Rich Sandor

weight (sprung or unsprung) does not affect your top speed, only your acceleration.

there is a bit of debate as to whether or not the 'stock' 944/951/968 series has lift or actual downforce at speed. It's very close to zero, imho.

I've driven a chevy cavalier (speed limited to 110mph - for good reason) to about 130mph, and the thing basically lifted up like an airplane wing ready to takeoff. That car had NOTICEABLE lift across the entire body.

My 951 is dropped about 2 inches, and with front splitter, the whole car felt like it sucked itself down into the pavement the faster I went. It felt VERY solid at speed.

The 968 with splitter, but stock ride height, did not feel quite as 'sucked down' as the 951. It felt a bit lighter.. but nowhere near as bad as the cavalier. I'd venture in this configuration it's very close to zero downforce/ zero lift average across the body.

Overall, it's a very slick body design. Definitely ahead of it's time when the original 924 debuted in the 70's!

Fox944

i've reached speeds over 160MPH (indicated) with my 968 when it was bone stock. I've also reached speeds close to 170MPH (Indicated) with the car in its current state of tune. It was still accelerating when i let off throttle.

From my experiance, the rear end of the car felt light at such high speeds. The Turbo S spoiler adjusted for max downforce has cured the problem, but also created more drag so the car does not accelerate as quick at triple digit speeds and i lost a few MPH off top speed.

Lastly, there is a video on youtube of someone reaching over 160MPH (Indicated) in a stock 968.

The other thing you people all have to take into cosideration is the fact that speedos are optimistic and are never 100% accurate. Different size wheels & tires affect your speedo. The faster you go, the less accurate the speedo will become.

rgs944

I have seen that video, kind of fun to watch but I wish they would have did it on a back road with no other traffic. As far as the exaust I think that is right. I wish I would have had access to a dyno to know for sure, but I really believe my car is noticable faster with the test pipe and airbox mod. I have also gotten rid of some weight since I got the car as well.

odurandina

yes, i thought this would be implicit to the discussion.






pretty sure you're running a 25.0" tires (like my car came with when i got it) and you've got plenty of defect in your speedo.

p-cars are notorious, (actually it's just the owners running different sized tires)...

your real speed is likely to have been closer to 150 mph.

in addition to running larger tires, i had to turn my speedo back about 3 mph to get it right. i don't have the ugly glass cover on my car,

so i can do that. that's making the slightest possible nudge, so be careful not to go too far.

at 100 mph on my speedo, my tach is stuck dead on @ 4,000 rpm, exactly as it should be,

and at 150 mph on the speedo, the tach is @ 6,000.




on an unrelated note, this is probably my favorite 968 video.




http://www.youtube.com/watch?v=uCkHW...eature=related



.

Fox944

The diff. btwn my current tire size as well as my stock tire size is less then 3/10ths of an inch. My current wheels are larger, but my sidewalls are thinnner and i'm also running R-Compound tires, so the circum. of the tire is smaller then an ultra high perf. tire in the same size.

I did not have GPS in the car during those runs, but have had GPS in the car as high as an idicated 140MPH and my speedo isnt off by more then a couple MPH at that speed.

P cars are notorious for being optomistic from the factory....even with factory tires. The reality is, no Speedo is 100% accurate.

JDS968

I really wouldn't rely on anything but GPS to accurately measure vehicle speed. Even if you calculate the exact ratio of engine RPM to vehicle speed for your setup, and you're confident that your tach is accurate, and you use that to measure vehicle speed, you'll never know how your rolling radius is varying based on tire deflection, which won't even be entirely consistent at any given speed or even at the same speed at different times.

Todd951968

I took my 968 6-speed to 156 and within 100-200 RPM of the redline, on a slight down grade. It seemed really stable at that speed, btw.

A 968 will need different gearing and such to go much faster, assuming you stay out of the rev limit range.

I think the 944 Turbos are geared to go in the low 170's max. I've only taken my turbo on short bursts to the 145 range, where it was still pulling hard.

