Nicolas Perrin gives an insight to the drag vs. power tug-of-war with the LMP1 cars on the Circuit de la Sarthe.
Le Mans week means sharing invaluable information on LMP1 car design by the ex-F1 aerodynamics engineer, as he said he would do so.
The Tuesday newsletter includes some very interesting ideas and details about the eternal conflict between drag and power.
Aerodynamics was at the heart of the development of myP1. Looking at the new regulation, the fuel consumption restriction gives a new perspective to aerodynamic targets.
In recent years, LMP1 engine power had been reduced from 850BHP down to 650BHP through smaller and smaller air restrictors. This had the consequence of dropping the optimum drag level at Le Mans from SCx of 1.15 down to 0.95.
Now with the engine power being limited by fuel consumption, there is a new parameter in the optimum drag calculation. Indeed when you alter the drag of the car, the fuel consumption changes around the lap. And so you can actually increase the engine power when reducing the drag for the same average fuel consumption. That is because you spend less time at full throttle (faster speed in straight lines and braking earlier).
The new regulation does push us designers to develop cars with a drag level of around 0.75 SCx this year. Lowest than ever before.
This is why you see bigger front wheel arches noses and thinner engine cover tails (to reduce drag signature of the car).
As you can see this year top speeds are about 10kph higher than last year even though engines are about 600BHP now (+ hybrid power at exit of corners).
I was involved very early on the meetings with the FIA regarding the new regulation and I think I was actually the first person to start sketching a 2014 LMP1 car back in 2011. It was a bonus to know that drag reduction constrain very early.
The interesting thing is that in theory cars would go even faster with lower drag but you end up with so little downforce that it becomes very difficult to warm up your tires, you degrade them more and also the car becomes unstable in the Porsche esses. So that's why you need to test on the real track before the race. Do you need to re-increase a bit the drag level so the driver gets enough confidence and a better balance? A tricky game.
myP1 has in theory an aerodynamic efficiency of around 4.5 which would put it right up there with the best manufacturers this year. Now there is always an adjustment to be made when going from virtual simulations to reality to recover these numbers.
For more information on the project, visit .
image from perrinn.com