This article has a graph from a lab test:

https://knowledgeiswatt.substack.com/p/20-120-vs-90-gh-of-ca...

I thought it would help illustrate what you're saying but, gosh, those Y axes aren't making things easy to interpret. For those willing to do the mental arithmetic, 1g of FAT is 9 kcal and 1g of CHO is 4 kcal. :)

P.S. It also only starts at 150W.