Electronic Fuel Injection M30

Your mixture will be richer if you disconnect the oxygen sensor.

Interesting post. Even if I could buy a hydrogen powered vehicle, it would do me no good. California has the only refill places, and these are 2000 miles away.

Jim

One of the easiest ways to alter mixture across the board is by reducing the fuel pressure. However, when running in close loop mode, the system will try and compensate.

The only way for you to lean out the engine mixture will be to fool the engine's fuel injection program into thinking that it is running richer than it actually is. You could probably devise a circuit of some sort to put in line with the O2 sensor feedback signal to do this. Or you could just remap the fuel injection table in the ECU eprom.

I know there are aftermarket fuel injection computers that are used for this sort of thing for motorcycles. Google on "Power Commander" However, the goal in that application is generally to increase the fuel charge in order to improve power and driveability.

Generally (if you ignore the action of the lambda sensor) it's easier to increase the fuelling by fooling the ECU into thinking the engine is still cold. IIRC, the coolant sensor starts high resistance at low temperature and goes lower as it warms up, so merely adding a series resistor has the effect of increasing fuelling. Hence the jokes about some of these 'power devices' costing pounds for a penny resistor.

That's not what I'm talking about Dave. A power commander actually has its own lookup table of throttle opening vs. rpm so you can program exactly how much of an increase or decrease in dwell you get on the injectors. It's pretty slick, but to tweak it in 100% requires the use of a dyno and exhaust gas analyzer.

If you want to help save the world, then why are you driving around in a '91

Hi

Running an engine lean means running it hotter and you risk blowing holes in your pistons or overheating and cracking the head. Think about your engine - a trashed 3.5 litre straight six is a damn site more polluting than a few extra ounces of co2. Anyway running the engine lean increases nitrogen burning to form NO2 which dissolves in the atmospheric water to form acid rain.

BMW set your mixture the way it does for many reasons. Minimising carbon monoxide ( from rich mixture ), minimising notrogen oxides ( from lean mixtures ), maximising efficiency ( low petrol consumption hence low CO2 ), maximum performance. I would suggest overhauling all the major parts both ignition and fuel, putting a couple of new filters on and leaving well alone.

Dave