mark kibort

Its amazingly straight forward how to design the chassis for just wanting to go fast and not lift off. You dont want to add wings , as that could be deadly at speed if they are not perfectly balanced for front and rear downforce. drag is not really the issue, since he has a lot of hp now to punch through the thin 5000ft air. Adding weight is good. putting on air dams will be good. And mostly, up to the driver to sense what is happening as far as grip. Most speed run folks havent a clue of how to handle a car in an emergency. Happens all the time on open road courses. They dont know it, because their skill set is not developed. That guy in the RX7 is a prime example. He caused his spin and subsequent lift off.
I dont think a blown engine is going to be catastrophic at speed. in drag racing, the cars going 300mph usually just coast to a stop, if the engine blow doesnt blow apart their chassis ! Lucky, the salt is flat and there is nothing to hit.

Certainly, might be warrented to add some vertical stabilizers to assure there is more straightline stability.

WallyP

Given that several 928's have been from 175 - 200 mph on the open road, I would not expect to have any lift problems - as long as you are going straight ahead. I would expect the car to fly if it gets sideways at high speed. I would give serious consideration to adding longitudinal fences on the top and down the sides of the hatch. Shouldn't increase drag much. but might help keep it on the ground in a spin.

Our Bonneville records (I/MS gas & fuel) were all only 145-150 mph, with small street tires, with shaved tread on a smaller car (Fiat 850 roadster). Tire growth and wheel slippage almost exactly balanced out, so speed was exactly at calculated rpm/gearing/wheel diameter values. In your case, I would expect 15-20% wheel slippage at speed.

Tahoe Shark

Go get'um Karl! Team Speednutz will be rooting for you. Just be careful and check everything twice, then again. Good luck with your goal! We will be at the Silver State or we would come and watch you.

Carl Fausett

Greg - my time is posted right here
http://director.usacracing.com/ppihc...09_results.pdf

at 13:46.791 which was not only fast enough for third place, but was also the fastest 2WD car in the Open.

No Sundial involved.

But the number is out there - so if you think its not good enough, stop armchair quarterbacking and go do it. Or shut up.

Carl Fausett

Wind Tunnel Time: the closest full-size tunnel I could find to me is in Tennessee and its $13,000 for the first hour, $11,000 an hour after that.

We also explored a scale-tunnel. The U or WI at Madison has one. You put a 1:18 scale model in the small tunnel and have a go. Trouble is you have to multiply the air velocity to match - to know what the full-sized car does at 200 mph you have to push air at the 1:18 scale model at 18 x 200 MPH or 3600 mph. Sorry, it doesnt go that fast.

We also lookes at water tunnels.

In the end, we thought if we could data-model a 928 into a point cloud, then we could apply the aerodynoamic software to the point cloud and try various wings and air dams and chord angles at will in the vitrual world.

Here are some pictures of that effort. You'llnotethe resolutionishigher at the front and critical curves - and not as high in sections that do not change dramatically (center of the hood, center of the rooftop) for exaple.

We have taken over 16,000 data points (x,y and z) measurements and enterred them into the computer.

Carl Fausett

and here are the first plots from the data cloud we created.

This is largely my son Ty's project, and I do not know if it will get done in such a time frame to be of any use to me. He's looking at changing jobs right now and spending no time on this project understandably.

But I cannot wait - so I proceed with a more analog and logical approach to the aero work. I have no other choice.

Gregg K

It seems to me that the only thing one can do, short of doing major body profile changes, is to keep air from getting under the car. I don't see any need for anything other than that.

The idea is that if air gets under the car, the whole thing begins to act as a wing. And the other big problem being ground lift. But that still comes down to just keeping air from getting under the car.

And I'm probably missing some crucial element. But I thought I'd blab.

mark kibort

Its not that complicated. there are very sensitive sensors that are available to measure pressure.I would measure about 20 points and then extrapolate the effects at 2x the speed. say, take those measurements at 110mph and then calcuate out to 220mph. hey, planes in WWII flew just fine using some of the basic rules of aerodynamics. some, not even fully understood back then. Now, with the shape you have, you just plug it into a aero model program and you can get anything you want out of it. you dont even need a wind tunnel. besides, using a wind tunnel , like the WC GT boys did in 2004, cost near $30k for the day in Canada. the Vet came in with 100lbs of lift up front and 200lbs of downforce and left with 150lbs of downforce up front and 350lbs of downforce in the rear. (fully aero equiped)

What Greg was talking about in regards to pike peak, was the winners overall. cars and professional drivers that ran quite a bit faster. I always try to be at least 108% of the best drivers and equipment for similarly prepared race cars. (like comparing my car to a Cup car for example).

Carl Fausett

Don't even TRY to ex-plain what Greg meant. He was speaking from ignorance and jealousy.

If he wants to beleive that a tube-framed, purpose built hill climb car is just like a unibody race car then I cant help him. The results speak for themselves - I was faster than some (Including a 2008 Mustang in my own Division) and not as fast as others.

The road is there - and they are paving more of it every year. The times will continue to go down.

Richard S

Actually George felt a shudder, saw the oil pressure guage drop, and shifted into neutral about 1 second before the engine grenaded. I'm thankful he did....

Rich

Carl Fausett

This would be a good event for an automatic trans.

Rob Edwards

I blew the GTS's engine at about 70 mph in a straight line. I reflexively put the car in neutral, but even if I hadn't, without doing the math somehow it seems to me that 3500 lbs at 70 mph is enough momentum to just continue driving the crankshaft and stir up the remaining engine bits. Maybe if a broken rod wedged itself in the girdle you'd lock up the rear wheels, but again, wouldn't the clutch just slip? Anyone ever blown an engine and had the drive wheels lock up as a consequence?

Either way, I'm glad I was only going 70.

James Bailey

OK "but again, wouldn't the clutch just slip?.." if the clutch has the ability to hold well enough under power to spin the wheels....it has enough clamp to stop the rear wheels from turning since the traction at the tire is the same either way.. Plus on a surface like salt BOTH happen much easier

mark kibort

oh yeah, there would be no problem in the clutch being able to lock up the wheels if the engine blew and got jammed. again, goes back to pilot capabilities. ive broken two engines on the dyno and on the track, and have been quick enough on the clutch and gas to keep from redlining the engine. but, if it happens instantaneosly and you lock up the rear wheels at that speed, you are in for a ride! However, i would suspect that a blown engine will give a few bucks and kicks before that happens

Tony

Carl..since you have all that tape on the car may i suggets one of these paint schemes.


On a serious note. I know Nascar uses a device in the roof to kill lift when the car goes sideways/backwards. basically acts like a spoiler on an aircraft wing. If you still have the sunroof, could a device like that be mounted there? Maybe enough to keep it right side up??