100 on the sameroad coming home was rock solid, so knowing that, it makes me wonder about aero issues such as the toe change due to maybe a lifting front end thus changing toe maybe?

My god

4 pages of replies about speeding and not one dressing down by the panty waisted wishy washy namby pamby "I only drive 55 on the road" , you child and woman endangering speed demon sadistic evil crime doer you crowd!

This must be a Pelican record

PTL Let it loose!

http://forums.pelicanparts.com/uploa...1119482050.jpg

wheeee :D


http://forums.pelicanparts.com/uploa...1119482447.jpg

I was kind of expecting a dressing down by some, but I really would like to figure out what is wrong with my car and thankfully this PP board has tried to assist me. Maybe I didn't come across as a punk street racer which I am far from. (now when I was a wreckless teen, that was a different story!) While I feel completely safe at 100 on SOME open back roads in SOME cars, I rarely do it as I can't afford to have ANY tickets on my record with a teen daughter on my insurance now (with #2 daughter to follow in 5 months).

How much gas did you have in the front tank? My mechanic told me to do high speed runs on a full tank. 10 gallons weighs how much, 80 pounds?

My vote though is for getting new shocks. I just raised my front end back up to Euro ride height (25.5F) and installed new shocks. The previous owner had slammed the car to the ground. The car rides so much better.

For responsible people there is always a time and place where it may be safe to push the envelope and have some good old fashioned fun at the expense of nobody.
Best of luck sorting out the front end issue. Mine is stock out of the box height and pretty stable at 90-120 indicated groundspeed. My speedometer might be a tad optimistic if past performance is any indicator.;)

It's interesting to note in this discussion that just about every road test on the SCs and the Carreras (84-89) made reference to the fact that these cars felt old compared to contemporary cars of their respective years! In one test of the Carrera CS vs. a Corvette Z51 in 1986, they made comment like, "Someone should tell the Porsche guys that things are easier these days." These cars do have charm, if not outright performance!

With respect to the tails, I believe that the turbo tail was a popular add on, but not a "factory option." One could get this added at Porsche Werks, or in the States at their dealer. The Carrera Tail is not correct at all to the SC, as it had not yet been introduced. Still, I think it looks better since the Carrera and SCs have the same body.

Same setup on my 79 SC
 

Turbo tail and front spoiler. It's been several years but I've had my car redlined in 5th gear. Very straight remote highway. It was rock steady. In fact, I used the lines in the road to gauge side to side movement. I could straddle the line and there it would stay. My car originally did not have the spoiler setup and it felt light in the front end around 110 mph. There was some side movement even at that speed that required constant correction. The spoiler setup functions as advertised.

I still get it up around 120 from time to time and its still rock steady at speed. However, age and kids have pretty much limited my high speed jaunts to the track. By the way, my car has been lowered and I'm running S03's on it.

Try some of the suggestions the others have made to steady things out. Also make sure all your bushings and linkages are tight.


http://forums.pelicanparts.com/uploa...1119498900.jpg

Hum..bushings? Check the front and rear stabilizer bar bushings for wear.

I think your shocks if past their expiration would play a significant role at the limit of the car's performance envelope. Also castor is very important. Think supermarket shopping trolley........

The last of the 911's (SC and Carrera's) were really just an early 70's design reengineered to deal with more weight. It will feel significantly 'older' than the 951 which was at the cutting edge of late 80's technology.

Simon

You should definitely check the caster. According to Herb Adams' book, Chassis Engineering, caster "is essential for high-speed stability."

You can find directions on measuring caster here in the SRP Smart Camber owners manual using whatever you used to measure your camber.

http://www.smartracingproducts.com/pdfdocs/011073_smartcamber_manual.pdf

Tim

There is something wrong. I have been 140+ in an '82 SC and an '86 3.2. Both had tails and chins spoilers and were rock solid.

There is a huge amount of down force from those spoilers. I would guess shocks and/or alignment or tyres. But could be a number of things.

Good luck.

New front shock inserts arrived yesterday (thanks Mitchell) and I hope to install B4 this Sundays trip to Mid Ohio to watch the vintage races.

While I am doing this I will check for "bump steer" geometry issues.

Just to clarify, my chin spoiler IS proper for the whale tail? (are there different black rubber chin spoilers for Carrera/SC's running tails/Turbo's?)

For those posting proof of going 100+ with in car photos, you're really reckless to be taking pictures while operating a car going at speed. both hands and attention should be focused on road and traffic (animals and people crossing road?

I think the shocks and bushings are suspect. With the correct front and rear spoilers the car should be stable if the tires are at correct pressures and alignment and shocks are correct.

See Weaver's thread on spring plate bushings and tire treads.

I have a `83 Euro SC coupe (204hp) with exact the same aero equipment which was delivered this way from the factory. The rear turbo tail was 1983 (in Germany) the only tail option you could get.
The car was tested from the magazine "auto, motor sport" in 1983 with a top speed of 245kp/h which is 153 miles/hour.
My car is doing easily 250 kp/h on the speedo, probably about 10km/h less in real speed, but it never feels unstable at that speed.
It really is very important to use the right tires with the N followed by a number 0-4 after the tire designation.
You don`t feel much of a difference at lower speeds but at high speeds you really do!
(We are only allowed to run these special N tires by German"DOT", it is written in our registration as the only applicable tires.) They are available in your sizes from Continental, Pirelli, Bridgestone and Michelin.
Avon is the worst tire anyway, had them on my Lancia Delta Integrale and even on this car it was frightening.

Sebastian

I will also mention something no one else has. If you were getting 5900 RPM out of the thing in top gear with the SC, you should have been doing about 145 or so. These speedometers are notoriously unreliable so you should find out what your car's speed is per 1000 RPM. My Carrera, which I believe has the same gearing as your SC, does about 25 MPH per 1000 RPM. So at 5900 RPM you should have been doing about 145, which would be a LOT faster than what you thought was 130.

BTW, I've had my car up to 120 with ease and it was pulling harder at that speed in top gear than it does at 80. Very stable.

Yes, SC top speed is more than 130.
 

I agree with you completely. I'm not sure where these top speed figures for an SC are coming from but when I was redlined in 5th, the speedometer was well over 140 mph, closer toward 150. I've found that the rpm versus speed as indicated in my car is pretty much spot on with the graph in my 79SC owner's manual; 30,60,90,120, and 150 mph corresponding to redline in 1st, 2nd, 3rd, 4th, and 5th gear.

Also, two of my books indicate that spoilers were options for the SC. The Porsche Red Book indicates that option code M470 is "delete spoilers" while M473 is "with spoilers". It doesn't indicate whether the rear spoiler in this option is a turbo spoiler or not, but the tea tray style was introduced early enough in the SC model years that it should have been available. Several of the SC photos in Peter Morgan's "Original Porsche 911" book show a couple period photos of the SC with the turbo tea tray rear spoiler and other SCs with the less aggressive style spoiler.

Hey, guys, get yourself (or borrow) a good GPS and check your speedometer error with it. They're pretty accurate these days.

While my speedo was pretty accurate at 80-90, I've not had the car above the ton yet, so haven't checked it up there.

I think alignment would be the biggest suspect. Caster plays an important role for high speed stability and is not easy to measure by a DIY.

Go find a shop with a newish laser alignment rack and even if they don't have 'Porsche experience', getting the alignment done accurately should not be a problem.