tapeman
"If the power delivered to the wheels is out of sync for a moment, I would imagine it could be catastrophic" The control software is probably updating every 3-15 milliseconds, so even if the software had a massive hiccup, it would have to last for multiple frames for it to actually get translated to the pavement. The drivetrains of cars are actually pretty mushy. Everything's mounted on bushings, there's backlash in the gears, and tires are rubber. All of this adds together to buffer out any kind of spikes. Much like a capacitor and resistor can be used to buffer electricity. So if, say, the front wheel was 5% underpowered for a frame, then all that would happen is the gears in the front differential would go slack for a few milliseconds. If on the next frame, the power was corrected, the differential would go back to being taut. If it was just 5% underpowered, you likely wouldn't even feel this. If the front motor totally locked up for one frame, you'd still probably only feel a little jitter.
Higher compression ratio = better combustion = more power with less fuel, regardless of turbo.
Higher compression will always mean better fuel efficiency. My moms Mazda CX-5 runs a 13.5 compression ratio and gets 27mpg. The power/efficiency trade off appears when you're talking about turbocharged engines.
Turbos compress air into the combustion chamber, so when you compress compressed air, you get exponentially compressed air. If you don't adjust the compression ratio for the turbo, you're going to get knock. An engine with a 13.5 compression ratio can run perfectly fine on regular gas, but an engine that runs the same ratio and 20 psi of boost with melt itself even on premium gas.
This is a problem for any kind of work vehicle. They almost always have turbos to give them the power to haul their loads with reasonable ease. But this forces the engineers to design the engine with a lower compression ratio, which means at light engine loads, when the turbo isn't doing anything, the engine isn't fulfilling its full potential. It's still compressing air at a low ratio, even though it's not taking in already compressed air. This is where Nissans innovation comes in. The compression ratio will change according to the degree with which the turbo is compressing air. Allowing the engine to run at peak efficiency through the entire range of engine load.