washington951

abbott-tach.com select 'products' then 'E.R.A.' this little black box allows you to dial in any adjustment you need to counteract different wheel/tire sizes, etc.....very slick. my speedo is dead on using this despite adding 17's....

capndar

>>abbott-tach.com select 'products' then 'E.R.A.' this little black box allows you to dial in any adjustment you need...<<

this kind of looks like a commercial to me....

BeerBurner

My 944 was accurate within the error of your angle of sight to the speedometer, checked with GPS.

On a side note, the Jetta reads consistantly 5 mph fast (those radar signs that tell you how fast you are going). The 911 is rediculously optimistic... Based on the rpms and transmission diagrams, when I'm going 65 the speedo reads about 80.

BB.

Mike1982

One way to tell exactly how fast you are going, find a straight highway. Go at 60 mph on your guage and time just one mile. From there you can tell about how much you are off. I have a watch that I can program distance then just time it. It will tell me exactly how fast I am going. I am going to play with it over Valentines weekend when I go on a 120 mile trip. I might like to see my average speed over all. See ya.

Rich Sandor

Handheld GPS.

100% accurate.

capndar

Final Follow Up..straight clear interstate....stock tire size, 3500 rpm, 100 mph indicated, 92 mph on gps. compared with my 2900 rpm= 80 indicated, 76 -77 actual, given that the speedo needle and markings are not all that precise (nor is my line of sight) sounds like a consistent 7% (+/-) error rate?

Done by a semi professional driver on an open interstate highway (no traffic) - Your results may vary

Rich Sandor

The standard agreed Porsche speedometer variation has always been 8-12%.

Ever since I started getting into Porsches, one of the first things I learned was that Porsche speedo's have always read a little high on all models.

944Fest (aka Dan P)

I agree with the GPS fun, I travel with one all the time. WHile you are at it, check out www.geocaching.com Lots of stashes!

Scootin159

Install the Microsoft .Net Framework 1.1

http://www.microsoft.com/downloads/d...displaylang=en

*Michael.*

My early '85 also shows 5mph faster then I am actually going. I think this is common on the early cars.

jeeper31

Why does everyone's seem to show 5 mph faster. Mine shows 5 mph slower?

Butters944

Resurrecting this thread after 7 years... Mine shows 5 over what I'm going, it's an 83. does seem like it's all on the early cars... Lots of posts on this thread, but no solutions!!??

odurandina

my speedo is dead accurate at 161 mph. it reads 96 when i'm going 100 mph. reads 70 at 75, etc.... when i got my car, i went to a larger, 275-35-18, 25.6" tires (you all run between 24.8" and 25.2" tires). i removed the lexan cover and wound my speedo back about 4 mph. since doing this, i've run 150 miles of mile markers on i-80 across Iowa and my odometer read exactly 149.9 miles traveled. now i'm content to pick up used 285-35-18 contisportcontact 3, w/ 2 mm of tread wear which measure exactly 25.7" (they're less-expensive Pilot Sport 2 clones). love em! you all need to go to bigger tires and wind your speedo's back a bit. then your GPS's will read perfect. maybe Porsche built this defect into our cars so we wouldn't be going as fast as we think, and kill ourselves less. what do you all think?


.

Voith

911?

kombatrok

I run about 75 at 2900 or 3k.