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(Post Link) post #1 of 17 Old 29-11-08 Thread Starter
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156 Aerodynamic Properties.

I'm planning on joining a club that does Auto-Testing and track days. So I plan over time to tweak the car to get the best out of it. Both the suspension and the body work to improve mechanical and Aero Grip. I'm not looking to do anything radical, but any small change can reap its rewards.

Now I've always been a bit of an Aerodynamic Anorak. I love looking at how F1 and Le Mans cars evolve and change year by year and even race by race over time to get the best out of their aerodynamic properties. I'm intrested to know if there is anywhere, or anyone who can shed some light into the Aero of the 156? For instance how much attention was paid to it during development, whats the drag-coefficient, is it known for lacking rear end grip etc?

Also I've been looking at the GTA style body work, does the GTA front Bumber/Splitter provide greater downforce over the standard front end? I have to change my Bumper anyway due to a rubbish re-spray job a previous owner did, so I'm looking at the GTA one. Side-skirts are also something I'm looking at to try and generate a small Ground-Effect. Would it be best to fit a full on rear-wing style thing, or would a Gurrney Flap style rear spoiler be better?

If anyone has any advice or opinion I think we could get quite a good discussion going on.
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Re: 156 Aerodynamic Properties.

I doubt you get any downforce from any of the spoilers. I'd expect the GTA reduces front end lift a bit, but side skirts are all about styling. It's also going to depend on what sort of tracks you are doing; it's going to have to be very high speed tracks that need more rear grip rather than front end.
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Re: 156 Aerodynamic Properties.

GTA bumpers are made to cool down the car....because on the GTA you have an oil radiator on the right side..and on the left you have hydralic steering oil radiator.

In terms of top speed you will suffer with the GTA bumper compared to the standard one...so if aerodynamics is your goal...forget about the GTA bumper.
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Re: 156 Aerodynamic Properties.

I have a chart for the 155 somewhere, which shows the downforce or lift forces that act on the entire body.

Considering the 156 is a disguised 155, with very similar measurements (just rounded out just about everywhere, and a slightly longer wheelbase), maybe this can be of help? The 155 has a Cx of 0.29 btw...
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(Post Link) post #5 of 17 Old 01-12-08 Thread Starter
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Re: 156 Aerodynamic Properties.

Hmm, the 156 has a Cx of 0.31, making it not as efficient. If you can find that data that would be a great help.

Intresting about the GTA bumper there, but with its larger splitter does it generate more downforce? I'm happy to trade off drag for downforce.
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Re: 156 Aerodynamic Properties.

its not a drag race, its a circuit lap.. down

change the brakes, brake lines, a clutch maybe.. tweak the engine a little bit.. thats all
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Re: 156 Aerodynamic Properties.

Quote:
Originally Posted by n3xus-cy View Post
its not a drag race, its a circuit lap.. down

change the brakes, brake lines, a clutch maybe.. tweak the engine a little bit.. thats all
Exactly.

At the relatively low speeds that you will be doing in your road car, you will not be able to get any aero working in your favour.
As for getting ground effect from fitting side sills, no that isn't going to happen!
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Re: 156 Aerodynamic Properties.

Slam it to the max!

"Lower = faster" because you speed up the air beneath the car to increase downforce.

You want a nice smooth underside too. Fair it in, using a sheet of alu'. Leave spaces around the exhaust (though if you're a fanatic you can flatten the bottom of the silencer to make it the same depth as the undertray).

You need a front splitter (sticking out about 6" will do it) and a rear wing. Go for a full length one with end-plates .. but mount it as far back as possible (ideally further back than the rear bumper) and about 4" lower than the roof.

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Re: 156 Aerodynamic Properties.

Surely the rear spoiler/splitter jobby will put more downforce on the backend of the 156 GTA?
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Re: 156 Aerodynamic Properties.

I recommend adding a big-ass Meccano spoiler to the bootlid
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(Post Link) post #11 of 17 Old 02-12-08 Thread Starter
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Re: 156 Aerodynamic Properties.

Quote:
Originally Posted by Ralf S. View Post
Slam it to the max!

"Lower = faster" because you speed up the air beneath the car to increase downforce.
Thats what I'm thinking, a decent splitter coupled with side-skirts and lowered suspension will created Ground-Effect style downforce on the front end of the car. The high-pressure area created at the tip of the splitter makes the area under the car become low-pressure. This speeds the air up as you say and sucks the front of the car down to the road surface. The side-skirts help to direct the air flow, though what they add to it I'm unsure of.

However I'm not sure I want to go down the road of bigger is better. Take a look at this one: Mulsanne's Corner: 2005 Pilbeam MP93 Great for generating downforce, but the bigger it is, the more it will create and that will then need to be balanced at the rear with a spoiler/wing. I'm just not sure I want a big olde Ironing board on the back of the car....

For the rear I'm thinking something along the lines of this Alfa Romeo Shop - Tuning, Styling, Fanartikel und Modellautos - Alfa 156 Cadamuro Hecklippe Cadamuro Hecklippe 21918 More of a Gurney flap than an actual wing, but it should creat a small amount of drag/downforce on the back of the car.

Of course this all mainly theory and my own thinking. Please add to it if you have any ideas etc.
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Re: 156 Aerodynamic Properties.

Unless you will be shipping it over to Utar for Speed Week, I think you are thinking way over the top for a 156.
After all, you did say it was for autotests & trackdays. In autotests you will be lucky to get up to 2nd gear!

So forget aero work, it just isn't going to make any difference at the speeds you will be doing, if it does it will just make the car slower!!
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(Post Link) post #13 of 17 Old 03-12-08 Thread Starter
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Re: 156 Aerodynamic Properties.

Ok,ok I relent, but I' still intrested in what could be done, even if its never actually done.
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Re: 156 Aerodynamic Properties.

As a point of reference, on the RX-7 there are 3 main different rear spoiler options. Apparently you can tell the difference between the smallest and mid sized one in terms of stability at about 150, but no difference in cornering; the largest helps cornering above about 100, but takes the edge off the top speed...... most people worry much more about cooling than downforce
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Re: 156 Aerodynamic Properties.

Hmm.. but GTA look bodykit looks really great..

http://www.autods.net/156gta/bodykit/eba1.jpg
http://www.autods.net/156gta/bodykit/eba2.jpg
http://www.autods.net/156gta/bodykit/eba4.jpg

p.s. Let me know mate, if you are still interested..
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(Post Link) post #16 of 17 Old 03-12-08 Thread Starter
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Re: 156 Aerodynamic Properties.

Quote:
Originally Posted by mave View Post
As a point of reference, on the RX-7 there are 3 main different rear spoiler options.
Which version does this concern? The Series 3 I'd have a guess at. I only ask as my Dad has a series 2 RX-7. It'd be intresting to know if this is the case for that version.
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Re: 156 Aerodynamic Properties.

Quote:
Originally Posted by DMN View Post
Which version does this concern? The Series 3 I'd have a guess at. I only ask as my Dad has a series 2 RX-7. It'd be intresting to know if this is the case for that version.
Series 3, unfortunately.
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