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Rear spoiler downforce specs


Guest KEINoze

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Guest KEINoze

I was wondering if anybody had specs on downforce the mass produced S30 wings had at XX speed. I've searched around but come up empty so far.

 

I'm currently trying to design a front underbody panel that would create a little downforce. I wanted to skimp on a rear diffuser for now and just add a spoiler to even out the front and rear.

I can calculate the numbers up front since I'm designing it, but I wanted to get an idea of what the rear spoiler does.

 

Any help is appreciated.

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Good question! I would think that any significant data would very difficult to obtain since there are so many variables to concider! However, you would think that someone at some time had some sort of data on the rear spoiler....but then again, it may have been nothing more than seat-of-the-pants engineering. I mean, thats how all the old boys did it back then!!!

 

I have a 1970 and while it sits pretty low (3.75" at the front crossmember) I still felt some front end lift at speeds over say 70mph. So, I decided to use the original type spoilers as were on the old 240 race cars (BRE front air dam/432 type rear spoiler). After installing them I went for a test drive, and hot damn the Z felt much more stable at speed. It was definitely worth the investment (approx $250.00).

 

I'm sure someone will jump in and provide a better answer than I provided.

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standard.jpg

 

I used this method one time just to get some kind of "idea" of the effects of the "nascar" type of spoiler. The weight of the pipe (steel thin walled conduit) on the end toward the floorboard was roughly 4 lbs, but I had serveral pipes in the car, and the hatch's pressure on the end pushing down, forced the long side up off the floor at about 80 mph.

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Car and Driver on had some front and rear spoiler downforce and drag data on a 240Z as part of their Project Omega series on the early 1970s. I've got the article at home somewhere and I used it to design the rear spolier I last ran on the ROD.

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Somehow I had the feeling you two guys would add to the post. You guys are always worth listening to...I always look forward to your comments.!

 

So, John and Terry...if I put flames on my Z will it make it faster? JUST KIDDING YOU TWO!!!!!

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Guest KEINoze

Thanks for the replies guys!

Everywhere I looked, there's only subjective answers. I wonder if I can get a hold of that old C&D article.

 

Terry, I saw your diagram while searching around. I didn't know that it was SEVERAL pipes. That BRE/432R type spoiler should be adequate enough.

I remember reading somewhere that the whale tail produced 240lbs of downforce at 80mph. Should have saved the link but I lost it . . .

 

Right now, I doubt the front underbody pan I am designing would produce any downforce at all. It would SIGNIFICANTLY reduce lift but not produce enough to have a negative value. I would need to lower the car to about 1 or 2 inches off the ground and use ways to suck air out through the top of the hood to do that.

 

I might just get the carbon fiber BRE type spoiler from MSA. I won't paint it so it matches my black window louvers and the satin black taillight panel.

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Here are two pictures of the spoiler I built for the ROD. Its height and rake are direct copies of the spoiler C&D fabbed up for their Project Omega Z in 1973. This design gave the best combination of downforce and low drag of the 3 they tested.

 

hatchandspoiler.jpg

 

rearspoiler.jpg

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By the way, is that your Harley I see next to the compressor

 

That is the Mini-Bike of Death!

 

Its thrown four people on the ground, two of them professional race car drivers. I've had it up to 40mph following a Lexus (that's how I know how fast I was going) and I gave up because my vision blurred badly and my hands and forearms went numb. Plus, it started this front end wiggle that felt like it was going to be real tank slapper. One clue about its modifications: it needs 112 octane leaded fuel to run properly.

 

I think Tim240Z has ridden it...

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John, would you care to share the spoiler angle and the dimensions of the blade? What's the row of holes along the top for? wicker bill?

 

Man, I knew someone was going to ask me that. I have a drawing around here somewhere but I can't find it. I know the spoiler was 7" tall measured from the hatch surface but I don't remember the angle. I'll look at the C&D article tonight.

 

The holes in the top are a row of rivets. You can't see it in the pictures above but the spoiler has a back section that makes a boxed triangle (see below). A simple sheet of aluminum wouldn't have had the strength needed.

 

eatmyrust.jpg

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