aerodynamics...

[toyz]

Hi all,

First off I will say that I'm new here and I feel this is an awesome source of information, thank you. A friend of mine has a 1972 240Z and it's sitting with the primer on it right now. He's been putting a lot of work into it lately (lots of body work) and we discuss color and design a bit. I've been slightly educated on foilers and spoilers and their real purposes other than just looks on cars. I'm wondering that if you put a hopped up fast engine into it like we've got in the works...at what point should you put a tail fin on it, and how big/small should it be and how effective will it be? Is it the fact that the bigger the fin, ie. porsche whale tail, drags more air to push the back end of the car down therefore keeping that light arse end more stable? How do the differnt styles of fins perform different? How does this work please, I need a little enlightenment. I had an 82 mustang gt when I was 16 and it had the wrap around type fin over the hatch. It was small but I assume the it served it's purpose as far as keeping the back end of the car down some to not tail swish. I feel that look is ok with the 240Z but I'm wondering about how much it is needed. I'm thinking effectiveness of overall performance for both speed with handling and keeping the car street legal looking and close to stock as possible.

Thanks a ton for any help, I may be back frequently about multiple 240Z Q's

[Dan]

I agree with you that that the stock Z looks good enough, however i really think that if your going to drive your Z at high speed a front air dam is needed. I found that my 240 started to get light under the nose when i approached 90. Unless your a serious racer then a rear spoiler is just cosmetic and for the most part i dislike them. However msa does sell some smaller spoilers that just provide a sort of lip coming of the rear deck lid. As for down force V's speed i would talk to 2manyZ's i belive he has had s good bit of racing experience and would know more about it than me.

[2ManyZs]

Well, my racing experience with a Z is racing in a class that didn't allow any type of rear spoilers. In my opinion you will never get a Z up to the type of speeds that you really will notice any effect from a rear spoiler as far as downforce. Too big and you increase the drag, so the big question is what do you like the looks of?

Dan is right. The single biggest aero add on you can put on a Z is the front airdam. If you have ever driven a Z with the stock valence on the interstate you will notice a bit of lift in the front and the car will tend to wander. The front airdam will not only look a little better, but they actually do work.

You would need to get the car up over 125mph to see any benefit at all from a rear spoiler, but you will notice the difference a front spoiler makes at speeds as low as 50mph. I've had my 280Z somewhere between 110 and 120 on the main straight at the track without a rear spoiler with no problem, but I know it would have been scary at that speed without a front airdam.:eek:

[jcdozier]

Ditto Dan and 2ManyZs on a front spoiler, and it doesn't have to be one of the big ones that replace the bumper and displace the parking lights to work.

Besides looks, the rear spoiler is probably better at disrupting the air flow and reducing the amount of fumes sucked back into the car than it is at improving handling at anything less than legal-plus-ten speeds.

I have a small hatch-mount rear spoiler on my 240 and I don't have the inside-the-car fume problems so many folks report. Of course, I also have good fuel-tank vent hoses and a good hatch seal............

[beandip]

I agree about the front spoilers , I dont have one because I really dont like the look , just personal. and I relly dislike the rear ones. I have read several test report done on the early Z-cars that were done when they were new on the market . The publication at present is on loan to a friend , so the numbers may not be exact but vary close . This is for '70 and '71 cars . At 100 mph the down force on the hood is in the area of 80 lbs and on the hatch it is about 113lbs if I remember right. I to have noticed that my car gets light in the loafers and it starts at about 85 . It is raire that I ever drive at that speed I resist installing a front air dam , how ever just the other day I was challanged by a 5.0 mustang on the FWY and the wind was blowing across at about 15 to 20 mph and I difinatly felt it best to knock it off at 85. I think at 63 I have some good sence left . The simple designs are looking better all the time. I will post the exact data when the book is returned. Did you read that escanlion ? Ha ha

[Ken]

Right on with the front spook! I use the "BRE" with no ducts. I can feel a big difference at 60 and above both with the spook and without one. For my driving, I like and use the ductless "BRE" spook. The steering is much more firn (road feel?). I would not like to have the front wheels getting "light" on the road as they do with just the lower center valance.

[240znz]

Front airdam is what you need. In my youth I raced superkarts (250cc twin cylinder 2 stroke Rotax...speed demon, 120+MPH 1 inch off the gound...yehar), in doing so I found out a lot about aerodynamics.... the painful and expensive way.

Most rear wings you see on street cars are for looks. To get the best result from a rear wing, it needs to be in clean air. There is little to be gained from slapping a little lip on the tail of a 240Z. 2manyZ's is spot on in saying that you'll need to be at serious speeds, not highway, to see the benefit.

The idea behind aerodynamics is to get the car through the air with the least amount of resistance. Any air going underneath the car will be slowed down. This will cause drag. Drag = slooow. Some high end production cars are now using F1 proven air channelling under the car to move any unwanted air out the rear with in minimal of resistance...check out the Ferrari Modena. I even think the 350Z is using this technology now.

So for the best result for your money, put a front airdam on. If you want to muck about with rear wings and tunnels , then don't waste your time on a Z...get a Ferarri. Don't get wrong, the lines of a 240Z are one of the most sexiest out there, but remember it is a 30 year old car and you can only do so much.

Zed not Zee

[hmsports]

I've been racing 240s for eight years in the SCCA and have tried several types of front air dams. The best is a simple flat pieces of sheet metal that is attached along the rear of the valance. There are two things that are important here. First, let the air dam run as far out to the edges as possible to move as much air around the front tires. The second, and maybe most important thing is to have a horizontal lip (about 1" wide) that protrudes from the front of the bottom edge. This will channel the air around and not under the car. I've had great luck with this up to my top speeds of 125mph. This type of air dam is easy to manufacture and provides a great custom look.