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Obviously there are a lot of Zs here capable of extreme top end speeds. Has anyone experimented to find what really works and what just looks cool? I've heard that the front air dam was one of the most important steps to achieve high speed stability, and that many rear spoiler designs just upset the airflow. Do the BRE dams/spoilers work? I like the minimalist approach here and they seemed pretty small.

 

[This message has been edited by John Scott (edited March 03, 2000).]

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The BRE stuff is hard to beat for being unobtrusive yet effective.

 

The lower air dam is a mixed blessing for some cars, but it's very effective for the Z, because 1) the Z has severe front lift problems, and 2) these problems are caused by relatively minor but far-reaching design mistakes. After some digging (I don't want to elevate it to the status of "research", so let's just call it digging), I've come to the conclusion that the original wind tunnel testing done by the Nissan engineers had the car elevated on blocks underneath the wheels, possibly in a misguided effort to get around flow quality issues in their facility. Thus, they completely missed some critical ground effect issues. The stock Z's smooth under-bumper skirt is consistent with this notion. Anyway, just about any front spoiler is superior to no spoiler at all - whether it's Motosport, Arizona Z-car, BRE "spook", etc.

 

The rear spoiler is more convoluted. Rice boy wings generally don't work, because they have a poorly chosen and incorrectly oriented "airfoil" cross section and because they are placed in a flow region generically called "turbulent", where their effectiveness is greatly reduced. Given the Z's rear hatch slope, the #1 problem is controlling large-scale flow stuctures over and the hatch and rear bumper area. They are responsible for a host of problems, like the exhaust smell seeping in through the hatch weatherstripping. A scaled down version of a NASCAR-type spoiler, of which I believe the BRE spoiler is an example, is the best bet. Properly designed, it even reduces drag, by calming down the big roller-type structures separating off the hatch.

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Michael, Thanks for the reply. So if I put on a BRE rear spoiler my monoxide headaches will go away? Bummer. Really, I would like something that works. I've seen the high side of 160+ and it would be nice to feel more attached to mother earth. Maybe this is the ticket. What about the ducting in the front spoilers. Isn't the idea to keep the air out from under the car? Does construction material make any difference?

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I can't say that the rear spoiler will entirely fix the exhaust fume problem, because there will still be some flow separation - just not as much.

 

The front spoilers often come with "ducts" to accommodate plumbing for brake cooling, or just to install fog lamps. If you don't have either, just fill up the holes with, well, duct tape. smile.gif

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I did a little research on the Rear spoilers and on belly pans a while back and what I lfound is that belly pans will help clean up the air under the car, however, I'm not 100% clear where venturies need to be plumbed within the sheetmetal of the pan.

 

As for rear spoilers, I went kwith the 930 style rear wing because it generates over 500# of downforce at 140mph.

 

To balance it, I'm also fabricating a chin splitter up front that will help as well. My car should be running somewhere in the range of 190-200mph, and I want it to be glued to the asphault.

 

If it were me, I would go for as much front spoiler as I could. The spook helps, but there are a lot better "Surface Area covering" spoilers out there, like the MSA and Arizona Z spoilers. The rear spoilers made by most manufacturers now are more cosmetic than functional, as Michael points out in his post. The question is Do you want a good looking car, or do you want it to be functional as well?

 

Look to the Touring cars, Nascar, and IMSA for fine examples of what REALY works and looks good!

 

Mike

 

------------------

 

"I will not be a spectator in the sport of life!"

mjk

 

[This message has been edited by Mikelly (edited March 05, 2000).]

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With even the relatively high weight/hp on the camaros, mustangs etc, it seems even 150 isn't that hard to reach. A lb/hp ratio of about 9:1 can give a reasonably aerodynamic car a trip somewhere in the 170s. The new Lingenfelter corvette, 5lb/1hp hits 226 with nothing resembling a spoiler. I know there is a big difference between hitting a top speed and being stable up there as well. I love the original lines of the 240. On the other hand if that pesky new Viper GTS in town starts bothering me.... What a quandary. I guess I'll start looking at spoilers. No one wants to be the test pilot to find @ what speed a 240 becomes airborne. (In the March issue, Motor Trend writer, Mac DeMere lists some pretty real concerns about top end testing. It ought to be read.) I don't condone pushing a almost 30 year old car to its limits, but out of curiosity, how fast has anyone else pushed your Zs? What have you done as far as ground effects? Thanks for your input Guys! biggrin.gif

 

[This message has been edited by John Scott (edited March 06, 2000).]

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I hit 160+ in the last Zcar with an L6 motor in it. It was pushing into the 7500RPM range and the car was stable, but I wasn't comfortable. Car was loud and drivetrain had a buzz to it, not a vibration, but a definate buzz. I had the motorsport front and rear spoilers and side skirts, and a rear whale tail on it at the time.

 

Mike

 

------------------

 

"I will not be a spectator in the sport of life!"

mjk

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