240mph 240z?

[Corzette]

Good info...

 

Rather than emulating an American style, Datsun chose to contour the Z with European lines. A strong case can be made that the 240 was a direct conceptual descendant of the Toyota 2000GT, but the Toyota in turn owed its stylistic origins to the fastback designs of Jaguar, Ferrari, Maserati, and other European fastback designs. When the Datsun 240 arrived on American shores, it possessed the angular body lines currently popular in Europe, as well as an engine derived from a European manufacturer.

 

While American aerodynamic design of the late 60's shared much in common with El Capitan and Mount Rushmore, European design was little better, with the slight advantage resulting primarily from lower and narrower cars; less flat plate area, in aerodynamic terms. Many European cars had less aerodynamic drag than American cars simply because they were smaller. The graceful profile of the Jaguar XKE predicted where aerodynamics would push cars in the years hence, but in 1969 little attention was paid to parasitic, cooling, body pan, profile, induced, and aft body drag. The Seventies would bring a move away from angular lines toward rounded shapes; the recessing of radio antennas, wipers, rear view mirrors and other appendages; reduced windshield angles; smooth belly pans; optimized cooling air apertures; and re-profiled noses and tails.

 

All the types of drag noted above appear in the 240 Z resulting in a total drag penalty that is significantly greater than if each type of drag had been addressed and reduced by the Z's designers (which in fact they did do as the Z evolved). If one now wished to reduce the aerodynamic drag of an early Z, one would have to create solutions to the problems found in each of these areas, just as Datsun did with subsequent Z editions. What we'll do next is look at each station of the car and ascertain what kinds of drag are found in each location, and what the relative impact is of each.

 

First, an explanation: "Stations" are hypothetical, transverse, vertical "slices" of a car, and of the air around a moving car. Station 0 is at the forward-most tip of the car, even with the center of the front bumper on the 240Z. Stations with a positive number (24, 48, 56, etc.) indicate the number of inches aft of station 0. Stations with a negative number refer to locations ahead of Station 0, and indicate pressure changes in the air ahead of a moving car.

 

Now for a walking tour starting at Station 0 and moving aft. Looking at Station -12 to -36, we see that the area in front of a moving car is a high pressure area formed by air damming up in front of the vehicle. The dammed air will try to flow around the car somehow--under, over, or around, but in front of the car, a lot of air will remain relatively stationary compared to that flowing near the edges of the car. The pile of air the car pushes, combined with other types of drag, eats fuel and limits top speed so aerodynamic improvements are helpful.

 

Looking at Station 0 from the side of the car, we find that the front edge of the hood and the front edge of the lower valence define the radiator opening, and do most of the work of channeling airflow. The bumper, which is not integrated into the bodywork, divides the airflow, creates drag, and reduces airflow into the area just ahead of the radiator.

 

The area between the hood on top, the valence on the bottom, and the headlight cans on each side can be thought of as forming a cooling air plenum which should guide air through the radiator. However, because Datsun designed the hood and valence for looks and not function, quite a bit of the air in this plenum "leaks" out into the front fender wells, through holes in the radiator bulkhead, and under the radiator. All the air that avoids transiting the radiator produces some lift (about 75 pounds at 60 mph) and raises the front of the car slightly, producing a slight reduction in traction, an increase in toe-in, and slightly more positive camber.

 

The waste of cooling air is important because any air that escapes the radiator 1) does not assist in the cooling of the engine; 2) causes drag as it tries to exit the engine bay, and 3) causes front end lift. Many newer cars are much more efficient at using cooling air, funneling the air from the body's cooling air inlet into the radiator with few leaks along the way. Improving the early ZÕs front end aerodynamics involves closing off cooling air leaks and adding ductwork to prevent high pressure air from bypassing the radiator.

 

If we were to get more specific about cooling air, we would pay attention to the rule of thumb regarding cooling air inlets and outlets: the exit area should amount to two to three times that of inlet area. The 240 would thus benefit from less air inlet area and tighter plenum ductwork.

 

The G-nose 240Z, produced in very few numbers, was ahead of its time and aerodynamically superior to the production 240. The G-nose extended the hood line forward and down to meet the bumper, trapping less air beneath the front hood edge, routing more air over the car, and reducing the cooling air entry aperture. Datsun would not repeat this integral hood/bumper trait in the Z line until the advent of the early 300 ZX.

