pre-programmed curves on 123 ignition - help please?

[malcolm]

Yes, stops at 29 at 3600

Ran it up to 4500 and timing stayed at 29/30

[Tom W]

Interesting. So from your tests with curve 0, your distributor has a maximum inbuilt advance beyond idle of 19-20 degrees measured at the crankshaft.

The instructions show it should have either 22 degrees, or 24 degrees inbuilt advance, depending on which version of the instructions you believe.

So either the instructions we’ve found aren’t for the exact version of the distributor you have, or the 123 doesn’t do what it says in the instructions, or there’s some other error we’ve not spotted.

The logic of the instructions suggest that curves 1-3 should get some of the extra intermediate advance you’re looking for but it would also reach maximum advance before 3600rpm.

I expect the only way to know for sure is to mount the distributor on a Sun machine or similar, and find out what it’s actually doing.

[mgcjag]

Hi Malcom....you have your static set at 10btdc...but how have you set this.....have you actually checked and set your tdc first and adjusted the pointer....Steve

[malcolm]

Hi Steve. I didn't set the distributor up. However, I have previously checked the pointer against TDC using a TDC tool and it is spot on TDC when the pointer is against the white markers. There is a separate 10btdc white mark. My advance Strobe shows at tickover the white mark of 10btdc exactly on the pointer, and when I advance the strobe to 10 the separate marks for tdc line up.
Tom, I suspect the 123 simply doesn't follow the curves laid out in the tables! SNG run an E (4.2) on this dizzie and say that 4 or 5 gives the best result. 5 should give max advance at 3000rpm.
I think I'm just going to have to map every curve on the drive using my strobe, choose one nearest the norm, and try it.
Anyone interested in seeing the curves?

[Tom W]

Yes please, I’d be interested in seeing what the curves are.

Steve, the position of the pointer won’t give an error when measuring the total advance applied by the distributor. The same error would exist at idle and at maximum advance, so any error is cancelled out.

[mgcjag]

You need to know the starting point....is the 123 actually set so that its setting led come on a 10btdc....Steve

[Tom W]

The LED is irrelevant once you’ve got the car to run. It’s only really a marker to set the distributor to when you first fit it, as you can’t set the static advance in the conventional manner.

It’s good practice to check what the timing actually is after fitting, and adjust as necessary by rotating the distributor.

If Malcolm is measuring 10 degrees at idle, then that’s what he’s actually getting relative to the crankshaft pointer, and relative to TDC, assuming the pointer is accurate.

[mgcjag]

Hi Tom...The 123 needs a referance point......from this point it will give its degrees of advance as per its spec(if the spec is correct )....Thats why you need to sync it on set up to 10 btdc..........if you were to sync it to tdc you would be 10 deg out on all readings.......If you going to give a list of advance/123 setting number then its only of value to anyone if they set their 123 to the same initial setting (10btdc)........Steve

[Tom W]

True, but it depends how you quote the curves. The different 123 manuals do it different ways, confusingly.

It’s either: “With the LED set to X degrees, crankshaft advance is Y degrees at Z rpm.

Or it’s: At X rpm, the advance is Y degrees beyond idle, at the crankshaft.

The latter is closer to what the workshop manual does, the difference being the workshop manual quotes figures in distributor degrees and speed, not crankshaft.

What Malcom’s going to be able to measure are the absolute figures relative to the pointer on his car. From there we will know the amount of mechanical advance within the distributor for any given curve, which is what’s important, and is where the 123 manual doesn’t agree with what the product’s actually doing. I would caution anyone fitting one of the preprogrammed 123s against just setting it by the LED, and trusting that the timing from there is correct. At the very least, idle timing should be checked with a strobe, and ideally maximum advance. Though that does require an advance timing light, or more timing marks. This way you remove any error that might exist between when the LED illuminates, and when the spark triggers. This error could easily come from just the fitting process, for example if all the backlash weren’t taken out of the gears when fitting the 123.

I look forward to seeing what the figures actually are.

[malcolm]

A further annoyance for me I've discovered is that there is no cap over the window where you access the switch for the curves - it's open to the elements. Think the supplier to the mechanic I used sold us a second! I've ordered a new cap from Holland which may "take a while" they tell me. Also, the way the dizzie is positioned, you really can't access the switch. I believe you can reposition the dizzie to make things more convenient then do the re-setting with the LED etc.
I'll wait for the cap to arrive, try the re-positioning, then do the curve measuring
So it may be a while Tom!

