Concept Report
- Super Hybrid Race Car Nürburgring 24h 2008-
from Heinz-Harald Frentzen

The idea of constructing a racing car which recovers energy wasted during braking is not novel. However, the hybrid concept I chose and deployed at the 2008 Nürburgring 24h Race breaks new ground.

The concept is a combination of the "parallel" and "plug-in" hybrid designs (the three hybrid systems are described in more detail below). My Hybrid Race Car Concept places the electric motor on the front axle because that is where braking energy can be optimally and efficiently converted into electrical power.

This distinguishes the concept from other racing series planning to adopt a hybrid energy recovery design in the future. Other innovators are currently only planning to have the electric motor placed on the rear axle or directly on the internal combustion engine in order to trim weight and cut costs. The rated output of our electric motor can even exceed 100 Kw (134 H.P.).

The main focus of this project was to determine what constant output data we can rely on while racing and how those figures can be enhanced. The decisive factor here is how much energy can be captured by the battery while braking the electric motor under constant load.

How high were the temperatures in the GAIA/LTC batteries and the electric unit? What I can share and want to share is that, under observation of DMSB/FIA, the battery temperatures stayed below 60 °C. While doing test runs on the Nürburgring, every braking operation was recovered and the recovered energy released again during acceleration.

The temperature curve and energy recovery were closely monitored during the event. Our goal is to keep storage and release of the recovered energy in balance, allowing our drivers to keep the battery charge at a constant level. If a driver has used up more power than he was able to recoup during one lap, he can either manually reduce the amount of electrical energy used or increase the battery charge rate during those portions of the race which do not place high demands on the vehicle (stop-and-go/yellow flag/safety car periods).

The battery capacity is geared to allow our car to do a lap on the Nürburgring (25 km) relying on electrical power only. We raced the car with the battery at a medium charge level, though, which was our objective in the first place. This gave us about 4-5 Kwh of battery capacity. This meant that if we had transmission problems at the beginning of a lap, we would be forced/able to return to the pit stop at a very low speed of < 50 KPH. If this happened 6-8 km before the end of a lap then it was possible to reach the pit stop under full electric power going at up to 130 KPH.

We also had the added benefit of all-wheel drive. When accelerating out of a curve with 60-80Kw on the front axle, the car was additionally stabilized by taking load off the rear axle using the pull principle. Our driving team therefore favored going through curves in higher gears and then to utilize the strong torque of the electric motor for accelerating out of the curve.

This gave us the option of driving economically or going after the best possible lap times. We also benefited from being able to use the clutch less. An even greater advantage was that we had far less brake wear than if we had been on the track without an electric brake. Tire wear was also very low. Based on the weight distribution achieved by the battery and electric motor layout, which is now at 50 percent weight balance, it was possible to complete four stints on one set of tires.

I would like to express my special thanks to Norbert Kreyer who, with an industrious and experienced mechanic, worked through a night shift to adapt the race car to match the North Loop (Nordschleife).

As has already been mentioned in the press release, the electric unit used with the HHF Hybrid Concept Car performed very well on the Nürburgring. A subsequent test conducted together with Auto, Motor und Sport magazine once again confirmed the concept's reliability.
This means that thanks to the quality of the components the electric unit is essentially maintenance-free. A negative factor is of course the weight. Our electric unit weighs about 230 kg. Because of budget constraints, we were unable to devote too much effort to get the car down to the weight limit of 1,300 kg.

Another problem we encountered was with the conventional transmission. The transmission failed too soon for us to be able to hold our own in the race. The second transmission also broke down after a few hours on the track.

Planning, initiating and executing the project was a lot of fun. Of course this is only possible if you've got a good team. I have already extended my thanks to all partners and team members who worked on this interesting project and can't say it enough. We had good and bad experiences and I hope we can apply what we learned to meet the next challenge.

Heinz-Harald Frentzen

Parallel Hybrid:
See the wikipedia article http://en.wikipedia.org/wiki/Hybrid_vehicle_drivetrain#Parallel_hybrid
Plug-in-Hybrid:
See the wikipedia article http://en.wikipedia.org/wiki/Plug-in_hybrid
HHF Hybrid Concept Car:
New Hybrid Concept.
Two separately operated drive units with one drive on one axle, the other drive on the other axle.
Driving range of 30-40 km in all-electric mode. The driving range can be extended or reduced. Like "plug-in-hybrid" or "parallel hybrid" technology.
Conventional operation with an internal combustion engine as found in "parallel hybrid" concepts.
The internal combustion engine can also charge battery much like in "parallel hybrid" and "plug-in-hybrid" concepts.