Interface with car's RPM and Speed sensors

Other Hardware Sensors
1

Hello,

I am rather new to the whole hardware side of making things (programmer by trade).

I am looking to interface with a bunch of sensors on my car to perform some data logging, etc...
I feel I need a bit of help interfacing with pwm sensors here.

My car has a redline of 7200RPM and I would want to have speed be able to goto at least 120MPH.

Here is some information on the sensors I want to capture.

Vehicle Speed signal:

Would I be able to use the following circuit for the RPM(engine speed) signal?:
This uses a signal coming off of a injector, my signal is some signal that is going to the ecu of the car.

From: GitHub - designer2k2/multidisplay: The MultiDisplay Project, An opensource datalogger, boost controller and display for cars

which is a variation on:

From: http://www.national.com/ds/LM/LM2907.pdf

Would I just use two of the same circuits for RPM and Speed?
I would like the measurements to be as precise as possible.

Thank you for any help you can give!

Jesse

2

I could just use a single 150ohm resistor right?

3

A more expensive route, but 99% acuurate way eould be to interface the obd2 connection and request that info directly from the ecu,
You could get tons of other things too like temps, pressures, and other readings
It would depend tho if your car has obd2 and you felt like buying a shield for the interface