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Question:

Would engine lid rearward-facing scoops such as these...

http://nabeck.web.fc2.com/hg-awaw.htm

... help the AW11 by forcing air back (instead of up) and potentially reshaping airflow down further toward the back of the car?

This seems (to me) like it would work, assuming one is running some aggressive upward-blowing fans and/or a scoop underneath to force more air up into the engine bay.

Let me know if this sounds like total :bsflag: .

Just throwing some thoughts out there.
 

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I'm no expert on aerodynamics but my guess would be that the airflow over the back of the lid will pull air out of the vents and aid in the designed bottom in and out the top flow the car has.
 

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Caprandom said:
I'm no expert on aerodynamics but my guess would be that the airflow over the back of the lid will pull air out of the vents and aid in the designed bottom in and out the top flow the car has.
The air over the engine lid is stagnant. I don't think this kind of engine lid has any kind of aerodynamic effect. It may actually cause less-dense hot air from the engine to reduce the effect of a rear wing if the car is equipped with one.
 

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USDMSW21 said:
The air over the engine lid is stagnant. I don't think this kind of engine lid has any kind of aerodynamic effect. It may actually cause less-dense hot air from the engine to reduce the effect of a rear wing if the car is equipped with one.
It's definitely not stagnant. There is a turbulent eddy over the engine and behind the window, more so on the taller MkI than the MkII. The eddy has a fairly high velocity and corresponding low pressure, thus it will induce flow from the engine bay out the top of the lid. The stock engine bay vents on the Turbo are in a perfect location to draw as much air as possible (not much) out of the engine bay. Putting big funny scoops like in the above photo will just serve to isolate the engine bay from the eddy and reduce flow out the back, unless it's fan-assisted.

The stock spoilers on both MkI and II do basically nothing because they're stuck in the turbulence caused by this eddy.

Superpilun showed in his CFD analysis of the MkI that a fan in the lid pulling down into the bay caused the airflow over the roof to reattach closer to the body and actually decreased lift because the air over the spoiler was not so turbulent, and vice versa for fans blowing out of the engine bay. If you spend a couple hours going through his thread you'll get a really good idea of the total aerodynamic package of the MR2.
 

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You know I never thought about it till now but it makes me wonder if the rotational direction of that eddy could actually plug up reverse scoops like that.
The direction of airflow on top is towards the back of the car and down low the air should actually be flowing forward theoretically hitting that scoop with a high pressure zone. I doubt enough to create a reverse flow. Id guess if anything just enough to pretty well minimize flow in either direction.

It's surely not an ideal design for air flow.
One that may work better could be a simlar scoop that goes all the way to the back of the car. If you were able to catch the low pressure zone right at the tail it could help pull air through and fill that low pressure zone a little.
 

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My plan for some time has been to implement scoops just like that and a piece of plexiglass across the flying buttresses that matched with the scoops in an effort to increase the velocity across them and hopefully create a low pressure area. Of course I'd need to conjure up a way to check the before and after to see if it actually worked. Yarn and scotch tape?
 

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supercharged111 said:
My plan for some time has been to implement scoops just like that and a piece of plexiglass across the flying buttresses that matched with the scoops in an effort to increase the velocity across them and hopefully create a low pressure area. Of course I'd need to conjure up a way to check the before and after to see if it actually worked. Yarn and scotch tape?
That will tell you a lot.
Unfortunately the butress is at too steep an angle. I think if you went across at that angle you would still have a turbulent pocket in that v between your Plexiglas and the trunk.
I can't wait to show every one my design but it's top secret till I can show it off :smile:
 

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Well for the transition from the roof to the plexiglass I was contemplating using some vortex generators, or even fabbing a little fiberglass lump. Getting any data on that might be more difficult, like having a friend take video of said yarn and scotch tape from my truck driving next to the 2. Don't really know how I'd handle the transition from plexiglass to trunk, but the possibility of having to extend the vents an inch or 2 out of the plexiglass has also crossed my mind.
 

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Smooth transitions are important but just about anywhere you read about laminar flow, be it an airplane wing or an intake system anything beyond 10-15 degrees off the angle of airflow will create turbulent airflow.
 

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True as that is, I really wonder if the good still doesn't outweigh the bad with even a poorly designed piece of plexiglass hastily slapped on back there.
 

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yoshimitsuspeed said:
Smooth transitions are important but just about anywhere you read about laminar flow, be it an airplane wing or an intake system anything beyond 10-15 degrees off the angle of airflow will create turbulent airflow.
thus the vortex generators on the back of evos, go off of what mitsubishi did, they wind tunnel tested it extensively. The plexi your talking about would be similar to a fastback engine lid right? To garner the maximum effect from that style you will want the vortex generators. 25 mm tall, the equivelant of the boundary layer, 100 mm upstream from the roof end, seperated by 100 mm (from eachother) and each vg should be angled at 15 degrees out of the airflow.

