"123" Programmable electronic ignition

[Volvo Canadian]

Hi. I can't tell you anything about your spark plugs, but that doesn't sound too bad, only your gas mileage does (right?).

I was going to post some new pics on here, but thought the better of it, and will post where I originally put up a few. I got a couple of days off, and manage to drive the car for the first time....

Looking-forward to getting the 123 on soon, and a few hours at the dyno.

[tsetse1986]

Originally Posted by asneddon

I did a little experiment in the weekend.

First, background on why Im not confident in my timing torch. Its a cheap one from Helfords (cant remember the price, but under 100), and it has a dial on the back so you can adjust the strobe. In theory this makes life easier as I just put a dab of whiteout on the TDC mark on the front pulley, then I adjust the dial on the torch so that the timing mark on the cam cover is pointing at this TDC mark. I can then read off the dial what the timing is. Well, the feel of this dial just doesnt fill me with confidence. You can wind it way past zero backwards, and there are no notches or anything to give me the feeling its a digital dial rather than an analoge one.

So this weekend I did two things.
Built a 'step' curve (ie, right angle jumps, not curved) for the 123. so 0d at 0 to 1000rpm, then 10 to 1500, then 20 to 2000, 25 to 2500rpm. No vacuume for anything

I then used my torch and reved the car and adjusted the dial to make sure it jumped in the steps I expected. This actually worked really well, and I got the 10, 10, 5 degree jumps I expected.

Next was to make sure the zero was correct. This is set by having the engine at TDC on number 1 and disconnecting the neg from the coil. You just turn the 123 clockwise until a little LED just comes on. Pretty easy.

Since my normal curve has 10degrees at idle, that means the total idle advance should be 10 degrees. Both my torch and a borrowed one (VERY old and dodgy looking) agreed within 2 degrees. I then loaded a curve with 5degees at idle, and tested again. Same thing.

so, timing is where I expect it to be, and I can probably trust my torch now.

I have put new plugs in, and replaced all the HT leads (with fancy spiral core 8mm ones). I'll check them again next time I get a chance and see if its fixed itself.

What does the colouration of my spark plugs mean though? Its like its running a little rich at the base of the plug, and a bit lean at the top. Is this to do with the heat range of the plugs? I'm using NGK BP6HS plugs with gap at .028

I've been reading this:
http://www.4secondsflat.com/Spark_plug_reading.html
and it seems to suggest I'm not far off, I've jsut never seen the distinct colour change up the earth leg before.

This thread is getting quite old, so you probably have things sorted by now. If not, hope this helps...

Your plug looks on the rich side of OK, but don't forget it's the position of the SU needle in its jet at the RPM / throttle position you were using for the couple of minutes before the plug was 'read' that you are looking at. If the engine was idling for any length of time before it was turned off, then you are looking at the idle mixture. If you cut the engine immediately after a foot to the floor run up a long hill at 5000 RPM the plug colour will reflect mixture strength produced by the narrow part of the SU needle. This is the basis of the classic 'road test' method of calibrating SU needles.

Fluctuating idle can be due to wandering ignition timing - hopefully not in this case - and air leaks around carb flanges / spindles and inlet manifold.

Poor MPG means either the mixture is set too rich or the engine is set up so the throttle has to be opened more to get the power needed. The latter can be caused by ignition advance being too retarded. The general rule seems to be use the most advance you can at all times to get best power / economy but not so much that you get preignition / detonation. That is why vacuum advance is important for maximising fuel economy under part-throttle (cruising) conditions where cylinders are only part filled and the rate at which the mixture burns is slower - it needs firing up sooner.

Des Hammill's book on tuning dizzy based ignition systems gives loads of good info on how advance curves work and gives rules of thumb to help 'curve' your dizzy.

I have just bought myself a 123Tune for my Amazon rebuild. I hope to get it on the road by Christmas, but there is lots of welding & rebuilding to be done first! Can anyone help by providing a set of advance curves to get me going? My engine specs are: B20 2l bored +30 thou, K cam, twin 1 3/4 SUs, cast 4 into 2 ex manifold with Simons sport exhaust. Any help would be appreciated.

All the Best,
Tim

[Volvo Canadian]

Hi Tim,

Good to know somebody else who has a 123Tune. By the end of August I will have mine all figured-out, so although we are not running exactly the same mill, I'll get back to you on that. Everything I've read suggests someone with a little bit of grey-matter can come-up with a workable curve that will work as a starting point, but we will see, I guess!

