This applies to all of you who have a Japanese import.

 

I have been investigating kph to mph convertors for a while now. Mainly because of the problems I have experienced. I think I have found an underlying problem.

 

As many of you are aware most of these convertors work by altering the number of 'pulses' going to the speedo from the speed sensor. In reality, when the convertor is fitted only 2 out of the 3 pulses are recieved by the speedo or there abouts hence the speedo only registering 2/3 a needle movement. A MPH sticker is then placed over the KPH sticker and there you go.

 

BUT..... These pulses then go from the speedo to the HICAS, Auto box etc. This means that they are only receiving 2/3 of a signal while all other sensors (like rev sensor, TPS blah blah) are correct. I have installed and uninstalled more than 1 of these convertors (diferent makes) and have found that the auto box in particular behaves slightly different in that the gear change is slightly later and a few other sutble changes. This is because the speed sensor side of it is 1/3 out to the rest of the sensors. This concerns me. I cannot find anyone who supplies a convertor that converts the pulses back (3/3 rather than 2/3)before its sent the the other parts, Gear box, HICAS etc. I don't think this has been thought through properly and tested to find the true effects.

 

The gearbox relies on many other sensors hence why it still performs relatively fine but im sure there is a difference.

 

This has probably not been noticed because many of you had the conversion done by the dealer before you bought the car and so don't know any different.

 

Comments please?

 

Andy

 

Andy,

 

I spoke to Luke at the Z center about this and the pulses are only changed to the speedo.

 

The steering, hicas and gearbox are controlled via the ecu which receive the correct information from the speed sensor.

 

Steve

 

I had heard that these convertors effectively move the speed limiter further up the range. i.e what used to limit to 111mph (say 160kmh - can't be bothered to work it out) then becomes 160mph and theoretically isn't a problem.

 

Is this true ?

 

Incidentally, mine seems to have had a 'proper' conversion - new dial, speedo reads correctly, odometer was converted to correct number of miles etc.

 

Steve,

 

This ain't true m8. I have just spoken to Luke and he has confimed that the the speed sensor does not go to the auto box, ecu etc on a separate circuit. Its on the same circuit as the speedo. The workshop manual wiring diagram shows this!

 

Speed sensor > speedo then ..... > ECU, auto box, cruise, HICAS, power steering (all on their own circuit).

 

This is why some people have problems with the power steering, auto box etc after installing a faulty converter box. The first convertor I ever had caused problems with the auto box, engine running, speedo, power steering.

 

I always thought that my power steering was too light especially on motorway driving. 70 mph and it thinks your doing about 45.

 

My gearbox feels more precise and the changes feel as like they engage sooner after removing the converter. This is not major. The difference is minimal. This obviously does'nt apply to those who have manual transmissions.

 

This all probably means that the HICAS is not operating at the correct speed!

 

Like Luke said, coverting to a UK speedo is probably the only 100% fix.

 

Andy

 

 

 

Andy P,

 

The limiter is changed by defualt m8. There is no wizzy electronics here.

 

For example.

 

Lets say in normal operation at 160kph the speedo receives 160 pulses a minute. The converter just reduces the number of pulses to 2/3 so the speedo will only receive approximately 110 pulses at the same speed! So....you can drive upto 1/3 faster than normal before the limiter cuts in.

 

It cuts in at the same number of pulses (160) but you are actually doing 160mph rather than kph.

 

Andy

 

Andy

 

My box is fine ;-)

 

Maybe I confused what Luke said.... it was a while back.

 

i'll wait for now and next year johnny will be hearing the k'ching of coin as yet another year of fiscal expenditure dissapears on the z when i but the nice clocks he has in his

 

Is it not possible to fit a UK car speedo head? I know that some other import marques can get away with that.

 

Yup. I can only see two ways of doing it properly. Convert the signal back again from the speedo but the the problem there is that it goes to so many areas, ecu, tranny, PS, HICAS, cruise etc. It would take some box with a shit load of wiring.

 

Or... replace with a UK speedo/cluster.

 

Steve,

 

'my box is fine' .... yeh, very funny. How much did you pay for your traction control?

 

does the speedo do anything with the signal though ? or does it pass it back out untouched, just making use of it ?

 

cant you just splice the speedo out and run everything else from the correct wire and signal, then run the speedo fro it's own little spur off ?

 

just a thought...

 

I had all these problems on my Jap Auto.

They took the converter out, replaced the speedo and all is well...

Apart from the fact that they fitted a speedo that only reads to 110MPH. Don't know where they got that from because surely UK ones must read to at least 160MPH and my old Jap one went to 190KPH.

 

Craig,

 

Don't know the anwser to that one. If all the signals are not altered in any way then it should be simple to bypass. I would have thought that the manufacturers of these coversions would have taken this into consideration. I have a horrible feeling that the signals are altered in some way, the auto, ecu, PS etc all having different alterations. Just speculating though. (I am sure there are multiple outputs from the speedo rather than one output. Each going to a their own wiring loom, ecu, tranny, ps, HICAS blah blah).

 

Need an electronics guru to compare the input to the outputs?

 

Chris. It sounds like they just changed the face of the speedo. 180kph still registers as 180kph but the new face they put on shows 110mph ish. The problem with this is that the the car stills clocks up in kph and the dial maxes out at 110 ish. Cheapest of solutions this one.

 

Andy

 

This is the reason I bought a UK speedo rather than a convertor for my auto. The importer I used said that they didn't like to put convertors on autos.

 

If you do buy a UK speedo, try to make sure that it's exactly the same type. The one I bought had slightly different connectors ( I think it was from a 1992 manual rather than a 1991 auto), so I had to swap the dials over rather than just plug in the new unit. It's still a fairly easy job though.

 

Andy, Craig.

 

The signal is changed at the ecu as Andy mentioned above.

 

I just checked my AVC-r and Techtom and the readout in kmh setting is actually mph

 

Still, my Z seems to change gear at just the right moment every time which is round about 7450rpm ;-)

 

 

Bloody manual drivers LOL. 7450 rpm you say. Does it still crunch though from 3rd to 4th? hehe

 

Just go careful next time you take a 130 mph bend because the HICAS thinks your doing 130 kph and won't adjust correctly. This could be a good thing though!

 

 

 

Don't have the technical knowledge to give hard facts on this one but just personal experience ...

 

When I fitted my convertor, I was concerned about these very things. I spoke to a number of suppliers and stuck with the first one who actually knew what I was talking about - a place called Far Eastern Services who are just by Brands Hatch. On the phone and in their documentation they warned that there are a lot of companies selling conversions which mess up the auto box and other sensors. Their convertor fits to the dash itself in (from memory) four different places. It is not into the feed INTO the dash but picks up points on the circuit board of the instrument panel itself.

 

I noticed no differences at all to feel of steering / auto box / etc. The conversion DID up the cruise control limit (to what I don't know but higher than is sensible!).

 

As I said at the beginning, I'm not technical enough to draw conclusions but they certainly said the right things. If anyone wants to get in touch, they were advertising in Exchange & Mart near the back (at the time).

 

Dave