As the 919 Hybrid Evo proved at Spa last month, an unrestricted closed cockpit car with fenders can be significantly faster than a Formula 1 car, even in qualifying trim. When there are no rules to break, or even to think about, Porsche can build an incredibly fast machine. As a driver, Neel Jani, has to completely rethink what is possible behind the wheel of an unrestricted Porsche 919 like this, as it is now capable of taking some corners much quicker than it could in race trim. The derestricted nature of the 919 EVO pushes the boundaries of physical possibility, but what does derestricted really mean in this context? What parts of the rulebook did Porsche get to disregard when building this wild-child lap maker?
Here are the five major changes between the LMP1-spec 919 and the lap-time killing 919 Evo
1. Passive Aerodynamics
By subtly changing the shape of the 919 without reworking the base chassis, Porsche was able to build more downforce into the bodywork of the Evo. The front nosecone is flatter and more wing-shaped, while the rear sees the wing widened and pushed out beyond the extremities of the body. With a deeper diffuser front and rear, plus huge body side skirts, the 919 Evo doesn't mess around. Much of the original 919 design is retained, but you can see that this is a much more focused car than the sanctioning body would have allowed to race. Downforce is up 53% over the WEC legal car.
Porsche dropped significant weight from the already welterweight endurance racer. Because the 919 Evo doesn't need to orchestrate quick pit stops, it no longer has an onboard jack system. AS it won't need to run at night, it no longer has headlights. Not required to run hour long stints in endurance style races, a lot of the onboard controls and diagnostics have been thrown away. Basically, it's stripped down to bare bones. In total, Porsche chucked 86 pounds of stuff in the garbage bin.
Because the WEC uses a fuel-flow formula, the 919 Hybrid was limited on how much gas the engine could use per lap. The team did not want to develop a brand new engine, or optimize the engine for a more combustive fuel, so they stuck with the E20 fuel they'd been running, but eliminated the per-lap max, bumped the fuel flow, and increased the turbo boost for a big power increase. Instead of the WEC-approved 500 horsepower, the 91 Evo makes an incredible 720 horses, and that's before we talk about electric propulsion.
4. Active Aerodynamics
In addition to a bigger wing and more efficient side skirts, Porsche developed moveable aerodynamics for the 919 Hybrid Evo, which is 100% illegal in sports car competition. In the case of both the front and rear aero, there are actuated flaps to divert airflow for increased efficiency. On straights, flaps under the nose cone will stall out the 919 Evo's front diffuser, and the rear wing trims out to make the car more slippery. Under braking and in corners, the active aero reverts to a high-downforce high-drag specification to help push the Porsche into the pavement. Aero efficiency is up 66% between the Evo and its competition approved spec sibling.
5. Hybrid Drive
The 919's hybrid motors are dictated in size and capacity by the rulebook, and drivers had to manage when and where around the circuit to use their electric boost. For example, drivers couldn't use the electric horsepower on the long straights of Le Mans, and were barely faster on top-end speed than LMP2 spec cars. With the 919 Evo, Porsche was able to develop a system that is more efficient, provides more power, and doesn't need to be metered out around the lap. The output bump, up 10% from 400 horsepower to 440 horsepower, means that the 919 Hybrid Evo is able to use all 1160 of its horsepower for the entire time it is under acceleration. If Neel Jani's foot is on the accelerator, it's deploying maximum thrust.