Flyin' Miata : The extraction hood

On the Track Dog race car, cooling is a big concern. So we developed our extraction hood to pull as much air through the engine bay (and thus the radiator and oil cooler) as possible. With guidance from aerodynamicist Dan Bond, we tried four different prototype designs before settling on the final version. Placed at the point of lowest pressure on the hood with ideally shaped vents, it has proven to be effective even under very demanding conditions. We also made sure it would clear all FM turbo systems and our shock tower brace.

The hump has been removed from the production versions because it looked a little odd.
The panel gaps will be smaller on the rest of the hoods and some additional reinforcement added underneath.
The first production version. The hole for the vents are now better cut.
A common question - what happens with the new hood when it rains? Keith's neighbours are a little worried about him now, but he proved that it has no effect on the car. The sprinkler ran for about 45 minutes and the car started right up.
Heat exits here.
In testing on the track. It works well at dumping heat - and check out that finish!
Here it is! We're not completely happy with the fit, so the mold will be tweaked.
A rear view of the vents. This was our race configuration for 2003 and it worked very well.
The drop-in vents fitted to a stock hood. Here they're riveted on, but a more subtle installation would involve bonding by a body shop.
More sanding with body filler to reach the final shape. This hood will be sent off to David Green to be used as the base for the production models...
Some finish work on the form. This was then covered in mold release and glassed over to make the vents that will go in the carbon hood.
That was fun. Here's where the vents will go.
You can see a carbon fibre hood in the background - that's going to be used to make the molds for the production carbon version.
The final configuration, as tested on the track.
The vents are widened by 3" on each side.
The next generation. This is actually the same hood we started with, only this time we hand-built vents and attached them with rivets. This hood worked better, but we wanted more flow.
The placement is correct, but the shape is wrong. The body shop misunderstood our request - but this is how we raced. The hood did not flow enough air at 140 mph, and started to lift. Back to the drawing board.
The first attempt. The welding caused the hood to buckle, so this one was scrapped for a fibreglass version. We were running out of time for the race.
Some early aerodynamic testing.

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