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MG Midget and Sprite Technical - Static Timing an Electronic Module

Hey folks,

Does anyone have a smart way of static timing a dizzy with an electronic module in it?

I have been messing and have totally lost any reference of where my timing might be. Also, my helper has gone to work (boo!) so I can't just get her to spin it on the starter whilst I strobe away under the bonnet! :-(

Cheers,
Malc.
Malcolm Le Chevalier

I don't Malc, but it would be very easy to rig a LT jump lead to the starter solenoid that you can connect/disconnect with one hand under the bonnet.
Many starter solenoids have a rubber cover over the solenoid pin that you just press with your thumb to spin the starter. Have you checked?
Guyw

When I used to run with Lumenition, I would connect a bulb across the coil terminals, turn the engine - either by hand, or pushing in gear - and when the lamp extinguished, it was at the firing point.
Dave O'Neill 2

thanks Dave, that has given me a spark of inspiration for how to do it.

full report to follow :-D
Malcolm Le Chevalier

OK, maybe not. I am confused.

Plugged a multimeter across the coil (to be precise, I disconnected the coil and connected MM in its place). Turned on ignition, MM says ~6 volts (ballast ignition system), fine. Turn dizzy until this changes, I thought it would flick to zero, but eventually there is a point it flicks to ~12 volts. 12 or 0 volts, whatever, this must be the trigger point.

But then my rotor arm is pointing pretty much exactly between two points on the dizzy cap, how can this be right?!

Doh.

Malc.
Malcolm Le Chevalier

Tried it with coil attached. Seemed to get 0 volts unless at a very small point (I assume the trigger point) where I got "some" voltage. But it only seemed to generate this voltage when rotating the dizzy quite quickly. Left it around that area, as it coincides with the rotor pointing about the right way.

Still confused and not sure what is right so just going to wait for wifey to come home!
Malcolm Le Chevalier

Malcolm

You don’t say what electronic ignition system you’re using (unless I missed it in a previous post). I’ll assume it’s one of the basic modules that fits inside the distributor.

My way of setting the static timing is to connect a 12v bulb in series with the coil, you could connect it in parallel (across the coil) but in series it limits the current through the coil while you’re setting it up.

Putting a multimeter in place of the coil could cause confusing results, the high resistance of the meter won’t allow sufficient current to flow to get a meaningful result.

Once you’ve got a bulb in series with the coil rotate the engine in the correct direction and the bulb will extinguish at point where it would fire.

If your module has variable dwell it could be a bit confusing, the typical way of achieving this is to switch the voltage to the coil on for about 3 to 5mS. This would cause the bulb to come on very briefly and then go out again.

Once you’ve got the engine up and running and timed I would suggest you check the maximum advance. A lot of old distributors have worn springs and weight pivots, this causes the auto advance to start too early. The engine will run fine at low speeds but will feel dead at high RPM’s. I built a test jig so I could map the advance curve and adjust it, that way I find the engines willing rev to the red line.

Bob
R.A Davis

Malcolm

As I do not have a strobe, and am an electronic ignoramus to boot, I rely on my ears and how the engine performs. Basically, after checking everything else - mix, fuel delivery, leads, plugs etc ad nauseam, I set the idle to about 2000 and rotate the distributor body ACW/CW to a point where best revs is achieved, then return the idle back to 800 or whatever. This gives me a reasonable start point.

After that, it is a question of road testing up my local hill. Essentially, I set it to as much advance I can get away with without the engine pinking when under load and simultaneously providing decent acceleration throughout the all the rev range. Again, this is a question of (carefully) rotating the dizzy body accordingly - not forgetting if you make matters worse, return it to the original position and start again. A small sticker on the block with marked graduations and a felt tip pen mark on the dizzy body helps matters. If like me you have Lumenition, you can also select the profile of your advance curves. This also assists matters somewhat.

For me, this iterative approach has worked pretty well, but I would recommend a visit to a local tuner sometime to ensure you have set it up reasonably well, and if not, to remedy the matter, and even if you have, to possibly fine tune further.

Oggers

OK, thanks for the advice everyone.

Yes it is just a "standard" elec. module.

There was no problem with how it was running before when I had the timing set as per the book. It's just that I have had a few bits apart, left it a week, moved some bits etc. etc. and now forgotten/lost my reference points so having to start again!

Cheers,
Malcolm
Malcolm Le Chevalier

Also, Bob, I am interested in your test rig, tell me more...
Malcolm Le Chevalier

Malcolm

It’s basically a stand on which the distributor sits, an old heater motor sits below the distributor which drives the distributor at various speeds. A disk marked in degrees sits between the motor and the base of the distributor. A rev counter allows me to set the speed and I use a timing light to read where a pointer is in relation to the disk to get a reading of the advance.

I can rotate the distributor to zero the initial reading at tickover RPM, I then increase the speed in 1000 RPM increments and note the readings.Once I have the initial readings (not forgetting it’s distributor degrees which are half crankshaft degrees) I can adjust the springs and test again until I get what I want.

I can measure the vacuum advance using the same procedure and small hand vacuum pump.

