Chevy Tahoe Hybrid SUV Breaks New Ground

By dancurranjr On April 20th, 2009

chevy-tahoeAmidst all the criticism of General Motors and the perception that it trails in the development and production of technologies and vehicles that meet current needs one fact has gone unnoticed.

GM produces the only volume-production, full-size hybrid light truck available anywhere in the world — state-of-the-art technology where it matters. It makes for good press to brag about 5-litre/100 km fuel economy in a class and size of vehicle where 6-litres/100 is the average.

While that 20 per cent improvement is worthy, the argument could be made that in a market where half of the vehicles purchased and driven are fuel-thirsty trucks, a similar reduction would save a great deal more fuel.

Put more directly, if you drive a compact hybrid 20,000 km a year you might save 200 litres of fuel. If on the other hand you drive a full-size SUV that savings would be in the order of 800 litres, conservatively. And there are more of these large vehicles on the road — making the impact even more significant.

I speak from personal experience with a 2009 Chevrolet Tahoe equipped with GM’s new Two-Mode Hybrid system. Conventional big SUVs powered by V8 engines, including both a Tahoe and a Yukon, driven over a particular 350-km test route involving both city and highway driving have averaged 16.3 litres/100 km. No attempt was made to save fuel. The vehicles were driven at legal speeds and the route included dozens of hills and long inclines.

I think of it as ‘real world’ mileage as compared to numbers generated in the laboratory of Saskatchewan-flat roads. The 2009 Yukon Hybrid averaged 12.1 litres/100 km over this same route despite string winds and cold temperatures. That is a real world saving of more than 25 per cent.

GM claims the two-mode Hybrid system can improve urban fuel consumption by as much as 50 per cent. While this may be possible under certain circumstances where the electric motors are used more often, the constant elevation changes in our area make that all but impossible.

But the 25 per cent improvement I witnessed is likely a worst-case scenario and if driven primarily and conservatively in the city, this big truck — and its GMC Yukon and Cadillac Escalade siblings would do much better than that. Like any hybrid, the big gains come in urban driving, with much of that from shutting the engine off when sitting at a light or stopped in traffic.

The Tahoe is the first vehicle to offer this new system, developed by GM in conjunction with BMW and Daimler-Benz. This cutting-edge two-mode hybrid system lets the Tahoe run on a big 6.0-litre V8 engine, electric motors or both. The V8 boasts variable valve timing and the ability to shut down four cylinders under low-load conditions. It also shuts down completely when the Tahoe comes to rest for more than a few seconds, restarted instantly and seamlessly by the 300-volt battery pack beneath the rear seats. Two electric motors inside the casing house the four-speed automatic transmission allowing the big truck to operate in two different modes — thus the Two-Mode Hybrid moniker.

In low-speed, gentle driving around town the Tahoe acts like other hybrids, shutting down at lights and drawing power from the battery pack and initial motivation from the electric motors, when crawling along in traffic or in the initial stages of accelerating away from a stop. The engine then kicks into life and, at higher speed or when more oomph is required, one or both electric motors go to work as well.

The Tahoe Hybrid gets a power-conserving air conditioning system and a deep front valance which may restrict off-road activity but it also cleans up airflow around the vehicle for improved aerodynamics. The 332-horse- power V8 and rugged chassis allow it to tow up to 6,000 pounds — well beyond the capability of any other hybrid on the planet.

While the Tahoe Two-Mode Hybrid offers welcome and measurable improvements in fuel consumption and exhaust emissions, it is restricted to a high-trim level putting it out of reach of the average buyer at a base price of $70,000.

The standard equipment list is extensive: heated seats, power adjustable pedals, power windows, seats and locks, OnStar, rear-view back-up system, navigation system, Bose audio, tri-zone climate control, on-demand four-wheel-drive and three rows of seats. The third row is best left for little or athletic people and there isn’t much room for cargo with all seats in position.

The Tahoe Hybrid breaks new ground. It is a big truck capable of towing heavy loads or carrying up to eight people. And it does this with technology that offers a considerable reduction in fuel consumption and exhaust emissions.

SOURCE: Chronicle Herald

Leave a Reply