MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Electronic ignition help

After much reading and talking to many people about the subject I've decided to "bite the bullet" and invest in an electronic ignition system for my 78 MGB Rubbernose.
BTW - I highly recommend the really excellent book by Peter Burgess, How To Power Tune MGB 4-Cylinder Engines, for anyone else out there with my lack of experience.

The only thing I am unable to decide is which system to install. I have narrowed it down to 2 choices; pertronix Ignitor or Lumenition Magnetronic.
Both appear to be very similar and the installation is easy for both. Does anyone have specific experience with both systems and would you recommend one more than the other?

FYI - I'm running twin SUs. I've done all the suggested steps in the Burgess book for running unleaded fuel (valve seats, etc) and for 6 months now been using premium unleaded with no problems.

Cheers,
Dave - Sydney, Australia
David

Don't butcher the distributor to fit them, and always carry points and a condenser as a spare.

Paul Hunt

I've been using a Magnetronic for a couple of years now. 100% reliable (so far) and child's play to install. One thing, the later cars (like yours) have a ballasted coil. This is done with a piece of resistive wire in the loom. To provide power to the unit, you'll need to run a new lead from the fusebox to get a 12v supply (find the one that's live with ignition). If you connect the "power" lead to the +ve side of the coil (as suggested in the instructions) it'll get 6v and cook itself(!)
I found that the adapter plate for the Magnetronic is arranged in such a way as to position the pickup so that the timing remains close to where it was. This means that the car will run straight away and you can get straight into strobe light timing.
There is no need to modify the distributor in any way and it's a matter of a minute's work to convert back to points in an emergency. I keep the points and condenser that I took off in the boot as I know these work :-)
From outside the dizzy it's really quite difficult to tell that anything's changed.....
T J C Cuthill

I used the Pertronix.
I have used a Pertronix on every classic car I've owned and they have performed flawlessly.

They are cheap, easy to install, need no modifications to be performed, and never need adjusting.

I've had mine on my 77B for 6 years now...set it and forget it!

Erik.
erik

Thanks for your replies.
Do the Pertronix require the same modification to the power supply as the Magnetronic? Both sound so close in other respects but that would tip the balance for me.
David

I've had the Pertronix in my MGB for 5 years with no problem, now in the TD, again, no problem. The only power issue is that they will run better with a 40,000 volt coil. Pertronix sells one called "flamethrower" that comes in basic black (the decal peals off) You'll also need to gap your plugs slightly wider.
Good tip to have either a back Pertronx or a set of points in the car though, with electronics, there is no telltale sign it is about to go, it just stops! However, I've found the reliability to be great, 5 yeras without a hitch.
Robert Dougherty

Well I just realised that it looks like Pertronix is known as Aldon in the UK. The label on the Aldon Ignitor gave it away (I was just a bit slow on the uptake). Pertronix/Aldon appears to be very highly regarded.
The decision is still a very tough one as Lumenition have a distributor in Australia and they're not far from my work place.
I guess I will go for the Lumenition brand and hope that the guys here in Sydney can look after me.
I'll be sure to check on the ballast resistor issue.

Thanks again for the worthwhile advice here guys.

Dave - Sydney, Australia
David

Just how much confidence can you have in a device where the manufacturers instructions tell you to connect 12v to a 6v coil!
Paul Hunt

I realize your decision may have been made, but to answer the question on coils to use with the Pertronix unit...I've used Bosch blue coils exclusively and they are excellent.

Also, to answer your question on modifications needed to fit the Pertronix...there are no modifications necessary.

The unit is a Hall effect sensor, essentially a magnetic collar and a stationary pickup.

erik.
erik

Further to Paul's comment above. Lumenition do specifically state that a 12v supply is required and that when using a ballasted coil a seperate 12v feed will be required.
The problem is the the MGB R/B doesn't have a ballast resistor "on show" so it's an easy (and potentially costly) mistake to make if you are not 100% au fait with the "resistive wire in the loom" concept. I see that I neglected to make this clear in my original post. Sorry.
I remember that when I fitted mine, I carefully inspected the ignition and, finding a direct feed with no resistor, wired as standard. It roasted. Lumenition, without any query, replaced the unit and in the meantime I'd read up more thoroughly and found this little "feature" squirreled away in the detail of the manual....
I don't regard this as Lumenition's problem, more BL's strange obsession with "if there's a standard way of doing it, we'll come up with a new one".

