Allan McNish gives an insight into Audi hybrid power
With thanks to Audi Sport, below is a Q & A with Allan McNish who will be driving the No.2 Audi R18 e-tron quattro with Tom Kristensen in the 6 Hours of Bahrain. It offers a fascinating insight into Audi's hybrid power system and the benefits it brings to the German manufacturer.
Is the hybrid constantly in use on every lap?
“No. The governing Federation Internationale de l'Automobile (FIA) limit the number of “zones” where you can feed those 500 KJ each lap that varies from circuit to circuit. Unlike permanent four-wheel-drive quattro, the front and the rear wheels are not connected because the rear wheels are only ever driven by the V6 3.7 litreTDI diesel engine. We gain approximately an extra 200hp in actual power."
Is the hybrid system available at all speeds?
“No. Another regulation stipulates that our Hybrid system can only be used above 120kph. The stored energy is delivered to the front wheel only. When you exit a corner where we can use the hybrid, there is an extra kick of power and when it has used its energy and returns to ‘standard’ – about 510hp of the V6 diesel engine – you can feel a difference. It is not a big drop off and so the energy is dispersed pretty quickly, within a couple of seconds. It is noticeable, but it is done in such a way that it doesn’t affect the car balance.”
Do you press a button in the cockpit to activate the Hybrid system?
“It’s an automated system and I don’t press a button like in some other formulas. It’s done automatically which benefits the driver because we are doing many other things.”
Is there a special sequence that must be undertaken to start up the R18 e-tron quattro?
“When we drive out of the pits, we switch on the hybrid system, prior to us starting the engine. The system is activated when we start to drive the first time and de-activated when we stop driving at the end of a session.”
Does the R18 ultra and R18 e-tron quattro have the same size fuel tank?
“The R18 e-tron quattro, being a hybrid, has two litres less capacity than a none hybrid but petrol and diesel powered cars have an offset. A petrol-engined car has 75 litres and the diesel has 60 litres fuel capacity. Therefore the hybrid petrol has 73 litres and the hybrid diesel has a 58 litre fuel capacity.”
Does the R18 e-tron quattro have extra batteries for the hybrid?
“There are various systems to store energy harvested for hybrid vehicles. One is a battery while another is with a flywheel. Audi Sport chose the flywheel system for its application. The R18 had to be made lighter by 10% to allow for the extra weight of the hybrid elements to be carried on the e-tron quattro and to still be on the 900kg weight limit. This means that the R18 ultra is ballasted to the minimum weight limit of 900kg. The weight ballast can be placed in the car wherever is optimal at any particular circuit. That can also be done with the e-tronquattro but only to a certain extent. A tremendous amount of effort went into that process. To take an already very light car [2011 R18 TDI], make it even lighter [R18 ultra] at the same time as improving the strength of it and to put in a quattro system, was certainly a feat of engineering.”
Fiona Miller (Q & A from Audi Sport)