Just because this Forum has remained empty for so long, I feel compelled to start talking about SOMETHING in here.

Byran Little and I have had a few interesting discussions about the early Z car rear spoilers, since the unit on his 1970 car is functional, and others of that era weren't.

The first spoilers I recall seeing on the 1970 cars were pretty and neat. They fit exactly across the trailing edge of the rear hatch and made the car look like it was meant to go fast. The problem with them was that they simply didn't do anything.

The rear hatch area of the beautiful Series-1 cars is a functional vacuum at speed. That was why Datsun initially decided to place the 1970's signature interior vent grilles in that area ~ they knew this low-pressure area could be used to scavenge air from the cabin and keep the interior environment fresh. (Actual use disclosed that exhaust fumes also found this area and leaked into the cabin, leading Datsun to move the vents to the side B-pillar on the 1971 cars).

But the early spoilers, which stopped at the left and right edges of the hatch, were also in this vacuum, so they did nothing aerodynamically. It wasn't until somebody provided the two "wings" which extended out to the left and right sides of the fenders themselves, that the widened spoilers were able to catch the passing airstream and provide any actual downforce for the car.

In my personal experience, it was never the rear of the car that needed help, anyway. The front of the car was what needed downforce. Mine got really light about 80mph and grew worse as speed increased. The early chin spoilers actually stopped the under-car windlift and helped to steady the ride at higher speeds.

With the advent of the actual Airdams, things got even better. These took control of the onrushing air and strategically placed it where it did most good for driver control. They did add frontal area, increased drag, and reduced mileage however.

A friend of mine attached a really aggressive airdam to his 260 for awhile and was happy with the improved feel of the car, but complained that it actually slowed him down by 15mph. It was the size of a snowplow and left very little ground clearance in front. One day he hit a high parkinglot tire stop and almost "surgically" broke the center off the dam, leaving the two "wings" ahead of the tires. He was amazed to find that this weird configuration allowed him to go faster than ever before, not overheat, and get pretty good mileage. If it haddn't looked so "broken" he probably would have left it that way.

At the May meeting, many of you probably noticed the beautiful blue 240 which was LOWERED to about 4" off the deck. I really want to hear the details about how that handles at speed.

Since I'm starting this thread only to get blood pumping in this Forum, you are openly invited to say ANYTHING about what I just said!

What happens when air hits YOUR Zcar?

Most all of it comes down to "FORM vs. FUNCTION" and although I personally prefer the look of the original Z even without air dams, spoilers or even a chin spook, you are absolutely correct about its less than stellar "aero" performance. It’s all about trade offs and there is no "free lunch". After years of info/data gathered from many sources like BSR, BRE and I'm sure countless other sources, many changes were made to the Z over the years. Some very much needed and some "not so much". Many of the improvements were quickly implemented by 'aftermarket" sources which put a "band aid" on the problem and which for the most part worked. The more significant changes came about in 1977 with the introduction of the ZX. Weather or not you like the “new" body style is anyone’s call, but they (Datsun / Nissan) did address the fundamental problem of its "Aerodynamics" using Empirical data gathered from countless hours of Wind Tunnel Testing . This process is very expensive and time consuming. I know, I was for some 15 years the Senior Operator and Lead Engineering Technologist at United Technologies Research Center's Main Transonic Wind Tunnel here in East Hartford Ct.. There are some good pics (flow vis.) in the original brochure distributed by Datsun at that time. If anyone would like to see those I can provide them. I would also be happy to provide better pics of my modified BSR "Duck Tail" that with a little help from UTRC's MWT (PILOT Tunnel) I came up with a good compromise in the "FORM vs. FUCTION". Oddly enough it supports Frank's friends contention regarding the "improvements after loosing the center section of the front Spoiler".

Z vs. ZX

Coefficient of Drag: .45 to .47 vs. .37 to .39

Coefficient of Lift: .4 vs. .15

Great info, Dave ~ and yes, we'd all like to see any Wind Tunnel pictures you have of the Z cars.

