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It’s Big, it’s Tough, it’s Powerful…it’s a Hybrid?! 2008 Yukon/Tahoe Hybrid Test Drive

July 26th, 2007 | Posted in: Hybrid, Test drive

General Motor’s has officially announced that it will begin mass production of hybrid versions of it’s popular large SUV vehicles the GMC Yukon and Chevrolet Tahoe. The cars will be available for purchase in the 4th quarter of this year.

GM-Volt.com moderator was given the opportunity to test drive one of the pre-production models right in the crazy yellow-cab filled traffic of NYC, and to discuss the cars with Vehicle Chief, Full Size Truck Hybrid Mark Cieslak and Assistant Chief Engineer Small block truck engines Chris Meagher.

These vehicles are unique for two reasons, they are the first-ever passenger vehicles to have a 2-mode hybrid system, and they are the first ever large SUV hybrid vehicles on the planet. While they aren’t Volts, they are a step in the right direction.

Standard hybrids like the Toyota Prius use a single mode hybrid system, meaning the electric motor powers the car only at low velocities, once speed or acceleration increases, the car goes to all combustion. In the 2-mode Yukon and Tahoe, there are two separate electric motors directly linked into the transmission. One powers the car at low velocities, whereas the other one kicks in at certain high speed conditions. This allows the vehicles to improve fuel economy both in city and highway driving. Indeed the car gets a 40% improvement in fuel economy in city driving, and overall a 25% improvement over the non-hybrid base models. Further gains in fuel economy come from the truck’s abilities to shut off 4 of the 8 cylinders, and to use a variable displacement oil pump.

The cars are engineering marvels and contain the most sophisticated on-board computer and software systems on the road. In order to achieve the best possible fuel economy, the computer analyzes the car’s driving state 50 times per second and determines which configuration; electric motor 1, electric motor 2, four or eight cylinders, or ICE shut-off will be most energy-efficient.

Some modifications of the vehicles structural components had to take place to make up for the increased weight from the hybrid system and batteries. This included an aluminum hood and improved aerodynamics of the front grill and running boards. The car uses a 300V NiMh battery housed under one of the rear seats, and has a 6.0 L engine.

Getting into the driver’s seat (I drove the GMC Yukon), it feels like any other large SUV. Differences become apparent when one looks at the dash. There is an indicator showing the driver’s role in the trucks ecomony. If you accelerate too hard the needle goes to the right (burning too much fuel), if you brake too hard it goes to the left (losing stored energy by activating non-regenerative brakes). If your driving is optimal, the needle stays in the green zone.

Starting the car comes straight from the electric motor, and you do not hear the whine of the starter. When stepping on the accelerator, one feels the unique instant responsiveness of the electric motor. While driving one can barely perceive when the gas motor switches on and off, and indicator lights show if the ICE is on or off, in 4 or 8 cylinder mode, and which electric motor is running. On the in-dash nav screen all of this data is displayed graphically.

Overall, a very responsive, agile and well-handling ride, and a lot of fun.

One might ask if it isn’t paradoxical to have a giant gas-guzzler as a hybrid, but Mark’s answer is that it is actually a “perfect marriage”. Since this type of vehicle is generally so fuel consumptive, making hybrid gains on it are very valuable. Plus one can do all the heavy hauling needed, while still reducing oil consumption. The non-hybrid version of these trucks get 14 mpg city/19 mpg highway. With the 2-mode hybrid system, those numbers go to 20 mpg city/? highway (not federally approved yet).

When asked what he’s most proud of in these vehicles, Marks reply is “best technology, best efficiency, and best capability of any hybrid vehicle on the road today”.

While they’re not Volts these machines bring us closer to that goal. Indeed, these are two of several hybrids GM is putting out this year. And expect to see the 2-mode systems in upcoming Escalades, Saturn VUEs, and pick-up trucks.

Pricing is not finalized yet, but will fall within the same price range of the current Tahoe and Yukon lineups.

Popularity: 3%

(1 votes, average: 5 out of 5)

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Posted by: Lyle

20 Responses to “It’s Big, it’s Tough, it’s Powerful…it’s a Hybrid?! 2008 Yukon/Tahoe Hybrid Test Drive”

Brian Says:
July 26th, 2007 at 11:23 pm

I got to drive a two-mode Escalade a few weeks ago, and I was very impressed. It was very smooth, responsive, and surprisingly quick (well, quick for a full-size SUV). I think GM has a real winner with the two-mode system if they can keep the cost down.

