Featured Electric cars could spell end of front-wheel drive, VW exec says

Why put it under? In a range extender scenario there's no need to keep it near the centerline. It's smaller and lighter than an auto engine. The car designer can have the freedom to put it kind of anywhere.

In the context of a minivan (re: post 32) I would try to hide it in the side wall in front of the right taillight. Sacrifice a little interior width, keep the floor for frame/batteries/foldy seats as needed and now the service techs don't have to dig all the way to the center of the car to get at it.

 

The Porsche 911 engine is a flat, opposed, boxer engine, and it hasn't been air cooled since 1998.
There is no need to use an air cooled engine in rear engine PHEV. The range extender in the i3 REx isn't air cooled. It piggy backs its liquid cooling system onto the rear mounted motor's. It is also small enough to sit below the cargo deck, next to the motor.
https://attachments.priuschat.com/attachment-files/2016/07/108943_12_W20-Engine.pdf

Advances in engine technology mean getting the same amount power in a smaller package. Depending on the battery size, the engine doesn't need to be sized to provide full power in hybrid mode.

Even if cargo space is loss be requiring a higher cargo floor for the engine, the loss can be made up by moving the other interior components forward into where the engine bay would be in a front engine car, or by having a front trunk.

 

The Porsche and VW engines I was referring to are flat block engines, opposed banks of cylinders with intakes and auxiliaries above the block. Picture here. The lines point to the spark plugs. Be assured you don't change them from the top of the engine. Thus the name of one of the Porsche models, the Boxster, a mix of boxer and roadster.

The water cooled versions came in the '97 model year for the US. Note the difference in prices for used '96 911s (last of the air cooled) and '97 911s (water cooled).

I've been lucky enough to have owned a '70 air cooled 914, a water cooled Boxster 986 and a water cooled '01S.

 

Four and six cylinder air cooled opposed engines have been around forever in light aircraft

 

I understand many of the engines used in that application still use carburetors. Then there is plenty of high air flow up there for cooling, and the weight of water cooling is undesirable, along with the potential of another system failing.

Cars are a different application. How many that are built now use an air cooled engine, and meet EPA or EU emission regulations?

 

Most opposed engines I know of were air cooled but earlier inline and V configured aircraft it was common to have water cooling.
During WWII some of our tanks had air cooled radial engines in them and they had oversized jugs for better cooling. I can't imagine the noise.

Wright R-975 Whirlwind - Wikipedia

 

The Sherman was originally equipped with that, but switched as production was deemed more important for use elsewhere. There were a couple of diesel models that were supplied to the Brits where that was the available fuel. I think the Ford V8 one became the most common one in US use, but there was a 30 cylinder Chrysler engine that was really 5 of their inline six engines driving a sun gear.

Chrysler A57 multibank - Wikipedia

 

I actually saw one of those Chrysler engines you are talking about. They had one at the Chrysler museum in Auburn Hills Michigan but they closed the Museum dow. I have a picture of it somewhere.