Hi there i have a 1991 TT jap import. As far as i no it is stock except for a visual mod of the rear light cluster that I have got blacked out.

 

Anyway there are obviously the converters out there to solve my problem of topping out at 112MPH. Im off to brunting thorpe run way soon you see. But i woundered if there is a cheaper way. Like pulling a fuse or knocking of perhaps a pin on the ECU conectors. Anyone have any ideas as my Z has already blead me dry for the mo.

 

Thanks!!!!!

I think there's only 3 ways to do this. Either buy a converter that changes your limit from 180kph (112mph) to 180mph or change the chip in the ECU or change to UK spec clocks.

Ok cheers. It was just when i was digging around on a gto sight when deciding what car to buy there was a bit about knocking of a pin on the ecu cable that got rd of the delimiter. But it's quiet possible that the is not the same with Z's

I've had a good look at the circuit diagram and there's only one pulse train feed from the speedo to the ECU and that's on Pin 53 (ECU). I'm sure that disconnecting this will de-limit your Z. Hicas/Variosteer shouldn't be affected by this as they are independant to the ECU. Let me know how you get on!

If you have fitted a delimiter unit and a speedo mph face conversion (180mph), but later you fit a JWT ECU chip, do you still need the delimiter unit? And if you remove the delimiter will the car have any limits and will the speedo revert back to kms?

Originally posted by jvnewcomb1961:

If you have fitted a delimiter unit and a speedo mph face conversion (180mph), but later you fit a JWT ECU chip, do you still need the delimiter unit? And if you remove the delimiter will the car have any limits and will the speedo revert back to kms?

 

Yes, to the first question (sort of) assuming that the delimiter is a kmh-mph converter. The speed limiter is actually in the ECU and you are just changing the number of pulses it receives.

 

Yes to the second question. There will be the same limits as applied in the JWT ECU (not sure what they are, but prob a high number) and as soon as you take the delimiter off (read converter) then the speedo will go back to indicating km/h.

 

The best option is to use a UK speedo/odo, this means speed reads in mph, odo is in mph, boost is in PSI (as opposed to 100mmHg), plus the speed sensitive power steering and HICAS systems receive the signal they expect.

 

Originally posted by Slippy Toad:

I've had a good look at the circuit diagram and there's only one pulse train feed from the speedo to the ECU and that's on Pin 53 (ECU). I'm sure that disconnecting this will de-limit your Z. Hicas/Variosteer shouldn't be affected by this as they are independant to the ECU. Let me know how you get on!

 

That is an interesting point and if it's correct then I can't help thinking that it would have been used before. How do the HICAS etc know what speed the car is doing, surely it must get it from the ECU somehow ? Also, I'm sure the ECU must have some reason for wanting to know the vehicle speed.

 

 

AFAIK the signal the ecu recieves is from the dash clocks. This is where the signal goes FIRST. I wonder if the ecu only wants to know the speed for its limiter though. But like andy says, surely this would have been done before. Maybe the auto box has its speed signal passed from the ecu??? Slippy Toad (???) do you have a wiring diagram for the inside of the ecu? Wonder if there are some pins that pass the signal back out again...

 

CheerZ,

 

Andy

I've been looking into the delimiting and KPH to MPH issue for Japanese imports for a bit now.

I'm not interested in modding my car and I'm a bit suspicious of adding third party 'delimiters and convertors'.What I think we should be doing to delimit and convert, is to change whatever the original manufacturer changes to achieve this.

What I have found out so far is that to convert a J-spec speedo to UK spec ie mph you need to change resistor R10 (from 33k to 20k) on the speedo PCB, retaining the original speedo face. This will not affect the the speed sensor signal to the ECU,Hicas,etc. Using a convertor to achieve this, will as far as I am aware trick the car (ECU,Hicas, steering) into thinking it's going slower than it actually is resulting in well, who knows ! Using a convertor will NOT remove the speedlimiter, as I said previously it will only trick the car into believing it's going slower than it actually is.

To delimit properly you should change the data in the ECU chip.

If the signal to the ECU is only used for speed limiting purposes it would be OK to remove it but if it's used for other purposes you would be taking a big risk removing it and to go back to my earlier statement you would be modifying away from the manufacturers spec instead of changing to the manufacturers spec.

Originally posted by andyduff:

AFAIK the signal the ecu recieves is from the dash clocks. This is where the signal goes FIRST. I wonder if the ecu only wants to know the speed for its limiter though. But like andy says, surely this would have been done before. Maybe the auto box has its speed signal passed from the ecu??? Slippy Toad (???) do you have a wiring diagram for the inside of the ecu? Wonder if there are some pins that pass the signal back out again...

 

CheerZ,

 

Andy

 

Unfortunately I don't have a cct diagram for the ECU. I've had another look at the wiring diagram and I now think that there's a secondary feed to the ECU on pin 35 from the speedo (Pin 14). I think the ECU probably does control HICAS, Auto and Variosteer now as the other pins from the speed sensor to the speedo are just doubled up - probably for reliability (NASA type design!). I'll have to drag out the oscilloscope and get the car's **** in the air !!!