Engine air intake locations Options

[Charles Freeborn]

My car has a downdraft fan and lowered roofline that AJRS was building in the 9o's.
When I installed a CHT I realized that it needed more airflow to the cooling fan. Methinks I'll add some scoop(s) to the equation to see if I can get the head temps down.
So, location, location, location. Three images below. Where will the optimum pickup location be? I've seen a webpage done by a professor who used his AX 914 as a model and did some computer and water tank tests, but I can't read the squiggly lines well enough to tell where the best place to locate scoop(s) is. What I've come up with so far:
Store bought scoops - of the kind one sees on hoods. Kinda cute, fiberglasss, would punch 4" holes through the sail panels, move other stuff out of the way and plumb to a plenum that seals to the top of the fan housing.


Build a lexan scoop / plenum (clear so I can see through it with rearview) and catch the airflow at the trailing edge of the roof. Opening would be roughly 2.5" x 12" to match fan opening (11" round fan)


Build a lexan scoop / plenum that catches air at the leading edge of the roof, would probably run through the interior of the car and out through the rear window opening. This seems the most obtrusive to the driver ergonomics, distraction, etc.



I suppose one more option would be to do a sort of hybrid of the two roof top collectors and have it punch down through the roof just in front of the rear hoop. I've seen one (also an AJRS car) done that way. It too had the raked windshield and lowered roofline as mine does.

What say ye? where is the optimal pressure on a 914?

BTW, I've worked with plenty of Lexan, have all the tools, so fab isn't an issue.

Thanks.

[Jake Raby]

Remember what I told you about upper cylinder pressure over on my Type 4 FB group? Yeah, you need it.


This post has been edited by Jake Raby: May 23 2021, 03:44 PM

[Charles Freeborn]

Remember what I told you about upper cylinder pressure over on my Type 4 FB group? Yeah, you need it.

Yeah, not helping. This discussion is about intake design and placement.

[Jake Raby]

Remember what I told you about upper cylinder pressure over on my Type 4 FB group? Yeah, you need it.

Yeah, not helping. This discussion is about intake design and placement.

Looks like your design is targeting forced air into the engine bay, which would increase those pressures that we conversed about.

I'd consider the old SCCA Production class trick that we referred to as "the stove pipe". We used it in FP with a stock cooling system with great results, some of the stock fans only had 8 impeller blades left in place, forced air did the rest from the left front headlight bucket area, through the cabin, and into the firewall. We were tempted to try running no fan at all, but never did.

The only time I have made the electric fan work was in AX on a Supervee, and once running M1 alcohol.

[SirAndy]

I'd consider the old SCCA Production class trick that we referred to as "the stove pipe". We used it in FP with a stock cooling system with great results, some of the stock fans only had 8 impeller blades left in place, forced air did the rest from the left front headlight bucket area, through the cabin, and into the firewall.

Rich Bontempi's FP 914 has the same "stove pipe" setup, from the front through the cabin and firewall and straight into the cooling fan.
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