 

Stations 0 through 20 contain the headlight buckets, and the turn signals and marker lights, located outboard, aft, and just below the lip of the valence. While the turn signals and marker lights are more fully faired into the body than many cars of the era, they still protrude slightly from the bodywork, and present a noticeably bumpier surface than their descendants on late 80's and 90's cars. Any type of protuberance creates what is known as parasitic drag. The role of parasitic drag in a car's overall drag equation is significant, if not primary, and the desire to address and reduce parasitic drag has created the smooth car exteriors we find today.

 

The headlight buckets are aptly named: they catch a lot of air, increase airflow turbulence, and produce a lot of drag. The cool solution to the bucketsÑheadlight coversÑcan really smooth up that whole area, but they are, unfortunately, frowned on by many motor vehicle departments.

 

Stations 20 through 62 contain the upper surface of the hood and front wheel openings. Air moving over the forward portion of the hood is still relatively high pressure air, though less so than the air directly in front of the radiator. The high pressure continues all the way to the windshield at station 60, which is why ventilation air intakes are located just in front of the windshield, and also why opening the hood slightly does not result in significant venting of hot air from the engine bay. One would think that such a large area of high pressure would push the hood and windshield down, but lift generated by the air dammed up by the front of the car is greater and the net vector is upward. Drag created by the hood's "engine bulge" is relatively small, compared to other early Z features, but it is significant enough that few modern cars advertising exceptional fuel economy possess them.

 

Parasitic drag in the hood area from stations 62 through 82 is created by exposed windshield wiper arms and shafts, as well as from the rearview mirrors. As with the several other protrusions from the 240's exterior, these components represent only a small portion of the total drag picture, but they do produce drag and noise. I have never seen a single allusion to the aerodynamics of wheel well openings, which is odd considering the size of the feature, and therefore can report nothing on their aerodynamic impact. But I have some places yet to check, and if more information turns up, I'll report on that in the future.

 

The angle of the windshield introduces another kind of drag: profile drag. Profile drag results from the general shape of an object, and is greater when profiles approach an angle perpendicular to the air flow. When the profile is closer to being parallel with the airflow, profile drag is reduced. The 240's windshield angle compares favorably to many cars of the era (the Jag XKE for example), but it is noticeably steeper than that of almost all modern cars. Park your Z next to a 1996 Corvette and check it out.

 

Looking down from directly above the car, the early Z windshield is also relatively flat, i.e.: the left and right sides do not curve around very much. Air flowing from in front of the windshield around the A-pillars to get to the sides of the car must make a sharp turn, and sharp turns always produce drag. Compare the Z windshield to that of modern cars and you will see how much attention current designs give to easing air from in front of the windshield around the sides of the cockpit.

 

Station 82 through 156 includes the top of the car, side windows, rear quarter windows, over-door drip rails, doors, door handles, rear fenders, hatch, and antenna. A lot is going on here, but the total falls into one of two general drag categories and we'll look at each.

 

The top of the car is one of the smoothest places on the entire Z, and while smooth is generally good from a drag perspective, here it has another negative effect. The smooth top of the Z, gently falling to the tail, encourages high velocity air to remain attached to the roof surface and that attachment produces lift on the aft section of the body. The figure that comes to mind is 120 pounds of lift on the rear of the car, but I don't recall now at what speed that figure is reached, though I believe it was either 60 or 100 mph. Lift on the aft body relieves load on the springs and the aft body lifts slightly.

 

The MacPherson strut rear suspension acts like the front suspension when the body is raised: camber becomes slightly more positive and toe-in changes slightly compared to the body's static setting. The mismatch of lift between front and rear at speed on the 240 is a major reason why the Z is known as an understeering car at low speeds and an oversteering car at high speeds. Oversteer and understeer characteristics are formed by more than suspension type and settings. An optional rear spoiler was available for the 240 almost from the beginning, though relatively few 240's possessed one. Changing the aft body lift characteristics of the 240 involves either creating downforce, as with the original rear spoiler, or "spoiling" the lift before it begins.

 

A more effective alternative than a rear spoiler would be small, integral turbulator strips in the roof near the forward edge of the hatch, similar to those now found on many upscale driver helmets. Turbulator strips placed perpendicular to the airflow detach flowing air from the curved surface of the helmet (or wing, or Z top) and make it turbulent. Turbulent air does not stay attached to the helmet surface, and lift is reduced or "spoiled." No one has ever marketed turbulator strips for the early Z or any other production car to my knowledge, but it is easy to see that such additions would fundamentally alter the unique lines of roofs and aft bodies, and thus probably be hard to sell. Reducing the downward slope of the hatch also would reduce the amount of lift generated, but then the distinctive Z shape would be lost.

