Custom ignition advance curve

[Tom W]

Has anyone tried a different ignition advance curve on the 2200TC? The factory curve from the workshop manual has a lot less advance at lower rpm than the 2000TC curve for the 9:1 compression ratio. The workshop manual also only lists one curve for all variants of 2200, whereas there are unique curves for all the compression ratio and carb options on the 2 litre. The parts book does give different part numbers for TC and SC advance springs, distributor cam and weights though, so there’s some inconsistency there.

I wonder if the 2200TC was held back to give a performance advantage on the V8? I’m also wondering whether adding more advance lower down without increasing the total advance would be beneficial.

 

[sdibbers]

I borrowed a friend’s 123ignition dissy for my car a while back. Started with the curve I’d created for our race mini, worked great straight away. No pinking, no over heating. I was loath to give it back. I’m running a 2200TC with a 2000TC and a fast road cam reprofile from Piper for reference.

 

[Tom W]

That looks like what I was thinking. Those programmable 123s are great, but they’re not cheap. In the meantime, I have a bag of assorted distributor springs to try modifying the curve.

 

[sdibbers]

Those programmable 123s are great, but they’re not cheap.

That was my thought! It really helped get more poke out of the mini. I think I’ll end up with one at some point, or send mine to advanced distributors here in the states to get a custom curve.

Although I like that you can have a non-linear curve on a 123, I think it’s up to 6 points on that curve, with a traditional dissy advance it’s only two.

 

[Tom W]

I have the programmable one on my Jag. It’s far more flexible than recurving a conventional dizzy, and second only to a full 3d ECU controlled ignition map. You can draw curves with a more complicated shape than just straight lines with a kink, including curves that drop as well as just climb or stay flat. The dashboard on the app serves as a useful tuning tool too. If you have access to a dyno you can tune the advance for maximum measured torque at any rpm by swinging the timing in the app in real time.

I had the switchable 16 pre-programmed curve one before. It was reliable, but none of the curves were quite right for what I needed, so it was a bit compromised.

 

[Tom W]

I’ve had a look into my distributor and the existing springs weren’t in great condition. The secondary spring was stretched so even at maximum advance it wasn’t doing anything. The primary spring was a bit distorted too. I have a selection of assorted distributor springs, so I’ve replaced them with something new, as close to the originals as I had. The new primary spring is a bit lighter, so there should be a bit more advance lower down and the secondary spring now does something, so the curve should have a more pronounced inflection point. On a quick test drive the car feels more lively than it used to, and there’s no discernible pinking.