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Guest Zachb55

Coefficient of drag for 240Z???

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Guest Zachb55

anyone know what the coefficient of drag is on a stock 240? or even someones racing one? downforce would also be cool to have, would be thankful for any info you guys have on this topic, thanks,

 

-Zach

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Got Plywood? The drag # sounds about right... I also recall hearing a VW microbus is only .48, and a 4x8 sheet of plywood is .50!!! cry2.gif

 

Our cars suck for areodynamics.. weird since the car has such awsome lines and agressive stance.

 

go figure.

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I just read that article, and thought it was excellent reading.

 

It makes me wonder about the effectiveness of those toyota supra inspired hatch spoiler (up near the roof... Thoough on the Supra (82-85) they were designed as a sunshade because the rear passengers heads are under the rear hatch glass.

 

I wonder if that type of spoiler.. maybe not that particular one.. but something installed in nearly the same location would really benifit out cars...

 

This kinda goes back to the hightech forum where I started a thread about bellpans.. etc.. to reduce exhaust fumes entering the car..

 

Hmm I think you could easily test this theory on our cars without drilling holes or making permanent alterations...hmmm

 

If you bent a piece of aluminum into a shape similar to that of one of the many variations of aftermarket/nismo rear wings.. but left a lip that could be tucked into the hatch/seal.. close the hatch and wedge in this aluminum wing...kinda hard to describe, but you could disrupt the flow of air enough for testing.....

 

I think I'll add this over in the other thread as well.. maybe someone with a z (not in winter storage) could try this...

 

Sorry to highjack the topic...

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I have thought about fabing a piece at the top of the hatch(and fully across the hatch)about 3" long pretty much paraell with the gound(maybe a little pitch).

 

It would hug the body and not look so wild.

I`m thinking something alittle smaller, but kinda the same(but different) as what Mike kZ has on the back of his car.

 

Pic of Mike KZ`s car

 

Any input?

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Scottie and I were taking about my wing at the last SE HybridZ meet. I have never noticed any exhaust smells in my car, I think it does have an effect. It's also supposed to add down force over the back wheels. Who knows, I just like the different look! rockon.gif

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I took the MSA catalog to an engineer friend(ME with NASA LANGLEY)and asked, Which of these spoilers/wings would give the best result?

He very quickly pointed to the "supra type" wing. With out quoting a long resonse from him, The key point was that the down force was over the rear wheels and not at the back of car.

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Creating down force is good, but from that aerodynamic article Doug posted, I think preventing lift is the key. The article says the smooth flow over the smooth, uninterrupted hatch acts like a plane wing to actually lift the rear of the car.

 

Makes me wonder if the classic Z rear window louvers would help. How do you measure lift on a moving car?

 

I just bought a BRE style spoiler. The BRE racers were incredibly successful. Figure those guys must know what they were doing.

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I did not want to imply any "fact of evidence"(I don`t have any)and was just making a comment.

I probly did not use the best term when I said "down force"(although where the down force takes place would seem to make a difference)(IMO), but I agree with Jim that the flow of air over the car is not very good.

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Guest Carlissimo

There is another, very effective way to combat the high drag of the Z-Car body... MORE POWER !!

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I would think that a small lip, perpindicular to the airflow, right above the hatch should disrupt the airflow enough to reduce the lift. It usually doesn't take much to trip the boundry layer, maybe 1/2 to 1 inch at most. It would be pretty easy to test with some angle aluminum and string taped to the rear hatch glass.

 

Similar to the fences that run parallel to the airflow on NASCAR cars. When the car gets sidewase on the track, those fences disrupt the airflow over the top of the car, helping to keep it from taking flight.

 

Scott

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Guest bluex_v1

Not exactly a cheap or common item, but it might work. I don't know how wide these things are, but the lines look about right to me. BMW z3 wagen hatch spoiler

 

I've thought about whether or not louvers would help on the hatch too, but from what *little* I know, I thought airflow seperated typically at around 7 degrees or something, and so most of the volume that all but the top most louvers would occupy would all be turbulent anyway. Is that about right?

