Pros and cons of modifying airflow in a Border front bumper - MR2 Owners Club Message Board
 
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post #1 of 8 (permalink) Old June 8th, 2013, 06:23 Thread Starter
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Pros and cons of modifying airflow in a Border front bumper

Greetings from across the pond

First off let me give you some background on what I have and have done.. I've got a rev 3 turbo which is, well.. far from standard (see below)



The history of how it started and ended up the above can be found here http://www.imoc.co.uk/forums/viewtopic.php?t=159087 for anyone who's interested in losing a couple of hours of their life..

Anyway, back on topic..

Due to the car having a Border bumper, along with the wide-arch kit, it is/was running without front undertrays and arch liners. Now while the ride is generally good, I've now turned my focus towards refining the car and first up if improving front end feel/grip/reducing lift etc. I've read many many pages of people's opinions on ways of improving things, along with the incredibly interesting thread on here related to aero modelling the MKII with different combinations of modifications. This inspired me to kick things off by fabricating a flat front undertray, one which also incorporates speed flaps as they are now standard on newer cars and are proven to have a positive effect. A full write-up of the build process (including a LOT of photos..) can be found here, for anyone who's interested http://www.imoc.co.uk/forums/viewtop...asc&start=1500





The results so far are positive, with the car generally feeling much more planted at speed. I'm currently working on the custom arch liners at the moment, which should complete the package and hopefully amplify results and feel. That's the thinking/logic at least

The next idea I have and the reason for this thread is are the two side pods there for any purpose other than aesthetics? My thinking is if they were to be internally blocked and then uprights pieces being mounted at the sides of the main (central) opening, this would channel air cleanly through the rad(s) and underneath the car. It would also prevent air from flowing towards the arches, which we know is something which it's better to reduce/stop. The downside of blocking openings on other cars seems to be the risk of affecting cooling in front engined cars. This however isn't a risk for us and air would be allowed in, just in the way we choose.

Is there any benefit in the above, or am I way off track on this? Suggestions or alternatives gratefully received, it's good to learn.

Last edited by Magic Beans; June 8th, 2013 at 06:33.
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post #2 of 8 (permalink) Old June 8th, 2013, 12:51
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In high end sports cars and race cars the side pods are there to cool the brakes. To make this really work you would want ducting from the pods to the brakes. In most cars and aftermarket bumpers it's purely aesthetic.
From an aerodynamics point of view the more of the bumper you can block off the better.
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post #3 of 8 (permalink) Old June 9th, 2013, 04:34 Thread Starter
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Thanks for the feedback

I'll look to cover the inside of the side vents and then test to see if there's any difference. After which I'll look to isolating the airflow through the main opening. Hopefully it might increase the efficiency of the chargecooler too.
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post #4 of 8 (permalink) Old June 12th, 2013, 17:16
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If you plan on tracking the car or doing a series of hard braking, I would recommend brake ducts.
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post #5 of 8 (permalink) Old June 12th, 2013, 18:43
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Quote:
Originally Posted by yoshimitsuspeed
From an aerodynamics point of view the more of the bumper you can block off the better.
Wont that increase the surface area the air has to 'hit' though?
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post #6 of 8 (permalink) Old June 12th, 2013, 19:45
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Quote:
Originally Posted by bionikal
Wont that increase the surface area the air has to 'hit' though?
Not in our case.
If we had a nice smooth channel for the air to flow through and exit in an ideal area it would be a different story.


For us that air will flow through the bumper and smack into some flat object like the frunk firewall, suspension components, fender wells, etc. It will likely hit multiple components to so instead of hitting one flat surface it will bounce off the firewall, into the suspension, into the fender well and then it will flow under the car creating more lift, back into the engine bay, rear suspension and rear firewall to finally get smacked by the lower lip of the rear bumper before getting pulled out the back.

If you can just route it all around the exterior of the car it will cause less drag. You will also have less air going under the car creating lower pressure and reducing lift.
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post #7 of 8 (permalink) Old December 19th, 2013, 18:13
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The first link is slightly overwhelming with 100+ pages in one thread! Lol

I am interested to hear what you think of the speedflaps, have you ever removed them and installed them to see if there really is a difference?
Your results won't apply directly to my case since I'm running all stock body and underbody panels, but it's nice to know as I see some new cars come with them and some don't. I apologize if it's in the thread, but there seems to be no in thread search function available on that forum.
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post #8 of 8 (permalink) Old December 20th, 2013, 16:24 Thread Starter
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Quote:
Originally Posted by Goopi View Post
The first link is slightly overwhelming with 100+ pages in one thread! Lol

I am interested to hear what you think of the speedflaps, have you ever removed them and installed them to see if there really is a difference?
Your results won't apply directly to my case since I'm running all stock body and underbody panels, but it's nice to know as I see some new cars come with them and some don't. I apologize if it's in the thread, but there seems to be no in thread search function available on that forum.
Yeah, it's become a bit of a monster thread

As the speed flaps were part of the custom undertray I made it's hard to say for sure what difference they made alone. However, the combination of the two made a significant difference. The front end felt more more settled and solid, as well as being far more stable at speed. Shortly after fitting it we did a 1600+ mile round trip to Le Mans via the Pyrenees and it felt great to drive. Less so when it was aquaplaning all over the place during a 300 mile leg of the journey in torrential rain! The 275 low profile rears weren't really helping then though..

I sold the car a few months back now, replacing it with something even less practical I do miss it from time to time though.
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