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VEMS looks to be just the thing I was looking for to go beyond carburettors. == My project == * Guzzi V75/4 V-twin * 748 cc * Normally aspirated * Now fuelled by 2x Dell'Orto PHBH 30 (30 mm) * Street-use only What I am after in an EFI system (apart from learning a lot about EFI, of course) is: * Simplicity * Reliability * Low fuel consumption / Low emissions * Reliability What I find interesting is * WBO2 control * VE learning, maybe even on a cylinder-to-cylinder basis (to 'learn out' (or just measure?) production tolerances?) * Ion-sense ignition * Reliability and robustness of electronics in an automotive environment == Regarding timing requirements: == I built an Atmel-based electronic ignition for the bike. Two units (one for each cylinder) operate entirely independently from one another. The only timing input each unit has is one pulse (VR, LM 1815) per camshaft rotation. This pulse comes at the moment of maximum advance, and turns out to be entirely adequate. At low RPM (and maximum ignition delay) timing as observed with a timing light is not perfect but the bike idles (and runs) nicely. Since ignition places more stringent demands on timing than fuel injection, this suggests to me that the whole VEMS could work off the same sensor. It is something I want to pursue. == Regarding the GenBoard V3 Hardware: == (is there a better forum for this? GenBoard/UnderDevelopment/VerThree ) I am curious about the Genboard V3 IGBT drive topology. A 1k resistor connects the IGBT gate to the driving 74HC259. When the IGBT self-clamps, a pulse of several volts or tens of volts appears at the gate of the IGBT. This is being fed through the output protection diode of the 74HC259 into the supply. Note that the self clamping does not happen normally. When the gate has 25V, the 1k will limit the back current to 20mA. It is for a very short time (the gate capacitance is <1nF, it discharges fast). With my ignition coils (Nippon Denso, somewhere late '80's)actually self clamping does happen normally. They are relatively high-Z primaries (Idc is only approx 1.8 A). I looked through the IGBT datasheet (HGTP14N40F3VL) to see if there is anything saying that you should not normally operate in the self-clamped regime but found nothing to that effect. I have been running this configuration for about 30,000 km now, so in practice it works, but of course that doesn't mean it is a 'good' solution. Actually the self-clamping of the IGBT is a non-issue: I don't know why I got it into my head that the clamping would occur when the IGBT drive is 'high'. In fact, of course, it occurs (if it occurs at all) when the IGBT drive is 'low'. The IGBT clamp is then injecting current into the low output of the 74HC259, and this (according to datasheet) can sink 25 or so mA, so there really is no problem. * the best would be explicit intelligent clamping (not by the IGBT) that would tell the ECM that there is problem with that sparkplug connection (diagnostics). That would be very nice, I agree. But more components -> less reliability. Especially since the intelligent clamp contains HV parts. The fewer the better: precisely why we like an internally clamped IGBT for ignition drive.
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