Time Attack Terror: FXMD’s Record Setting Acura NSX

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A good view of the cars aero package can be seen from the rear.  A carbon rear wing adds several hundred pounds of downforce as does the rear diffuser.  The exhaust blows over the top of the diffuser which actually improves its efficiency.

The front nose section which contains the front splitter, front canards and lower belly pan quickly detaches from the car in seconds to make repairs easy and to allow access to the front stuff on the very complicated car.

Finally we will have a look at the FXMD NSX’s aerodynamic system.  As time attack cars become more and more sophisticated, the cars aero systems are becoming more and more critical for the overall performance.  Aero is the final frontier of tuning. it is often the extremely difficult to engineer aero package that will determine who will be the winners.  A cars aerodynamics must provide grip enhancing downforce and improve stability with minimal drag.  The downforce must be consistent as the cars angle of attack changes in cornering and in pitch and heave.  The FXMD car uses all of the usually known aero tricks. 

The cars flat bottom makes the rear diffuser more efficient,  and reduces drag.

The rear diffusers job is to make the overall shape of the car more like an upside down airplane wing.  The vertical strakes in the diffuser sever several purposes.  They generate vorticities to help keep the airflow attached to the top side of the diffuser, helping keep it active across a wider range of speed and make the diffuser less sensitive to side flows of air as the car might see when the side angle of attack changes in cornering.

The carbon rear wing makes a lot of downforce.  The Gurney flap at the trailing edge of the wing makes it more effective with only a small increase in drag.

Something that is overlooked by most people is that the rear wing mount must be very sturdy as it takes hundreds of pounds of force.  If it fails, the sudden loss of downforce can be very dangerous.

The carbon front splitter and its mounts must also be able to take several hundred pounds of downforce.  The NSX’s blunt front shape and vertical fascia above the splitter cause stagnation of the air flow and make the splitter more effective.

This sealed duct diverts the air through the heat exchanger for the rear mounted water to air intercooler and the engines radiator.  The shaped duct then directs the air up and out though the louvered hood.  This helps with downforce greatly as well as improves aerodynamic drag.

The NSX features a flat bottom for good underbody air flow.  This leads to a large volume diffuser after the rear axle centerline.  The diffusers job is to activate the underbody air flow to create a low pressure area under the car much like an upside-down airplane wing.  A large carbon rear wing also provides a great amount of downforce and its low pressure wake also helps with diffuser activation.  The exhaust flow is introduced on top of the diffuser which also helps it work more efficiently. A large front splitter creates downforce in the front of the car as does the ducting for the engine and intercooler heat exchangers.  The air is diverted over the splitter and up into the heat exchangers exiting the hood through vents.

The side canards main job is not what most people think, to generate downforce.  Instead they are there to generate side voticites that swirl down the sides of the car that effectively seal off the bottom of the car to prevent air from curling under it.  This makes the rear diffuser work better.  Canards contribute to the total amount of front and rear downforce but they do increase drag a lot.  Thus their use should be considered mainly for cars with lots of power.

Several canards create front downforce and also generate vortexes that help keep the underbody airflow free from influences caused by air spilling from the sides of the car.  The sideskirts work with the canards to reinforce the side vorticities to effectively seal off the car bottom from side airflow at speed.  All of the cars vents and scoops are functional diverting air for cooling or to help enhance the aerodynamics.  We estimate that the cars aero package creates about 700-900 lbs of downforce at 100 mph, very impressive for a full unibody production based car.

The side skirts work with the canards to help prevent air from spilling and curling under the car.  The small fence you see on them makes them more effective.