The Dallara P217 is the first Le Mans Prototype for a few years to be built by the famous Italian constructor. Its last LMP was of course the early generation Audi R18, and its deal with the German marque meant that it could not build Le Mans cars under its own brand during the whole R8-R10-R15 programme. However with that partnership coming to an amicable end (another Italian firm, YCOM, was responsible for the final generation Audi R18s) Dallara set out to develop an all new design for the new LMP2 technical regulations.
The first sighting of the new design came unexpectedly via a press release on a completely unrelated project. In the background of this picture of senior Dallara Manager Andrea Pontremoli the early wind tunnel model of the P217 is seen in the working section of Dallara’s own wind tunnel.
The official reveal of the car did not come until late 2016 and then with very little fanfare indeed. At a motor show in Bologna a P217 was briefly shown off with very little fanfare. Pictures of it testing in Italy had already leaked in the print media. The overall design of the P217 appears fairly conventional as is expected from Dallara, which had a reputation for making conventional, but well executed and fast racecars.
A better look at the P217 came when the Racing Team Netherlands car took part in a number of test sessions including a Dunlop tyre test at Sebring. The car features a raised nose in common with a number of other LMP designs including the ORECA 05, though it is not as extreme as that used on the rival Ligier JS P217.
Front brake cooling is via oval slots on the leading edge of the front bodywork these feed ducts mounted inside the nose of the car leading to the disc and uprights. The front suspension features pushrod actuated torsion bars mounted in the front bulkhead (below).
Rear brake cooling is via ducts on the leading edge of the rear wheel pods (below)
The social media account of Racing Team Netherlands has given a good overview of the Dallara LMP2 design including this look inside the cockpit (below) all 2017 specifcation LMP2 cars use identical electronic equipment supplied by Cosworth, the only realy variance is how the various components are mounted.
Cadillac DPi-V.R
Dallara collaborated with General Motors throughout the development to create a Daytona Prototype International (DPi) specification variant of the car. This version of the design made its track debut in private testing in late 2016.
Despite the dazzle ship wrap on the car it is possible to discern some of the differences between the Gibson V8 powered P217. In some areas the bodywork is far more angular, partly for styling reasons and partly for aerodynamic performance.
A clearer look could be had when the Action Express and Wayne Taylor Racing teams ran thier new cars in testing at Daytona. The ducting in the nose is reshaped for brand identity/styling reasons but serves the same brake cooling role. (above)
The headlamps have been restyled again for brand identity reasons and the leading edges of the front wheelpods appear to have been reshaped with the leading edge of the bodywork on the DPi version (Above) slightly more pronounced compared to the LMP2 version (below)
Work on the car seemed not to have been fully finalised when the ‘dazzleship’ shakedown pictures were taken of the Cadillac DPi-V.R. Note the four horizontal louvres on the side panel of the car (below)
These were absent on the cars which ran at Daytona in late 2016, instead a set of Porsche 919 inspired louvres further forward on the bodywork were fitted instead (below) – these were absent on the shakedown – as was the NACA duct clearly visible on the test cars at Daytona.
These curved louvres also appear on the Dallara P217, and appear to have carried over after the horizontal ducts were abandoned on the Cadillac, though the Dallara has four slots and the Cadillac just three, note also how the trailing edge of the front wheel pod differs completely between the P217 (below) and the Cadillac, as does the turning vane in the outlet.
A look at the side panel from the rear shows the outflow from under the nose and around the inner edge of the front wheel pod. Note the position of the central turning vane which has either failed or is flexing under load.
Now look back at the louvres in that first of the three pictures of the side panel above, does something look a bit off about them? Well looking at the pictures we thought so too and looking at them from a different angle it becomes apparent that they are just printed on!
Indeed looking elsewhere on the bodywork in the shakedown pictures there are a number of other misleading shapes on the wrap applied to the car including fake brake duct shapes and an air outlet on the engine cover.
These are all shapes you may expect to find in these areas but the fact that GM went to such lengths to hide the true shapes of the car (which are readily visible from other angles in the same shoot) seems a bit bizarre.
Such an approach only really works when a car is view from a specific angle, so in the image above it looks as though the Cadillac has a ducted nose, but in another image (below) released at the same time the effect becomes obvious.
This follows the first known attempt at such visual deception on a modern competition car – Red Bull Racing in 2006, printed fake exhaust exits on its bodywork, exactly where you would expect the real thing to be. What Red Bull was trying to cover up eventually went on to become known as a ‘blown diffuser.’
The Cadillac is fitted with a new normally aspirated 6.2 liter V8 engine which GM claims shares inherent architecture with the engines of the third-generation Cadillac CTS-V prodcuction car and fifth-generation Cadillac Escalade. The the rear wheels are driven through an X-TRAC paddle-shift transmission, it is not yet clear if this requires a different casing in DPi specification, but certainly will require a different bellhousing for the much larger engine than the P217 which was designed around the 4.2 litre Gibson V8.
As a result of this different engine the DPi version of the car features revised rear and side bodywork, not least because it accomodates an entirely different engine. Note the twin exhaust exits on the engine cover where the P217 has a side exit exhaust.
The air intake on the rollhoop of the car has been reshaped on the DPi for similar reasons. Compare the P217 (Gibson) version (above) with the DPi (Cadillac) version below.
The DPi version also features some interesting detailing just behind the intakes (below), air is ducted out from around the restrictors.
It is an approach used on the 2011 Audi R18, also built by Dallara, though with slightly different execution (below)
During the second outing for the Cadillac DPi, again at Daytona the rear wing of the car was adjusted with the addition of a gurney flap over part of its span (below)
To off set the rearward shift this would cause an extra dive plane was added at the front of the car (below). It is not clear if these parts were introduced for Daytona only or if they will be used at other circuits.
Le Mans 2017
The Dallara P217 was equipped with a new low drag body kit for Le Mans, and it certainly worked, at least in a straight line. With a peak speed in excess of 341kph the car was the fastest of all on the 2017 test day, however a number of drivers fed back that the car was difficult to drive in the corners and lacked downforce.
The most visible element of the low drag Le Mans kit are longer front wheel pods with a curved leading edge. A small dive plane sits atop the outer edge of the front splitter.
Compared to the standard higher downforce version of the bodywork the difference is clear to see. Compare the alternative front sections sat next to each other in the pits at Le Mans, note the additional length of the Le Mans variant.
The rear wing is mounted far lower on the end plate in Le Mans trim compared to the normal WEC/ELMS specification (and indeed Dpi) specification.
Note the rear wing adjustment, neatly integrated into the end plate.
At the trailing edge of the engine cover there is a small gurney used on the high downforce package (above) but it is absent on the low drag version (below).
This design is vaguely reminiscent of the solution controversially used by Porsche on the 919 LMP1 in 2014
The Porsche design was controversial as it flexed at high speed (below),
reducing drag
Porsches design had to be modified in 2014. Racecar Engineering’s ‘finger test’ suggests that the Dallara bodywork only flexes a small amount if at all.
While the top speed of the Dallara was good the low speed performance of the car was not so good. As a result two of the three teams running Dallaras at Le Mans tried out the high downforce package. But both proved to be slower than the team running the low drag bodywork.
TADAH
A look inside the cockpit of the Dallara, the Cosworth electronics equipment seen is common to all LMP2 cars built to the 2017 rules.
The front bulkhead of the Dallara can be seen here fully built up and with the master cylinders moved aside (below)
