Kill switch how-to

[Clev]

Originally Posted by dcb

Update, sorry this didn't sink into my head till now, but on the metro at least (and probably many other cars) YOU ONLY NEED TO INTERRUPT THE CAMSHAFT SENSOR CIRCUIT. I just ran some real world tests to confirm this. This would be a good wiki thing.

Oh, excellent idea! Does doing this trigger the Check Engine light?

[dcb]

Not on a 98 metro. But if it does on other cars then we should add a column to the hypothetical wiki table to indicate that.

[FunkSkunk]

Ok I'm lost is there a write up for 96 & newer EOC cut-off switch? Or will the original work for any year Metro? GREAT THREAD btw!!

[bbjsw10]

Originally Posted by FunkSkunk

Ok I'm lost is there a write up for 96 & newer EOC cut-off switch? Or will the original work for any year Metro? GREAT THREAD btw!!

Thanks, and I believe you could adapt this to work on 96 newer as well, or any car with enough knowledge. I may switch mine to dcb's way of the camshaft sensor. Especially when my MpGuino stuff is waiting at post office for me.

[FunkSkunk]

Sounds good! I'll have to look over my factory service manual and see where I need to splice in to make this happen! Thanks again

[hypermiler01]

Hi, I have a 1993 Metro that I am modding.

What is the benefit of cutting the injector wires, or the coil power, or the cam sensor, etc, instead of just cutting the ignition wire from the key switch?

Is there any reason I shouldn't simply install an SPST toggle switch in the ignition wire (black with blue stripe) coming from the key?

Also, can anyone tell me the purpose of the big yellow wire with the black stripe? It is currently disconnected with no apparent effects.

[MetroMPG]

Depeding on the OBD-II protocol your vehicle uses, cutting the ignition may cause a ScanGauge to shut down and take an unacceptably long time to re-initialize after you turn the power back on again. During that time, it's not recording speed/distance, and over time will skew the SG data and become a pain in the butt.

The ISO protocol in the Metros is one like this.

The other kill switch methods stop the engine witnout interrupting power to the SG, so it continues happily factoring speed/distance into the MPG calcs while instant MPG sits at "9999" (the SG value for 0 fuel use.)

[hypermiler01]

A 1993 Metro doesn't have OBD-II, does it?

[Clev]

Originally Posted by MetroMPG

Depeding on the OBD-II protocol your vehicle uses, cutting the ignition may cause a ScanGauge to shut down and take an unacceptably long time to re-initialize after you turn the power back on again. During that time, it's not recording speed/distance, and over time will skew the SG data and become a pain in the butt.

The ISO protocol in the Metros is one like this.

The other kill switch methods stop the engine witnout interrupting power to the SG, so it continues happily factoring speed/distance into the MPG calcs while instant MPG sits at "9999" (the SG value for 0 fuel use.)

Well, that and I wouldn't want to power cycle the ECU any more often than necessary...

[MetroMPG]

Good point, Clev.

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Nope, it doesn't, hypermiler01.

I didn't know what kind of car you had when you posted your first question. You'll be wanting to build yourself an MPGuino for your instrumentation, and it's not affected by ignition-off.