 

Aft body lift produces drag of a type known as induced drag. Modern designers have moved a few paces down the road since the 240 and actively attempt to profile car bodies aft of the cabin area to reduce turbulence, lift, and drag while maintaining visibility and marketable style. Function can always be improved, but is in the end beholden to style. Buckminster Fuller's Dymaxion, for example, took streamlining to the nth degree, totally ignoring style. The result was a teardrop shaped vehicle that looked (and sold) more like a fighter drop tank than a car and thus passed into history. But for its size, the Dymaxion had good aerodynamics.

 

An aerodynamic comparison of the 240 to two other high performance rooflines is useful. The first is the elevated rear deck style as found on the Toyota MR2, Lotus Europa, or Ferrari Dino. Air flowing off the roof burbles turbulently back over the rear deck, creating less lift than is found in the 240. The turbulent air carries its own drag penalty, but that penalty decreases as the distance from the rooftop to the rear deck decreases, and the distance is small in these three cars. Ferrari also makes use of the low pressure formed by the sudden dropoff of the roof to the deck to assist engine cooling airflow, reaping some benefit from the profile.

 

The other style, found in the elevated aft roofline of some late model Honda Civics, carries the majority of cabin height all the way to the aft end of the car. Lift and, in some cases, even drag is reduced with this style, but negatives tend to include relatively poor aft visibility and an excessive high position for the large, heavy window that's used to improve the poor visibility. This style contains a subset of cars such as the Nissan 300ZX and Dodge Stealth (and the new Z??) possessing tall aft bodies and general wedge shapes, and having aerodynamics similar to the Civic.

 

The 240's side windows, quarter windows, door handles, and drip rails are not flush, and all the bumps produce parasitic drag and noise. The same is true for the radio antenna. While these components do not comprise a major percentage of the overall drag of the 240, they cumulatively represent a drag penalty that is worth avoiding.

 

Hidden from view, the 240's bottom is a last place to take stock. Of course the 240's belly is rife with all sorts of odd shaped valleys and projections, all of which interfere with the smooth passage of air. But the 240 is not much different from the most modern autos: full belly pans have become neither practical nor popular. Current cars do have better developed front belly pans than does the 240, but underbody aerodynamics have only been adopted and explored by formula cars to date. This could easily change; all it would take is another fuel supply crisis. But for now the 240 is pretty much on par with other cars.

 

Conclusion

Reasonable aerodynamic improvements for the early Z are limited to cooling air inlet plenum improvements, cooling aperture alterations (G-nose kits), headlight covers, aftermarket front air dams, and rear spoilers. Other improvementsÑrecessed wipers, antennas, marker and turn lights, and handle-less door latches are possible with a little more effort, and still preserve the Z's shape. Still others including windshield angle, flush windows, and altered aft body contours are only for the most advanced do-it-yourselfer to whom aerodynamics have become more important than style preservation.

 

 

Terry

[(goldfish)]

Why does the radiator have to be front and center? Alot of drag is the air hitting the firewall. If we can move the radiator and block off the front opening entirely...

 

not to mention a run what you bring class.

[Z-TARD]

You'd have to find another method to maintain engine cooling if you block off the front entirely. It's easier to just tweak the original design to displce air somewhere other than under the car, via the firewall. Ducting the air either up and over the hood, or out the left and right sides is the most realistic option. Ommiting the passenger seat and running a large duct through the cabin and out the back of the car would be another idea..... Overall, I think the shape of the Z would lend itself very well to areodynamics once most of the parasitic drag areas are taken care of. Driving a 2500 lb car at 240mph is another story though. I'm sure the car could be made to do it, but I'd opt to wear a diaper for the test run, just to be safe.

 

Mike

[Guest zerpie1]

The only way to get a Z to go 240 mph is to push it out the back of a cargo plane at 30,000 feet. Save yourself the trouble and send me the money I just saved you.

[Z-TARD]

Sadly, I think it might not actually reach 240mph in free fall. Not positive though, too lazy to do the math right now. Heres the formula if you want it though: http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

 

Mike

[v8260]

Reminds me of this guy who showed his 80yo dad a picture of a "flats" car' date=' he said "dad this car will go 700 miles an hour." His dad told him time and time again NO WAY, NO HOW would any car go 700MPH. He finally threw up his hands in dispair and ask the old man WHY he didn't belive it. "Because son there ain't no road around here you can drive 700MPH on."

 

Besides the flats where in the hell are you going to drive 240 MPH, I just can't stop laughing here, my co-workers are beginning to wonder if I've lost my mind. Are you going to drive that thing up the 405 at 2AM?

