Consider using TWO engines...?

Sadly I think you would defeat the purpose by lugging 2 engines around. Even if you made them both completely out of aluminum the extra weight would be self defeating. Not to mention you would lose the trunk, and would need to find a place to store the gas. Plus 2 transmissions would be a rigging nightmare, and you really aren't supposed to drag/tow a FWD type vehicle on the ground. So there would be a lot of design that would go in to it. A great idea in theory, but I do not think it would work in reality. They did this on a Cadillac a number of years ago (put 2 Northstars in it) for performance reasons. Worked well, but was a nightmare to do right.

Mosler Twinstar Eldorado

 

lol. Two engines are more expensive and heavier than one. The question is can they be more efficient? I'm sure they can, but for the money and weight, you can do something like bmw's vission efficientdynamics. Instead of adding an engine up front, they add a motor and a plug-in battery pack. The pack is probably about the same capacity as the one in the prius phv, but built to put out higher power for short periods of time, weight of the pack is 187lbs. Instead of a miller cycle they use a 3-cylinder turbo diesel, but for the market toyota could probably build a good 4-cylinder miller cycle that has close to the same efficiency. At low power the car draws from the batteries. At highway cruise the car runs the engine at an effiecient mode. A 40hp engine would likely be 2-cylinder and a little rough. Cylinder idling technology could be used on the engine to simulate this without much loss of efficiency. Toyota claims they are getting a turbo-charged engine in the lab up to 45% efficiency. BMW's 4 cylinder turbo engine will be running in the next generation of fisker karma phev, current uses a more standard less efficient gm engine.

The bmw reference vehicle does a couple other things that may be very expensive. It has a cd of 0.22 and smaller cross section area than the prius. It also uses a heat generator on the exhaust to recharge the batteries.

 

Four motors would be a better idea, as in one electric motor on each wheel.

 

Mazda's SkyActiv-G does it with one engine using variable valve timing to switch from Atkinson to Otto cycle.

 

Don't want to have this discussion with you again. I said toyota turbo, which is what they say they are working on. Toyota claims 45% peak efficiency in the lab, nothing about it says miller, but I'm sure they do some late valve closing techniques

bmw seems pretty effective and efficient running at low rpms with their twin scroll turbo. You can also use a hybrid turbo, which is a exhaust generator electrically coupled to a super charger through wires and a battery. You get most of the efficiency gains through a twin scroll though, and it is simpler and less expensive.

+1

Yep, cyclo said it right. Give it DI to get the otto compression up, then electronically controlled valves to quickly switch mode. The RX450 h never makes it fully into otto mode.