The Spark-Renault is evolving. Pictures and video captured at tyre testing in France over the past few weeks show how the electric racing car has been upgraded and modified throughout its shakedown period.

Our electric vehicle expert and former F1 engineer Chris Vagg pinpoints the changes, examining the original static version revealed last September (and photographed in detail recently by Current E at Donington Park), the first “covers off” image released in November and the latest images released by Michelin.

1. Suspension

When the Spark-Renault was first unveiled, it featured conventional push-rod suspension with steel components. That would have been perfectly adequate for the speeds predicted, but looks like something you’d find on cars in junior formulae.

Now, however, the car is running with carbon fibre upper and lower wishbones on the front suspension. The push rods (which control vertical motion) and the track rods (which transmit steering input) are located between the wishbones; both appear to be metallic still and are much rounder in cross-section than the elliptical wishbones. But the immediate impression is that the Spark-Renault is now bristling with a proper, race prepared suspension.

Why such a change at this stage, when the cars are due to be delivered to Donington Park in a few short weeks? Carbon fibre offers a weight- and aero-optimised solution. It’s a much lighter material than steel, and it offers a much smoother, weld-free surface. It is an obvious way for a high-tech racing car to unlock the best possible performance from the package. In this case, it is a choice that could help to reduce drag and so save battery energy, as well as reducing unsprung mass, allowing the cars to accelerate faster and giving them better road contact.

The metal components that we saw early on simply indicated that the car was still a prototype. Carbon fibre is expensive to make, and there was a lot of other carbon work to do, such as the chassis, survival shell and bodywork.

In F1, carbon fibre parts change at every race, and teams have many components that never even get to the track. In the real world, however, you wouldn’t commit to manufacturing carbon fibre parts until you were absolutely sure of the design.

Spark, which is leading the consortium that is building the car, probably wanted to make sure that the geometry of the electric racing machine was correct, that it was well balanced and cornered sweetly, before taking the plunge and investing in carbon moulds which can’t be changed. This gradual replacement of parts over the shakedown periods is the logical approach and appears to be working well.

2. Rear wing

As well as being set low down and fairly far back on the chassis, we’ve already commented that the rear wing is skinny compared with what we see on other racing cars. Examining the new powertrain pictures gives us a clue as to why this might be, and it’s probably down to weight balance. The positioning of the battery pack, motor and transmission means that there is a lot of weight right next to the rear axle; additional downforce isn’t a requirement to keep the rear tyres in contact with the road.

This assumption can be backed up by looking at how the front wing is set up. In the testing videos, we can see that the front wing aero surfaces – the “flaps” – are raised up to about three quarters of their maximum. This advanced angle of attack is needed to produce enough downforce to keep the front wheels pinned down, balancing the weight of the rear.

3. Battery box

When we first saw the internals of the Spark-Renault, there was a space frame sat where the full battery pack was planned for. We can now see the complete battery box in place, with two white mushroom buttons, just above the motor on either side of the car centre line. They are probably circuit breakers.

4. Cooling circuits

It looks as though the team has rethought the routing of the cooling pipes. The motor is being cooled through the right hand side radiator, and the power electronics – the inverter – through the left hand side.

The battery may be on the same cooling loop as the inverter, but it may not be cooled at all. The team might be evaluating how it performs without cooling during these tests, and do without it completely if the system behaves itself.

There are bright yellow plugs on the battery box, facing the rear wheels, that look like blanking plugs on the ends of shafts or pipes. These are particularly intriguing, because you can’t see the yellow caps in some of the pictures, suggesting that they have been removed and that, therefore, something has been attached to those pipes. My guess is that those are part of an optional air or fluid cooling circuit for the battery box. The technical regulations allow for fluid cooling of the battery, as long as the fluid used isn’t water. So perhaps Williams, which is supplying the batteries, has built in a cooling system that can be connected up if required. It could also be that the battery box has an internal fan to help with cooling, but that’s impossible to tell from these pictures.

Where does the airflow through the radiators exit the chassis? Looking at its flow path you might expect it to come out over the rear wheels, but that would cause heating of the tyres which could be difficult to manage, and the rear wheel fairings appear to be sealed. My guess is the air is taking a right angle and coming out over the rear suspension.

5. Cooling fluid

What fluid is being used in the cooling system? Looking at the steering wheel display, we can make out “N” (presumably for “Neutral”), and then “85” and “Water T” – which probably means water temperature. That surprises me. I would have expected the fluid to be a dielectric oil, something that doesn’t conduct electricity, for safety reasons.

The steering wheel looks like the SX Dash unit supplied by DTA Fast, so it’s just possible that the wording is standardised and doesn’t reflect what the actual cooling fluid is. Given that it is a programmable LCD display, however, and that there is a large battery icon, it would appear to have been adapted for Formula E use. Why change some units on the display and not others?



So: water may likely mean just that. The regulations stipulate that water cannot be used to cool the batteries, but the other powertrain components aren’t mentioned. Water would be cheaper than using a dielectric oil, and we know the teams will have strict budget caps, but I can’t see a non-conductive fluid breaking the bank. The fluid has to be passed as close as possible to the electrical components in the motor to do its job, and squirting water in there doesn’t seem like the brightest idea.

As always, we await more revelations from the sport with interest; but everything is pointing towards a smooth, controlled development process and a final product that will be reliable on track.

Images courtesy of FEH, ABT and DTA Fast.