Exactly my point. How do you fill the void more quickly when you're not creating an inlet for more air???...and in the case offered in the original post, air intakes were actually REMOVED from the front end of the hood!!!

You can't increase airflow through a space without increasing intake and exhaust. The reverse vents allegedly take care of the exhaust part but since the air isn't going to move into the engine bay more quickly than the car is traveling down the road unless you're also adding add'l venting to the front of the car you've accomplished NOTHING. And, in the case of the EVOIII hood in the pic, they've actually REMOVED intakes.

The physics behind this one really aren't that tough.

-Eric

 

i was just looking at it again, and the first rotor hood or w/e looks a whole lot like the star trek symbol

 

Sue,

Actually what he is saying makes complete sense, In my line of work (E-3 AWACS Flight Engineer) we actually have a system on the airplane that works much the same way. I'll use the aircraft as an example...

When the Aircraft is sitting still we have a couple of fans driving the electronics cooling system. This draws air from the cabin over the electronics then dumps it out through a vent (hole) on the side of the aircraft. Now, as the aircraft speeds up the fans gradually turn off, Due to the fact that the negative pressure of the air moving over the exterior vent on the aircraft is such that it actually draws (sucks) the air out of the cabin (which is replaced by airconditioning and such) and over the electronics. The negative pressure of the air is so extreme that if the fans did not automatically shut off they would burn up the motors from spining them so fast. Its really that effective!

This hood works on the same principle... The air moving over the hood creates that negative pressure over the vents causing a vacume, there by sucking that hot air out of the engine bay. You are correct is saying the 'void' in the engine compartment is not being filled any faster. However.. The hot air is not given a choice about leaving or not.. Its getting sucked out regardless. But since there is more positive pressure from the the intake area on the front of the car, we can assume that the air leaving will be replaced by the cooler air coming in the nose. Now, how well does it work for auto purposes? I really can't say, airplanes are my biz. Is it ugly?.. Umm yes! very! :p But the principle is sound.

Also you realy can't compare Ram Air to this idea, as Ram Air is ducted directly into the engine. It's essentially a cold air induction system. This hood is aimed at air evacuation.

So, Long explanation aside.. the hood is still ugly, Ram Air is cool but for a different purpose. Sorry if I bored anyone! :D And now back to our normal programming!

 

I haven't had physics since college, but it seems that this would only be the case if intake and exhaust were a balanced system. However I don't think that they are balanced in this case. I think the exhaust is restricting the airflow, not the intake. Airflow through a parachute would be greater if the parachute had a hole in it for the air to exit through (an "exhaust") wouldn't it? Isn't this why a hole in a parachute will make it ineffective?

Or am I just totally off base here?

 

Very cool! That's actually very helpful and interesting!

But, I still have the same questions and doubts about its application on the RX8. I certainly defer to you on the physics behind the negative pressure principle but it seems to me that two key points are very different on the RX8:

1) Speed sufficient to create the negative pressure. In the case of an aircraft, you indicated that fans are required when the aircraft is on the ground, and are gradually shut off as the aircraft increases speed. Aside from the radiator fan, the RX8 doesn't have fans dedicated to assisting this principle. How fast does an RX8 need to go in order to create sufficient negative pressure over the hood that will suck the hot air through the reverse vents?

2) Intake. (Read this as more of a question for you too) If air is removed from the cabin and not replaced at an equal rate, air pressure in the cabin will drop, right? Now, obviously air isn’t flowing through the cabin at 200mph (talk about a bad hair day) but in the case of an aircraft, the jet’s “air conditioning and such” has to be calibrated to handle the rate at which air is removed from the cabin in order to maintain some consistency in air pressure. Right?

In the case of the stock hood vs. Veilside hood with all other things equal, assuming the RX8 can generate enough speed to actually create sufficient negative pressure to extract the hot air, wouldn’t you need to increase the rate at which air also enters the engine bay (e.g., larger vents in the front bumper, etc) to compensate for the reduction in air pressure in the engine bay, and thereby allowing increased airflow into and through the engine bay?…or wouldn’t there be a decrease in pressure under the hood (which isn’t good for generating power - for those who doubt, try driving a naturally aspirated car from the plains into the Rockies)?

-Eric

 

i'm bad with physics, but if equal air were being inducted to the same amount being pulled out, wouldn't it create an equal balance in pressure, and not do anything?

I have had revers vented hoods before, and yes you can feel hot air coming out. I've taped a ribbon to the area of the slope to see what it does, and it does move when the air is being pulled out. Usually at freeway speeds. It's unscientific, but thats how i could tell.

 

IMHO you guys didn't prove much at all with your argument...and where are the FACTS??? I'm sure SOMEONE knows about car aerodynamics/mechanics enough to kill this bad boy....