Measuring the dwell was a bit more of a challenge and although I have a meter that will measure dwell it’s only a cheap one that I couldn’t be sure of the calibration so I used an oscilloscope. I did a comparison on a number of electronic modules and points, including a well know supplier of cheap variable dwell unit. The real surprise was the Lumenition Magnetronic unit I’m using on my B, it measured 70 degrees (points from memory are 60 degrees), it warms the coil quite a bit but it does work well. I was using the variable dwell unit which although the dwell was getting a little bit less at the top end (probably the processor struggling a bit) started to cause a misfire when it got warm after about 20 minutes. Changing back to the Lumenition sorted it.

I know people will say that fuels have changed over the years so original advance curves aren’t relevant, I haven’t had my cars on dyno but they do seem to make good power and run cleanly with these settings.

I’ll try to post a picture of the jig later, it’s not pretty but it does work.

Bob
R.A Davis

Interesting Bob. I have often thought about how I could rig up something to test distributors but could never quite figure out the full details.

I tried contacting the Distributor Doctor on a few occasions for parts and to test/calibrate the advance on a distributor, but sadly it was more a case of the Does-not-respond Doctor.

You seem to know your onions, would you be interested in testing/calibrating a spare I have? Feel free to say no if it is too much faff.

Cheers,
Malcolm
Malcolm Le Chevalier

To spin the starter from the engine bay is easy and no tools needed

put car in N.

if you want to start the car. Put the key in the hole and turn to on

if you dont want to start car and just spin the starter DONT put key into ignition hole

make a 24 gauge jumper wire 12 inches long with a female electrical connector on one end and bare wire on the other end

dis connect the red/white wire (signal wire) from the side of the selinoid connect the jumper wire to that connection

flash the other end of the jumper wire agianst the battery cable on the selinoid.

and watch the engine spin

prop
prop

Malc wrote

(((As I do not have a strobe, and am an electronic ignoramus to boot, I rely on my ears and how the engine performs)))

Malc... NO malc NO !

This is not setting the timming... all this is for is to get the dissy into a basic setting to safely start the engine after an engine rebuild or if had to removethe dissy out of the block without setting alinment marks

you still have to hook up a strob light to properly set the timming

and NO you can not hear 10 degrees at 1000 rpms its not humanly possiable...if you can then id just look at the timming marks and blink real fast and time it that way

you need a timming gun... simple as that... there not expensive ebay a used one for $5 and new cheapo guns on ebay are around $12 and can go to several thousand dollars

bottom line if your not using a timming gun then pull the engine and get a lone at a pawn shop take the cash to a riverboat and play black jack or roulette and win enough money to buy a brand new engine installed


there is no differance between what im saying and your doing ...its a huge gamble ither way thats really expensive

agian the way your setting timming will just start the car safely... its not supposed to he run on the street like that

prop
prop

Hmm, I wonder how they did it before strobes became available for DIY.
Guyw

Guyw

My father’s method was similar to Oggers, ie get it running then just adjust the distributor for fastest/smoothest running, if it pinked under load back it off a bit.

Malcolm

See image

As you can see it’s relatively simple, you can see the pointer on the scale below the distributor. Once switched on I can adjust the speed with knob on the RH side and read the RPM on the tacho (ex rubber bumper B). It’s then just a case of pointing the timing light at the pointer, rotating the distributor to get the pointer on a convenient part of the scale, then raising the RPM and reading the advance of the scale. It’s not a very large scale and you need to multiply the reading by 2 but even so I can measure the advance to within 1 or 2 degrees.

As I mentioned I can also measure vacuum advance and although my vacuum gauge isn't calibrated it gives a good indication. I can also measure dwell but to get an accurate reading is a bit of a faff, alternately I do have a meter which should give a reasonable indication.

You can just see one of the plugs to the right of the distributor, the other 3 are behind it.

I don’t mind testing and calibrating distributors and I believe they should be reasonably accurate but I can’t certify them as my jig isn't calibrated.

Bob


R.A Davis

I said nothing of the sort Prop, I use a timing gun, don't you worry! :-) Wifey helped, five min job once I had her.

Bob, what's your email? or give me a shout on malcolmlechevalier at gmail.com. It's a great looking rig you have!

Cheers,
Malcolm
Malcolm Le Chevalier

Bob

I am a little doubtful, though in your case full of admiration, for folks who often go to some lengths to get the timing "right". For sure, one can measure the advance very accurately indeed by using either your method or a strobe, but surely the question is what is the correct advance setting to be? Ignition timing is but one piece of the tuning jigsaw, the other pieces being valve timing, any head mods, exhaust mods, mix, coil, fuel, plugs, leads etc etc. All of these can lead to a wide variation in what the optimal advance should be.

For a standard engine with a recommended advance one can eliminate any possible errors - as one should do before setting ignition timing - but there must remain a degree of variability nevertheless - within the distributor itself even, wear in the mechanism as you say - all of which may also affect the point at which advance should be set to in order to achieve optimal performance.

