I thought it was about time I put my display driving code on the FPGA to good use 
So I added the X, Y and Z values to the power value already transmitted from the Arduino, and got the display up and working.
A minor annoyance was the Arduino IDE crashed at one point in a way that was completely unkillable (even kill -9), so I had to reboot my Mac. Also, my Merc seems to be ill so I’ve moved the accelerometer over to the Porsche with the new engine – which seems to be running very smoothly now.
The end result is here:
The dot moves up/down for acceleration/deceleration and side to side as the car goes round corners. Or it’s meant to – as you can see, it is certainly skipping about, but you need a reasonable amount of imagination to believe it is related in any way to the cars movement… This could be harder than I first thought!
I think the next step will be to try and improve the data rate from the car – currently I can only hope to get back 10 readings/sec.
As ever, I’ve updated the Arduino and FPGA repos with the latest code.