Frank, I was going to post this information last week and unfortunately work interfered..... Rather extensive wind tunnel testing was performed last summer by a group of Hybridz.org forum members. They collected funds via the forum and bought seeveral days of test time in a wind tunnel down south. Hybridz.org has a dedicated forum for the wind tunnel tests results.

http://forums.hybridz.org/forumdisplay.php?f=112

They plan on conducting more extensive testing in the near future. There is a large volume of data to wade through on the forum, but if I remember, the results were summarized into one post, probably a sticky on the forum. (I'd look, but that work thing is interferring again....)

BTW, I enjoy monitoring dicussions on Hybridz.org and Zcar.com and have learned alot from these through the years. Since I drive a S130, I tend not to visit forums that cater to the earlier S30.

Wow ~ who ARE those guys? That's a bunch of serious research (sounds like some fun, tho).

Kinda funny ~ these guys spent mucho dinero conducting "Test #28", which sounds a LOT like the parkinglot surgery my friend did to his airdam! And with the same resuts! They called it a Catamaran and I recall a few racecars built around that same frontal design.

Thnx ~ I'm saving that one!

i find that i like the look of the chin spoilers and the rear deck ones. i did put a air dam on my 280zx , it looked good but , the scraping is a real pain in the neck. so i wont be doing that again , i have had my 260 to about 125 mph it was just fine , had my 300 to the same speed , again no problem , my 280zx . well that spedo stops at 80 so .. i was out running every body else .. hehe , did not feel a differance with the air dam . looking for a chin spoiler and a rear deck one for my 260 cause i like the way they look .

OK BadGuy, your 280 doesnt show anything on it right now, but it went 125 OK for you. Was it "clean" then, or did you have the dam on it?

My 240 would go 124 and REFUSE to go 125, no matter what I tried (Well, maybe if I drove it off a high cliff...?) But anything above 80 made the front end very light and over 100 you just sort of "wished" it to go where you wanted it. I had no ground effects on it at all.

my 280 had a airdam , its in the pic , i dont know how fast i went in it , the spedo only goes 85 , , but it didnt feel and differant at speed than my other 2 cars ,

Well, it's the windlift that scares me at speed. Not that I'm afraid the car is gonna "flip over backward" or anything (altho I've seen some F-1 racers do just that), but the fact that the front gets so light that the steering just sort of "goes away"...... that bothers me a lot.
In the later ZX cars they punched a hole thru the hood above the induction system. Most will bet this was for releasing heat or offering fresh air to the injector system. NAW! That racy little vent in the 280 and ZX hoods lets pressure out from under the hood, which allows the car to go a little faster and still stay on the deck.
The Ferrari GTO, Mercedes 300 SL and SLR, the Jensen Healey Interceptor , Cobra Daytona Coupe and many other cars have used side vents behind the wheels for the same purpose. The XKE used louvers on the bonnet which did the same. One hot summer while driving across Kansas I removed the inspection lids and popped the hood open to the safety catch to let the engine run cooler. That worked, but I was surprised to ALSO find that with just that much under hood pressure released, the car went 17mph faster in top gear at the same RPM I had been holding at before I did the "hood surgery". The front end also seemed to "hold" better (less lift), altho not as solidly as a spook would have made it, I'm sure.

Dave or Phil, did either of you come up with any In-Tunnel pix of the ZCars "at speed"? I'd love to see a "smoke shot" of the Series-1 cars, as compared to the ZX.

my brother had the same problem on his 65 mustang , i remember the wheel getting light on him , i also figure the 280zxs are a lil heaver than the old z cars mebe that helps , i will be at your show in ct on 7/21 so i will see you there.

before i start...theres a book called HOW TO MODIFY YOUR DATSUN. Its a really old book and came out before the 260Z and 610 we're available.
It mainly covers 240Z and 510. But it also has full write ups on what to do and not to do with Datsun engines. Eg, port and polishing is unecesary because the heads flow so good anyways.. its these bucket GM made engines that need re -e ngineering...
This book has lots of stuff on the Bob Sharp and BRE cars. Heaps of info on soilers and aerodinamics... I luv this book. Its like my Bible.

Front spoilers...
-Factory 240Z front spoiler. Very basic. 1 peice. Bolts straight onto excisting splash tray under bumper bar. good clearance.

- BRE style. small brake channels. We call it a blade spoiler cos its very straight out and sharp... Same used on the BRE Z car.

