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GM’s VUE Hybrid System: Simple, Low-Cost and Targeting a Broad Base

GM’s current hybrid strategy calls for implementing three distinct hybrid propulsion systems targeting different levels of fuel economy and price points.

At the high end is the two-mode hybrid system that GM will apply first in the Tahoe and Yukon full-size SUVs, followed by the Cadillac Escalade and the Silverado/Sierra pickup truck. At the low end is the current extremely light hybrid implementation in the Silverado Sierra. And in the middle is the hybrid powertrain to be first applied in the Saturn VUE Green Line hybrid (earlier post) that will begin sales later this year.

The VUE hybrid powertrain is based on a Belt Alternator Starter system—essentially what underlies a Start-Stop system—albeit one with some modifications that provide a small degree of traction assistance.

A plot of estimated combined fuel economy vs. suggested price for four hybrid SUVs. The VUE is a price-performer.

Combined with other vehicle modifications to decrease fuel consumption, however, the VUE Green Line hybrid delivers an estimated 20% improvement in fuel economy (+5 mpg) that brings it very close in consumption to the other hybrid SUVs with more complex hybrid drives that are currently on the market—and at a substantially reduced price.

The design targets for the hybrid system were, according to Steve Tarnowsky, Assistant Chief Engineer for GM Powertrain Hybrids in a talk given at the SAE Hybrid Vehicle Technologies Symposium 2006:

  • To create a simple, elegant hybrid architecture flexible enough to implement globally on a broad spectrum of both powertrains and vehicles. To that point, GM will deploy the system on the Malibu sedan next year, and will also deploy the system in a car in China (model and timing yet to be publicly announced).

  • A system that required no compromises in vehicle utility or performance. For the SUV customers, this partly means towing and acceleration—the Saturn VUE has a 1,500-pound towing capacity.

  • To deliver exceptional customer value. To be priced at less than $23,000, the Saturn VUE hybrid offers an estimated 29 mpg US combined, compared to the Ford Escape hybrid with 33 mpg US combined at a starting price of $27,500. The Toyota Highlander and Lexus Rx 400h both are rated at 30 mpg US combined, and priced at $33,000 and $48,500 respectively.

The hybrid accessory drive. The dual tensioner assembly that controls the motoring and generating loads is patent pending. Click to enlarge.

Functionally, the VUE hybrid system offers start-stop and regenerative braking—features expected in a simple Belt Alternator Starter system. GM, however, developed a dual tensioner assembly for the hybrid accessory drive (the motor/generator package) that will transfer a small amount of torque to the drive system for very brief periods of time.

The assembly combines an hydraulic strut tensioner and a friction-damped rotary tensioner on a common pivoting arm to the control the bi-directional loads (motoring and generating).

This assistance takes three forms: electrically motored creep at startup, light power assist during acceleration, and light electric mode during deceleration.

Upon startup, prior to the driver pressing the accelerator, the hybrid system will begin creeping the car forward to assist with a smooth transition to motion. This creep will last a maximum of 2 to three seconds, at which time the engine automatically kicks in even without the driver pushing the pedal.

The different modes of operation in driving a VUE hybrid. Click to enlarge.

During acceleration, the motor will contribute a small amount of electric assistance. And under deceleration, fuel cuts off to the engine, and electric assistance briefly kicks in case the driver wants to tip back into motoring mode. The goal with the latter assistance is, like creep during startup, to smooth the transition from no-engine to engine mode.

The assist is small: the motor (provided by Hitachi) is only a 4kW (mechanical) machine (5kW generating power), although it provides some 60 Nm of motoring torque.

GM’s approach with the VUE has been to eliminate any excess cost. The battery pack (from Cobasys) is just 36V. The hybrid control system is implemented within the existing 32-bit Engine Control Module. The instrument cluster only minimally reflects the hybrid drive.

But the VUE also will be the lowest-cost hybrid SUV on the market.

A Belt Alternator Starter system typically improves fuel consumption in city driving by about 8 to 10%. GM’s other modifications to the VUE (weight, aerodynamics, engine, management regime) contribute the remainder of the 20% improvement—and also highlight the importance of the interplay of a wide range of technology and design decisions in increasing fuel economy. (GM would not disclose the relative contributions from the different systems and changes.)

A different hybrid vehicle based on this BAS system—such as the upcoming Malibu or the Chinese sedan—may not deliver an equivalent 20% improvement. But BAS technology, widely applied, could provide a broad-based boost to fuel economy and reduced emissions.

Market researcher K. G. Duleep, Managing Director of Energy & Environmental Analysis, believes that there is growing possibility that regulators will require idle-stop as a means of reducing inner city emissions. And beyond that,

Within 10 years, all vehicles may be required to have stop-start.

