medea vs border style ducted hoods - Page 2 - MR2 Owners Club Message Board
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post #21 of 73 (permalink) Old August 28th, 2009, 17:52
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Originally Posted by bentheswift
So what you're saying is, your car now oversteers more the faster you go?? And if we for a moment believed that this was true, how would this be a good thing??
I don't know about oversteer but the stability is definitly there and also the heat that gets trapped between the radiator and the firewall when the car is idling seeps out through the air dam as well! Doesn't that sound like a good thing to you? I'm not an expert as yourself about this but I can only tell you from my experiences. Before I did this to my hood I got the Idea from the Japanese JGTC racing MR2s in my Hyper Rev book. The design of the hood must be functional if they were utilizing it .............. right? And to top it of IMO I think it does look bing as well!
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post #22 of 73 (permalink) Old August 28th, 2009, 18:11
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If you add grip to the front of the car but not to the rear, what happens... oversteer! And oversteer progressively getting worse as speed increases is... a recipe for killing yourself. Aero packages must be thought out so as to provide a top view center of pressure that is near the center of gravity, so as to provide stability and intuitive grip as speed changes... but big, blunt, closed-cabin passenger cars such as an MR2 and every other street car don't generate much if any downforce (at least not even on the same order as mechanical grip) without much more aggressive modifications than your scoop. Nor do they go fast enough that it matters (regardless of how much we'd like to think it does). Otherwise we'd have a lot more MR2 owners spinning when they decide to go street racing at high speeds, or if lucky at track day.

Super GT (once known as JGTC) cars have aero packages that are intelligently thought-out and crafted throughout the entire car. They use significant amounts of drag (such as would cost you noticeably more money at the pump when highway driving) to generate significant downforce at the speeds they corner at... 80-140mph cornering speeds. The focus is always on stability and predictability rather than total grip, as any safe car (street or track) should be.

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post #23 of 73 (permalink) Old August 29th, 2009, 01:34 Thread Starter
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so the ducted hood idea is a benefit (if even small) or a draw back

when properly ducted to help create a vortice as described earlier to speed the air up upon exit to the air above the car.

What im trying to get at is do we really want the air from our radiators spilling out under or over our car?
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post #24 of 73 (permalink) Old August 29th, 2009, 03:16
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To the people saying this will make your oversteer, that is easily fixed by adding a rear wing. Increasing rear downforce is really easy...its increasing front end downforce on a mr car which has no weight up front which is difficult.

Personally, I feel a big difference in front end lift when I drive on the freeway at 80 with the front underbody panels off. I also feel a difference in lift when I drive on full soft versus full firm.

More downforce is always good, what usually is the downside is that getting more downforce usually requires increasing your drag as well.

Lucky for us, MKII aerodynamics are terrible in stock form. Huge lift at higher speeds, unstable air flow underneath the car, and a useless rear spoiler

With a welder it would be pretty cheap to cut up an oem hood and relocate your radiator. There was a link to a japanese mr2 site which had a good pictorial write up of what he did, it was in one of the other 1000 threads about a vented front hood.

Your also going to need to cut your front firewall so the air can travel upwards from the radiator...
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post #25 of 73 (permalink) Old August 29th, 2009, 11:33 Thread Starter
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cutting the front fire wall is a given, how else is air going to flow up into a vented hood if you dont have any holes for it to go that way?

and front end downforce isnt that truly difficult, slap in some true flat underbody panels, canards to get air away from your front wheel wells and a good sized splitter. Splitter alone can create too much downforce if you dont moderate it with the other aero mods the car has

https://www.mr2oc.com/showthread.php?t=356509

this link has alot of good information on how to overcome the lift issues of the back end and goes into alot of talk on the use of splitters and how to properly design the front to keep air from going under our cars
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post #26 of 73 (permalink) Old August 29th, 2009, 17:38
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cutting the front fire wall is a given, how else is air going to flow up into a vented hood if you dont have any holes for it to go that way?
Do some research on the border hood.

The vents are forward of the front fire wall. You remove the plastic cover over the radiator (between the headlights), and the vents open into that area. It doesn't effect the frunk at all.
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post #27 of 73 (permalink) Old August 29th, 2009, 18:09
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Quote:
Originally Posted by bentheswift
If you add grip to the front of the car but not to the rear, what happens... oversteer! And oversteer progressively getting worse as speed increases is... a recipe for killing yourself. Aero packages must be thought out so as to provide a top view center of pressure that is near the center of gravity, so as to provide stability and intuitive grip as speed changes... but big, blunt, closed-cabin passenger cars such as an MR2 and every other street car don't generate much if any downforce (at least not even on the same order as mechanical grip) without much more aggressive modifications than your scoop. Nor do they go fast enough that it matters (regardless of how much we'd like to think it does). Otherwise we'd have a lot more MR2 owners spinning when they decide to go street racing at high speeds, or if lucky at track day.

