Aerodynamic aids and 1/4 mile time improvements?

[johnc]

FYI... in case anyone's interested.

 

I'm doing some research on rear wings for the 240Z. These are REAL race wings and are a Trans Am design all in aluminum (only a 1lb difference between AL and Carbon Fiber but there's a $250 price difference). They will have to work in conjunction with a good front end aero design because they can generate lots of downforce.

 

I'm working on the front end too. Most likely a dam, front underbody tray, a 6" splitter, and some tunnels with vortex generators in front of the front wheels.

 

This will be a a track only setup (ground clearance issues with the splitter) and I'm hoping to get them done by the end of March. We'll see if it pans out. And the whole setup will be expensive.

[A. G. Olphart]

John... Earlier in this old thread, you referred to a Car and Driver test indicating that a 7" tall rear spoiler set at 30 degrees was optimal for a 73Z.

 

Do you know how the measurements were referenced? Did they mean 30 degrees from vertical or from horizontal?

The short BRE style lends credence to 30 from vertical, but the later (Bob Sharpe?) 280zx's had a longer spoiler much more horizontally oriented.

 

Even the 7" measurement seems open to interpretation... vertical 7", or 7" along the plane of the spoiler? Probably not all that critical.

 

Wondering what I should build for my highway 240 for a little more stability and that 1.3mpg.

 

 

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[Tony D]

Wander onto the wrong side of the street, and look at what you find!!!

 

Andy's car had at any one dyno session between 280 and 320HP to the rear wheels, the one and only time it was run at a 1/4 mile track it had a severely traction limited 13.08 at 108, with a noticable 3 second stutter session in the second third shift till the cam came back on and the tires were spinning through the traps. This was with street radials, with a 3.36 rear gearing, and a (shudder to remember this) a Predator Carburettor on an old four-barrel manifold. It picked up much more HP when we went to 45 Webers (25hp at 7500) and more again when we went to TWM TB's (over 300 hp and picking up 40hp over the webers at 8500rpm....)

 

ANYWAY the question was aerodynamics.

Stock, the S30 unmodified runs like .465 as stated above with a cd of 22 sq ft.

 

In total G-Nose, headlight covers, underpanned to the rear of the tranny with the Nissan OEM pan (PZR) and with a rake of 2-3" (I forget which) the cars drag coefficient is around .38.

 

I have talked till I am blue in the face about this topic, and people who discard the OEM answer of the G-Nose to improving aerodynamics are fighting a loosing battle!

 

Our experience in 1.3mile racing was that the car, in the Predator Carb version lost 3mph when the "Small" BRE style spoiler was on the back of the car. It was more stable from traction, but was slower. We made a run in the morning, and went 140mph. On our second run of the day, with a temperature that had risen almost 30 degrees, and no tailwind, we went 143mph---so this is actually an underestimation of the drag effects of that "traditional" spoiler on the back. Like JohnC is investigating, using an alternate wing configuration with modern design will be far more effective---if you want something that WORKS, go with the new tech. If you want ricerbling nostalgia, go with the old drag adds stability and traction old-school FRP pieces.

 

So with the G-Nose and underpan smooting airflow, along with a rake to prevent air from getting under the car in the first place you can get a considerable, significant decrease in Cd with the aforementioned mods. These numbers are also verifiable with some of the NIssan Literature that is out there.

 

Anyway, those are the numbers for the mods being discussed, and some other information.

 

As for the record being "only" 150mph....rent a copy of "World's Fastest Indian" starring Anthony Hopkins, put up your money, and see how easy it is...

 

BTW, the car ultimately went 173mph and change, and that was with .080" scores in the cylinder walls from the pressed-in piston pins walking over and making contact... Everyone said "never seen that happen before..." With good sealing bores, the car should pick up the less than 2mph needed to qualify for the "long track" at Bonneville, and then we can gear up further, and hold the throttle open for five miles instead of three.

 

If you think your car can stand staying within 50rpm of redline for six to ten miles, give it a shot! It's a different experience. Kind of like making a single point load run on a Mustang Dyno for two minutes 50 rpm below redline...

 

I'll go see Norm race next Thursday, and maybe give him some pointers in person then! LOL

[johnc]

John... Earlier in this old thread, you referred to a Car and Driver test indicating that a 7" tall rear spoiler set at 30 degrees was optimal for a 73Z.

 

Do you know how the measurements were referenced? Did they mean 30 degrees from vertical or from horizontal?

 

30 degrees from horizontal and the length of the spoiler itself was 7". The term "tall" actuall referred to its length. Below is what I built for my car back in 2004.

 

 

I think its still being run on a FP 240Z up in the bay area.

[Guest Mike]

JOHNC... Your wing is functional/utilitarian, yet very nice-looking. I like it... and I seldom like wings. I like what you did with the hatch window too. Given the straight-edge design with a tight bend, it seems logical to make this a variable spoiler. It could be controlled within the cockpit with a cable(s) or hydraulically. This may be a PITA and completely unnecessary.. dunno.

[A. G. Olphart]

Many thanks!

 

I'll not be anywhere near LSR territory, but enjoy the tech.

 

John, having seen the Rusty Old Datsun at thunder hill, had I a MEMORY :confused:, your clarification would not have been needed. Thanks for the picture: I (and certainly others as well) will make good use of it.

 

 

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