 

With my complete inexperience with physics, and engineering, would like to say, that even THAT slight of an angle on the hood would create SOME downforce, helping the car stick down up front, slightly(almost inexistently) increasing traits of FWD.
The vents look, as if they would certainly help a little, in removing hot air with other air, regardless if it is hot or cold. This would, without any intake, slightly create more drag(because of the air trying to go in and out thru the same vents; havoc.) but somehow increase airflow under the hood.
If you add up downforce+drag, this equals slightly less speed(I'd say 5 mph max....), but, if you have a turbo or something, somehow it might keep temp. down....
That's from speculation, and what I learned from GranTurismo 3 tuning....

 

Simple physics here....heat always travels from hot to cold. So the vents will provide a means for hot air to escape from under the hood. As to whether that design will pull air out at high speed I have no idea. I guess it would all depend on the flow of the air over the humps and what sort of pressure zone it would create by the vents. The reverse duct hood of the early 70's TA sucked air into the engine because of the low pressure zone at the bottom of the windshield if I am not mistaken.

 

1) Of course you're going to feel heat coming through a vent...regardless of its direction. Stick your hand over an erupting volcano and you'll feel heat there too.

2) I once taped a flag to my antenna. You know what it proved? Turbulence. Flag even waved more quickly as I sped up. Imagine that. <rolling eyes>

-Eric

 

Said that. Read my post.

Very scientific. Physics by GT3. Yeah, you're right...uh huh.

And, my freakin' Sim keeps playing the guitar instead of partying with his roommate. Idiot's gonna starve too.

-Eric

 

Sue,

Okay here we go, I'll do my best to apply my knowledge to a car. Never thought I'd say this but airplanes are way more simple.. lol (not really) :D

Okay on to your first question. The aircraft uses the fans to 'push' the air, through the ducting, and over the electronics for cooling, then discharging it out the vent. When sufficient negative pressure is available the fans automatically shut down, as sufficient airflow is now 'drawn' (sucked) through the system. This is because as speed increases so does the negative pressure over the vent and as such, so does the 'draw' of the airflow through the ducts.
Now, your absolutley correct in saying that the aircraft would in fact depressurize if we left this process alone. This is because the aircraft in flight is a sealed vessel. If air is drawn out faster than it is replaced, you end up with a negative pressure differential. This would be really dangerous as you descend and outside air pressure becomes greater. Negative pressure inside, positive out is an implosion waiting to happen.
(The system on the aircraft is actually designed to prevent this, and will simply open all the valves automatically and let the pressure equalize. Bad for the ears... good for the plane.. hehe You can deal with the pain, be hapy the plane is still flying right? :p )
But as you might imagine, we don't just leave it. There is a system of valves to regulate the amount of air allowed to be 'drawn' out, no faster than the system can replace it. This prevents the cabin pressure from fluctuating.

For the purposes of the car this isn't nessecary. When the car is moving it has loads of positive air pressure coming in the front, and few places for it to go, except down. We all know hot air rises, so essentially you end up with a hot air 'pocket' or layer, above the point where the air can escape beneath the car. Your question essentially was: Would we need to increase the airflow into the engine bay since we are extracting it via the vents? Simple answer is no, as there is already excess pressure available due to the fact that the air is trapped. We are just providing a fast way for it to escape through a small area.

Also, the amount of negative pressure developed is directly related to the speed of the air over the vent. (Assuming the lip of the vent is designed correctly) Hence, the faster you go, the faster the vent 'draws' out air. Until such time the demand for exhaust is greater than the intake. (meaning you can only suck out as much air as you shove in)

So, I hope this made a little sense. Sorry for the aviation systems lesson up top. Hopefully it was a little interesting.. lol (probably not)
It's kinda interesting to see this cooling idea attempted on a car. Let me just say though, that although the principle is the same, this idea on the car isn't nearly as effecient as the one on the aircraft. This is beacuse the aircrafts system is a 'ducted' or closed system. Under the hood of our beloved 8' is most obviously 'open'

Okay, "This has been your un-official RX8Club.com Daily Aviation Systems Lesson" *Wings Channel Mode off* :D

PS - I still think the hood is ugly... :p I mean, really really ugly..

 

Thanks for the explanation, Jason!

Ditto on the ugly...actually, I'd call it fugly.

-Eric

 

"Jim...vulcan battlecruiser approaching...
you've got to do something!"

(use the cloaking device, sooloo)

 

Man, someone needs to line all the guys up at veilside and shoot them. Everything single one of their designs looks like ricey crap, including this hood.

 

I'm 14, 9th grade, so sue me....:D
oh, and you can change your sim's "free-will" in the options....

and GT3 is awesome!!!yeaaaahhh!!!

 

who cares. it's pretty

 

Ricey???Is it ricey because it has some design flare to it? I guess these kits below are also ricey, because they are made by VeilSide. VeilSide makes what sells, and 9 times out of 10, the more aggressive stuff sells better.

 

VeilSide skyline wide body

 

that s2000 looks nice

 

I second that.....there's no rice in that skillet

BTW...I like that Veilside hood that everyone is putting down...what a concept "people are different".:D

 

At least it might drain the water that collects in the valley on the stock hood while driving.

 

veilside knows whay's up. we should all mindlessly spend all our hard earned denero on thier priducts.

 

That is one sick *** Rx8

 

looks soooo useless. but it doesnt look all that bad.