A&Q about Lotus
Q:
Originally Posted by perryeyges
Tim,
Won't it accelerate the air flow? In other words cause the air speed in the intake pipe to flow faster when fed by the funnel shape? Makes sense to me but I'm no aeronautical engineer. More of an ignatowski..
Well, you can increase the speed of the flow, but you won't increase the quantity of the flow. Faster flow, will reduce the pressure of the flow, which reduces the density - so faster flow and lower density is the same as slower flow with higher density - the total amount of air that passes through the opening will be the same (for all intents and purpose, because I'm ignoring any small variances due to temperature changes, etc.).
It's still incompressible fluid flow. There is no "ram" effect. You can't get air pressure higher than the static pressure (the pressure of non-moving air). You can open up the intake opening to maximize the total flow, but that's it - you can't get more than the natural maximum in. Making a bigger opening will insure that you get maximum flow, but you can't get more than that without using some kind of compressor (super charger or turbo charger) to increase the pressure above static.
A:
Thanks for the explanation....Very interesting....
A:
I've been thinking that the Exige side scoops (and larger ReVerie ones) may actually add a fair amount of drag. They work like an air brake.
A:
From my reading of technical books, a sealed RAM air can increase power a bit. But only at quite high speeds. Even 150mph is only around 3% increase, and it is quite a bit less at not much less speeds.
That is with a totally sealed intake and of course all the proper mixture adjustments.
Most of the things I've read are a little older, and perhaps a bit more than 3% with modern engine controls- but still very little and still won't do much at all below something like 120mph.
Mark
A:
Originally Posted by TimMullen
Well, you can increase the speed of the flow, but you won't increase the quantity of the flow. Faster flow, will reduce the pressure of the flow, which reduces the density - so faster flow and lower density is the same as slower flow with higher density - the total amount of air that passes through the opening will be the same (for all intents and purpose, because I'm ignoring any small variances due to temperature changes, etc.).
It's still incompressible fluid flow. There is no "ram" effect. You can't get air pressure higher than the static pressure (the pressure of non-moving air). You can open up the intake opening to maximize the total flow, but that's it - you can't get more than the natural maximum in. Making a bigger opening will insure that you get maximum flow, but you can't get more than that without using some kind of compressor (super charger or turbo charger) to increase the pressure above static.
Well.... my understanding is that you CAN get a pressure increase above static via the ram effect... but that it is so low at anything below supersonic speeds that you ought not bother with trying. Turning a funnel into the wind at 100mph might be same as running 0.001 pounds of boost or something like that. But at least you're sure to always get at least static pressure that way. If you aim a funnel into the unobstructed oncoming airflow, at least you're sure you aren't going to accidentally locate the intake in a reduced-pressure area.
xtn