R32 GTR Digital Dash Swap (Atessa Question)

[Dyzzii]

Hi all

Am about to do a digital dash swap in my 32 GTR, and am currently investigating the speedo signal issue. I'll be converting the car to run an electronic speed sensor using an R33 GTR unit, and wiring that into the ECU to give it a speed signal.

My question is, will I also have to do something with the atessa system, since the OEM speedometer will no longer be fitted? Am struggling to get clarity anywhere as to whether the R32 Atessa system uses the OEM speedometer output for any of the stuff it does.

Any insight will be appreciated!

[GTSBoy]

R32s have cable speedo drive to the speedo head. The speedo head creates the one and only speed signal (VSS) in the car. That speed signal is a square wave (PWM) signal that varies in duty (on time) with speed. You can see the waveforms in the workshop manual.

R33s have an electronic speedo sender. That feeds an AC sawtooth wave signal to the speedo head. The speedo head then creates essentially the same squarewave signal that the R32 speedo head does. The details might be different, but it is otherwise the same type of signal. This again, is the only speed signal in the car.

So, presuming you do use an R33 electronic sender, you will need to convert that from AC sawtooth to a squarewave with the same characteristics as the original one from the original speedo head. If you don't, the ATESSA will either not see it or it will misinterpret it, with whatever shitty results come from those options.

You do not need to do anything with the ATESSA system. You just need to feed it what it wants. And that's just a matter of creating the right signal. You might be able to do that in the dash, or you might be able to do it in the ECU. Or, if desperate, you could do it in an Arduino, which is relatively trivial these days.