Simplify ignition

[Monkeyzak]

Hi

Can you modernise or simply the ignition system in a 1985 LC? Thing to get rid of the lucas spark amplifier.

Would a modern lumination system remove any of this?

Just new to lotus so don't know the system very well. I had a tr7 and put lumination and it made a massive difference getting rid of points etc

Is there anything I can do to modernize and improve reliability on this?

[Pete Boole]

Lumenition will work fine. You could go the whole hog and fit a "123" system to allow for programming of the ignition curve if you wanted to.

Pete

[Monkeyzak]

If I just go down the cheaper route like acu spark. Is it worth it?

I've had mostly minis as classics so this is all new to me. My minis were all mpi.

[rbgosling]

Honestly... in 12 years and 70,000 miles, I've had three issues with my ignition that I can remember:

• One was caused by me missing out a washer when I rebuilt the distributor (as part of a full engine rebuild).
• One was caused by an aftermarket immobiliser that was in the car when I got it; now bypassed.
• One was a broken rotor arm, poor quality aftermarket one probably.

The sensor in the distributor works well, and unlike traditional points requires no adjustment, and never wears out or needs replacement, or a condenser. The AB14 ignition module, and the rev limiter, are solid state electronics and work reliably. I think one or two may have had an issue with the rev limiter, but you can just unplug it and the problem goes away (along with the rev limiting...).

Essentially, then, the stock system works well and reliably, or at least it always has for me.

A fancy aftermarket system should give improvements, since you can replace the mechanical vacuum advance and speed advance mechanisms with a proper map that will give optimum spark timing under all conditions (in theory, if set up correctly), which should improve both performance and economy.

More basic aftermarket systems often are simply aimed at replacing the points with an electronic pickup within a standard distributor, while keeping the existing mechanical and vacuum advance mechanism. Lotus has already done that for you, so unless there's a problem with the current system that cannot be fixed, I cannot see the benefit of this sort of system for an Excel.

[richardw]

Good summary Richard!

Cheers, Richard

[Lotus-e-Clan]

Yes I too have had no significant problems with the std Excel SE ignition system in 24 years ownership beyond precautionary replacement of the leads and cap when I first bought the car. And that worked wonders at the time given the PO's lack of attention to detail.

In terms of improvements, switchable maps would be nice IF you know how to optimise the curve for different octanes. At the low cost end, a programable 123 Dizzy might have switchable maps.

Beyond that you have to go dizzy-less ignition with a trigger wheel ECU, TPS, ecu and coil pack(s). Because here you eliminate the weakest links with dizzy ignition, namely the rotor arm, cap, and single coil.
Having twin coil wasted spark, or individual coil on plug firing makes a significant difference to ignition efficiency and reliability over any dizzy system, as there's no air gap for the spark to jump, and the short dwell time for coil recharge at high rpm is eliminated.
But fully mapped ignition will cost a lot and maybe not worth the bother as the std ignition system is perfectly fit for purpose if it's working as it should.
Acuspark or luminition won't offer any advantage over std.

[Monkeyzak]

Thanks gents. Those are fab replies. I appreciate it.

There's a bit of a hesitation and poor starting and I've no idea what it is.

Obviously start with new plugs, leads, etc.

[Pete Boole]

I'm partway through designing/building a cam position sensor to enable sequential fuel/spark and coil-on plug. Mission creep? Surely not

Like everything it's on hold at the moment

Pete

[Lotus-e-Clan]

I'm partway through designing/building a cam position sensor to enable sequential fuel/spark and coil-on plug. Mission creep? Surely not

Like everything it's on hold at the moment

Pete

That alone is a reason we need you to get through this

A bespoke mapped ignition system made from readily available parts from other cars would be a winner for me. Not so interested in the EFI bit as I'm a dyed in the wool carb man .

[Pete Boole]

Thanks Peter. I'm planning to use some home-made bits and some readily-available bits for the cam position sensor, so not entirely off-the-shelf. I've already bought several coil-on-plug ignition coils to find a suitable length one and I think I've got a winner - we'll see!

Pete

[rbgosling]

Thanks gents. Those are fab replies. I appreciate it.

There's a bit of a hesitation and poor starting and I've no idea what it is.

Obviously start with new plugs, leads, etc.

Yes, no harm in replacing plugs, leads, dizzy cap, rotor arm, coil - they are not expensive (although don't go too cheap - see my rotor arm failure!) and then you'll know they are good. The Distributor Doctor sells quality products. Check that the mechanical and vacuum advance are working as they should. Check that the multiplicity of vacuum hoses are all connected up correctly, and check the hoses for leaks (someone on here has produced an excellent "map" of these, worth digging for). And, of course, check the ignition timing, up through the revs as well as at idle.

Hesitation could be fuel starvation due to weak pump or blocked filter, but that shouldn't affect starting as the carb float chambers should be full when you try to start, and that should be enough to start it fine even if it then dies. There's not much that you can fiddle with on the carbs; the idle mixture can be adjusted, but above idle there is no adjustment (unlike the SUs I've had on previous cars), other than ensuring the float in the float chamber is set up right. But debris in the carbs can totally ruin them; after my engine rebuild some crap must have got into the carbs when I was re-assembling them and the car ran dreadfully. So a carb re-build with a rebuild kit - in impeccably clean conditions - may improve things if nothing else does.

Other than that, air leaks carbs-to-manifold or manifold-to-head can mess things up a bit by making the mixture too lean. Incorrectly-timed camshafts would cause poor running. Poor compression can leave you down on power and fuel economy, but shouldn't affect starting or cause hesitation unless it's really bad.

[HypnoToad]

I'm partway through designing/building a cam position sensor to enable sequential fuel/spark and coil-on plug. Mission creep? Surely not

Like everything it's on hold at the moment

Pete

I'd be interested in to seeing how this goes, if you do it I'd be tempted to try something similar maybe if I ever get issues with the standard setup.

I think some of the later 912 engines may have come with fuel injection from the factory, so I'd imagine that would also have crank and possibly cam position sensors.

[Pete Boole]

I don't think any of the four cylinder engines has cam position sensing. I've worked out in my head how I'm going to built it and ordered some "experimental" parts but it's on a bit of a back burner while I re-design the oil pump!! I'll save that for another thread

Pete

[DavidOliver]

Just for the book, the 85 LC distributor does not have vacuum advance.
My Excel goes fine without vacuum advance.

Dave the cog.