Mapping ignition timing on "alternate" load axes like VE

I've been chatting with some folks in another forum about tuning based on less common load inputs, and the topic of using the best available indicator of air entering the engine for the purposes of tuning ignition timing came up. It seems it's common on Bosch Motorsport ECUs to RL/VE as the load axis for ignition timing on that platform. The explanation for doing so sounds to be well grounded in reality, but this doesn't seem like a common (or at least commonly discussed) strategy.

The basis here is that the best available indicator of cylinder pressure is an ideal candidate for scaling ignition timing. When tuning a given engine, this is (theoretically at least) linear at a given VE level. By proxy, an engine could be tuned this way in one configuration and boost (or more boost) could be added...only requiring more load sites to account for the enhanced efficiency. Granted, the same could more or less be said of MAP...to an extent.

It appears that Haltech supports using VE as the primary axis for the timing table. Is anyone familiar with this strategy on ECUs that support it? The theory above seems to pass a general sniff test, and it seems like a sound foundation for rationally tuning timing.

Anyone see major holes with doing this?

The calculated air mass determined by the engine efficiency would have to be well calibrated and accurate before you switch the axis on the ignition timing table, otherwise you would be constantly chasing a moving target trying to tune both at the same time

True, given that doing this effectively ties ignition timing to the fueling map...the former definitely needs to be 100%. I'm generally striving for ~3% accuracy in my fuel map, but compensations may not always be accurate enough to support that. 😅 I'm not sure if Haltech applies long/short term trims to the VE figure but, if it doesn't of things drift, that could mess things up too.