A question came up while looking at some speedometer faces. A strange question, but here goes.

There were 180mph and 200 mph speedometers for 993s, as far as I can tell. Looking at the dials, it appears that 180 and 200 marks are in the same place on the faces. In other words, it seems that the faces would not be interchangeable.

How, than, are these speedometers calibrated? If one takes a whole 200mph speedometer and puts it into a 180mph speedometer car, will the speedo read correctly? Is the difference in internal gears or in the signal coming to the speedo? How would odometer operate? Can anyone shed any light on this?

 

The gears have to be different. Clearly, 200 MPH speedos are faster

 

180mph speedo goes to 10

200mph speedo goes to 11

You have to drive FLAT OUT to use a 200mph speedo ... Or be named Frank... And you have to turn it so 200 points straight up.

 

Nile13. Its a really good question. I also posted Fullboost for the dial cards but the kmph ones which also read higher. Unfortunately i suspect the speedo will nee to go to a shop to be recalibrated and the internals changed...thats the only way I can see it would work....

 

Lewis, while I fully agree with you that those 200mph speedometers go to 11 (wanted to work it into my first post too)... and I don;t need one, but that's what a Rennlister had for sale and it got me thinking.

Did Porsche actually made two different speedometers with different internal gears? Would seem odd from production standpoint. Or did they just bin out the fast ones?

 

I believe turbos got the 200mph speedo while the NA cars got the 180mph speedo. Not sure if they have different internal gears, but I'd bet they are calibrated differently. It's also possible that the central informer computer which controls the gauges could be different to accomodate the 200mph speedo. You may want to check the PET to see if the turbo and NA have different central informers.

Cheers,
Joe

 

I'm sure they have different central informers to accommodate OBC, boost light and other things.

It's a shame as I was looking forward to having nice shiny white faces on my gauges.

 

OK, tell me that these two 180mph speedometers do not look different from each other. Compare where 100mph mark is. Anybody with any insight?

http://cgi.ebay.com/Porsche-911-964-...#ht_500wt_1156

http://cgi.ebay.com/ebaymotors/Porsc...s#ht_500wt_956

 

I'm pretty sure the differences are internal because I believe the cable and gear at the tranny are the same for NA and Turbo - so assuming similar OD wheel dimensions the cable turns at the same rate on both cars. As such the instrument gearing has to be different to cover the different calibration on the face.

 

That sounds reasonable.

But I still can not understand the differences in the two 180mph speedometers referenced above.

 

Cable?

Speedos have been electric since 1978............

 

Maybe its just the 2 different angles of pictures giving the impression they are different?

 

I thought it might be a different angle. But looking at it, enlarging it and looking at it some more... seems that it's actually a different face.

 

I guess I'm too old school. Same principle though.