Dear Rod,
the graphs are from a v12 HE engine, for what it’s worth. You can generate these from any datalog you take. I always run with the laptop connected and datalogging. It serves as a second (digital) dashboard, showing air:fuel ratios in the four downpipes, the EGTs on each exhaust port, the water flow rate through the thermostats vs the bypasses, the pre and post radiator temperatures, rpm, speed, mpg, you name it - it’s there! You can look at this in real-time or afterwards, tune in real time or afterwards.
Importantly for everyone else, an engine is still just an engine, whether it is fueled by carburettors or injection, so much of this data can be applied back to the standard cars to understand them better and debunk myths so often quoted. I posted those graphs because the early v12s had a vacuum retard factory fitted to their distributors and many users have reported the vast improvement of replacing it with an advance capsule, but then arguing about whether ported vacuum or full manifold vacuum is better, without being able to quantify why. This way, you can see how much vacuum is being applied and when in each case. Ported always, by definition, applies less or equal vacuum than full manifold vacuum, but the cut-in from no vacuum to some vacuum is clearly sharper. (Not plotted is another variable, the rate of change of vacuum advance.)
Another interesting area of study is how to start a car. It’s already datalogging how fast the crank is turning on the starter, when the fuel is injected and how well the car starts at different temperatures. From that, I’d deduce most starting problems are getting the right amount of fuel into the cylinders, as most injected cars start right on the button, whilst our carburettored cousins crank away and then start muttering about fuel pumps, or maybe lack of spark, or jet height… In my case, I run a dual fuel lpg and petrol setup, so I can even learn a bit about fuel atomisation at low temperatures - it starts fantastically well on lpg at low temperatures, better than on petrol. Doing the maths, sometimes it is on the third cylinder to be sparked - that’s just just half a crank rotation and the revs have taken off. It’s all in the datalogs and without them, you’ll always be needing to ask someone else what the answer is.
kind regards
Marek
EDIT: compare that to the limited experimentation available without a datalogging feature - see Vacuum Regulator Advance Experimenting