I think the fuel pump might be the biggest draw. The O2 sensor uses
essentially nothing though the heater for it in 2.1 would take some.

The ECU powers the injectors and in a 2.1 also has the ignition circuit.
In the 2.1 it gets hot so clearly is using some power. It has cooling
fins and is screwed down to a metal case that removes some of the heat.

Mark

Jake de Villiers wrote:
> Our race car had no alternator fitted and would run the starter, fuel pump,
> gauges and ignition for 2 practice sessions and a race without needing to be
> recharged.
>
> Prolly the biggest consumer would be the oxygen sensor - I can't see the ECU
> needing bags of current...
>
>