Lucas ignition amplifier replacement by Bosch 024

'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.

Quote:

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Originally Posted by bee utey

I'd be checking the clearance of the pickup to the rotor and tightening it up by a bee's dick. Cold idle is often faster than hot idle. Then go around and check that every connection is completely clean and tight.

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Hey bee

Since getting the d1 running I've had a slight misfire at idle and when I pull away.
Changing the module was one of the things I done to get it running.
After having a skim through should I go back and adjust the pickup gap to the bare minimum?
I have a 5mm aluminium heatsink but I'm going to make it cover more area it's not much bigger than the module.
And if the polarity is wrong I'm assuming it would be running really bad? It runs fine after 1500rpm. I've gone over the connectors a few times now they seem adequate enough.

Cheers Jim

Quote:

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Originally Posted by LRJim

Hey bee

Since getting the d1 running I've had a slight misfire at idle and when I pull away.
Changing the module was one of the things I done to get it running.
After having a skim through should I go back and adjust the pickup gap to the bare minimum?
I have a 5mm aluminium heatsink but I'm going to make it cover more area it's not much bigger than the module.
And if the polarity is wrong I'm assuming it would be running really bad? It runs fine after 1500rpm. I've gone over the connectors a few times now they seem adequate enough.

Cheers Jim

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You're probably on the right track although misfires can be a real bugger to track down.

I run this system and i have no misfire so i can testify to it being a solid system.
To be fair i have been advised the amplifier is not the best one for the job but does work. (from an ignition joint in Scorsby)
But it does work.

Look for your miss. At night is always a good way to check.
Bonnet up is different to bonnet down, could have a coil spark on the bonnet for example. Had it happen.
I watched a guy spray water mist at night to detect a miss. Worth trying, but google it first.

Try it again with the alternator charge wire to the battery disconnected.

Jc

In my case the problem seems to have disappeared since I finished the install properly (coil mounted solidly and wiring tidied up). Lots of WOT runs to redline on the last trip without a hint of a cough. Lovely. Haven't done a data log yet to see if the signal is still noisy, but runs well so I'm not touching it!

Well I just remounted it all, I used the original z shape heatsink. I changed the dizzy rotor to a Bosch one also. It seemed to run better but I didn't let it get to temp or go for a drive. I'll see how it goes before adjusting the pickup. I eyeballed it last time and from memory got as close as possible so I may just leave it alone. Hopfully like discoclax it disappears now it's a bit neater. The module is near the intake horn now but when I make a snorkel that will go.

Cheers Jim

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Originally Posted by bee utey

Possibly. Your heat sink must be big enough, and the white paste applied thickly enough to take the heat out of the module. I've seen plenty of dodgy versions of this conversion done by other people who use things like tiny scraps of stainless steel, no paste or low quality crimp connectors. However, my guess is still on slightly loose or dirty power connections.

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The following is the dogs business:

Heatsink to suit SY4084/SY4086 | Jaycar Electronics

Quote:

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Originally Posted by Old Farang

The following is the dogs business:

Heatsink to suit SY4084/SY4086 | Jaycar Electronics

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I did think about a heatsink like that. The one ive got should be fine, I've seen other people here with good results with the original one. I'm pretty happy with the setup now just hope it helps with the misfire.

Cheers Jim

Quote:

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Originally Posted by LRJim

I did think about a heatsink like that. The one ive got should be fine, I've seen other people here with good results with the original one. I'm pretty happy with the setup now just hope it helps with the misfire.

Cheers Jim

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Considering that the original module was designed to be "cooled" whilst bolted to a hot distributor, the stock LR heatsink should be fine. I've used quite a few of them without problems.