'94 D1a 3.9 auto based vehicle with 4.9 stroked HiComp engine running the standard 14CUX (with a MAF intercept to retune fuelling). Alternator is a P38A 120A genuine item, if that has an effect...
For many years I've been running the standard Lucas dizzy with the BIM024 module conversion and a MEC717 transformer coil. I have just swapped out the dizzy for a new 'Scorcher' unit (ie. Bosch HEI) hooked up to the same MEC717 coil. Brand new, made in Australia, custom graphed, etc. New BIM024 module came in the dizzy. All genuine parts.
I still have the same issue where I am getting a dirty rpm signal to the engine computer. The Lucas had this and now the Bosch as well. When I log the signal I see rpm spikes here and there during normal running (but doesn't show any symptoms), and this is more prevalent when the engine is wound out past 4,000rpm under load. This manifests at higher rpm as the engine computer reading an over-rev condition momentarily and cutting the injectors. It's seeing rpm spikes of well over 10,000rpm which trips the factory limiter. Logged data on a mate's D1a manual showed the same dirty rpm signal, however the manuals have a higher >15,000rpm rev limiter in the ECU and therefore the hard-cut doesn't manifest in his. Note that this doesn't show up in a Rovergauge log as it's too coarse between readings to catch it. It does appear with a 10Hz capture, though (refer below). I can tell you it's REALLY not nice having a 520Nm motor honking along hard and suddenly switching off and back on again rapidly at high revs and foot buried. Not great for the driveline either... Cue Transfer Case replacement happening today with an Ashcroft H/D rebuild.
Attachment 141693
Has anyone seen that before? Is that something that can be cleaned up with a filter, or is related to something inherent in the vehicle? Is there a fix that anyone knows of? It's not the suppressor hooked up to the coil (capacitor) or anything simple like that is it? * please let it be simple *
I'm about to head off into the desert for the next three weeks and having a clean-running engine would be really good. I had the (expensive) Scorcher dizzy made to hopefully fix the problem but hasn't helped that at all (but it does run better given the re-graph, etc. so still well worthwhile).
PM sent to Bee Utey, but then I thought I'd chuck it out here for all to see...
Any help very appreciated. Thanks.
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