Power FC speed reading adjustment? Is it possible?

[NismoR31Jet]

Hi all, Ive got an R31 with an RB26 in it with a power FC. Im also running an RB25det gearbox so my speedo is a mile out! at 100 KMH it showing 80 kmh and the stock speedo is never fantastic. I was looking at hooking up the speed signal from the gearbox to the Power FC, and using the speed reading on the hand controller. But, I was wondering can the speed reading be adjusted on the hand controller to be accurate?

I know I can just use a GPS speedo, which I am using my GPS for speed on the car, but id like a better option.

 

Thanks.

[Rusty Nuts]

use a Jaycar speedo correction module.

https://www.jaycar.com.au/corrector-speedo-module/p/AA0376

[NismoR31Jet]

Will it work with the PFC? I bought one of those to try and adjust my original speedo and it didn't work. 

[Rusty Nuts]

I have only used it to adjust a R33 speedo signal mate

[GTSBoy]

1 hour ago, NismoR31Jet said:

Will it work with the PFC? I bought one of those to try and adjust my original speedo and it didn't work. 

I will type this out for the 300000000000668684873276347th time.

The signal from the sensor to the speedo head is a sawtooth (AC) voltage +/-1 volt. The speedo head converts that to a square wave PWM 0-5V signal for the ECU (and every other CU in the car that looks at speed). You have to set the Jaycar jobby up for the type of signal you are correcting, and you can't ever try to direct connect the sensor to the ECU, because they just don't speak the same language.

The Jaycar one, I think, works well on AC signals and not on PWM signals. If you have a need to convert a PWM, the smart approach these days would be to program an arduino to take in, modify and spit back out. Would only take a few dozen lines of code and possibly a variable resistor to allow you to adjust the effect without reprogramming.