Nissan Spec-V: Part 20: Improving Aerodynamics Part II
1/24/2007
In our last segment, Brian Kono of Afterhours Automotive was modifying our Syndicate Customs carbon aero kit to give it true downforce. In this segment Kono completes the finishing work.
We used the vented Syndicate Customs hood to encourage as much air as possible to flow over the top of the car instead of under it, most importantly the large volume of air that passes through the very front through the radiator. This contributes significantly to the car’s overall drag and the air can cause quite a bit of lift if it is allowed to exit through the bottom of the car. Kono had to trim the vent of our carbon hood to clear the top-mounted Garrett turbo, not too hard of a job but important so the hood could close. In my next installment Kono will install some of his exclusive hood vents to increase the amount of top venting. All of this venting reduces lift, improves engine cooling and reduces drag.
Syndicate Customs supplied our vented carbon-fiber hood. It had to be modified to clear our Garrett GT turbo.
A VIS carbon-fiber trunk will shed about 15 pounds off of the back of our car. It will be modified to accommodate our rear wing.Kono also installed the Syndicate Customs carbon side skirts. These had to be extensively modified to withstand the rigors of racing. Side skirts help prevent air spilling from the top and sides from curling under the car causing lift. Kono improved the skirts’ effectiveness by adding a flat bottom and a lip made from an aluminum honeycomb material. The lip and the flat bottom will also help generate downforce. He also fabricated sturdy brackets to hold the skirts as the original typical sheet metal screw and double stick tape method of mounting would quickly get torn off under racing conditions.
Brian Kono modified our Synicate Customs sideskirts with a lip and flat bottom to make them more effective.
Kono added these additional brackets to positively attach the side skirts to the chassis pinch weld area. The skirts would be quickly ripped off under racing conditions without this additional reinforcement.At the rear of the car, Brian finished off the diffuser he started work on in my last segment. Two exit ducts relieve air pressure trapped in the rear wheel wells to reduce drag. The diffuser has a 10-degree kick up to prevent flow separation from reducing its effectiveness while the vertical strakes act as vortex generators to improve flow attachment in the diffuser, improving its effectiveness over a wider range of speed. Kono fabricated the floor of the diffuser from sheet 6061 aluminum and the end plates and vortex generators from an aluminum carbon sandwich. Kono used a hand-shrink device on the aluminum support rib’s compound curves and used aircraft rivets to hold the assembly together. The whole diffuser is bolted to the rear and can be quickly disassembled for repair if need be.
Kono installs the diffuser assembly to our chassis. Bolted to an aluminum support structure, the diffuser can be easily and quickly removed for servicing and repairs. This is important on a race car.
These ducts vent high-pressure air from the rear wheel well to reduce drag.
The rear diffuser itself has a 10-degree upward kick to reduce the chances of flow separation and stalling. The vertical strakes act as vortex generators to energize the air flow thru the diffuser and reduce the chance of it staling and rendering the diffuser ineffective. They also make the diffuser more efficient at lower speeds.
A diffuser can be a significant contributor to grip at high speeds.
Complex compound curves in metal such as those used by Kono to make the support ribs for our diffuser are created by the art of metal shrinking. A shrinker puts tiny crimps in the metal to make it shrink so it can bend without buckling.
For the car’s interior Kono fabricated aluminum floorboards with a grip tape surface to help the driver hold his feet in place. A carbon-fiber dash was also constructed. To fill the hole created when we removed the sunroof panel, a carbon-fiber plug with a foam core was created to make a sturdy but lightweight cover.
Aluminum floorboards protect the driver’s feet from exhaust heat.
A carbon-fiber dash is ultra light.
To cut out the carbon/foam roof plug Kono firsts uses masking tape to mark the cutting path.
Next Kono cuts the plug into shape using a saber saw.Side windows were cut out of scratch resistant Lexan sheeting from Shields Inc. Kono also mounted the rear Lexan window which was also molded by Shields Inc. The Lexan front windshield will be mounted soon. While mounting the passengers’ side windows, Kono also cut out and fabricated a NACA duct for the driver’s onboard fresh air systems in the rear window.
The Lexan side window was cut out for a NACA duct.
The NACA duct feeds the blower for the driver’s fresh air supply system.
The heavy glass rear window was replaced by a lightweight Lexan part custom-molded by Shields Inc.Kono also added an oil cooler to our QR25DE motor. The oil cooler and a remote filter system will be mounted on the right side getting fed air from a vent in the front bumper. An airbox for the engine’s air filter will be force-fed air rammed in from a vent in the left side of the bumper.
Kono fits our 13-row Setrab oil cooler.In our next installment, Kono will continue to finish out the car’s interior and aero systems.