They are! I am equally confused by that. I just refitted the Bosch to map the curve I had pre 123 and experimented while I was at it. Symptoms were like 25-30 advance!
I've done something that I should have done earlier snd mapped my actual distributor mechanical advance. Compared to the average from the advance graph above for my distributor, my advance starts 1000rpm earlier at 1050, it's 4 degs more advanced at 1500, 1.5 degs more at 2400 and ends 1 degs sooner because I bent the max stops. I put it back because messing with jetting and curves is the way to madness.
I don't think the engine is really worth the effort of changing and I do enjoy the endless complexity of the carbs.
Always found it odd that, given how many injected type 1s there are in Mexico and elsewhere, there aren’t any bits - throttle bodies, manifolds, etc - around in Europe. That would probably be a quick conversion.
So many must be scrapped awaiting plunder. You could do steady business with a container load to refurb.
I have actually got a CIS K jet FI setup almost ready to go with the plenum that bolts on over the fuel pump area. What puts me off is the massive heavy injector control valve and air flap assembly .. fitting it in the engine bay will need some solid metalwork. It all came off a T1 Beetle but the throttle body and CIS bits are off a Golf ..
So, thinking about the stock curves and how they would have been arrived at with the limitations of two springs... What you get from the mechanical centrifugal advance is two staight lines. What you really want is the curve that those lines are doing their best to represent. So going on the theory that what looks right often is and vica versa, I've made a more curved one. And as a nod to controversy I've reduced the timing once it's over the cam as I read this can be successful. I'll fine tune that if it works.
Many aftermarket ECUs have a baseline cranking advance of 12 degs pre programmed as this suits the majority of engines they tend to be used on (Zetec, Pinto X flow A series etc.) Most have the ability to redefine it and flash it to memory if it's an arse to start (lack of choke, high CR, hot temp or whatever). No experience of the 123 Tune but I'm guessing you'd set it with the crank position at 0 TDC no.1 firing as a reference and map it from there, ignoring anything below 500rpm. Easiest way to verify would be to run it at idle with a known good tach attached and a timing light (assuming you have a degree wheel) or guestimate if not, based on the static timing marks on the stock pulley. In theory it should work however you install it but the map would look different relative to what you're actually seeing. The dizzy doesn't know where TDC is unless you tell it, but you know this already the other consideration is if you're using ported or full manifold vac and what that actual value is. Plenty of maps for full manifold signal stick a big glob of advance in a max vac low RPM for starting, but then they often have an additional input for air temperature (megaquirt, emerald etc) so there's even more variables to play with (aka make a mess of!)
Yep, it's not like a map with real numbers, it's a simple advance curve. The instructions and videos are clear, set to timing mark, not TDC. The versions of the 123 where you choose maps are the same, if you static time them at 0 degs they don't work. Though you can set it at TDC and draw the curve accordingly and it does work, it's fighting the starter and will barely turn over.
sounds like they've pegged the cranking advance then, if it's kicking back when set at TDC. When they brought the vac version of the Tune out I asked one of the tech bods at 123 how the vac software deals with the actual signal received to see whether it can be rejigged to work with ported vac Dells/IDFs and I didn't understand a word of it
Back to this I had a quick run with the smoothed out curve. Then remembering the bosch went ok from 4 or 5 degrees I retarded the whole curve 3 degrees apart from idle. This is why I wanted one, this is impossible with a mechanical distributor. Max advance is only 26 degrees but it seems as good as ever so I'll do another curve retarded another 2 degrees and see what happens. 24 max. You just can't make a mechanical one do a 3 to 24 curve but tickover at 8. It's a big advantage being able to keep the idle timing while messing with anything above.
Yes , you would only get advance if you werent pumping the throttle frantically without a choke as you crank..
