Hi, I'm new here and my cD is .37, can you help me get a .30? - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum

razordave · 01-19-2015, 04:01 PM

Your car has a speed sensitive wing does it not?

I was behind one when they first came out going down an off-ramp and once we got below 45 mph the wing dropped down level. If you do anything in the back, be sure to not interfere with that thing.

AutoDeutchland · 01-19-2015, 04:02 PM

As you said, its a very nice car and thank you. So I really don't want a boat-tail. Plus I need that downforce from my spoiler. The .37 is measured with the wing up.As for "coroplast" I have been working on cars since I was 8, I have the paint code and it will look like it never had lower grilles. My goal is to achieve a higher top speed at Michigan mile and gas mileage to boot. Only the inside half of the lower grilles are real. I wonder if opening them all the way and sealing the upper grille would be better.

jeff88 · 01-19-2015, 05:49 PM

Quote:

Originally Posted by AutoDeutchland

As for "coroplast" I have been working on cars since I was 8, I have the paint code and it will look like it never had lower grilles.

This. I'm excited to see your final product! I love the look like it came from the factory.

I edited a previous post as I forgot to add the pic that I was referring to. If you have a speed sensitive spoiler, I don't think what I'm talking about in that pic will work as you already have a spoiler. Maybe you can change the parameters so that the spoiler opens at a different speed, or you could have an on/off switch to control it manually?

I think the lower grill will be better to block if you do a full belly pan and the bottom is almost perfectly smooth. Otherwise, I say do the top and help direct the flow over the top. You can probably do both and just leave a very small section in the bottom grill for cooling (maybe the portion that is "real").

NeilBlanchard · 01-19-2015, 05:52 PM

You have got the template drawing too far forward - the 0 point should be lined up with the high point of the roof. When you do that, the rear roofline will be fairly far away from the ideal line, which is why I think you need a Kamm back to get the Cd a lot lower.

AutoDeutchland · 01-19-2015, 06:02 PM

Yup, and by real I mean only the inner halves of the lowers allow air through. I intend to lower the suspension as much as possible. I'm guessing it would be better to drop the front more. Now Should I try to avoid letting air under the car?

jeff88 · 01-19-2015, 06:16 PM

Quote:

Originally Posted by NeilBlanchard

You have got the template drawing too far forward - the 0 point should be lined up with the high point of the roof. When you do that, the rear roofline will be fairly far away from the ideal line, which is why I think you need a Kamm back to get the Cd a lot lower.

Oops, you're right. I fixed it for clarity's sake. It's still a bit off, since the pic is slightly angled. I agree a Kamm will be helpful, but how to do it while not interfering with the spoiler. And if it's important to the OP, how to do it while still looking "nice".

AutoDeutchland, I would block the whole upper grill and bottom up to the inner halves. If you're still getting enough cooling, then you can start to block the inner halves as well. Lowering will certainly help, but how much lower can you go without causing rubbing?

At this point, I'm not sure what's worse... air over the car with nothing following the template, or letting the air under the car if you do a full belly pan. Hmmm...

AutoDeutchland · 01-19-2015, 06:34 PM

Without the exhaust, I can do a diffuser as well. But I'm not sure what the proper angle would be. I guess it depends on how much pressure is underneath. I do have a basic understanding of this, nothing like most of the folks on here tho.

Cd · 01-19-2015, 07:42 PM

I found this blueprint of the car.

Very nice looking car.
As others have said, it would be a shame to mess up the look of the car.

I would do the same as others have mentioned and block the grille down to the very bottom slat that you can leave open.
If you take your time and put some effort into it, you can do a grille block that won't even be noticed to the casual observer. Personally, I would have the grille block behind the grille mesh and painted flat black so it will be stealth.

A few here have done some really nice blocks that look totally factory : http://ecomodder.com/forum/showthrea...eza-30402.html

Lower the car and this will not only improve the drag, but the handling and looks of the car.

The rear of the car is very rounded and this is a problem as the wind separates and causes a lot of turbulence. There is not much you can do that wouldn't mess with the look of the car and the function of the spoiler, but you can create some professional looking trip strips that wouldn't mess up the look too much.

The open spoke wheels could be replaced with smooth wheels when you race, and a full underbelly pan would be invisible unless you flipped the car :-)

jeff88 · 01-19-2015, 08:14 PM

Cd, that's a great find! the-blueprints.com seems like a good source, especially for doing the template.

OP, notice the pic that Cd posted shows the low hanging stuff on the bottom of the car? You can see it in the profile shot and especially in the front on look. If you can clean that up, along with lowering the car even further, I think you'll be well on your way to that .3 cD.

AutoDeutchland · 01-19-2015, 08:17 PM

Wow, I cannot believe how much effort people go to to help you on this forum. Ok, whats a trip strip? I would also be willing to cut a hole on each side of the license plate as shown and use fans to fill the vacuum with air from the interrior (not my car pictured, only the one with the bike to the side of it was mine)