[Martinjlm]

Originally Posted by bishopts

Fuel burning is the core of it all. 14.7 parts air 1 part fuel is total an efficient burn.
Inject fuel into a chamber of air at this ratio, let it mix then ignite it and the only thing left will be hydrocarbons and carbon monoxide. Move the same concept into an engine, then you have time working against you. You have less time for the air and fuel to mix as the piston is moving faster with every increasing rpm. So then you need to adjust when the fuel is injected and when the spark is ignited to start the burn. And also how long can it burn before the the piston hits the bottom of its travel

LS1 had 24x crank signal to keep track of where in the rotation of the crank was. And port injection that needed to account for travel time of fuel being sprayed through an opening valve. LS2 had a more accurate count to base all needed timing off of since it went to 58x crank count. Still sloppy with is port injection but better. LS3 was a bigger more refined version of the same things as far as efficiency was considered. Still 58x crank. LT1 brought in direct injection. The efficiency benefits of that is now you don't need to worry about how long and when the intake valve is open because the fuel is spraying directly into the cylinder at the most precise time it can be. Also the risk of pre ignited fuel from compression was reduced so higher compression ratios are allowed. And also fuel pressure is significantly higher which reduced the time it takes for the fuel to mix with the air.
So LT1 vs LS1 is no comparison in efficiency.
But LT1 vs LS6 gen6 is going to be an odd one. Since the LS6 has port injection on top of direct injection i can't see it being any better than the LT1 and at best it would be as good in that area. But if they do something like make the crank count 360x, then they can control everything on a much more accurate level. Which would replace rotation predicted algorithms with actual signal references.
I'm interested to see how it all works out.

Great points!

Part of the reason for adding port injection is that direct injection at start up generates a lot of hydro-carbons and NOx. Port is less susceptible to NOx. So starting the drive cycle with port injection at low speeds then bringing in DI at higher speeds provides better emissions control.