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Anyone have a trick way to connect the oil cooler duct to the bodywork NACA duct? Industrial strength Velcro maybe?

The duct work on my new/old SRF is in sad shape to say the least. Duct tape holds it to the oil cooler duct and nothing to the bodywork.

The duct itself looks to be a piece of aluminium washer/dryer ducting. Anyone have pics of what this is all supposed to look like?

Seems like a lot of work for not a lot of gain. Why not just spec a cheap electric fan for the oil cooler and be done with it?

Even if the duct was sealed I can't see it flow much when the outlet of the oil cooler is blocked like it is. I only have a small 1x9 inch opening at the bottom.

Rumor has it that the NACA duct doesn't flow much/any air. The cooler gets more air flow from other places. Whether you connect the hose or not depends on where you want all of your small tools and parts to end up when they inevitably enter the NACA duct.

I have a "real" neoprene/cloth hose that I occasionally shove onto the NACA inlet.

Well that is a thought. At least I'd have one place to look for all those tool, washers, bolts, etc.

and cell phones... (right, Tony?)

trakmnky wrote:Anyone have a trick way to connect the oil cooler duct to the bodywork NACA duct? Industrial strength Velcro maybe?

The duct work on my new/old SRF is in sad shape to say the least. Duct tape holds it to the oil cooler duct and nothing to the bodywork.

The duct itself looks to be a piece of aluminium washer/dryer ducting. Anyone have pics of what this is all supposed to look like?

Seems like a lot of work for not a lot of gain. Why not just spec a cheap electric fan for the oil cooler and be done with it?

Even if the duct was sealed I can't see it flow much when the outlet of the oil cooler is blocked like it is. I only have a small 1x9 inch opening at the bottom.

Okay, first -- fastening the hose to the NACA duct. Use a big ol' hose clamp and it'll stay put. Prop up the center section with a wood block to reach it when installing, removing, etc. Also, drill a drain hole at the low point of the hose to prevent it from being blocked off by trapped rain water. And it's a good idea to seal off the oil cooler shroud with duct tape to prevent air leaks that cut flow.

Second -- the oil cooler outlet design. Blame me for that!

It was discovered years ago that high air pressure in the wheel well was, in effect, stalling the flow through the oil cooler and rendering it virtually useless. Jon Mirachi of Racer's Edge detected this when he noted high oil temps on his fleet of rental SRFs. After a conversation with Jon, I sussed out that the best way to get that cooler to flow was to reduce the pressure at the outlet with a baffle that would block the high pressure air coming off the spinning rear tire and divert the oil cooler flow into a lower pressure area of fast moving air underneath the car. I then had a chat at Watkins Glen with the Enterprises' tech director at the time, Dave Liddle, and proposed the baffle/duct that we have now. He agreed it was good idea and included into the car's design. Works pretty well.

So there you have it...my one and only contribution to the design of the Spec Racer.

Mr Devol's description is spot on. Unlike a "scoop" inlet which is located in the free stream air flow and rams high velocity air into a duct. A NACA inlet draws boundary layer (essentially no velocity) air into the duct. Flow is created by low pressure at the duct exit. Scoop inlet equates to increased drag while a NACA inlet is essentially no drag.

bob gardner wrote:Mr Devol's description is spot on. Unlike a "scoop" inlet which is located in the free stream air flow and rams high velocity air into a duct. A NACA inlet draws boundary layer (essentially no velocity) air into the duct. Flow is created by low pressure at the duct exit. Scoop inlet equates to increased drag while a NACA inlet is essentially no drag.

Thanks for adding that point, Bob. I had forgotten to add that NACA duct systems are designed to suck. (Um...rather than scoop.) If I'm not mistaken, boundary layer air is low pressure to begin with so the pressure at the outlet needs to be somewhat lower than the inlet to generate decent flow.

I would guess that leaving the baffle on with the new GEN3 fan system would still be useful as it would be easier on the fan's motor.

(I'm not an aerodynamicist, but I play one in the paddock.)

Note that in the Gen3 the NACA duct may be removed entirely. I assume the new oil cooler will have adequate flow with the fan so additional ducting is not likely to add any cooling advantage (which I assume was insufficient in the first place.)

breton wrote:Note that in the Gen3 the NACA duct may be removed entirely. I assume the new oil cooler will have adequate flow with the fan so additional ducting is not likely to add any cooling advantage (which I assume was insufficient in the first place.)

Actually, the flow is pretty efficient in the GEN2 when set up properly. My car was and it contributed to my low overall coolant temps.

That said, I'd guess that (other than perhaps adding a little cooler air to the mix) the NACA duct is kind of redundant on the GEN3.

I'm curious about the 1x9" opening. The picture shows the rear panel of my right side pod, which is mostly wire mesh for the oil cooler exit. Is this an old configuration? Can someone post a picture of the baffle being discussed?
I do have the neoprene cloth inlet hose, and a hose clamp at the NACA duct. That seems to work fine.