T J C Cuthill

I managed to split the plastic trigger disc, Lumenition sent me a replacement free of charge and were very helpful over the phone.

Tim.
Tim Jenner

Thanks for the clarification. I understand the "quirks" in the instructions and my mechanic (who is helping to install the unit along with a bunch of other things he is working on for me) tells me he is fully aware of the 12volt/6volt issue.
He looked up the data sheet for my car (he keeps this info on file for all his customers) and informs me that I AM using a 6volt coil and he will replace that with a 12volt coil, also bypassing the resistor in the loom with a new feed.
Let's hope Lumenition in Australia are as forgiving if we make any mistakes. I don't think we will get this wrong though. My main concern now is using the opportunity while I have the bonnet open and all tools available to tackle a range of other small problems/bugs (like my intermittent horn). Also I am looking forward to retuning the SUs once the timing and other aspects are 100% perfect.

Once again, thanks to those that offered advice. I appreciate and agree with all of you, however for convenience more than anything I will go with the Lumenition. Maybe next time I'll try a Pertonix and compare the experiences. Let me get my first MG perfect before I double my headaches :)

Regards,
Dave - Sydney, Australia
David

Hi
After a bad experience with an aftermarket electronic ignition I agree with Paul Hunt --carry a set of points & condenser and know how to fit them, or your going home on the tow truck
Ron
R. Algie

Replacing the 6v coil and loom ballast with a 12v with direct feed can have a detremental effect, that of loss of the 'boost' voltage to the coil when cranking which can make the difference between starting and not starting under adverse conditions. Abingdon were hardly innovative given the design age of the suspension, engine, electrics and pretty-well everything else in the MGB. That and the penny-pinching leads me to believe that if it was provided it was necessary.
Paul Hunt

I fitted a Lumenition magnetronic kit about 2 weeks ago to my 1980 B. I found that it runs much better through out the rev range with a bit more low down power. It has hower not been with out fault. After about 3 days the revs started going up and down when cruising at 60 between 2700 and 3400. I took the dizzy of and had a look and found the screw ( that was the points gap adjuster screw ) had came lose allowing the sensor to crash against the disk. This scractched the sensor quiet badly and scared the disc also. When seeing this was slightly dispointed thinking my electronic ignition was all over but thankfully not. i put it back on and it works as good as it ever did i dont think the senor will take another 100 mile battering against the disc but provided that screw remains steadfast I belive i should have indefinte relability which is good really as when i sore it i was in the process of thinking how to explaine how this one happened in the post.

Oh when i first did up that screw it was nicely nipped up i am not at all sloppy when i redid it i seriouly over torqued it to the point that the thread would take little more so rember make that screw tight not just nipped up as you would do when setting your points as I did. The other thing is on a Right Hand drive 1980 model you conect the wires to the coil the black wire i belive and the red one to the fuse box the second fuse from the bottom facing the front of the car. Probably obvous but i had real problems when figuring this out as i could not see any where in the hayness manual that told you what fuse is for what.
erfrefewrffre werfwerfetrtg

It's in!
I bought the Lumenition Magnetronic despite feeling some hesitation due to Paul Hunt's suggestions (which are always the most comprehensive and knowledgable when I visit this board). Fitting it was pretty close to as easy as the manual says. Finding a new power feed was tricky, and I eventually used one which sounds like the one mentioned by Erfrefewrffre from ACT.
The manual tells you there must be a .75mm gap between the disc and the module, and it won't work unless the gap is very close to this range. No matter what I tried I was unable to get a proper gap and the disc "almost" touches the module. Despite this I tried it anyway and it runs fine. I removed the cap and disc to inspect the module after a 50km drive and there is no visibile wear or scratches. Maybe I'm just lucky.
I found the car very sluggish while driving, and particularly no "guts" when trying to accelerate. It did seem very smooth though. Oops! I forgot to reset the static timing after installing the new electrics.
Now I've done the static timing and performed a quick road test. What a difference! I'm actually accelerating in 4th gear up the steepest hill in my area (I call it MGB Test Hill) with more power than I ever remember in the car.

Next job is getting it down to the mechanic next week to tidy up any loose ends I've left behind. Also, the inlet manifold has a very bad leak around the gasket area so he will be fixing that for me and then performing his SU magic on carbies (I still haven't got that part perfect).

Now if only I can forget the image of that 4.5L V8 engine sitting on a stand at the Lumenition shop. Next year's tax return maybe :)
David

This thread was discussed between 22/07/2003 and 27/07/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.