Vilhuer

Few years ago friend and I were on autobahn A1 north of Hamburg heading towards ferry to Denmark. We were in friends BMW 535d which is officially limited to 250kph. Stock looking 968 coupe sailed pass us at maybe 265kph on slight downhill while BMW was at limiter and GPS showed 254kph. I'm quessing 968 would have topped at 260kph (161-162mph) on level ground. Official Porsche numbers are 252kph (156mph) but they are slightly pessimistic as usual. 535d goes 270-275kph (168-171mph) when limiter is removed. Friends car is chipped now and has 330hp and 800Nm so there's no contest anymore unless 968 has turbo or SC.

Few year earlier there were three of us in another friends 928 GTS automatic in A1 also. This time heading from Nurburgring towards Luxemburg. Similar 535d gave good run for GTS from 120 to 250kph after which it hit to limiter and was left behind. GTS went up to true 275kph with few more kph left to spare. Lesson here is that don't mess with big diesels on Autobahns. They will easily win on economy and can match the speed unless there is serious hp under the hood in Porsche.

odurandina

if you do the math, you'll discover that the instruments call for about 25 1/2" tires for the speedo to read properly.

guess what, my instruments are reading properly... my speedo is reading exactly 100 mph when the tach is showing 4,000 rpm... how do i know my tach is close to correct ?

a couple of weeks ago i hit several of those speed posts on i-95 in georgia and the carolinas... when my speedo says i'm going about 70, my tach indicates higher by a few mph. that's exactly what the radar boxes on the highway also say. they say i'm going 75 when my speedo says about 71. but when i hit one of those going 90 mph on my speedo, i got 92 mph on another of those boxes.

the defect in my instruments is isolated to the lower speeds because i set my speedo back.

this is a defect built into the cars. ask about it on all the other forums and you'll hear the same.


the same week i had my car up at 158, i drove 100 miles of i-80 mile markers... my odometer showed 98.8 miles.

btw, my tack says about 6,350 rpm when i hit the limiter, pretty close, there too. this means that on my high speed run, i had the car somewhere between 157 and about 162 mph when i hit the limiter...


it was a very unpleasant feeling, having that happen right then.

Rich Sandor

LOL, well now that depends on how you're driving. I did a few runs from Stuttgart to Munich and I can tell you that if you drive with your foot down all-the-way for 15-20minutes, you do not get good fuel economy whether you are in a diesel or a gas car. At 280kph you can see the fuel gauge falling down!!!!

mattipuh

surely doesn't make difference whether your car goes 260km/h or 270km/h.. it's fast already. how fast it goes from 100 to 250 would be interesting. which car is more stable and drivable in those speeds is interesting.

Erkka, BMW big diesels are interesting cars, would be nice to get 330d or such some day - does chipped + with proper hardware close to 300bhp + 800Nm.

Vilhuer

Talking about bad fuel economy at autobahns. Very few cars come close to 928 S4 with Vortech SC and wrongly adjusted fuel maps. 4k rpm and 180-200kph traveling speed meant 5.6mpg, once again on A1 in Germany heading towards Nurburgring. In general diesel consumption do not get anywhere near those kind of numbers. Not even on racetrack.
http://www.youtube.com/watch?v=QN4-KA0VGzs
968 is very good on consumption up to a point. 160-180kph is ok speed and possibly fastest way top travel. Faster than that and too frequent fuel stops will actully start to slow down average speed.

Matti, are you coming along to next excursion to the ring? Even though trip is fully booked you got to come along. Driving at autobahn is almost as great as in ring itself.

odurandina

one reason why those old 5 cylinder audis did so well against the old bmw 6 series cars...

made a lot of torque but were easier on gas running one less cylinder.

Thom

FWIW the fuel consumption on my 944 S2, which has a similar engine to the 968, will vary drastically depending if it's driven below or above 4000rpm.
Below 4000rpm and regardless how I open the throttle it never does less than 28mpg, but when driven above at constant speeds on the Autobahn I can almost see the fuel gauge moving down.

wiseman

I thought I saw a guy on You Tube hit over 160 mph. Took a shot of the Speedo when he did it.