I'm considering having a km/h to MPH conversion carried out on my car but I'm not convinced that it's technically a good move. I have a couple of doubts about it.

1. I've been advised by one supplier of a speed convertor /de-limiter that they use a 2/3 factor of the speed sensor signal to change the speedo read-out, surely this is a pretty poor approximaion of the correct 5/8 factor.

2. Also, the 2/3 signal is the fed to the ECU for delimiting purposes ( the speed limit data is held in the ECU?),surely this will result in incorrect operation of speed controlled items (Hicas, auto transmission power steering) as the electronics will think the car is travelling 2/3 slower than it really is.

Because of these problems I'm considering only fitting a 120MPH face to the speedo meantime.

Anyone have opinons, experience or

alternatives. Thanks in advance.

 

 

Yes to all of the above.

I had one and had to have it removed because of problems.

If you can live with the inaccuracy it should be OK but if they are not wired in at the right point on the system you get HICAS warning lights on and all sorts of wierd problems with the power steering and the engine cutting out on hard acceleration.

I ended up with a 120mph speedo face which is an embarassment on a near 200mph car.

I regularly wind the needle off the scale round to the 0mph end stop!

Does nobody make a decent convertor for these cars?

Someone posted here the other week about the speed difference shown between a UK spec and an import with a convertor - quite a difference.

The mph conversion was done on my car by the importer before I bought it and so far (3yrs +) it has been 100% reliable its pretty accurate, when compared with my GPS. Also it means you have a 180mph speedo.

 

I have noticed no odd effects with any of the other functions, but that may depend on how and where the conversion is done. If it is only the signal to the display (eg speedo) that is altered then it doesn't affect the ECU and presumably other functions. Not really looked into this though, but others will have done.

Peter,I have seen many customers cars with speed reading problems due to low quality convertors,my advise is to fit a `UK speedo assembly,its a direct fit and has no problems with the aformentioned errors,of course if you need to remove the 112mph limit it`s best to chip the ecu I have doen many customers this way and never a problem.

 

Jeff TT

Whoops! Should've read speedo. I've had a think about this, suppose I should've done it before posting.

1. The 2/3 versus 5/8 factor problem with the speedo won't really matter as long as the speedo face is calibrated properly.I initailly thought that the inaccurate conversion factor would result in an non- linear reading but it won't.

2. As Jeff says the proper (only!) way to de-limit is by chipping the ECU. Jeff, am I

correct in what I said before that if a 2/3 signal is sent to th ECU the Hicas, power steering and auto box will operate improperly.

I've have some experience of eprom programming and access to programming equipment could this help.

 

 

 

Peter - when I got mine, I asked a number of people about this and everyone gave me different answers - including yours - so I kept to the mph sticker face and left it restricted. Wimp!

 

I also heard that the speedo is connected to cruise control (if fitted), boost sensor and alternator harness (someone at Nissan told me so don't take it as 100%!). Jeff, is that correct and would it have any bearing on using a UK speedo?