I was looking at converting my Jap spec speedo from 180 KPH to 180 MPH until I found out how it is done. The convertor works by using a two thirds ratio so the speedo will register 2/3 of what the speed sensor sends it. The conversion from miles to kilometers is

 

1 Mile = 1.609344 KM

1 KM = 0.6213712 Mile

 

So the conversion is off about 7%.

 

Here is a table of how fast you are actually going at various speedo readings.

 

30 MPH Speedo = 45 KPH = 27.96 MPH Actual

50 MPH Speedo = 75 KPH = 46.60 MPH Actual

70 MPH Speedo = 105 KPH = 65.24 MPH Actual

100 MPH Speedo = 150 KPH = 93.21 MPH Actual

150 MPH Speedo = 225 KPH = 139.80 MPH Actual

180 MPH Speedo = 270 KPH = 167.77 MPH Actual

 

Do Z's drive around at 93 MPH to make sure they do not get banned for going over 100?

 

I recently read that this can also cause problems with the speed sensitive steering. Which makes sense because the car will think it is only going 2/3 of the speed it actually is.

 

Has anyone used other methods of speedo conversion? I was considering buying a US speedo and speed sensor to install in my car.

What experiences have you had. Is the speed sensitive steering controlled from the speedo or something else that reads the speed sensor?

 

Hi Bruce,

 

Downunder we have a dude that converts our speedos for us, at the speedo itself (ie we have to take it out of the car he fiddles with it, and we put it back in the car), for a not so disturbing sum of money. I am looking at (well once I find my old speedo anyway for a stock face plate) getting a whole bunch of 300kph Sonic speedos made up.

 

He gets the speedo to a far greater deal of accuracy than the stock speedo is (you'd be surprised at how inaccurate it is). And doesn't alter any of the signals going to the speed sensing for HICAS.

 

If you can organise a spare speedo and send it down this way with a money order I can ship it back up to you converted to MPH. Say 40quid excl shipping ? A 300kph faceplate will add to the cost significantly (maybe up near the 150quid mark.. don't know yet), but I'm assuming you only want it in MPH. Turnaround only a week or two.

 

Feel free to email me about it.

 

Rowan Hick

Sonic-Motorsport.com

Auckland, New Zealand

 

If the speedo conversion is done AT the speedo (rather than at the gearbox) then you shouldn't suffer any problems with ancillary equipment (e.g. HICAS & power steering). I used a converter from a place right by Brands Hatch. Can't remember the name but they were in Exchange & Mart. Their address will be West Kingsdown.

 

The actual conversion rate is down to the convertor. I had problems with mine due to a previous 'attempt' at conversion and went along to the guy. After fitting we did a calibration run (of sorts) running behind another car - it wasn't out at all.

 

Hope this helps.

 

Dave

 

P.S. The conversion is OK to fit apart from the tricky bit of changing the speedo face and, particularly, removing and realigning the needle - needs a LOT of care to avoid damaging. The problem with mine was that someone in the past had done it but superglues the needle to the pin. This I didn't know and so I pulled the pin out rather than pulling the needle off the pin. As a result, I need a new speedo head ! Mine jams at 100 mph. If anyone knows of one available, PLEASE email me !

 

 

 

 

 

Hi Bruce,

 

I have had my Jap spec ZX changed into mph from kph via a converter.

 

The real speed of the vehicle should never change, whether you are driving at 50mph (75kph) or 100mph (150kph). I think that the coverter is slightly more accurate than just a two thirds ratio.

 

I have run at 80mph showing on my speedometer and confirmed this speed with another ZX running at the same time.

 

I have also checked my RPM reading at different speeds and reconciled these with Jez who has a UK spec ZX and the conversion appears to be very accurate ;-)

 

The ZX has many dependant components that require an accurate speed reading including the speed sensitive power steering and hicas.

 

I'm not sure what your conversion does, but our conversion involves taking the speedo unit (including circuit board, motor, dial, face plate etc) as one thing.. (but removing it from the gauge cluster) giving it to our electronics wizz and getting the speedo back. We don't have to take off the face plate, nor add in any black boxes anywhere.. so we don't interrupt the speed sensor signal going to the HICAS/Steering etc.

 

For those who use kph as well as mph we can have a switch to switch between mph and kph, pretty nifty huh ?

 

As a general note, if you intend to take off the face plate/needle, make sure you firmly grip the shaft just underneath the needle with some needle nose pliers, and then pull the needle off, otherwise you'll damage the interals (from experience). Noting that also all the faceplate conversions such as Mines, Nismo, Impul, Sonics future one etc involve replacing the whole speedo not just the faceplate.

 

The stock speedos have varying accuracies along the speed range, we've found variances of +/- 8% on my old speedo from memory (doing it the electronic way, not travelling beside another vehicle), but it wasn't consistently out .. and we did account for parallax error.. so I guess thats a word to the wise about how (in)accurate these things are - especially with your GATSO's!

 

Rowan

Sonic-Motorsport.com

Auckland, New Zealand

 

Think the place Dave (Hairsy) is thinking about is "Far East Services". The General Manager is called Keith Chapman. I had my speed convertion done there too. Paid 150.-