Where are the speed sensors located?

[dirtyd88]

Anyone know if the speedo in these cars are ran off a speed sensor or internal calculations (based on engine RPM, gear ratios in trans and rear end, and tire diameter)?

Since I am running a staggered tire setup (255/40 front 275/40 rear) I need to know if the tire value I have in my tune is actually the correct one or if I need to average the two revs/mile values out.

Thanks

 

[NickSezz]

Have a passenger sit next to you withe a smartphone and GPS app. Hold her steady and see if you speedo matches the GPS readout. Should be within 1-2mph.

 

[dirtyd88]

Have a passenger sit next to you withe a smartphone and GPS app. Hold her steady and see if you speedo matches the GPS readout. Should be within 1-2mph.

I've done that with one of my apps, but I'd still like to know for sure.

It seems that my RPMs are running higher than I calculate they should be given my approximate tire OD/circumference. I would really have to measure to know for sure what the circumference of the tires really is, so I may go that route.

 

[bmyles]

When I switched to 275 40s my speedo was out like 2 mph slower

 

[bam2012@TBR]

275/40 vs 255/40 should only be off 2-3 at 70.

 

[nosympathy]

If the 275 are on 19" rims, your revs per mile should be 729 with a 275/40/19 tire.

 

[Quesplosive]

Im looking for the same thing, but I need the actual pin coming from the ecu for my boost controller. Anyone have a pinout?