Z aerodynamics

[ZwolleY]

I drive in the Columbia River Gorge where the east wind is really raging now. If it is not the east wind, it is a strong west wind. The car really gets pushed around by the wind. I read somewhere that the Z does not handle well with a cross wind and I can confirm that. Is it design or just the light weight of the car? '72 Z

[D-Webster]

I have driven through the gorge many times (my mother lived in Portland) in a variety of cars. Around The Dalls (sp) I haven't found anything that works very well ... but then I've never driven a M1 Abrams througth there either. I don't think the Z is at fault. I drove both models of the old 914 through there, both the four and the six, 68 Corvette, and even a Cobra and none of them relished the drive through there.

[260DET]

The usual stability enhancing mods should help, front spoiler, lowered with a bit of rake, rear spoiler, tight steering and suspension, right tyres, maybe more caster - mine is 5 degrees plus.

That run sounds like a good test.

[26th-Z]

The S30 was designed in the late sixties when air flow around a car was not given thorough consideration. Contemporary styling at the time did not take into account air flow modeling the way it affects design today. Air tunnel testing was performed on the S30 chassis, but remember that air tunnel technology was not what it is today. Coupled with the light weight of the car, it is no surprise that top speed is limited by air flow stability.

I remember driving through the Ocala National Forest one morning on my way down to Daytona. It was cool and calm. I noticed a great deal of front end drift at an indicated 120 mph - enough to awaken my better judgement and convince me to back off a bit.

We also complain about exhaust gasses coming back into the car because of the pressure differentials off the tail of the car. Another air flow fault.

The S30 sure is beautiful with classic flowing lines, but for all it's grace and beauty, it flies like a turkey and smells like turkey farts!

Later versions of the S30 included modifications to suppress some of the early faults. A small spoiler was added to the front valance and then the valance was lowered. Interior venting changed almost immediately. Later version weigh more as well.

[260DET]

While the first gen cars are old tech as far as aerodynamics go, in my experience they respond very well to the mods mentioned previously eg the nose lift problem is quite easily fixed.

Having driven my '77 at over 200 kph I can report that it is rock solid at high speed, has excellent directional stability, yet still turns nicely as required. But the proper work has to be done to get them that way.

[TomoHawk]

Originally posted by 260DET

... the proper work has to be done to get them that way.

I hate it when hes puts that little kicker in there..

OK, so what is the first thing you could do? Air dam? How far down would it have to be?

FYI: Enzo GTOs had 2 air dams- one under the nose and one in front of the rear axle.

[RB30-ZED]

I Also drive through an area which has bad gusty cross winds, and very early on I found that once I modified the inner lower control arm points to reduce "Bump steer", the problem of swerving in my lane durring cross winds went away.

If you think about it, ever with a small amount of bump steer this problem is worse in a cross wind situation as you have one side of the suspension compressing and the other side dropping.

I know this is slight but you have both wheel toeing in two different directions which will cause it to steer. If it steers in to the wind , its not to bad, but if it steers with the wind it will be all over the lane as mine did.

I raised my pick up points 30mm and I have very little trouble with cross winds now.

What do you guys think?

Steven

[TomoHawk]

wow, 30mm (~1 3/16 inches)?

That's more than the usual 3/4 to 7/8 inch (19-22 mm)

But if it's what you need, then that's exactly the right amount.

[RB30-ZED]

Yes its quite a bit.

I removed the springs set it at ride height on a jack and graphed the toe change up 50 mm and down 50mm till i found the least change. I used a slotted crossmember and once i had found the best spot, i redrilled a second cross member and rechecked.

Steven

[260DET]

Interesting point Steven, you may have something there. I've got rid of the bump steer on mine too, essential for nice handling.

TomoHawk, you start with the suspension and steering in first class condition. In view of Steven's point this includes no bump steer. Then lower the car all round but with a bit of rake. Fit a modern scraper type front spoiler, not a spook or similar, I've seen a US one that I would love to have. Rear spoiler as well.

That will make a hell of a difference. Other things to do include a fully adjustable front suspension particularly for more caster, bonnet air exit vents and a front undertray.

[TomoHawk]

Undertray....

I think I could build in a narrow air dam into that. Like an upside-down lip spoiler.

Those are about 2 feet wide ( about same width as radiator)?

You could use it to scoop air for the brakes too.

[zorro]

Its interesting to hear u say that i wondered why myself a car so low would blow around with a side wind the only thing i noticed was lowering it and putting a front air dam on helped mine to be more stable as has already been mentioned.....