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Old 04-13-2008, 10:46 AM   #1 (permalink)
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Cool Newbie Question !! Next car opinion?

Hi !
Firstly id like to introduce myself ...
My names Mark and i come from sheffield in the U.K. !!
Curently i do not have a car, however a couple have caught my eye I hope to buy one in the next two months.
I am trying to select a car which will be good for long straightline speed only.( constant 70mph u.k. motorway speed limit )
Now this is where i could do with some of your experienced opinions...
The following choices are pretty much "dirty " shapes, however they have small frontal areas , so with a few select tweaks i hope to bring the cd down , and with the multiplication of the frontal area , bring that overall cda very low.
Now...
My first choice :
MKIV Triumph GT6

This is basically a triumph spitfire with a slightly different bonnet , a bigger engine ( irrelevant - the engine will be swapped to a modern smaller unit ) , but a fastback rear end !!
Mayfco.com specify , for the 1980 spitfire to have a cd 0.420 , which isnt great but with the low frontal area of 1.437 makes a nice cda 0.60 .
Going back to the GT6 , i have read , from unofficial sources , that the CD is around 0.38 , giving a total cda 0.431 ..... Better than the opel calibra 8v !!!
I would also be intending on adding an undertray and rear wheel skirts. Perhaps a windshield deflector ( its pretty steep in my eyes the windscreen )
Opinions? can anyone confirm my above figures ??

My second choice.
MG Midget
Now this is another one of my favourite cars , However , it is extremely hard to find any cd or frontal area data on ! ? !
It is a lot lighter ( roughly 3-400 kg) , due to it being the smaller car, smaller engine and probably a lot of other factors !
The mg midgets dimensions are 55"wide x 48.6" tall , 137inch long. ( these are based on a 1972 model , specs from carfolio.com, which im not too sure about trusting. )
I have only been able to find one value for the cd of this car ... 0.49.
Once again, unnoficial data so probably innaccurate. This is where i could do with some help !!!!

Here are some pictures of both cars.
Perhaps you could make some suggestions what could be done to these? ( im not after any boattails or other " extreme " mods !!! ) thanks for reading this post !!!

Triumph GT6





and the Midget
With a soft top, however i would be after the hard top add-on ( easily obtainable - however it is pretty much the same shape, so i dont know whether a custom fastback roof would be a good alternative ? )





Many thanks all look forwards to your replies !!!

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Old 04-13-2008, 11:55 AM   #2 (permalink)
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Hi Mark -

I'd say the Triumph is the better choice. It's aerodynamically cleaner to begin with, and probably a better platform for future mods.

The Midget's windshield looks to be nearly flat, which makes it pretty much irrelevant what kind of roof follows, since the flow off the top & sides of the windscreen will be highly turbulent anyway. The trailing wake coming off this car is pretty much going to be the size of the projected frontal area.

As for the Triumph, if I had to guess (always dangerous in aero) I'd say the rear hatch angle is too steep to permit clean flow off the roof & sides all the way to the tail end. But the opportunity is there to add a spoiler to clean things up, along the lines of Ernie Roger's VW New Beetle: http://max-mpg.com/html/tech/main.htm

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Old 04-13-2008, 12:21 PM   #3 (permalink)
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Thanks for the reply metro
I was also thinking of the triumph , as its a bit heavier id imagine it to be a bit more stable on the motorway at higher speeds.
I see about the windscreen, to be honest i hadnt really noticed that much !
May have to consider the spoiler idea, however i wouldnt want to go that large.
Would you of thought the spoiler would have to stretch the total width of the rear or just the rear hatch ?
As you can see also, the wheels are extremely exposed, the rears could probably do with a skirt , to clean up the front id go with "wheel deflectors " , a nice rounded bumper and under tray. i dont think there would be much potential in lowering, but im no expert
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Old 04-13-2008, 07:06 PM   #4 (permalink)
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Welcome to the site! I've always had a love for the GT6 (or gt6+ as it was made in the states), so I'd say go for that.

Always nice to have another brit aboard,
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Old 04-13-2008, 08:06 PM   #5 (permalink)
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yes it is really hard to say, but I'd definitely have to say the triumph would be the best bet. For separation, I'd say that it'd probably separate somewhere mid-window, a small spoiler for re-attachment would be good, although I wouldn't know. try a water test, although those aren't reliable either .
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Old 04-13-2008, 08:19 PM   #6 (permalink)
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Oooooh, i have found some hard tops for the convertable triumph ( spitfire )
take a look.
version 1



version 2


version 3

However, chances of finding these tops would be very very slim i would of thought, and secondly , they are to fit the ealier model ( rounder rear end )

Now, the spitfire and gt6 are very similar, the spitfire is more common and cheaper... i wonder if a custom rear end would work out cheap? a shop in the uk willing to make one ?
Im not bothered if i get a spitfire or gt6, i just want the more aero friendly one

Last edited by chipX; 04-13-2008 at 08:34 PM..
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Old 04-13-2008, 08:26 PM   #7 (permalink)
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get the spitfire is it's more common and cheaper... if it's more common, you can get more parts, and if it's cheaper, you can get MORE parts cheaper. Use the rest of the money to spend on aero mods and the like. and fixing it up too.
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Old 04-13-2008, 08:53 PM   #8 (permalink)
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yeah its roughly 1- 1500 cheaper , however , finding an aerodynamic hardtop would possibly offset the cost.
a custom/homemade top may not look pretty
thanks for all the replies everyone
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Old 04-13-2008, 09:02 PM   #9 (permalink)
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Wow - that hardtop really does look like a proper aero improvement. I've never seen one quite like that before - thanks for posting it.
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Old 04-13-2008, 10:23 PM   #10 (permalink)
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There aren't too many of those cars over here in the US. We can only drool.

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