Lucas Constant Energy Ignition unit.

jenand40 · Post by **jenand40** » Sat Jan 04, 2014 11:21 am

Changing from Flapper EFI system to Hotwire system and want to retain the original Flapper Constant Energy ignition system.
There are 3 cores which go to the Constant Energy ignition unit;
1. Tacho input from negative side of coil, White/Black core.
2. Ignition controlled supply to the positive of coil, White core.
3. Input to Flapper ECU from Constant Energy unit, White/Slate core.
The Hotwire ECU only requires an input from the negative side of the coil. Can I reuse the Constant Energy unit with only the cores connected to 1 & 2 above?
Is there a circuit diagram available for the Constant Energy unit?
Any help appreciated.
Thanks.
Andy.

DaveEFI · Post by **DaveEFI** » Sat Jan 04, 2014 2:45 pm

I'm not quite sure which Lucas system you're talking about. Which dizzy - DM, or DLM? If it's the older Opus system I'd be looking at something better.

(The DM has its amplifier mounted beside the coil - the DLM the amp is on the dizzy itself - although it may have been repositioned as they fail with heat.)

However, the actual tach signal for the ECU will be similar since it's from the coil negative. IIRC, the difference is the flapper has an inline resistor to limit the current - the hotwire has it built into the ECU.

jenand40 · Post by **jenand40** » Sat Jan 04, 2014 3:25 pm

Not sure which distributor I have there are only 2 cores coming from the distributor itself, red & blue, they go to the remote constant energy unit that the coil is secured to. Complete system came out of a 1983 SD1 Vitesse I bought for the engine & gearbox.
I have taken some photos but cannot see how to attach them! Any one advise please.
Just looked at the Haynes manual and it is a Lucas 35 DM 8 ignition system.
My main question is whether the constant energy unit will work with just the positive & negative feeds to the coil. But thinking on it now that is all that is normally connected to the coil.

DaveEFI · Post by **DaveEFI** » Sat Jan 04, 2014 3:59 pm

Yes - that's a DM. The connection to the ECU has nothing actually to do with the ignition working - it's simply a tach feed to tell the ECU how fast the engine is turning. If you had carbs, it wouldn't be there.

jenand40 · Post by **jenand40** » Sat Jan 04, 2014 4:09 pm

Thank you Dave.