Super GT (once known as JGTC) cars have aero packages that are intelligently thought-out and crafted throughout the entire car. They use significant amounts of drag (such as would cost you noticeably more money at the pump when highway driving) to generate significant downforce at the speeds they corner at... 80-140mph cornering speeds. The focus is always on stability and predictability rather than total grip, as any safe car (street or track) should be.
Thats why Border Racing sells all the parts, ie GT wing, front air dam, cannards, etc, to balance things out, no?
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post #28 of 73 (permalink) Old August 29th, 2009, 18:15
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post #29 of 73 (permalink) Old August 29th, 2009, 18:32 Thread Starter
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id like to actually see the border radiator relocation kit on a car to get some ideas (not just the hood).

in those pics above the fender vents have me interested

on many supercars the wheel wells are used to pull air out from under the car and direct it over the car.

thanks for the pics gmtran

*edit: i took a look at the two hoods i posted in the first picture after what you said about the border hood and noticed that the asksport hoods vent sits almost flush with the the top edge of the lights where the border vents sit a good 4 inches closer to the front of the car.

that seals the deal for me. Im not a fan of cutting anykind of holes in cars if i dont need to.

Last edited by Eversor; August 29th, 2009 at 18:35.
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post #30 of 73 (permalink) Old August 29th, 2009, 19:28
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ben, i think you are over analyzing the whole thing. the border hood works. it's not a HUGE benefit, but they knew wtf they were doing and it will help. will it work wonders, no, but it is part of the bigger picture.

add a functional wing, body kit, lower the car and the benefits start to stack up.
post #31 of 73 (permalink) Old August 29th, 2009, 23:47 Thread Starter
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its like cutting weight on the car. a little something here, a little something here, pretty soon your sitting at 200 lbs of crap you didnt really need and a car that feels significantly better.

this is my goal here with the aero, a well rounded 2 thats got just enough of this and that, effective on the track, looks killer and still isnt killing me at the pump.
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post #32 of 73 (permalink) Old August 30th, 2009, 02:19
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Look at the Border's car front bumper. You can see that the radiator is moved and angled so that the air flows in, up and then out hood.
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post #33 of 73 (permalink) Old August 30th, 2009, 13:29 Thread Starter
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ah good call, makes sense, I wonder if the border car puts 100% of that air up through those two vents

i was lookin at the mad psi site and the little diagram they did for their border hoods, it doesnt look the same as the picture you showed, having the radiator angeled so that air seems to just pass across the surface instead of flow directly through the radiator

Now if what was said earlier is true and air can only travel through the radiator at roughly 54 mph, then for optimal effectiveness i would probly want the whole front air damn built to utilize as much flow through the radiator as possible and up through those vents. Sealing it so that the hood vents are the only true exit the air has. With the map psi diagram i see alot of air still going under the car, which to me is less than desireable.

With the whole set am I basically trying to design a velocity stack to get the air moving as fast as possible coming up from the ducts to maximize effectiveness

im just trying to use common sense here. Feel free to tear it up and tell me what needs to be done to do it right

Last edited by Eversor; August 30th, 2009 at 13:44.
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post #34 of 73 (permalink) Old August 30th, 2009, 14:13
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Quote:
Originally Posted by Eversor
ah good call, makes sense, I wonder if the border car puts 100% of that air up through those two vents

i was lookin at the mad psi site and the little diagram they did for their border hoods, it doesnt look the same as the picture you showed, having the radiator angeled so that air seems to just pass across the surface instead of flow directly through the radiator

Now if what was said earlier is true and air can only travel through the radiator at roughly 54 mph, then for optimal effectiveness i would probly want the whole front air damn built to utilize as much flow through the radiator as possible and up through those vents. Sealing it so that the hood vents are the only true exit the air has. With the map psi diagram i see alot of air still going under the car, which to me is less than desireable.

