Greg Fishman

Well here is a 993 that actually hits 180mph at Sebring during a club race. He doesn't have an undertray and the car doesn't look unstable to me. http://www.trackvision.net/uploads/goldrich_sebring.wmv

When was the last time Ruf raced a car?

c993k

Greg
These are race cars with huge wings and suspensions set up completely different than our street cars, Again we are talking about streetable 993's in a straight line top speeds. I liked the video thanks, but it almost seemed like it was in km.
Chris

Greg Fishman

Chris,
You have a point but I don't buy it that it is necessary. Ruf Racer (roland) used to race his Ruf 993 on Open Track at speeds over 200mph. I don't think he is still around but I don't remember him ever saying he used the undertray. I am going to do a search though.

Not a chance it was km, this is a 800hp GT2,notice how he makes a 996 Cup car seem slow on the back straight.

Edward

We're all far more likely to heat-soak the head and valve train than even approach top speed in our 993s. FWIW, I've only been able to hit about 130 and change at local tracks and the car was so stable I could have popped in a CD and picked up the cell. "Stability" at the rated top speed is a moot point (or bar-room bragging rights) for most I think. Shedding engine heat is of far great concern, but maybe that's just me

Edward

Coleman

Hmm.. So is it better to have melted exhaust guides or instability at 180MPH.....


Crap- I don't like either option.. F*ck it.. I'm Getting a WRX!



Coleman.

Mike in Chi

Good point.

na 993 rock solid at Road America at 140 without the belly pan.

tj90

I likes Gregs video. I can sit there and watch it 10x in a row. Hearing the turbo spooling up gives me a shot of adrenaline!

ca993twin

Roland is still around, and still actively running the Nevada open road races... AVERAGING over 205 mph. The key piece of data for this discussion is if he uses his tray for those events, and if so, why. I don't have that data.

Dr. No

No, the tray is not disrupting the airflow under the car, which at speed would be compensated for by splitters directing air away from the area and a big wing supplying lots of downforce. And the factory rated top speed of a stock 993 is, what, 180 mph? Is it that hard to believe?

chris walrod

Its rare that any 'typical' road car will actually make downforce. Splitters, wings and spoilers, if designed properly, will, at best, negate any inherent lift at speeds less than ~170mph.

Smoothing the bottom of road cars are typically for purposes of reducing aero drag such as the 993 engine cover. The engine covers on these cars also reduce drive-by engine noise for countries such as Switzerland, who are quite strict about this.

pjc

Chris,

Isn't negating lift the same thing as creating downforce?

PJC

chris walrod

Yes, to a point

I guess what I am trying to say is its really tough for a road car to generate net downforce, more downforce than lift..

mrsullivan

the funniest thing to me about all this is that it goes to show you cant trust everything you read...

there have been several very definitive posts on this board about how the tray was "ONLY for noise regulations purposes that were established in certain European countries"... "you MUST remove the tray"...

who knows if RUF is right or not, but since it is RUF Germany, I have to say that there is at least a strong chance that they are right... (?)

Reynard38

Having played with the aero on my racecar (with the help of Lockheed engineers) there may be a bit of thruth to what RUF says. We placed a diffuser at the rear of the car (Reynard). What this did was to draw more air under the car. From Bernoulis law we know that as a fluid speed increases between 2 plates the pressure drops. I think the truth may be that the undertray keeps the flow more laminar and acts as one of the plates, keeping the low pressure area together. Again as the car is sitting several inches off the road (not 3/4 inch like my Reynard) this is only going to have an affect at VERY high speeds.
Oh and my engine tray is off. It gets hot hear in Atlanta.

Ruf-Racer

Although I don't really average 205 mph (thanks Steve) I frequently run at 205-210 mph for long stretches. I run with the pan in place because that's what Rul says I need to do. Yes, I presented the standard "heat" arguements to Alois as well as his #1 wrench..Joe Huber.That pan stays!

I know other Porsche drivers that regularly run in the 195 mph range and have reported experiencing an uncomfortable instability with the pan removed.

That's my experience. I certainly plan to run with the pan in place next month in Nevada.

I would guess that Steve's Ruf car would benefit by having the pan removed for around town driving.

When the car is parked after a hard run it really gets hot and the pan traps a lot of heat..enough to "coke" the turbo oil that always spills right before I need new turbos.

Thanks to Kevin..I love the ZC mod's he did on my factory Ruf turbos...don't tell Ruf but they do spool fast. I am hoping to get officially timed at 212 mph in July with my long geared almost stock Ruf Turbo.

Hope this helps.


Cheers

R