MX5 MK1 Ignition Timing

[Elmar]

Hi,

Can somebody tell me what would be the net result when a mechanic does the ignition timing but does not short the 2 pins out in the diagnostic unit (GND and Ten)
while doing the adjustment.

Cheers

[Steve]

Net result will probably be nothing as he has adjusted it while the ECU is in closed-loop mode. With the jumper in place, the ECU is in open-loop, which allows you to change the idle (it disables the ISC) and set the timing (I believe it does this by disabling timing advance in the ECU and signal reading from the O2 Sensor also, am not 100% positive on this though).

open loop : it uses the flashed map in the ECU basing its adjustments on rpm, coolant sensor, throttle position, air flow meter
closed loop : it uses the flashed map in the ECU basing its adjustments on rpm, coolant sensor, throttle position, air flow meter and the O2 sensor

It might look like its advancing but on restart it'll probably be the same as it originally was. You can check this with a timing light though.

[Elmar]

Thanks for that Steve