 

Sorry I'm being closed minded here...

 

ds[/quote']

 

 

kinda stupid of a move but i did 130mph in my super eta and 5am on the 405 haha. Was racing a turbo'd eclipse....anywho....seriously thou u could take it to the autobahn in europe. heard there are plenty of ferraris to play with over there. haha

 

btw im in ur area of HB. I live in costa mesa. When you start on the project i can help u out. Me my self i like goals that everyone doubts. go for it man!

[boodlefoof]

Interesting that this post got revived. I guess I wasn't the first one to think of building a streetable 200+ mph early Z car.

 

My plan is to have a 240-Z that can drive legally on the street down to the local diner every once in awhile, lay down an impressive quarter mile time, and then hit 200mph open road racing.

 

Of course, with the extent of modifications I'll be performing to the car... you might not even think of it as a 240-Z anymore...

 

The Plan -

 

Chassis - complete tube frame chassis that the modified Z body will then be welded to.

 

Body - lowered roof, swept back front windshield, custom body panels throughout. I've already lowered the roof... you can see pics at http://forums.hybridz.org/showthread.php?t=101672&highlight=chop+top (scroll down to bottom of first page)

 

Aero - underside of the car will be completely flat with a 2/3-3/4 length diffuser. Lots of air flow management ideas incorporated in engine bay and wheel wells. There is a full-scale wind tunnel at Langley, VA that I may look into using.

 

Suspension - custom front unequal length control arms, probably using C5 spindles. Out back, solid axle with either 3-link or Satchell link suspension (still debating that one).

 

Drivetrain - lots of ideas... still no definite decision.

 

When all is said and done, a budget of $50k is pretty reasonable. Thus far, I've bought the car, created the custom fiberglass body, chopped the top and repaired the rust... all for less than $500!

[IBZINYA]

Well, Here we are 5 years later and has he begun the build? Anybody? Hello.

All is quiet in Bonneville?

He has obviously been inspired... by whoom I have no idea. But good luck with that.

[D1CNAR]

i hit 175 almost everyday on my way to work in a rb26dett 260 and it has a little left

[BurnoutZ]

175 in say a 70?

[SkYBlue280Z]

only the Devil Z off Wangan Midnight has that kind of power =]

[ZX2+2]

my dad did 167mph in his 75` 260Z 2+2.

L28ET did about 300whp

[dhp123166]

Just buy a Koenigsegg and and get it right the first time...

[htownz]

Well, it looks like this post is 5 years in the making. I didn't read all the posts but here's my 2 cents. Whether you hit 240 or not, I'd suggest a GM LS series motor with a 6 speed. An LS-with a speed would be pretty damn fast right out of the box and drivable. The options for the LS motor are pretty wide, the new ZR-1/CTS-V are pretty crazy. They are light and make a ton of power bother for their weight and displacement. I don't know if a Z-31 or Z-32 rear can take the kind of power required to try and push a 240Z to such insaneo-sonic levels.

 

Have fun with the aerodynamics too. You could lay the radiator at an angle and suck air in from below the air damn and vent through the hood for cooling and aerodynamics. I don't think a belly pan would be all that hard on a Z but depends on how crazy you get.

 

Good luck.

[L.S.Racer]

The Z will creat lift at around 170 mph and with a lach of mechanical knowledge you need alot bigger budget, closer to 150k. But good luck.

[L.S.Racer]

B.S. The car will always spin between 166 to 172. That is unless you add atleast 350lbs plus driver. You should get your spedo checked.

[Tony D]

B.S. The car will always spin between 166 to 172. That is unless you add atleast 350lbs plus driver. You should get your spedo checked.

 

Hmmm, interesting claim. Anything to support that claim?

 

What is the F/GALT record at Bonneville currently, and what vehicle holds it, and at what speed?

 

With a screen name like that, I'm sure you will be able to easily answer the question...

 

Just for the record.

 

Obviously some of the above claims are B.S., but that statement bears investigation...

[Daeron]

Just for the record.

 

*collective*groan*

[LVSALT]

I stumbled upon this sight (google) looking for Z nose kits. Havent gone 240mph. but I think it is possible. Our car is NOT street legal by any means but it is a Z car.

[Challenger]

Hmmm, interesting claim. Anything to support that claim?

 

What is the F/GALT record at Bonneville currently, and what vehicle holds it, and at what speed?

 

With a screen name like that, I'm sure you will be able to easily answer the question...

 

Just for the record.

 

Obviously some of the above claims are B.S., but that statement bears investigation...

 

 

157.178 mph or is it 173.125 mph...