On Friday GM dedicated a new advanced powertrain engineering center in Pontiac Michigan. The 450,000 square foot, $450 Million facility will use new specialized technology and procedures to more rapidly roll out advanced fuel efficient powertrains.   It should be able to cut 10 weeks off of the typical powertrain development cycle.  The Volt's hardware will take center stage at the facility and per GM, "the Volt’s electric drive unit, motors, power electronics and engine will be tested in this center."

At the dedication, automotive blogger Sam Abuelsamid had the chance to interview GM's executive director of hybrid powertrain engineering, Larry Nitz, about why GM went with the 1.4 L non-turbo 4 cylinder engine and found out some other interesting things.

For one thing, per Nitz, "the 1.4L NA four has better brake-specific fuel consumption than the 1.0L turbo when used in steady state mode, as it will be in the Volt application."

Also Nitz claims the four cylinder engine will provide for a smoother transition from EV to range extension saying "the objective is to keep the engine off and when the engine comes on, you don't want to know it's on. You want it really smooth and four cylinder is smoother than a three."

Nitz also noted that the four cylinder has a lower cost and that when the turbocharging architecture is added to the 3-cylinder engine, the non-turbo four cylinder engine setup is actually lighter.

Since the four cylinder engine is also longer, GM has had to reconfigure the packaging somewhat to make it fit, which as per Nitz is "turning out nice."

Nitz goes on to say the generator produces 50 kw, whereas the electric motor produces 100 kw, and assures us that the "vehicle will never use more than 50kW on a continuous basis," and says "zero to sixty, passing maneuvers, you'll be fine, the ability to actually use more than about 50kW doesn't exist very frequently."

He notes that the engine never has to perform dynamic response, that only comes from the battery and electric motor side.

Nitz also states that GM has refined the charging window of the pack as 35% to 85%, whereas previously GM had said it would be 30% to 80%. He does say though that the battery could be discharged below 35% if it has to on rare occasions, but that when steady state resumes, the battery will recharge as the engine then produces more output than the car requires at that time.

And yes that's the actual Chevy Volt range extender in the graphic above (Thanks BillR)

Source ( GM ) and ( Green Fuels Forecast )

[UPDATE: Sam Abuelsamid indicates that Nitz did not specifically say the available charge window would be 35% to 85%, but rather that was Sam's understanding from discussions with others at GM, slightly different than the information I had been given of it being 30% to 80%]