I only differ with your review on one point: you said “While driving one can feel when the gas motor switches on and off”. I have driven a Prius, and in that car you can REALLY tell when the engine turns on. The whole car literally shakes. In the Escalade, I could tell when the engine turned on, but it was a very minor vibration, nothing close to the Prius. It also happened at a higher speed (about 10 mph or so) than in the Prius (basically 1-3 mph). I think the main reason for the lower amount of vibration is that the Escalade is much heavier than the Prius, and so can absorb more vibration.
Lyle Says:
July 27th, 2007 at 9:08 am

Brian
When I mentioned the ability to recognize the engine turning on and off, I sort of meant it in a positive way. Indeed, it was extremely subtle and I had to pay very close attention to notice it. I thought it was positive because it gave me a good feeling to know that I wasn’t burning any gas.
J M Stewart Says:
July 27th, 2007 at 10:13 am

Brian:

We have now owned three Priuses. The firt a 2002, Then a 2004 that got drowned in hurricane Ivan, and now a 2005. Total milage about 120,000. Never in those miles has the starting and stopping of the ICE been noticable. The one time it does show up is on decending hills in the “B” (brake) position. If the hill is long enough the battery gets fully charged so there is no longer a place to dump the electrons. At that point the ICE is engaged in the conventional way to aid in slowing the decent.

Now waiting for a Volt!

Jim
Tim Says:
July 27th, 2007 at 10:44 am

I’ve heard some really great things about cylinder deactivation. Apparently, those who have vehicles so equipped are very happy with them. Cylinder deactivation combined with a 2 Mode hybrid system is perfect for vehicles designed for heavy hauling & towing. GM should have started with the Pick-Up version first and marketed them to fleets. Now, add plug-in capability to this system and give us e-Flex passenger cars! GM is back on track baby!
AES Says:
July 27th, 2007 at 11:02 am

Sounds interesting and very useful, but personally I’ll hold out for a series hybrid or pure EV. I’m a fan of elegant simplicity in engineering, and unfortunately the complex two-mode system is about the opposite.
Dave Says:
July 27th, 2007 at 11:24 am

AES,

Good point. I’ve heard about the complexity of the hybrids in general. The Volt’s system sounds much simpler, relying on the electric motor which means little or no maintenance. I’ll wait as well.
Brian Says:
July 27th, 2007 at 11:44 am

J M:

I don’t want to get in a big argument here, but I’m telling you I owned a 2006 Prius for about 6 months and yes, the vibration was extremely noticeable. I have driven two other Priuses and noticed the same thing, so it wasn’t just my car. If you don’t notice it, maybe you drive differently than me, or maybe you don’t pay attention to such things.
Ziv Says:
July 27th, 2007 at 1:12 pm

Man, that is one large vehicle! The old one got 15/21 mpg, 18 combined, so a 25% increase in fuel efficiency will save the owner about 166 gallons a year, or $500, if they drive a normal 15,000 miles annually. Not too bad. Improving ‘horrible’ mileage to merely ‘bad’ mileage may save us more gasoline than going from good mileage to excellent mileage.
MikeFromEastCoast Says:
July 29th, 2007 at 7:32 am

This is a good thing. Going hybrid on larger vehicles makes more of a difference. Hybrid Semi Trucks would be even better. I’ve wondered what percent of their power could come from photovoltaics on top of the trailers. There’s a fair amount of area available unlike on a passenger car.

PS: I have a Prius and I can tell when the ICE starts and stops if I pay attention but it is fairly subtle. It’s something you feel more than hear and not nearly as noticeable as a conventional car starting.
Matt986 Says:
July 29th, 2007 at 10:02 am

Mike,

Even with the whole trailer top covered in PV cells, it wouldn’t generate all that much juice. Considering how much a semi weighs (sometimes up to 80,000lb or more), a little power from solar would barely be a drop in the bucket.

