I've done kill switch on fuel pumps in the past, but for the RX-8 I want to leverage the eccentric shaft sensor. Seeing that the ECU operates ignition and fuel only when there is valid data from the sensor, when it's disconnected engine will crank but never start (and ECU doesn't get upset). I've looked at the wiring diagram and think the sensor wiring is part of the ECU harness in the engine bay. The idea is to run a modified harness/junction from the sensor connector from engine bay to inside to a concealed switch. The question is where I could run the wiring from the engine bay to passenger compartment - existing points that can be used for two wires? Location?

 

You don't want to do that. The sensor wiring is a very sensitive circuit and is run in shielded wire. It is very susceptible to interference.

The fuel pump or ignition wiring power circuits are more than enough to keep someone from starting your car

 

Great advice. The original question still stands though...

 

You can run it in the grommet that goes through the firewall/dash under the brake master that the body harness uses.. Just poke it through the rubber. Or you can drill a hole on the passenger side where the dimple behind the washer bottle is.... it is where the RHD steering stuff goes through. And put in another grommet.

Or you can run it under the. Car and up through the shifter rubber into the console

 

Seriously, don't modify the ESS sensor wiring. You could much more easily place an interrupt on the clutch pedal sensor circuit (already inside the interior of the car), or interrupt GND to the gauge cluster (adding a hard lock-out to the ECM/BCM/Meters key authorization).

 

For those who advised on the ESS wiring, were there specific issues that you found in your experience? Can you describe a little more? I can understand the design and precise nature of how the sensor is supposed to work, and therefore how physical debris, etc, can deteriorate its performance. The resulting signal could be susceptible to some form of external interference along the signal's path but what is the shield composition of the harness? I'm sure that Mazda engineers created a signal profile so that it would usable in a variety of conditions rather than being prone to even the slightest interference.

 

The sensor produces a weak voltage signal when the metal tooth crosses over the sensor. It is a small voltage and is very susceptible to interference. ANY dropout or messed up signal will cause the PCM to loose synchronization and result in a missfire

Rotarys do not like misfires..... especially if they cause detonation. One good ping and you can say goodbye to a rotor and housing... and often the irons as bits of Apex seals go careening around in the chamber gouging everything.

Much better to interrupt the process somewhere else. Fuel pump cutout or cutout to the coil power supply.is much easier and a lot safer.

Shielded wires are shielded for a reason.... don't mess with that

 

Engineering is designing a product without waste, meaning no extra effort in shielding, security, durability, or capability, beyond what is explicitly designed. Safety factors are used to determine how much 'overhead' to build into an assembly/component; something that little consideration with low voltage electronics where human risk is very low. Mazda designed the component to operate in their designed conditions, including shielding requirements, cable composition, diameter, length, defined connections, position, and routing. Changing the routing, length, or introducing splices/connections beyond what Mazda intended, is possibly enough to compromise the signal given how low the margin for error is with this specific component. Unless you yourself are an electrical engineer, you aren't or you wouldn't be asking this forum, don't modify their design.

 

You noobs and your silly ideas

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