I recently had the chance to be one of the few people outside of GM to get behind the wheel of a plugin 2 mode hybrid prototype at GM's test grounds in Milford. I was accompanied by Larry Nitz, GM's director of hybrid powertrain development.

Originally this vehilce was set to debut under the Saturn brand in 2010 but due to the brand's sale, that was changed.  It was then slated to appear as a Buick compact crossover, another plan that was recently shelved due to customer feedback.  The car will still launch in late 2011, but the brand and design remain unknown.

The mule I drove remained in the original Saturn VUE skin (shown above).  You can drive along with us in the video below.

It uses an 8 kwh LG lithium-ion pack pack, which is essentially half a Volt pack. The mule car was at this point highly refined, though only about 90% production intent.  I was told the instrumental panel will be slightly changed from what was displayed in the mule.

The final car will have a silent start though the engine went on at start in the mule.  It contained a 3.6 L DI 270 hp engine and two 55 kw electric motors, utilizing a power-split engineering architecture significantly enhanced by the large lithium-ion pack.

The car drove off very silently though a thrust of the accelerator brought on the roar of the gas engine.  It was capable of 40 mph top electric speed but it was tough to get above 25 mph pure EV with acceleration.  In theory, the car could go 10 miles as a pure EV under 35 mph.

Components were changed from the original 2-mode VUE, in particular the engine and inverter were changed and modifications to the transmission and electric motor were made all for the purpose of reducing cost and increasing efficiency.  In fact the Volt's inverter is used.

GM would not release a target price at this time.

I found the electric acceleration solid and quiet as GM had paid special attention to the noise and vibration of electric motor

Notable was the very smooth transition to engine on, and also well done was the fact that there was no shudder when the engine turns off.

This design and concept is significantly different that found in the Volt.  The PHEV is not an EREV.  Operation is almost always a mixture of gas engine and electric motors to allow generous power and maximum efficiency.  Though like the Volt, GM wants to discharge the battery as much as possible on each trip.  I was told the aim of the car is to try to discharge the battery in about 20 miles.

The car differs from traditional power split hybrids like the Prius.  Here there's a second mode of operation to gear down the traction motor for bigger vehicles.  It uses a power split architecture and both electric motors are working almost all the time.

Also with two modes it is possible to both have an efficient electric drive and operate the engine efficiently.

In operation, the ICE follows the load and does not only run at certain RPMs and even though the car weighs in at 4500 pounds with its battery, it still has a lot of power.

In the end, the car clearly does what its supposed to do, and does it well.  And for those needing the power and size of an SUV and desiring a plug and double the fuel economy of traditional SUVs, this car may be the answer.  GM expects it to be the first commercially available plug-in hybrid SUV produced by a major automaker.