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Re: aerodynamics
[Re: ]
#1200682
12/04/2011 10:33
12/04/2011 10:33
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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I'm not sure I could take any advice seriously from someone with If you decide to use fire extinguisher mod for a IC spray make sure you dont use the powder type in their admitted technical ability range.
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Re: aerodynamics
[Re: ]
#1200704
12/04/2011 12:36
12/04/2011 12:36
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Nobby
Unregistered
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Nobby
Unregistered
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Would a foam one work better Jimbo?
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Re: aerodynamics
[Re: ]
#1200730
12/04/2011 14:01
12/04/2011 14:01
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sediciRich
Unregistered
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sediciRich
Unregistered
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couple of things i have picked up on, firstly putting in bonnet vents,
Ill mention scoops even though your not talking about them , they are stupid! unless you need them for a top mount IC they are stupid, end of
Now back on track with vents
you have to be very carefull and watch that they do,. with airflow under the bonnet,
there also then needs to be sufficent air flow through the engine bay to give it the push that it needs in the right direction,ie not just mountains or air getting pushed in from the top . alot of boys find that putting vents or scoops actually pressurises the engine bay and the hot air cant get out, (ME infact) being totally unproductive. these vents are there to tease the air from under the bonnet out to a certain threshold and then to get whipped away by the airflow passing outside of the car,
ie might need to be running with a improved undertray( better sealed) and then have very well placed air scoops underneath the car flowing air into right areas to help with this,
many have found this a complete waste of time so do the very best you can , but have a spare bonnet around just incase,
Next thing, how lowered is your car?
next thing, POWER
If you decide to use fire extinguisher mod for a IC spray make sure you dont use the powder type>( yes me again)
have you thought some nitrous?
you have pm no we are not talking scoops, we are talking exhaust venting, using the high velocity air over the mid bonnet region to extract the higher pressure air from behind the wheel with a duct hose(the pressure gradient is as its max here, if you put the vents nearer the wind screen the effect could be no pressure gradient or flow.). Venting the bonnet with rearward facing NACA ducts would aid the pressure gradient across the radiator and help cooling, but reducing the rad opening area will cut drag and thats the plan here. Rearward facing ducts especially with a gurney placed mid to front bonnet can be pretty sure to have an extraction effect on the bay; we arent pushing any air in from the top! The test method with tufts would prove if the vents are effective, if not out with the gaffer tape. Also don't consider what fools in RS turbos do and raise the rear of their bonnets, because at speed the lower edge windscreen pressure will force air into the engine bay, keep the rear edge sealed.
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Re: aerodynamics
[Re: ]
#1200846
12/04/2011 18:07
12/04/2011 18:07
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sediciRich
Unregistered
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sediciRich
Unregistered
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Jim not sure what you are estimating here, its is the high pressure that lifts the wipers off the screen not some venturi effect sucking them off. If you vent the bonnet here air will flow from the windscreen base into the engine bay - we don't want that. But convesely a scuttle panel 'fill in' creating a smooth transition from bonnet rear edge to say half way up the windscreen would reduce the transition and seperation like you mentioned but in a different way. Not sure about visability mind.
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Re: aerodynamics
[Re: Jimbo]
#1200907
12/04/2011 20:24
12/04/2011 20:24
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Alesi
Unregistered
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Alesi
Unregistered
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@Per: Why don't you give the bearded guy in the picture a shout? As you've bumped into mr.B himself recently you might have his contact details. If not why don't you try his office Chris Bangle Associates in Italy.
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Re: aerodynamics
[Re: Jimbo]
#1200985
12/04/2011 22:22
12/04/2011 22:22
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sediciRich
Unregistered
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sediciRich
Unregistered
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Sure Jim that would show what you want to know, but having seen countless wind tunnel reports via McBeaths aerobytes column I can be sure that what I mention is for real. Your analogy is a little too simple, sure if the body was a continuous ark then the velocity would potentially create a drop but the change in vector from the bonnet to the windscreen is huge, which creates turbulance at the base of the screen and a high pressure zone. But some tufts would tell the story real easy, and the coupes ranked screen may just level any pressure differential - you know another way is a U tube manometer, simply get some clear cappillary tube, use fence staples to make the U shape on a board, fill the U with some water, mark it in a level position (vertical board), the short end of the U is open to atmosphere and the other end extends and is taped to the test area - in this case the scuttle panel. With a friend holding the board drive the car at speed (the long end should not be facing into the direction of travel). If the water come flying out of the short end you have greater then ATM pressure in the scuttle, if its sucked towards the scuttle then you have lower than ATM pressure there. KTM the u tube manometer test is useful for testing behind the wheels and in the engine bay to establish pressure differentials. the chap made a huge manometer but the plan is the same http://www.youtube.com/watch?v=0nKaGEMLZjsHave a look at this and some of autospeeds other articles on practical things you could do http://autospeed.com/cms/article.html?&A=2159
Last edited by sediciRich; 12/04/2011 22:34.
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Re: aerodynamics
[Re: Jimbo]
#1201024
12/04/2011 23:19
12/04/2011 23:19
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shinyshoes
Unregistered
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shinyshoes
Unregistered
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I'm not sure I could take any advice seriously from someone with If you decide to use fire extinguisher mod for a IC spray make sure you dont use the powder type in their admitted technical ability range.
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Re: aerodynamics
[Re: ]
#1201143
13/04/2011 11:24
13/04/2011 11:24
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Per
Unregistered
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Per
Unregistered
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SediRich is right, all cars of this basic body shape have pressure at the bottom of the windscreen. And underpressure (not sure that's the english word for it..) over the bonnet centre, if anyone's considering extra engine bay venting.. @Per: Why don't you give the bearded guy in the picture a shout? As you've bumped into mr.B himself recently you might have his contact details. If not why don't you try his office Chris Bangle Associates in Italy. Yes, we've already had some mail conversations. Quite interesting, and he's a very laidback guy . For example I found out it's the same guy who designed the Pininfarina proposal for the Coupe (and of course also the 406 Coupe) and the E60 BMW 5-series.. Davida Archangeli. " a nice irony since I later hired him into BMW and did that super-special E60 5Series I love so much (and died in the process, the poor guy)"
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Re: aerodynamics
[Re: ]
#1201548
13/04/2011 23:26
13/04/2011 23:26
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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this is getting very involved and interesting i have to say..its gone from taping up and possibly fashioning a splitter to some serious posts ..thats why i spend way more time than i should on the forum! .. even if a little above my head in parts i appreciate the time and suggestions .. i am trying to take it all in but without having time to spend learning the basics of aerodynamics in order to grasp all you are telling me i can only take in so much..so i would be grateful if we can try and come up with practical suggestions i can fabricate with my limited facilities..i am happy to spend some time testing various ideas but what would really make this attept succesful would be someone that actually knows what they are doing/talking about physically helping ..so if someone fancies getting involved inbreaking the record i am happy to cover thier expenses ..i am probably asking a lot there but i have a serious lack of time with which to fill my head with enough to understand what i am doing so in truth unless someone does it will be basic stuff from whats been mentioned so far..i already know way more than i did from the links and whats been said so can at least make a better go of it will be glad of any more thoughts though
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