that of the rears: the vehicle thus runs wide. If the car runs wide not because of slip angles but as a result of variable geometry at the front wheels causing the outside front wheel to toe-out under load, the car is not actually understeering — though it will certainly feel as though it is.)

The most basic iQ model, with narrower tyres than the Cygnet’s, achieves a very creditable drag coefficient of Cd 0.30.

In the interest of weight-saving, Toyota has created what it claims is the world’s lightest exhaust for a front-wheel drive car. It weighs 6kg and uses a long tailpipe and a single, low-resonance silencer, with no additional sub-silencer. This design also contributes to iQ’s low floor and low overall height.

The iQ is equipped with a centre take-off steering rack and a speed-sensing electric power steering (EPS) system. Assistance is controlled according to vehicle speed. The rack ratio is 15.3:1, and Toyota boasts of a low yaw rate gain at motorway speeds — the steering is quite high-geared, but not too twitchy at speed.

Toyota’s 1.3-litre iQ comes with 16-inch alloy wheels and 175/60R16 tyres. No spare wheel is offered. It is possible — but far from certain — that Aston Martin will specify different wheels and tyres, though there is little space remaining in the iQ’s wheelcarches.

We have mentioned the Cygnet’s engine already. It is the larger of two options available on Toyota iQ models; the smaller, a three-cylinder engine of 996cc and 67PS, is effectively three-quarters of the four-pot 1.3-litre unit, with variable valve timing for the intake camshaft only. Like both Toyota derivatives, the Cygnet will be available with either manual transmission — with six forward gears in the case of the 1.3-litre iQ and the Cygnet — or Toyota’s Multidrive CVT. The latter provides similar performance to the six-speed manual but with a nine per cent. deterioration in urban fuel consumption.

As an aside, the 1.4-litre diesel version of the iQ, which is not offered in Britain, delivers superior standing start performance to the 1.3-litre petrol variant, offers an identical maximum speed, and yields eight per cent. less CO2.

Toyota iQ D-4D 1.3 &
Cygnet
Cylinders 4I 4I
Bore/stroke 73.0/81.5 72.5/80.5
Swept volume 1364cc 1329cc
Compression
ratio
16.5:1 11.5:1
PS/rpm 90/3400 98/6000
Nm/rpm 190/1800 123/4400
Maximum speed 104 104
0-100km/h 10.7 11.8
Urban MPG
(l/100km)
60.1
(4.7)
48.7
(5.8)
CO2 g/km 104 113
Emissions EU5 EU5

Driver assistance

Anti-lock brakes are standard. This system provides the basis for a number of other braking and traction control systems which are also fitted as standard.

Electronic brakeforce distribution works with the ABS to ensure the most effective brake force is applied to each wheel, according to road conditions. By preventing the wheels from locking, EBD helps maintain stability when braking during cornering.

The Brake Assist system applies maximum braking automatically if, according to its algorithm, it detects that the driver intends it. This overcomes the apparent inability of some drivers to apply adequate braking force in an emergency, though it does prevent an experienced driver from modulating brake pressure to hold the wheels on the point of locking. It is fair to say, though, that this comment applies only to conditions in which this would be fairly straightforward: broken or split-µ surfaces are probably best left to the car’s electronics.

Traction control is an aid to maintaining grip when driving on slippery or uneven surfaces. The system monitors and controls the amount of torque applied to the road and detects if one or both of the driving wheels starts to lose traction. The skid control computer automatically decreases the amount of power being sent to the wheel that is about to spin; in more extreme cases, it might apply braking force momentarily until the wheel regains traction.

Steering Assist Vehicle Stability Control aims to prevent loss of control in certain situations — for example, when entering a bend too fast and encountering a slippery surface. Sensors around the vehicle monitor wheel rotation, brake pressure and car movement. If the system calculates the driver is about to lose control of the car, elements of the traction control and ABS systems are deployed. In a skid, for example, the system will apply braking and apply steering torque to help the driver regain control.

Structure

The safety structure of a small car is hard to engineer. Front and (particularly) rear impact volumes are necessarily small, and load paths have to be proportionately more ingenious than would be the case for a larger vehicle. The iQ uses six countermeasures to overcome the effects of an impact.

  • The engine is mounted towards the rear of the engine bay, giving more room for the energy absorbing structure at the front of the side members. In a heavy collision, the engine can also function as a barrier, reducing impact on the passenger cell.
  • The location of the front wheels right at the front of the car provides initial protection in a frontal collision.
  • Total energy absorption capacity has been increased by using the suspension member side rail in addition to the standard collision area formed by the front side member.
  • By attaching the rear part of the front suspension member to the body in four places, the load from the front side members can be transmitted to the cross member.
  • Body strength has been increased by directly connecting the front side members and the sill together.
  • Strengthening across the dashboard means impact forces towards the cabin can be more evenly distributed.

Nine airbags are fitted as standard, of seven different types: a rear window curtain shield airbag (a world first, though clearly a larger car would not need one); two side airbags; a front passenger seat cushion airbag; a driver’s knee airbag; two curtain shield airbags; and conventional driver and front passenger front airbags.

In line with the size and shape of the cbin, the side airbags are larger than usual, the others smaller. Additionally, the knee airbag is positioned closer to the driver than would be the case in a larger car, which means both size and deployment time can be reduced.

A new kind of twin-chamber bag was developed for the front passenger airbag. First seen on Lexus models, this design ‘catches’ the passenger and cradles his face between the two sections, so that the passenger actually travels slightly further forward in a collision than the driver.

The front passenger seat cushion airbag inflates under the thighs and inhibits movement of the hip, reducing any impact on the head and chest.

The driver and front passenger sit close to the doors and would normally be particularly vulnerable to injury in a side collision. The side airbags are divided into silicon-coated bags with different pressures to provide appropriate protection for the pelvis (high pressure) and chest area (lower pressure).

The iQ’s novel curtain shield airbag for the rear window deploys in two stages: first, between the roof panel and headlining; then from the edge of the headlining along the rear window.

Toyota iQ 1.3
&
Aston Martin Cygnet
Cylinders 4I
Valves 4
Bore/stroke 72.5/80.5
Swept volume 1329cc
Compression
ratio
11.5:1
PS/rpm 98/6000
Nm/rpm 123/4400
Maximum speed 106
0-100km/h 11.8
Urban MPG†
(l/100km†)
48.7
(5.8)
CO2† g/km 113
Emissions EU5
Transmission
— 1
— 2
— 3
— 4
— 5
— 6
M6 (CVT)
3.538
1.913
1.310
1.029
0.875
0.743
Driven wheels Front
Fuel tank 32l
Kerb mass * 955
PS/t * 102
Nm/t * 128
Length 2985
Width 1680
Height 1500
Wheelbase 2000
Track: front
Track: rear
1480
1460
Cd 0.30
* Kerb mass for Toyota iQ with either manual or CVT gearbox. Aston Martin Cygnet 988kg.
† Figures for model with CVT: 44.1mpg / 6.4l/100km /120g/km.
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