With the whole set am I basically trying to design a velocity stack to get the air moving as fast as possible coming up from the ducts to maximize effectiveness

im just trying to use common sense here. Feel free to tear it up and tell me what needs to be done to do it right
Call me silly, but are our radiators tilted back like that? lol... I have never really checked. But the MadPSI site still said that to make the hood functional, you should use it along with the Border Racing radiator relocation kit.

"Is the vented hood functional?
Yes. When paired with a Border radiator relocation kit, the vented hood can offer a couple of functional benefits. For one, the fresh air that heats up after passing through the radiator will now exit through the vents in the hood providing an improvement in cooling. In addition, air that would regularly contribute to "front end lift" will also exit out of the vents in the hood, improving stability at higher speeds. This is especially beneficial on the Mr2 since it has a twitchy and sometimes "floaty" feel at higher speeds. (MadPSI)"


I'm no expert here and far from it. But it seems that if you block off/seal off the front air damn, wouldn't you cause back presure? That leads to drag/resistance/pressure or whatever the term would be? Since air could only pass the through the radiator at a speed of 54 mph, the remaining air that cannot pass or is waiting to pass through will build up and have no where to exit, creating more resistance for the car? Wouldn't that be a bad thing causing more unstability to the front end of the car?
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post #35 of 73 (permalink) Old August 30th, 2009, 22:15 Thread Starter
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well if it effects the car as much as you think it might then by simply adding a duct on the right and left pulling the excess air out the front wheel wells you could solve the problem *Also help cool the brakes*and possibly keep air from coming in under the side of the car behind the front wheel wells. If im not mistaken air going anywhere other than under the car is a bonus.

Stock radiator set up pulls all of the air under the 2.

+ if you do like what the border pictures have and properly vent your front wheel wells i think that could have a significant bonus. Along with splitter, canards etc

on all cars you will get a high pressure zone at the leading edge, that high pressure bubble (likely) helps push the incoming air up and over the car rather than under it. So make a bigger bubble, stretch it out alittle bit with a splitter, stop as much air from spilling under the car and directing it up and over.

What might seem counter intuitive could in fact lesson the drag a good bit, or at the very least increase the frontal downforce of the car
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post #36 of 73 (permalink) Old August 31st, 2009, 06:14
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Originally Posted by Eversor
on many supercars the wheel wells are used to pull air out from under the car and direct it over the car.
its more about getting air out of the wheel wells than from under the car. with the wheels rotating and a load of stuck air it creates a lot of drag, and also high pressure that results in lift. if you can evacuate the air as best as possible then you reduce the drag and reduce the lift - which effectively equates as an increase in downforce.

look at racing prototypes, like Le Mans LMP cars. they very often run louvres above the wheel wells for the same reasons. usually theyll have a removable panel with the louvres on so that they can alter the number of them to use it as an aero balancing device. e.g. they can increase or decrease the downforce on the front end with a very quick and easy part swap.
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post #37 of 73 (permalink) Old August 31st, 2009, 11:54 Thread Starter
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interesting idea, louvered wheel wells, hadnt heard that one yet. sounds like not a bad idea though
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post #38 of 73 (permalink) Old August 31st, 2009, 13:12
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Originally Posted by Eversor
interesting idea, louvered wheel wells, hadnt heard that one yet. sounds like not a bad idea though
Been used in auto racing for a bit now.
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post #39 of 73 (permalink) Old August 31st, 2009, 17:34 Thread Starter
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well its something to add to the picture
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post #40 of 73 (permalink) Old September 1st, 2009, 03:58
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louvres are harder to implement unless youve got extremely flared arches. you need to evacuate air at quite a high point otherwise it will still stagnate above the louvres. most road cars converted for racing tend to go with a large exit to the rear of the front wing.

so heres a DTM Audi, using mostly louvres, and a little vent at the rear of the front arch as well. but these arent converted road cars, they are silhouettes that just resemble the road car, much like a Nascar really. so they have much more freedom with space. on the rear they exit the air through a vent at the back and then use winglets to create some additional downforce as the air passes out quite quickly.


and heres the more common way of doing it when giant fender flares just cant be large enough...


thats a Ford Escort Cosworth, i dont think you get them in the US? it came like that stock from the factory. you can see the vertical vent behind the front wheel well. it just evacuates as much air as can fit through at once to reduce the drag and the lift, it doesnt harness the downforce quite as effectively as the louvres over the top though.

doing it this way is probably fairly easy as you could simply space the front wing away from the chassis at the rear edge and then weld metal into the gaps so it doesnt look stupid. louvres are also very doable though, but they wont remove as much air.
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