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Subaru is developing turbo hybrid for 2007
Posted 15 September 2005 - 08:53 PM
The engine uses the Miller cycle, where forced induction over-fills the combustion chamber, but the intake valves are left open during the beginning of the compression stroke, to allow good fuel-air mixture. The torquey electric motor makes up for the lack of low-end torque on the part of the turbo Miller-cycle engine.
It's a pretty interesting article, and it's cool that Subaru is doing yet another thing a totally unusual way. I'm impressed with how quickly they expect to get this technology to market. If they do pull off the numbers they're talking about in 2007, they might just get the attention and brand recognition they crave.
Posted 15 September 2005 - 08:59 PM
Posted 15 September 2005 - 09:35 PM
Normally it is the increased expansion ratio (on the power stroke) that is the primary reason for the increased operating efficiency as a result of increasing the what would normally be refered to as the "compression ratio".
The miller cycle engines run static C.R.'s of around 13:1, but lowers the effective C.R. (compression pressure) to conventional levels by way of hanging the intake valves open longer to allow a partial reversion discharge. However the expansion ratio remains 13:1.
Not sure if that made sense.
Posted 15 September 2005 - 10:45 PM
Posted 15 September 2005 - 11:28 PM
There is a good article on Wikipedia and on howstuffworks.com on the Miller cycle.
Posted 16 September 2005 - 10:51 AM
Good point about the variable valve-timing. It'd be neccessary to close the intakes earlier at low rpm/ high-load conditions to preserve usable torque and turbo spool-up.
I think I originally learned of the miller cyle through Wikipedia. I had a difficult time understanding their description at first, but it's pretty simple once you see the big machine.
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