Split-engine set-up could link two small capacity engines into one unit

BMW is working on a hybrid system that uses two engines, detailed in a recent patent application.

Described as a ‘hybrid vehicle having a split engine’, the idea is for the car to be driven by one of the engines and the electric motor at low speeds or when power demands are low. When more speed or power is needed, the second engine cuts in.

See BMW split engine patent drawing

The engine is described as “comprising a first internal combustion engine unit… and a second internal combustion engine unit,” suggesting that the two engines will effectively form one unit. The second engine effectively supports and assists the first.

Although the application does not specify the size of the engines, it does mention the possibility of each being a two cylinder unit. It also says that the two engines could be different sizes – so a four-cylinder unit could be supported by a two-cylinder, for example.

The electric motor would automatically generate extra torque to compensate for any loss when the system switches between the two engines. As with BMW’s current hybrids, the electric motor is contained within the transmission.

Dan Stevens

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Comments
10

8 January 2010

the permutations and combinations of engine / hybrid / battery layouts is endless.

has autocar got a mole at the patent office.

www.KOOOLcr.com

 

8 January 2010

Interesting as Honda has been using "Active Cylinder Management" for a while - instead of two engines it shuts off two or three of the six cylinders in the v6 for when power demand is low. I can imagine that Honda could use a small electric motor to add extra assistance, requiring those extra three or two cylinders to kick in less often. Perhaps because Honda already has the best cylinder management technology patented BMW is looking down this "two engines" route - which would not seem to be optimal as you would have the weight of two engines (two two cylinders will weigh more than one four cylinder) - though you wouldn't have the friction losses of cylinder management if that second engine "decouples" - though how it would work when the engine (s) are cold seems difficult - if it only works when the engines are warm then it won't help much for short journeys.

8 January 2010

Credit where credit is due, the 'mole' is actually a forum user and prolific tweeter - RacingPuma.

He spots the applications, we translate them...

Jim Holder

Editor, Autocar

8 January 2010

This sounds way too complicated and, as others have said, means carrying a lot of dead weight. What's wrong with fitting a supercharger with a clutch on the drive-belt/chain/gears? No power-loss when it's not running, less additional weight and complexity, and should be more compact. Seems much simpler and, for anyone who's ever watched an early Mad Max film, far cooler!

8 January 2010

Reminds me of a bike I saw on You Tube, with 16 chainsaw engines.

8 January 2010

[quote GaryW]This sounds way too complicated and, as others have said, means carrying a lot of dead weight.[/quote]

I agree. You would be undermining the efficiency gains of using a small engine by carrying around another two engines too!

9 January 2010

BMW already had the capability to run on half a bank of cylinders back in the late 80s with its 750li. It didn't use the tech for consumption purposes, but rather as a back-up system should anything happen on the one bank alone.

9 January 2010

[quote Giom37]BMW already had the capability to run on half a bank of cylinders back in the late 80s with its 750li.[/quote] I think Ford also had a similar set-up back in the '60s. Seem to remember their V8 Galaxie could do this.

9 January 2010

[quote theonlydt]Interesting as Honda has been using "Active Cylinder Management" for a while - instead of two engines it shuts off two or three of the six cylinders in the v6 for when power demand is low. I can imagine that Honda could use a small electric motor to add extra assistance, requiring those extra three or two cylinders to kick in less often. Perhaps because Honda already has the best cylinder management technology patented BMW is looking down this "two engines".... route[/quote]

Honda aren't the only ones using the ability to shut off cylinders when not required though, Chryslers hemi engined 300c runs on four of it's eight cylinders in normal running and Cadillac's northstar engine had the capability to shut cylinders down back in 1991 (albeit as an emergency get you home measure in the event of coolant loss), so I can't see it being a patent issue stopping BMW from using it.

9 January 2010

the problem with just shitting the cylinders down is that they still pump up because the valves cant be lifted to let air in and out so you get much more than simple frictional losses I wonder if fiat's multiair will solve this. I think that you could package these engines in the same block certainly with the same water jacket, fluids and sump, just a clutch between them. I would probably have a small (1.4-1.6) 4cylinder with a couple of very small turbos and high compression then a 1.5 twin with a big dog turbo and lower compression, with the electric to boost in the transition form 4-6 cylinder. massive power massive economy (M1 supercar engine???)just an idea.

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