By Philip Royle

It’s possible to make a racecar faster without adding power. How? Aerodynamics. Over time, SCCA’s General Competition Rules (GCR) changes. In the case of our project ITA Miata, one somewhat recent rule change meant that we could add a front airdam to the car. In a large (although still abridged) nutshell, is what the GCR’s 9.1.3.8.b says on the topic:

A front spoiler/air dam is permitted. It shall not protrude beyond the overall outline of the body when viewed from above perpendicular to the ground, or aft of the forward most part of the front fender opening. This body outline does not include bumpers or bumper mounts. The spoiler/air dam shall be mounted to the body, and may extend no higher than four (4) inches above the horizontal centerline of the front wheel hubs. It shall not cover the normal grille opening(s) at the front of the car. Openings are permitted for the purposes of ducting air to the brakes, cooler, and radiator. Dealer installed or limited production front/rear spoilers/air dams/wings are prohibited. The spoiler shall have no support or reinforcement extending aft of the forward most part of the front fender wheel opening.

NOTE: Integrated bumper assemblies are defined as those designs where an external non-metallic bumper cover completely encloses the primary energy-absorbing bumper and where this cover could be installed in its normal position with the underlying bumper removed. On cars with integrated bumpers, the front spoiler or airdam may be attached to the bumper cover.

Where an air dam/spoiler is used, two total openings may be cut in the front valance to allow the passage of up to a three (3) inch diameter duct leading to each front brake/rotor assembly.

9.1.3.8.c also plays a role in the airdam design:

No part of the car, except for the exhaust system and suspension components, shall be lower than the lowest part of the wheel rims.

Conclusion? We can use almost any airdam that cannot be seen when viewed from above the car, and as long as it doesn’t extend below the bottom of the wheel rim, we’re golden. However, since our ITA Miata has no brake issues, we’d prefer to go with a more aerodynamic airdam than one with brake ducting.

Why do we need an airdam? The less air that goes under the car, the faster the car will go. How much faster? It really doesn’t matter – any amount of “faster” is what we’re looking for, and airdams are a fairly tried and true solution to cutting through the air more efficiently.

Our search for an aggressive airdam led us down two roads. One road required us to fabricate an airdam to mimic the airdams that are currently being run on F and E Production Miatas, and the other road had us shopping for a more turnkey solution. We started researching the Production-class airdams, but one issue we were coming across was front tire clearance. Production allows for a wide body, where Improved Touring doesn’t. The end result is the Production-style airdams on an IT car wouldn’t allow the car’s tires to turn without hitting the airdam. The airdam could be adapted to work, and maybe one day we’ll give it a shot.

The second road involved searching for something that was already on the market. We soon came across the G-Style front lip from Tougerun. This lip is made from durable and flexible polyurethane, and looks like the factory Miata front lip, but on steroids. It also has two openings in the front for brake ducting, should you need it – we don’t. The G-Style lip cost $199 and comes with all the hardware you need. However, the hardware it came with was mostly self-tapping screws, so we purchased 3/4-inch bolts so we could remove the lip should the need arise.

With the unit installed, we broke out some 0.060-inch black plastic, trimmed it to fit the brake ducts, and bolted it into place, using silicone to seal any openings. We also cut a large piece of the plastic to fit under the car and used aluminum to sturdy the tail end of the under tray. It’s important to note that, per the GCR, the airdam can’t extend beyond the front of the fender opening, and the airdam can only connect to the bumper, so when you’re fabricating the under tray, be sure you stay true to the rules.

What’s behind us doesn’t matter

With the airdam attached, we tackled the next issue: making the car narrow. 9.1.3.9.c in the GCR says: Any interior or exterior mirrors may be used. To us, this means no exterior mirrors are needed. Consequently, we ordered up a set of Longacre clamp on spot mirrors from SafeRacer. These mirrors are designed to clamp onto the cage inside the car and offer a convex view of the world, allowing you to remove the side mirrors, smoothing the airflow around the car.

Unfortunately, the clamp on design of the Longacre mirrors didn’t work in our Miata. To solve the problem, we adapted the stock side mirror mounts to hold the Longacre mirrors by drilling holes on the inside of the doors and stripping the Longacre mirrors of their roll cage clamps. We then used the same black plastic to manufacturer covers for the holes that removing the exterior mirrors left.

Did any of these mods make the car faster? We’ll find out in June 2010 when we take the car to Auto Club Speedway and run it in an SCCA Double Regional with SCCA’s Cal Club Region. But for now, we know it made the car look meaner – more like a racecar.

SOURCES:
Longacre, www.longacreracing.com
SafeRacer, www.saferacer.com
Tougerun, www.trougerun.com

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