Estimation of the Cd-reduction

[Kilpuri]

Originally Posted by The Toecutter

There's members here who would definately be able to make use of any information pertaining to how you built it and affixed it to the car!

It was just flat plate fixed with screws to the bumber and the body. Cut using power tools where needed to fold the plate better. Picture shows that it not such "high design".

Originally Posted by The Toecutter

Did you involve any books on aerodynamics in figuring out your design, or did you just go by looks and what you already knew about aerodynamics?

Yes, Katz: Race Car Aerodynamics and Milliken, Milliken: Race Car Vehicle Dynamics for example...

One thing which I forgot to mention. While driving on long straight the hood starts to act like a sail, when air went in from the hole which is now closed. Note that all stiffeners from the hood is removed to get rid of the extra weight. I assumed that this is causing lots of drag, correct? You can see the phanemon from attached video link (about 5MB). Needs close look under the wipers! BTW, Wipers are also causing drag I assume...
http://mallasracing.info/videot_2007...hun_kanssa.wmv

[The Toecutter]

It was just flat plate fixed with screws to the bumber and the body. Cut using power tools where needed to fold the plate better. Picture shows that it not such "high design".

Ahh. It looks pretty darn good though. Any plans to make a fiberglass nose piece off of that design? It's a very nice mockup. Perhaps if you build a fiberglass one, there may be a market for it that you could make money off of.

Yes, Katz: Race Car Aerodynamics and Milliken, Milliken: Race Car Vehicle Dynamics for example...

I'm going to have to obtain a copy of that.

[Nerds laugh at me]

I would think that you could benefit from some vortex generators since the back glass angle is not very steep.
If you mount them on the glass just below the roofline you can also avoid the added frontal area that they add.
You would have to do some tuft testing to find the 'sweet spot ' for them though. Also a 'shelf ' style spoiler could help.
( I didn't read all the posts here, so I'm not sure if these two mods are even allowed . )
If allowed, on race day, you could also remove your wipers and mirrors ( which may be a really stupid idea now that I think about it ... nevermind the mirrors since you will actually need them. )

[Kilpuri]

Originally Posted by Nerds laugh at me

I would think that you could benefit from some vortex generators since the back glass angle is not very steep.
If you mount them on the glass just below the roofline you can also avoid the added frontal area that they add.

Do you think they would help while attached on the glass? On Mitsubishi study they were attached on the roof 100mm frot of rear window. VGs are more or less on the gray area of the regulations, but I have to think of using them at least testing them on tests.

Does anyone have any hands on ideas what to do the rear of the car. I assume that rear has very big influence to the total drag created. Our car is crashed from behind, so it is already quite "interesting".

http://mallasracing.info/kuvat_2007_...o/IMG_3194.JPG
(Currently exhaust pipe comes out from the side)

[GasSavers_SD26]

LOL! Well, there's no bumper cover to develop a parachute effect...

And who needs mirrors on the outside. This is racing, right? You're not racing to see who can parallel park. Use the one inside and be done with it, unless the rules say otherwise...

How about tape over the door handles that you don't use? Minor, yeah, but...

[Kilpuri]

Originally Posted by SD26

LOL! Well, there's no bumper cover to develop a parachute effect...

Originally Posted by SD26

And who needs mirrors on the outside. This is racing, right? You're not racing to see who can parallel park. Use the one inside and be done with it, unless the rules say otherwise...

We have to have both windows installed...

Originally Posted by SD26

How about tape over the door handles that you don't use? Minor, yeah, but...

Actually rear doors will be welded for season 2008. Handles are removed and "flattened".

[GasSavers_SD26]

Originally Posted by Kilpuri

:
We have to have both windows installed...

I think I meant mirrors...

[Kilpuri]

Originally Posted by SD26

I think I meant mirrors...

I meant them also... ...but wrote something else.

[red91sit]

Originally Posted by Kilpuri

...Does anyone have any hands on ideas what to do the rear of the car. I assume that rear has very big influence to the total drag created. Our car is crashed from behind, so it is already quite "interesting"...

After looking at your car, it seems like there won't be too much you can do to reduce rear end drag without major work. A spoiler might actually improve aerodynamics. Other than that, there is really no attached flow to work with here, so your going to be left with a large wake above and behind the trunk as far as i can figure.

I would run the exhaust back out the rear of the car, where it can help reduce the wake (albeit, by a very small amount) as well as stick a nice smooth underbody/diffuser there.

[Kilpuri]

Originally Posted by red91sit

I would run the exhaust back out the rear of the car, where it can help reduce the wake (albeit, by a very small amount) as well as stick a nice smooth underbody/diffuser there.

We wanted to have the exhaust from side due to other reasons, but I will proceed with the diffuser. According to Katz: Race Car Aerodynamics diffuser should be in 4 degree angle when lowes drag is preferred.