Vehicle speed sensors and boost control

[alain]

Hi,

I currently have a speed sensor connected between my automatic transmission and the mechanical cable in my '69 Dodge Dart. The sensor works fine above about 40km/h. Under this speed, the V88 says the vehicle speed is 0 km/h. I haven't really made an issue about it because I didn't really do anything with this speed reading. It was more for just an indication of where I was driving and how fast I was going while data logging. It is a 4 pulse per revolution sensor.

I am now looking into setting up electronic boost control with two tables. One uniform boost level for street driving and I want to setup another table for drag racing. In this drag racing table, I want to control boost based on vehicle speed, allowing me to dial in soft at the start of the track, when the track is bad and then ramp the boost in as the car goes down the track. Considering I will then also need lower speed readings than I am currently getting, I am looking at a new sensor. I have my eyes set on a 40 pulse per revolution sensor from Painless Wiring (part# 60117). Will my V88 accept that many pulses per revolution? Travelling at around 250 km/h, it will be receiving approximately 4250 pulses per second.

[Simon]

Hi Alain

Need to keep the frequency under 500Hz for the digital inputs.

So around 10 pulses would be good for your application.

Go for a Hall sensor to get good low speed operation.

 

 

[alain]

Ok, thanks Simon. The available sensors, where you can still retain your old cable, have an AC signal and there's not much choice. I might need to play around with the Active Edge setting. I currently have the pullup resistor off and the edge set to falling.

[Simon]

For the Di to see the signal, the positive part will need to go above 1.5V before it is seen by the ECU this is why it can take a bit of speed before the signal is detected.