Hence the need to revert to how the engine actually performs rather than ensuring the advance is spot on to any recommended setting. By adjusting the timing according to engine performance, you are essentially taking into account of all variables and errors. It is why I do not set too much store by any recommended advance, using a strobe or similar to set it up, and prefer to set the advance as described. I guess I must also add that as my engine is fairly heavily modified, I have no clue at all as to what the advance ought to be in any event!
Oggers

Oggers

I'm in complete agreement with you. I have the advantage that my engines, except for a few minor changes are stock and the only reason I go to the trouble of setting the distributors up like this is to eliminate one of the variables.

I appreciate fuels are different to what would have been available when these engines were first produced and over the years who knows what cam, head, needles excreta have been fitted to these engines. I try to base my approach on an holistic principle in that every single part has its role to play. By setting the distributor to the factory original setting it may not be an ideal setting but it does give a known starting point. In an ideal world I’d put the car on a dyno and fine tune everything, but I don’t have that luxury.

My background is all about measurement and adjustment, what I’d like to do is fit a wide band O2 sensor and have an electronic distributor that I could easily adjust preferably while driving. You can buy all these things readymade but where’s the fun in that. I've made a couple of electronic ignition systems over the years and I even fitted an O2 sensor to my Midget, unfortunately I tried to use a narrow band sensor.

I'm now looking at an Arduino based ignition system but that’ll be a winter project.

Bob
R.A Davis


Vacuum gauge anyone?

http://automotivemileposts.com/garage/v2n8.html
Gavin Rowlesx

Bob

I guess my point was that one can go to an awful lot of time, trouble, effort and cost to correctly measure distributor performance to obtain minimal deviation from recommended advance, only to see all that good work not fully replicated in the resultant performance of the engine - especially if that engine is highly modified.

Yes indeed, the more standard the engine the more likely the work will pay off - other things being equal - but it would be interesting to see how the optimal advance changes from factory fresh standard car to 40 year old standard car, and what effect - in terms of +/- degrees from recommended various modifications have.
Oggers

Vacuum gauges are brilliant! I am going to integrate one into my new dash (when I get round to it).

Car back together but running pretty badly. Possible causes, 1. I put in colder plugs and they are fouling, 2. Timing not right, 3. My low compression reading from the other week was something more sinister.

Are these projects ever finished?!

Malc.
Malcolm Le Chevalier

But... a word of caution about vac. gauges for setting idle advance is that at idle an engine tends to like quite a lot of advance, often more than the 10 degs or so specified. Just using the vac. advance to guide you might lead to way too much advance at higher revs.
Malcolm Le Chevalier

Malcolm

The internal distributor weights and vacuum advance take care of the need to further advance the ignition at higher speeds. With simple mechanical distributors this is more or less a linear function of the engine speed and thus may or may not be spot-on correct for the engine at some point in the rev range, though it is usually adequate for standard engines. The beauty of Lumenition - and other similar ignition systems are available - is they allow you to select a variety of advance curves, thus increasing the chances of achieving optimum advance throughout the rev range. This is particularly useful for modified engines.

Recommended advance for standard engine at idle - well actually 1000 rpm for mine - 73 RWA - with vac advance unplugged is IIRC 16 deg BTDC @1,000 rpm. Clearly you would be wise to rev the engine to say 4/5,000 rpm and note what advance you are seeing - you should see 28-32 deg - which is a function of the distributor weights as aforementioned.

As for your problems, why not try the method I described. Simple to effect, simple to return to prior setting if it fails.

Oggers

RE: my waffle at 13:01, I meant vac. gauge not vac. advance. Also, it doesn't matter what method you use, vacuum gauge or "listening", engines like more advance at idle, so it is likely you will end up with too much idle advance that will then mean you have too much advance at all speeds above that. Too much advance at higher speed can cause damage to your engine.

I have no doubt that it could be set this way, but I don't and wouldn't, I spent the few quid and got a timing gun. I believe you can get fancy guns that allow you to advance/retard the "flash" to check advance at higher RPM, but I don't. The best I can do is set it to 10 deg BTDC as per the book. Done.

I understand how the mechanical and vacuum advance works and I have no reason to think there is anything fundamentally wrong with my engine/dizzy/timing/whatever as things were fine a couple of weeks back. The rough running now is probably just that I have missed something simple.

But that said the current dizzy is a bit tired, so I was going to (am doing) rebuild a spare and was interested in Bob being able to OK the calibration of it as I don't know what might have been done to it in the past (likewise with my current dizzy).

The static timing of the electronic ignition module question is moot now. I was just curious if I could find a way to set the timing myself. As it turned out, what I thought was about right was actually miles off. In the end I just got my helper to spin the starter for me. It took less than five mins to set.

Cheers,
Malc.
Malcolm Le Chevalier

Malc

Not sure where you get the idea that engines like more advance at idle. They simply don't. They like more advance at higher revs. If you set the advance correctly as per recommended at idle, chances are, and if your distributor works correctly, you should be OK at the higher rev range. If however you believe your dizzy is "tired" it is well worth checking out the advance at that higher rev range and assessing whether it is anywhere near the recommended settings.

As the engine generally operates at a far higher rev range than idle, ensuring optimal advance at these higher revs is crucial.


Oggers

This thread was discussed between 28/06/2016 and 29/06/2016

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