Originally Posted by JimG
Ram air does work at much less than supersonic speeds.
Not really - you have to be approaching supersonic speeds to get compressible fluid flow
Why do you think they have those big intakes above the driver's head on F1 and Indy cars?
They are no where near compressible fluid flow speeds. The big intakes about the driver's head is to get lots
of air - lots of unrestricted air flow at static air pressures. A scoop can give you more air flow
, but it isn't going to give you more air pressure
. Now, if you have a restrictive air flow, the engine could actually pull a slight vacuum, reducing the air pressure - but that's a different matter.
In incompressible fluid flow - high pressure air will move to low pressure area. So even if you had some magical way of generating extra pressure in that big old scoop, it would simply back flow out the opening to the surrounding air.
Basically you are increasing the inlet air density by converting the energy from the moving fluid (air) into higher pressure (and temperature) in the airbox.
Depends on your point of view (moving or not). But you are correct in that you can raise the air pressure to the static air pressure that "still air" would have. You still aren't going to get higher than that static air pressure unless you are approaching close to supersonic speeds (compressible fluid flow where, basically the air can't move to the low pressure area fast enough).
Originally Posted by R'elise Me
My understanding is that cooler air is more important than "ram air" since cooler air holds more fuel.
Yep, and more "air" too - you get a denser charge of air/fuel.
Removing the snorkel presumably increases intake air temp which is why Lotus put a snorkel on to begin with (as do most mfrs).
Some manufacturers use a "snorkel" to route cooler air to the intake instead of under hood air. But just as important reason is to quiet the air intake - this is one reason that the snorkel is on our engine - one, Toyota made the air box that way, and two, Lotus has to meet relatively strict European noise standards. You can't have a noisy air intake bothering the people now can you?
but the air temp should be significant given the removal of the snorkel puts the airbox opening in a catchment zone for engine heat. Does anyone more scientific out there have any comments?
With or without the snorkel, the air box is going to get plenty of cool air from outside the engine compartment - not engine heated air. The air is flowing into the side vents, into the engine compartment, and out the vents on the engine cover. The air going over the top of the car is going to create a relatively low pressure area there that will effectively "suck" the air through. The air intake (with or without snorkel) is getting the fresh air from the side of the car, before it passes by the engine.
Now, sitting still at the light, you may get a bit warmer air, but it shouldn't be enough to notice...
Compare the Elise to a typical car where the air intake is in the engine compartment, behind
the radiator. It will get significantly more heat from the radiator than it ever will from the engine. Even when moving, it still gets air that has passed through the radiator, heating it up. For those installations, a "cold air intake" (not just a K&N filter on a tube) or a snorkel that gets it's air from in front or the side of the radiator can help a lot with intake air temperature.