[Tom W]

That’s not ideal. The cap on mine is an allen head plug. I guess in the interim, any short section of bolt of the correct thread, or even some tape over the hole will suffice.

You should be able to rotate the distributor 180 degrees so the access hole is facing outwards. It’s still awkward to get to, but it’s possible to change curves with it on the car. At least on my car with the Webers it is. SUs with the standard airbox might restrict access a bit.

I wonder if your distributor was timed on cylinder 6 instead of cylinder one? Basically, you’ll rotate the distributor body 180 degrees, and then move all the leads round 180 degrees, so the firing order is still correct, and then accurately reset the timing from there.

[malcolm]

Yeah, thanks Tom. I'm thinking of a 180 degree rotation. It will leave the window facing forward towards the offside front wheel where at least I can get to it. I was thinking a bit of duct tape while I wait for the proper plug to arrive.

[malcolm]

Haven't forgotten my promise to map each of the standard curves for info. I've only just had the chance to re-orientate the distributor today! Fitted the new plug over the adjusting window after setting on curve 2.
Car definitely had a bit more urgency at lower revs, but only got as far as mapping the curve to 3600 rpm before the heavens opened, and I have to do this on the drive!
I will get round to mapping them all when we get some decent weather again.
One thing I've noticed already - none of the curves are anything like the curve that Jaguar developed. Curve 2 gives 34 total advance (10 static and 24 advance) at 3600 rpm, more than the max for the E 4.2, yet the early advance figures are still behind the Jaguar curve. The engine showed no sign of pinking despite the 34 degrees max, tested on a long run, so I've left it on number 2.
The other thing is that the curves aren't as suggested in the 123 instructions! Curve 2 according to the bopok should give 34 max advance at 3000rpm; 34 came in at 3600.
And yes, my rev counter is spot on!
I'd have thought that as this is supposedly the jaguar specific 123, they could have got one of the curves the same as Jag specified.
Still, it does start, run and tickover well, so I suppose I shouldn't worry!

[Tom W]

It’s a bit disappointing that none of them match the factory curve. More worrying, if it doesn’t do what it says it’s supposed to do. I wonder if they all show the same variance to the instructions, or whether it’s different from one 123 to the next.

[malcolm]

I wondered about that Tom. Next week is looking bright, so I'll get all my mapping done and send it to you. Mind you, still hellish difficult to get to the little arrow, despite now being in the best possible position.Think I need a trained hamster that can hold a tiny screwdriver to switch curves!

[mgcjag]

Hi Malcom.....just letting you know im watching with interest.....Steve

[malcolm]

Ok Steve - I'll put the maps on the thread as well.

[malcolm]

So, I've now managed to plot the curves.

In the end, I didn't do all 16 curves, for two reasons:

1) It's still a sod getting at the marker on the dizzie to adjust curves, guessing which curve you're getting to and then checking with a phone camera, but main reason was -

2) The total advance was getting silly. I didn't want to damage anything, although I guess with the engine not being under load it wouldn't do any harm?

The photo below shows the curves in table format. The very top line is RPM, the next E type recommended figures.




You can see that none of the curves are really even close to the correct numbers. Also, curves 4 and 5 should only reach a max of 36 but go to 38, and curve 7 is at 41 rather than the 38 the instructions say.

Some of the numbers may be 1 degree out or so with me wriggling around on the drive under the car and relying on 'er indoors to get the revs right, but the picture is clear.

I stopped at curve 7 as the manual shows that higher curves simply reach even higher max figures, so couldn't see the point.

Just as noteworthy is the fact that none of the curves advance as steeply as the Jag figures.

Bit disappointing really when this is the dedicated Jag 123 dizzie.

I contacted 123ignition.nl and asked if they could send me the curves for all the settings, and they said they didn't have them - bit hard to believe?

I've left it on curve 2. 34 max advance is a bit much, but I get no pinking, and early pick up is a bit better than on curve 0.

On the plus side, it starts, ticks over and runs very well.

[mgcjag]

Thanks for posting Malcolm.......Steve

[Tom W]

Thanks Malcolm.

So it doesn’t seem to match the instructions I found for the 123 Jag. Disappointing if it doesn’t do what it says it should, and also disappointing that none of it matches what the factory says the curve should be. With 16 to pick from, you’d hope one or 2 suited the E-type.

It’s very surprising the manufacturer doesn’t have any spec for what they make.

I shall have to buy a better timing light, or add some more timing marks to my crank damper, and see what the maximum I actually have is. As you found, my car runs fine and doesn’t pink with the 123. Also in its favour, 123 has been completely reliable since I’ve owned the car.