The Ligier JS P2 is the first racing car to be entirely designed in house at Onroak Automotive design. It was intentional that the JS P2 was going to compete in LMP1, but customer demand saw them switch to the lower class of LMP2. At all four corners of the globe, the JS P2 has been competing from 2014, a design which is easily modified to fit the new LMP2 rules, which come into place in 2017.
The JS P2 is a multi-usable racer, which has been designed so that three engines on offer, the HPD, the Judd HK and the Nissan VK45, can all be installed in the car’s engine bay, this was implemented to save costs as well as making it easier for its customer’s.
Most of the aerodynamic work took place in 2012/13 in Switzerland, the same wind tunnel the Perscarlo 01 was designed, which was a very successful P2 car back in the day. Back when the car was being designed, the low drag philosophy of Onroak remains, which can be seen by the tiny air box on the cockpit, as well as large
slats after the front wheels.
Onroak had constructed an all new Carbon Fibre monocoque for the JS P2, which saw a separate survival shell with the bulkhead and rear sub frame attaching afterwards. All connections are made from Carbon composite tubes. When looking at the front bulkhead in more detail, we can see it’s pretty standard technology. Torsion bar suspension is mounted quite high, this is due to the high tub line of the chassis. It’s a very tidy design which sees a nice layout of front brake cooling as well as the wishbone mounts.
When looking at the engine installations, there are three possibilities; Judd 3500L V8, Nissan 4400L V8 and the HDP 2800L V6 turbocharged. The profile of the Nissan block is very flat and low, with a small plenum on top for engine combustion. The Nissan has been the best by far in 2015, which has seen the G-Drive team win on multiple occasions.
The HDP engine has been the worst of 2015. Being turbocharged means more space has to be taken at the rear, so you lose out on aerodynamic efficiently. A turbocharger need’s an intercooler which is heavy and bulky - not what you need in a tight area. Turbo boosting issue have led to problems for Extreme Speed Motorsports and Oak Racing this calendar year as well as Wastegate failures. The Judd unit is very simple to that of the Nissan by being naturally aspirated. The block internals also remain very similar to that of the Nissan, and the biggest difference is that the sub frame has to be extended slightly so it can house the bigger engine block. Judd have brought new crankshaft and connection rods, all in the gain of more performance.
When looking into the HPD installation, we can note the twin pipes leaving the left and right hand side engine bank. For the exhaust there is a small collector which leads out of a 90° pipe ass seen on the rear deck. For the Low drag set up, the exhaust is moved to the very rear, for less downforce.
Meanwhile on the Nissan engine cars, they have a far more conventional air box with the restrictor mounted at the rear of the intake. You can also note the legality bumps in the roofline too, all this can been seen on the G-Drive car.
HDP powered cars run an unconventional shape air box, which is an upside down triangle shape. Air boxes are shaped so they can control the quantity of air that goes in them in LMP racing - which is why turbocharged and naturally aspirated designs are different. For the HDP turbo, they mounted the intercooler below the engines radiators, for a tighter rear end.
Additionally, on HDP cars, you can witness pipe housing, which can been seen by the bumps in the rear engine cover. The upper bump is from the turbocharger position, which only just fits into the tight packaging of the rear.
The chassis of the Ligier has an elevated keel, which sees the side impact structure and front nose section connected. This was a big design feature as costumers are able to run one of three engines without modifying any of the chassis. Gearboxes are Xtract six speeds for all of the engines. Push rod is used on all four corners of the car which are steal, with six pot calipers all round.
The aerodynamics are fairly simple for this P2 racer. When the car first rolled out, it ran double dive planes on the front leading edges, they were in fact so big, and they were supported by a mini pylon that was shaped into an aerofoil. This was to help the nose from diving into the tarmac under braking.
Ligier had trouble with this, and so went back to the drawing board. The new design saw a mini endplate being installed along with mandatory foot plate of the car. This was the help accelerate the vortices downstream of the car, with only one dive plane being used. Furthermore Onroak installed a brake duct flow condinener for optimised brake cooling. The new design saw a clean flow of air to the duct. This can be seen on the inner edges of the front wheel arches, opposite the nose cone.
At the rear deck, you are able to witness the exhaust outlets. For more downforce, they used the concept of the blow diffuser, although in a slightly different manor. The rear exhaust plume will hit the lower rear wing main plane to help push down on the car. Come Spa and Le Mans, Onroak moved the exhaust outlets to the very rear of the car, so they couldn’t be used for a downforce benefit. This is a neat setup change teams can do.
Come Le Mans we were able to witness the high bulkhead height. This is an ageing downforce concept, but works very well still. Keeping a high nose means flow can accelerate to the rear diffuser more, so the venturi effect (expanding high pressure air) can be even greater. By having a low nose means the splitter and foot plate would have to generate most of the downforce. Ligier would take away the fluid projectile method of the Coanda effect at the rear, as this downforce generator can provide an extra 10%, which simple was moving the exhaust to the very rear of the deck.
For controlled flow to the rear, Ligier have four side louvres which are twisted. This will control the flow down the side of the car, of which will be a very smooth profile. By having this controlled, the rear wing and diffuser will produce less vortices so less drag, so more speed is gained.
Many components of the Ligier JS P2 have much in common with the Onroak version of the Perscarolo 01, so much so that the rear ends of each are almost interchangeable and many components are identical.
Looking back at the rear wheel pod and the slats within, these slats help use the rear tyre wake as downforce. When the air hits the slats, the rear outer ends of the car is pushed into the ground, so is basically and full width diffuser in a way.
The Ligier JS P2 is a brilliant little LMP2 racer. With more than average aerodynamics and chassis internals, the car has had great success in America as well as WEC and ELMS championships in Europe. It’s also only in its second year of development, so there is much more to come from Onroak.
LIGIER JS P2
Image: Octane Photographic