slim_boy_fat

That how i did it, my videos were posted up here a few weeks ago, not sure if they are still available.

Started the run at about 50 and accelerated throught 60 with my mate holding the vidoeo camera. All in 3rd gear.

So that was a 2 up 60-100 in 5.6sec..

Not too shabby me thinks. Comsidering i have minimal mods...

Jake951

Part of the problem in getting truly accurate 60-100 mph times in our cars is that the 951 speedometers are notoriously inaccurate (I know mine is) and typically overestimate speeds by 5% or more. This means at an indicated 100 mph you are probably really doing closer to 95 mph.

Some of the error results from real tire rollout (revs per mile) being less than the numbers you calculate from tire specs. The rest, I think, is a built-in speedometer error from the factory. Third gear redline occurs at a true 97-98 mph, as I recall, if you assume the ideal (calculated) stock tire rollout. To get to a true 100 mph in third you have to exceed redline, or otherwise shift to fourth and lose a few tenths in the shift. In my car the rev limiter kicks in at about 6500 rpm so I can't make 100 mph in third.

I've found the tach is more accurate in percentage terms than the speedometer, so a better measure of acceleration using the in-dash gauges might be based on time between rpms as someone else already suggested.

slim_boy_fat

3rd gear is good for 102mph, according to my calcs... maybe streatch to 104 if you feel lucky....

Dont forget 100 might be 95 but 60 will be 56, so theres still aprox 40mph incrament. But i get the drift, the only true way is to strap timing gear onto the car and go for it, but hey its more fun with a mate, a video camera and a BMW M3 trying to keep up

Danno

I've seen the tach be off by over 200rpms as well. Best way to measure would be with a radar gun... How about GPS?

rage2

My Blitz power meter is calibrated to my GPS, and is accurate up to 250km/h (haven't tested any higher). On my speedo, up to about 200km/h it's perfectly accurate when I'm on my 18" summer wheels. It's a bit off on my 17" wheels which are close to stock in rolling diameter.

JonM..

Even if the speedo or tach is off it would be off on both ends. And when you make mods unless you change tires your pretty much still comparing the same speed differential. Besides were not handing out trophies so it's just for fun anyway.

rage2

You mean I don't get a cookie???

JonM..

Cookies yes....trophies no

Jake951

Here's the 951 transmission diagram from my owner's manual:



You can see that if you take 6400 rpm as redline, then in third gear you're a little bit short of 100 mph at redline. I calculate exactly the same result as in the chart from the gear ratio, axle ratio, and the theoretical tire rollout for the stock tire size.

JonM..

Right but I don't get your point though since the max RPM Porsche recommends is 6500rpm (at least on the 86 turbo and N/A cars) and at that speed we look to be a tick over 100. (See your owners manual)

Just do what you need to in order to calculate you speed, run the test and have fun.

Jon

slim_boy_fat

Some folk on hear need to take a chill pill!!!

I mean its not as if we are sending our results into the guiness book of world records!!!

As we are all driving the same cars, then surely we are all comparing like for like, regardless wether its 60-100 or 56-95 or whatever.

Just nail it and see what happens!!

special tool

Slim - forget that sht, man. If Pluto is not throwing a shadow on the Kuiper belt, you are not even close.

rucool

So what,we all know we have fast cars,just relax and enjoy the
pleasure of driving a 15 year old Porsche that will still kick s##t of
most cars on the road today.
The best part of all is it is only 2.5L ...
Safe driving,
Russell.

B951S

Guys
In comparion, what are some other fast stock cars quoted as pulling 60-100 in 3rd?? Thinking something like a Z06, viper, 996, 996t, etc

slim_boy_fat

996 is around 5.8sec

996t is 4.5sec

Not sure about the others...