Can you add power at speed by directing air into the intake? (i.e. ram air intakes)
 

I'm sure this has been covered but I have to ask.

Do ram air intakes work; i.e. can you get added power by directing fresh air right into the intake? One obvious challenge is that the added air pressure is proportional to speed, which causes some real tuning challenges. But with a good standalone ECU running closed loop (i.e. using the O2 sensor real-time), you should be able to handle this.

Surely there are good reasons NOT to do this, but I don't know what they are. I ask mainly because I've seen a race car that has front ducts bringing air directly into the airbox. Seemed odd.

Several reasons, cold air is denser, more 02. The ram effect of pushing air into the intake really doesn't do much at low speed. There is a drag penalty on some intake designs. Having the intake around the rear, where the engine is, is where turbulent air is, not good for intake air.
The race car guys will chime in and yes it has been addressed. I do like the intakes on the lower wing supports of a GT3. That looks like the best area for cold air.

it adds about as much bhp as the infamous "electric supercharger" you can get on ebay as shown in the post above. actually, in F1 the ram air effect is good for several bhp, but that is on a 700 bhp engine at speeds of 180 mph.

This idea was tested many years ago and you need a road speed over 120 mph to get positive manifold pressure. Most ECU only used closed loop only at light load, not WOT.

A real good report was done on Motorcycles when Kawasaki came out with Ram Air. The extra HP is real and measurable. Most of us on Motorcycles with a weight to HP ratio 2 Pounds per HP can get the necessary speed real quick and take advantage of it in a Quarter to 1/2 mile. A car in the 8 to 12 pounds per HP is going to take a Lot longer hence tile for the Police to see you and stop you ! :D:D

With Nos my static HP on my Kawasaki ZX12R is about 300 Rear Wheel HP SAE and the Bike weighs about 450 and with me about 690. So I can reach 200 in about 1 mile. My problem is more Aero Drag than anything else

690-450=240 lb. driver? Maybe try one of those 18 y.o. light weight drivers? I bet that will increase the speed curve!! And yes, that's my problem also....

Everything has been tried with every type of 911. Hard to manage the fuel injection (no race cars I know of run closed loop with oxygen sensor). I have seen some clever ideas, and I have some based on some concepts from the old IMSA days. There is a neat picture of a 934 or 935 on another thread here which appears to have a ram air intake in the front hood area. Lots of opportunities for fooling around, but best to start by pinging people that were around when all of this stuff was tried in pro racing.

actually large openings on the 935 are for the intercoolers, not the intake. Ram air is useless on a turbo car. Clean air is good

ram air has been proven on many a drag racing car, even at lower 3 digit speeds. Check out the restricted intake race classes: They all have forward facing intake