I've only got about a week, but I'm hoping to dyno test mine. I'm curious at to what difference it will make as compared to a standard curve.

(don't forget to upgrade your ignition wires if you haven't already.)

Jim

[tsetse1986]

Hi Jim,

Thanks for your reply. Tony Barrett has promised to send me some B20 ignition curve data to get me started. You are welcome to see this if it will be any use.

My Amazon is some way off being on the road. Took it round to my welder mate to get the rear arches sorted and found lots of cunningly painted glass fibre and a piece of roofing lead moulded to form the spare wheel well. I am no virgin when it comes to rusty cars but this one had me fooled! All said & done, it will make an expensive restoration but a good spares car.

Meanwhile, I had heard of a 123 GT that was mounded up in a garage locally. Went to see it and could just make out an Amazon shape under the piles of crap that had accumulated over its 25 year layup. It will be a major operation to excavate it but I could just get round it for a look-see. A bit gouty around the rear wheel arches & the spare wheel well is non existent but it has not been previously bodged like my old one so actually looks to be a better prospect! A deposit changed hands and I should collect it soon. Now I have to find someone to buy my Riley 1.5 to fund the project!

So, on to plan B - restore the 123GT and fit my rebuilt B20 engine and overdrive gearbox.

Cheers,
Tim

[222s]

Originally Posted by tsetse1986

Now I have to find someone to buy my Riley 1.5 to fund the project!

BMC B Series, or Riley twin cam hemi?

[tsetse1986]

Originally Posted by 222s

BMC B Series, or Riley twin cam hemi?

B series, but just had a nut'n'bolt restoration, rebored/rebuilt engine, rebuilt gearbox, vented discs, tubular shocks, lcb manifold/SS exhaust.

[Volvo Canadian]

Hi - sorry I haven't been on here much, but this seems worth sharing.

I was rooting around in my tool chest the other day, and found a vacuum pressure guage, so decided to hook it up, as I've still not really figured out the vacuum advance, even though I drove it across the country twice.... Oh-well.

I've been a bit unhappy with the performance, it idles rough, it slow to respond off the line and valves are noisy. I thought maybe the valves needed adjusting, but am pretty sure the carbs were right.

Well, when I hooked up the guage, I found pretty-near zero vacuum at idle, increasing with throttle. Looking around on the web (and previous posts) the standard vacuum seems to be the opposite!! Reason-being, it depends on where the vacuum pick-up is, and on my manifold, it is in front of the throttle/butterfly valve, not behind it, as is the case for most american junk, if not european. Sooo I looked a bit more on the net and confirmed SU's are different.

I played-around with the settings for a couple of hours. As I was able to adjst the timing on the fly, I found that going from zero to fifteen degrees advance at idle, the rpm went from just over 800 to just under 1100rpm. Wow! This was definitely doing something! I backed-off the carbs, and and finally settled on the following:

Vacuum adv. at idle of 13 degrees (on top of 8 degrees static), staying flat until the pressure is down 20%, then rapidly dropping the advance down to zero when the pressure (with no vacuum it is atmospheric pressure) drops by 25%. There are all kinds of units used, so let's just go with percentages.

FYI, the rationale for advancing the spark at idle is that the mixture is lean, causing it to burning more slowly. One site (for performance cars) suggested 15 degrees, which I tried, but it seemed to run better with a little less. My engine is not stock - bored 30 thou over, shaved head, larger exhaust valves, ported and header.

Centrifugal advance I had set to increase gradually at 1000rpm, up to a max of 21 + 8 degrees static to 29 degrees. Testing on a dyno might cause me to change my mind, but with no load, it seemed to hesitate, and I found it ran better with the advance kicking in at 1100rpm, going up to 30 degrees (total) by 3500rpm, maxing-out at 32 degrees at a hypothetical 8000rpm.... I believe the factory setting would be reaching the max of 36 at 3000rpm, so a considerable difference.

Overall, the car starts better, runs quieter at idle, burns cleaner at idle, accelerates better at the bottom, and has a little more zip. I believe I had a curve in there for the advance which was the exact opposite for awhile, but changed it to flat (zero), because it was not running well, and I didn't know what else to do.

I have some good gas-mileage figures, and plan to make a similar cruise soon, to see what difference, if any. It may be the more significant improvement is in the city, waiting for lights, etc....

I hope that helps, and am open to more suggestions!