 

Just something I found: "Twenty years ago an average new U.S. car had a 0.48 Cd; today that figure is 0.33, with the very best mass-produced vehicles achieving 0.28. Pickup trucks and SUVs, with their choppy shape and high ride typically have coefficients of drag that are over 0.44" cry2.gif

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Doug. The wing over the rear wheels would not neccessarily be more effective.. the wing over the rearmost part of the car will act like a lever, and the wheel will act like fulcrum. Any gains in downforce would be multiplied over the distance from the wing to the wheels (fulcrum)

 

But the idea of the "supra style" wing may not add downforce, but may reduce "lift".

 

My Q stands though.. anyone with a fume ridden car want to try this experiement..I'm not sure I can wait till spring to find out.

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Ya know.. you could paint the aluminum body coloured to kinda hide it, or... or you could make it from Lexan...hmm kinda high tech looking.

 

I made a flat wing from lexan years ago on my Z, and left it clear. looked kinda neat.

 

I'm kinda picturing this in my head...growing on me a bit, as long as its not too extreme looking.

 

Chrome it... hmm my personal fav.. stainless steel (insert mental image of Homer Simpson drooling) bonk.gif

 

Ok I'll shut up.

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Ok so I can't shut my mouth. My brain won't stop working ok?

 

Speaking of the BMW spoiler brought to mind the later model 300zx's 87-89 had a third brake light mounted on the top of the hatch..and it was almost 2" deep, and left a 1.25" vertical drop to the glass. I wonder if that made a difference in handling?.. or was it just their for safety?..Nissan did some unusual things to make mods to their race cars legal. Ie "Gnose", "ZXR" wings etc...

 

I also wonder if it would fit our 1st gens?.. hmm I'll have to look into this further....I recal mine was screwed to the hatch some way.. it just might be removeable.. (maybe for bulb access?)

 

Ok ok..like a fat kid playing dodge ball...I'm out!

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Originally posted by Carlissimo:

There is another, very effective way to combat the high drag of the Z-Car body... MORE POWER !!

Unfortunately, that doesn't cure the problem. The lift and drag still exist, and the Z in stock form will still suffer no matter what power plant is in it.

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Guest 240hybrid

It would be nice if someone had access to a windtunnel and could see what worked the best at disturbing the air flow thats creating the lift over the rear end. Louvers seems like it would disrupt the air enough to eleminate some lift on the car, but how do you know for sure :confused: how well of a job/help their doing? As far as downforce on he rear end the BRE style spoiler looks to be the best.

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I guess if I could rig up some type of suspension height sensor right on the struts that could be viewed while driving. A ruler and a video camera? That way you could drive at steady speeds and measure the change in suspension travel to determine lift or downforce. Would be a good testbed for different spoilers/air dams.

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Guest Carlissimo

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

Originally posted by auxiliary:

Unfortunately, that doesn't cure the problem. The lift and drag still exist, and the Z in stock form will still suffer no matter what power plant is in it.

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

 

Unless you are trying to take turn 8 at Willow Springs flat out in 5th gear, I don't think you need to worry about lift. As far as drag is concerned, my car pulls strong thru 160+ MPH...even suffering with all that drag.

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Guest 240hybrid

Id like to see the rig you make to postion the camera on the undercarriage. Sounds feasible to me.

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Ever heard of the X10 cam that you see advertised on the web?.. well I bought one... Works pretty good to!!

 

Anyways, I found that it runs on 12volt, and I was able to wire it to me inputs on my camcorder (RCA type), and wired on a cig lighter adapter on the camera, and wala! I have a very small camera with full colour and sound with 25ft of cable!!! My buddies and I are going to mount it on my airdam, and maybe out behind the car, and do some trick shots on the racetrack etc. Wouldn't be too hard to mount it to the rear control arms.. just like in the Nascar!.. small enough (golfball size) to hold in your hand, and put on on the dash to do driver shots etc... a camera like this would work perfect for this kind of stuff.. only $80, and keeps your camcorder safe in the car.

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