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Technical Analysis: DPi derivation from LMP2

DPi derivation from LMP2
11/09/2017 -

January 2017 DPi prototypes made debut at Rolex 24 Hours Daytona, opening event of IMSA Weather Tech Sport Car Championship. Given recent withdrawal from WEC by Porsche and effect that this will have on Toyota programs, it seems interesting to see DPi as a possible addition to top level prototype class.

DPi Cars are, by IMSA regulation, derivation from ACO/FIA homologated 2017 LMP2 chassis produced by one of the four approved constructors (Oreca, Onroak Automotive, Dallara, Riley /Multimatic ).

In order to ensure Manufactures a clear brand recognition and evidence of their own style, IMSA introduced design freedom area on nose, sidepod, rear wheel arc and rear valance. In addition Manufactures could use their specific engines and electronics control systems.

As a consolidated approach IMSA  guarantee a proper balance in terms of aerodynamics performance between LMP2 and DPi, by means of comprehensive wind tunnel tests, so that diversity is promoted but equally tuned and balanced to create real competition between participants. Engines from different manufactures are verified in terms of power and torque level.

Mazda RT24-P shows clearly how starting from Riley chassis and using design area freedom on front nose creates a prototype with Le Mans body shape with production features and family style of street car.

Front fender is wider and more squared, front brake air duct wider and positioned on leading edge of the side nose surface. Headlamps are thinner and swept back. Front nose is modified with oval shape air inlet that determines higher position of top surface from the splitter leading edge. Bigger channel for airflow is located inside front fender. It seems that slightly more fraction of incoming airflow is pointed under the nose.

Rear brakes duct inlet area are extended sidewise rather than vertically on rear fender curved surface.


Mazda RT24-P (left) vs. Riley Multimatic Mk30 - front nose comparison


Nissan Onroak Dpi, based on Ligier JSP217 LMP2 shows a top panel creating smooth continuity from nose to front fender. It is a big aero change on suspension cover area with wider surface and bigger chord.

This create a tunnel between splitter top surface and top panel surface guiding flow to side pods.

Duct on nose tip shows greater area and is collocated few centimeters below that on Ligier.

Rear brake air duct is positioned on maximum pressure coefficient area on rear fender leading edge.


Nissan Onroak DPi (right) vs. Ligier JSP 217 LMP2 - front nose comparison


Cadillac DPi-V.R front nose shows very limited changes from Dallara LMP2. Fender is less “squared” designed with top surface curved on the front part, as on high downforce configuration of most LMP2, air duct are collocated in same position on nose leading edge but with slightly wider inlet.

Front aero in terms of airflow on top of splitter are almost identical to sister car.

Most noticeable feature that comes from Cadillac’s road car are headlamps, with vertical led strips on later side of the fender.

Engine airscope inlet is wider on top with trapezoidal shape.


Cadillac DPi V.R  (left) vs. Dallara P217 LMP2 front nose comparison


Acura ARX-05 DPi has yet to make its debut in IMSA series, as this is planned for 2018.

Differences from the Oreca 05 are evident. Front aero concept is focused on added V-shaped canard as link between “floating” nose and front fender. This creates a defined airflow path on area above the splitter.

Chassis nose is finer on leading edge with air duct with increase height. Top surface of Oreca splitter is unchanged.

Front fender leading shape is modified integrating headlamps with boomerang style and front brake duct.

Engine airscope inlet is smaller with top chamfer corners.


Acura ARX-05 DPi (left) vs. Oreca 05 LMP2 front nose comparison

article by Ing. Riccardo Romanelli
Drawings Antonio Pannullo

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