Quote:
Originally Posted by saand
yep i could very easily fry something in the ECU, but i dont plan to send a voltage over .9v to the ECU and have it current limited by a fairly conservative resistance so should not have too much of an issue.
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While it's a good idea to buffer your signal so that you don't fry your ECU, I think you may still want to reconsider this idea. When I mentioned that you might fry engine internals, I meant pistons, valves, and rings.
Once you start operating lean, your engine will start to experience detonation. This is explosive quick (supersonic) combustion of the air-fuel mix, which is in contrast to the slow (subsonic) combustion of air-fuel mix at stoichiometric. The difference is that detonation causes a shock wave to propagate from the point where the detonation started. You can actually hear the shock waves hitting combustion chamber surfaces, as a knocking noise originating within the engine (hence, it's commonly called engine knock).
At relatively low loads, this is usually not a problem. However, under moderate or heavy loading, detonation may scour away combustion chambers, may shatter piston crowns, or may jam piston rings into their grooves. In addition, detonation may cause combustion chamber surfaces to become really hot locally, which will lead to pre-ignition.
Pre-ignition is when air-fuel mix combusts prior to when it's supposed to when the spark plug fires. As the cylinder travels upward on its compression stroke, the air-fuel mixture heats up. If this mixture is burnt while still in the compression stroke, combustion chamber surfaces will quickly rise in temperature to the point where piston crowns may melt, valves may melt or get burnt, or you might even have a nice engine backfire, where the air-fuel mix will actually combust while still in the intake manifold.
This is why you want to be very careful when running lean.