Speed conversion

All,

Bit of an odd question, but what makes speedo read in km not miles? Is it the signal generator or is it the speedo itself?

The reason I ask is that I would like to fit the parts as if it were a uk car, whether that would be a UK speedo or a UK signal generator.

At the moment I've got some dodgy box behind the dash of unknown origin, which seems to be a speed cut defencer as well, but the thing is it justs clamps the max speed signal to 75 ish mph. I'm thinking about removing this as it's screwing up the AEM (which doesn't have a speed cut anyway), powermeter and sat nav, all of which need a speed reading to function correctly. TBH I would have thought the company that fitted the AEM/powermeter would have known about this having apparently fitted hundreds of powermeter's and a couple of AEM's. Oh well - Anyway,

The speedo I've got looks like it's a half decent one, ie it's not just a sticker over the kph, or a card to sit over the jap one, and goes up to 180 mph, with a corresponding KPH scale under it. so my only guess is it's a bona fida UK one? How can I tell?

This has done my head in a bit as the powermeter is giving me 1/4 times of 14.9 secs, 'cause the max speed it sees (which it uses to calculate distance travelled) is 75 mph. Perhaps my car is just slow assed.

Any thought's much appreciated.

Regards

Its the speedo itself. The UK and J spec speed sensors output the same pulses, but the speedo reads them differently depending on whether its a KPH or MPH version.

Your speedo does sound like the UK model. So does the needle stop moving at 75 MPH? Even if you do have a clamp-type SCD wired in wrongly. 75 is very low for a speed cut.

No, the speedo reads fine, so I guess what I have is solely a speed cut defencer, which must be wired twixed speedo and ecu, so the speedo reads fine but the input to the ecu is limited to 75. Hence no speed cut at 112.

Seeing as any speed cut defencer is not totally redundant I think I may have a good go at it with a pair of snips...

Cheers Darren.