Take a close look at the lancer evo and the ones they used on it to get a better idea of what they did. Here are some pics

Without VG
[/IMG]

With VG
[/IMG]

Side by Side
[/IMG]

Combine this with a fastback style engine lid, or a plexi style like on some mr2's and you WILL drastically increase your aero efficiency on the back end. Worried about too much air in the engine bay from underneath, seal the bottom with an underbody panel. Which will also increase aero underneath the car.
 

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The other issue is the sharp transition at the base of the plexi, I suppose a step could be formed to help alleviate that. Now if the engine bay were sealed then there'd be no point in having the vents would there? Maybe if you were to seal it off with the exception of some NACA ducts down there. Where did you get the figures for placement of the VG's and the thickness of the boundary layer? Those aren't universal, are they? Do they vary with speed?
 

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Has anyone considered using the low pressure zone behind the car as a means for pulling air out of the engine. If one were to route air from the enigine thru the trunk and somehow outside via ducting between the taillights this would help draw air out from beneath the car. Combine this with the type of fastback sealed engine lid design you mentioned and i feel this would definately help with rear end and underbody aero. Comments?
 

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I know Bill mentioned before that low pressure area out back can affect the airflow all the way to the front of the car so it really makes a guy wonder if what you said were done what would happen up front as well.
 

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The engine bay still has side vents, so sealing the bottom wouldnt be a problem, as long as there is drainage for water. A naca duct would be fine down there as well, they wont cause turbulance. The numbers for vg's are what mitsubishi used on the evo, they found that at those numbers you achieved the happiest medium, both a decrease in drag and lift were achieved.

The boundary layer on the mkII is about an inch, I would imagine it is pretty similar on a mkI, which is close to height of the vg's, 25 mm(almost 1 inch, .4 mm short). 15 mm doesnt do much to decrease lift, just lowers drag, and 30mm increases drag slightly.

And Bill is right, your aero needs to be balanced, with the fastback lid and the vg's your going to see a significant difference in front end downforce, it will mess up the balance of the car if you dont take care of that too. Our cars mki and ii need more downforce up front anyways. So a more efficient back will enhance the effect. If you do what I was showing then you would probably want a splitter to compensate, fender vents up front would help alot too, big high pressure zones.
 

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Eversor said:
The engine bay still has side vents, so sealing the bottom wouldnt be a problem, as long as there is drainage for water. A naca duct would be fine down there as well, they wont cause turbulance. The numbers for vg's are what mitsubishi used on the evo, they found that at those numbers you achieved the happiest medium, both a decrease in drag and lift were achieved.

The boundary layer on the mkII is about an inch, I would imagine it is pretty similar on a mkI, which is close to height of the vg's, 25 mm(almost 1 inch, .4 mm short). 15 mm doesnt do much to decrease lift, just lowers drag, and 30mm increases drag slightly.

And Bill is right, your aero needs to be balanced, with the fastback lid and the vg's your going to see a significant difference in front end downforce, it will mess up the balance of the car if you dont take care of that too. Our cars mki and ii need more downforce up front anyways. So a more efficient back will enhance the effect. If you do what I was showing then you would probably want a splitter to compensate, fender vents up front would help alot too, big high pressure zones.
 

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mjbenoit11 said:
Has anyone considered using the low pressure zone behind the car as a means for pulling air out of the engine. If one were to route air from the enigine thru the trunk and somehow outside via ducting between the taillights this would help draw air out from beneath the car. Combine this with the type of fastback sealed engine lid design you mentioned and i feel this would definately help with rear end and underbody aero. Comments?
i wouldnt do a sealed engine lid, seal the underbody sure, but not up top. Still have the air from the side vents to deal with, that would go up and out the vented fastback, think of a louver. If your wanting to pull excess air out from under the car you could make naca ducts and use tubing to route the air out the back, that should help pull air from under the car.

Hell, there was a formula car years and years ago that achieved some great downforce numbers by rigging up a vacume to pull air from under the car and venting it out of the top. Until they got busted. Cool idea though.
 

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Eversor said:
Hell, there was a formula car years and years ago that achieved some great downforce numbers by rigging up a vacume to pull air from under the car and venting it out of the top. Until they got busted. Cool idea though.
Chaparral 2J ---> Click
 

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Eversor said:
i wouldnt do a sealed engine lid, seal the underbody sure, but not up top. Still have the air from the side vents to deal with, that would go up and out the vented fastback, think of a louver. If your wanting to pull excess air out from under the car you could make naca ducts and use tubing to route the air out the back, that should help pull air from under the car.
IIRC, according to some software simulations, the airflow to the side vents was disrupted by the mirrors and thus rendered them relatively ineffective. I wonder if you lit a smoke bomb behind a dyno fan if it would reveal anything about the airflow characteristics of the car.
 
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