I think semis would probably benefit from a diesel electric arrangement, like trains use.
Jessica Says:
July 29th, 2007 at 9:16 pm

There’s something about making SUV’s more fuel efficient that bothers and concerns me. I’m currently a driver of a Mini Cooper (desperately waiting for the Volt) and I struggle every day with huge SUVs. Yes 1-5% of the population of SUV drivers actually need the extra space but the rest really do not. I wish the world of cars would move in the direction of being smaller, cause less damage to the roads, and be less obtrusive on the streets instead of just slightly improving (”horrible to bad”). I cheer for increased gas prices in hopes these monstrosities will be slowly phased out. I worry about the focus moving away from the Volt and onto the SUV “efficient cars”. I see this as just another excuse for there to be more of these horrible cars on the road and people actually thinking they’re making a difference. Please please please, if I’m seeing this in the wrong light let me know I just don’t want anything to come in the way between me and my Volt; especially not an SUV.
Steven B Says:
July 30th, 2007 at 9:32 am

Jessica, you are definitely seeing this in the wrong light. 2-mode hybrid technology has been in development for years before e-flex was introduced as a concept. 2-mode hybrid technology from GM is very significant and so is its use in large vehicles. It was first introduced in city buses and is available as the Whispering Wheel city bus. I’m very optimistic about 2-mode hybrid technology and its use in large SUV’s for one reason: if fuel prices continue to increase, the large SUV market is likely to be reduced to only those who NEED them for personal or business use, and high fuel prices will result in full amortization of the hybrid premium by indvidual buyers. That means that there will be fewer SUV’s on the road and economics will result in all of the new ones being hybrids. But it in no one way inhibits the development of e-flex or affect the Volt’s development timeline.
Jessica Says:
July 30th, 2007 at 11:07 am

Steven, Thank you very much for explaining all of that. It helped a bunch.
Matt986 Says:
July 30th, 2007 at 1:05 pm

I think it’s maybe more of a Sword of Damocles in a way. Getting 25-40% better fuel efficiency out of the worst vehicles will be great. It should help reduce prices at the pump..

But on the other hand, it continues to feed the ‘bigger is better’ fad that Americans seem to be stuck on. Using less gas will reduce demand and reduce prices. If prices stay down, people will continue to needlessly buy larger vehicles.

We’ll just have to see what happens…
Nick Says:
July 31st, 2007 at 10:36 am

I’m with Jessica & Matt986. Unless you often need to tow a boat or something, you probably don’t need one of these full-size SUVs. Minivans make more efficient people haulers, but don’t have the macho factor. Using one of these monsters for single-driver, daily commute (as many do) is wasteful in the extreme, even after mileage is improved a bit.
Mas Says:
July 31st, 2007 at 11:27 am

I still think People are the problem and not the vehicles. The American People need to learn self-disapline. They need to choose a fuel efficient vehicle that they need, and not a vehicle that they want, just because. I don\’t agree with the mentality that gas should continue to rise in order to control people, because there are some that absolutely need a large vehicle due to the size of their family. Most of these people\’s budgets would seriously become strained if gas was too much to afford. My wife will soon give birth to our third child, add to that a German shepherd dog and all of a sudden, trying to take a trip or go camping and fit all our stuff, us and the dog into her wagon is no way, shape or form possible. However due to the current gas prices, having her drive a large SUV would absolutely bury our budget. Our solution was to buy an older Suburban to keep as a third vehicle, that only gets used for family outings, trips or camping. For everyday use she will continue to drive her fuel efficient wagon and I my fuel efficient sedan.
texasguy Says:
August 3rd, 2007 at 8:12 am

It’s good to see this. Large vehicle hybrids and large vehicle PHEVs would help out because a lot of people own pickups for their ease of moving things. I know people that have a pickup and only drive them when they need to once a week.

I think the market will sort out who buys pickups/SUVs and who buys smaller cars in the future because even at 20 city 30 highway, the gas bill is pretty high. Also the larger SUVs cost a lot more up front.

IT’s a move in the right direction.

Some people here hate large vehicles but most really just want the volt to be built and have the technology available.
queenb@supernerdio.com Says:
August 3rd, 2007 at 6:51 pm

I want a hybrid.
Met Mad Hatter Says:
October 27th, 2007 at 9:14 am

Gasoline is never going to disappear, and that’s fine what these SUV and Cars that are hybrid, flex, electric, and Fuel cell are doing is taking a piece of the market away from the greedy oil industry. If they reduce the oil markets share by 50% in 10 years then they’ve accomplished their intended purposes and we get a cleaner environment to boot. BRAVO
honda prius Says:
May 15th, 2008 at 6:16 am

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