- Emerging around the place are these huge front spoilers. I've seen 3 different variaties here, but mainly they look the same.
These spoilers replace all the lower front section eg. Middle splash pan, and side indicator/park light. So you junk these three parts and bolt the big spoiler straight on. Blinkers fit back into spoiler. Really big, really LOW.

I bolted the factory 240Z spoiler on my 260Z and loved it. Handleing was great especially at speed. But then i found as the front was getting pushed down at high speed, the back would start to lift..only a small amount but enough to make the arse wanna step out.
It can be very hairy..... so i guess the remedy is to put a spoiler on the back....


Rear Spoiler.

- Factory nissan. Same as 240ZG in japan.
Single peice. bolts only to hatch. Extends slightly over hatch.
Im not sure if nissan made a couple variations of this. Easy to install.
There also seems to be a difference between 2+2 and 2 seater.
They usually dont like to fit onto 2+2's/


- A rare one i've got myself. a 3 peice rear spoiler. this thing is really pointy. and looks just like one off a Camaro. It almost points straight up.
1 peice bolts to hatch. 1 peice on each side bolts to side body.
Performance= unknown?



Most spoilers arnt gonna do you any good unless your flying along above 80mph. If its a race car then go nuts... If its just a road car, go with what ever style you like...

Right Pete~ it's my dream to someday have the simple, basic front Spook chin spoiler and a clean hatch. But when it comes time to repaint the car, I will also invest in a pair of those louvered inspection lids on either side of the hood, to relieve the underhood pressure. I'm old now, so I don't plan to be driving as fast as I used to when I first owned this car. But if I ever take it above 80 again, I want it to stay in touch with the road better than it did when we were both young.

(When my 240 was less than 5 years old, I had free access to a newly-made, fully cleaned and traffic-ready glass-smooth 8 lane highway in Hawaii. They had just built it, but a federal judge put a Restraining Order against opening it for nearly two years because it had been laid over an Hawaiian burial ground without permission. I had the key to the gate at the very end of the highway, and on Saturdays I could drive my Z as fast as it would go without fear of any other traffic. With everything tuned and prepped, the car would do 124 mph and not a smidgen more. I was never able to reach redline in 4th gear, and by the time I hit 120 I had absolutely no roadfeel back thru the wheel at all because the front was so light).

Frank

Thats it Frank..
Takes a bit to get 'em to start lifting.
The small front spoilers make a hell of a lot of difference.
I found that it made the arse more lighter as the front was getting pushed down. so a small spoiler on the rear would of fixed this..

I had the same problem with my first Z, lifting at speed.
I fitted a BRE blade front spoiler with the small "bobtail" rear spoiler, I an confirm that this works at 145mph, you'll need a cam, triple webers to
oh and a good long freeway, some turkey who wants to give you a run is fun to!!
another problem with early Z's, the bushs that hold the rack had a lack of grip problem,I made some aluminuim bushs, much like a crack bearing, fitted that up , made a big difference, you can check this easily, get some one to move your steering wheel to turn your wheels from side to side while you watch for movement of your rack, this of course is best done while car is standing still!!!!
another thing is to lower your car by 2 inchs, this helps with " steering wander" to
Pete and I will be making the spoilers for these soon using a thick ABS plastic, I have some pics of the front spoilers, the rears I dont as yet, one is a small "bob tail", one piece, the other is a 3 piece similar to the BIG SAM rear spoiler
These will fit 240-260-280Z 2 seaters,we will be looking at a 260 2+2 rear spoiler as well as sets of wheel arch flares
I ran a blade front spoiler which didnt have the vents,I never had a brake problem
enjoy

That's exactly the little Spook I want for my car. It was the original model, made plain and simple, back in the day when BRE and BSR were battling for domination in C Production. (They also invented the shock tower brace at that time).

Steve, about the rack shimmy ~ I think I had the same book Pete mentioned, and I recall a lot of guys in my day who cut small strips of old carpet and fit them up inside the swaybar and rack braces, to make them hold tighter. Today's polyurethane (did I spell that right?) bushings are a LOT tighter than the old originals were, so that's one of the many minor problems the original cars shared, which got fixed by aftermarket parts.

Frank

* (...best done while the car is standing still! )