—K. G. Duleep

The sales performance of the VUE and subsequent GM BAS systems will provide good feedback as to how the market values this type of low-cost, low-impact approach.



Did anyone notice the electric motor attaching to the compressor. It seems that the AC would run even when the engine is shut off. I couldn't find exact information on how long it would run, only that there is a driver selection to go into conserve mode. Anyone know the details. Comming from GM this looks great. Independent study found that it would get 29.7mpg in real world, niccccccce.

Tim Russell

Abraham - Seems to me that the missing component would be a crank pully clutch so the motor/generator could turn the AC compressor without turning over the engine. Might be a easy upgrade to this system to provide full time AC with the engine off.



Their hybrid technologies are designed with limited potential. The GM hybrids cannot evolve into Plug-in Hybrids. Plug-in Hybrids offer a portable power supply of batteries that would be invaluable in an emergency, power shortage or price gouging. The homeowner gets a lesson in household electricy consumption. Combined with rooftop photovoltiac solar panels, the homeowner or apartment dweller can sell excess power back to the grid. This homepower system inevitably leads to public power, which greedy Enron-esque energy corporate rats oppose.

In addition, batteries lower a vehicle's center-of-gravity, improve handling and stability and reduce accidental rollover, a perfect application for high-riding SUVs.

Don't buy a GM hybrids. They're crap and planned obsolescence! !! DIE GM, DIE !!


Abe/Tim...why not just go electric AC compressor? as at present auto-stop only works with AC off. I assume the motor/generator is the only starter? If so, that belt is getting a workout. Compatable with a diesel motor? Then 60+mpg with great performance is in range.


Take it easy on GM. 20% is still an improvement that is worthwhile. Their goal is widespread adoption, which is more likely with this setup that costs less than a typical navigation system. The technology is far more simple, so less peopole are likely to be scared off by maintenance issues.

Yes, Toyota's system is better, but you have to start somwhere. If you don't like the GM product, there are plenty others for you to choose from.

Once again, I ask the question....would you rather have a 20% improvement in mpg for 30% of the model sales, or a 40% improvement for 2% of those sold?

This approach has plenty of merit over the short term.


One other thing.....it would make a ton of sense for this setup to be applied to Saab's Biopower concept. It almost compensates for the increased fuel consumption using E85. In conjunction with being able to size-down the Biopower engine to make the same power as the gasoline version, it would probably result in virtually the same mpg using E85.


What drives the power steering pump, I wonder?


You just don't get it, Angelo. GM doesn't give a damn about the future of human civilization. GM executives derive income from a transportation monopoly. The car, no matter how fueled, is a "Constitutional Inequity". The GM hybrid drivetrains are a ruse. No alternate fuel can be developed to replace petroleum as it is used under today's paradigm of transport dependency. GM knows that their hybrids will fail to make any appreciable reduction in transportation dependency, let alone fuel consumption, and they don't care; just as that lying sack-a-crap Bush cares for noone but the ultra-wealthy. GM executives practice the same Nazi idealogy they praised in the 1930's.

!! DIE GM, DIE !! Eat your pollute-mobiles and DIE !!

factory rat

The steering is electric, by Delphi


It is a nice twist if the system can really deliver 60nm of assist - that's enough to feel it in the seat of your pants.

Stop/start is probably very good bang for the buck, which if true would mean we'd do well to spread it quickly. Seems easy to understand, easy to add to most vehicles, amenable to cost reductions with volume. How does the cost per gallon saved or ton of GHG avoided compare to other hybrids?


Trust me, I get it. I'm as disappointed as you that so much of the available technology that could virtually eliminate our petroleum consumption is not being put to use fast enough.

However, I'm a realist. If you think that any publicly traded company, such as Toyota, is driven by anything other than making more money, you are lying to yourself. Toyota just believes it found a niche where it can ultimately make more money.

GM has the right to create their own business model. It's obvious that they feel more strongly about fuel cells than hybrids. Do I agree with that? No. Do I think that it will bit GM in the ass? Likely. It's a little too early in the hybrid game to start declaring winners and losers though.

Although GM could have a lot of influence, they are not solely responsible for the survival of the human race. There are plenty of consumers who are too stubburn to give up their SUVs. Are they free of blame? Is a coal-fired power plant who spends more money lobbying to avoid environmental regulations any less at fault?

I'll agree with you about our government being at fault though....


I hope one day soon some manufactory will put together a car based on available today technologies with

1) Quasiturbin engine from

2) Continually variable transition and drive train like in Toyota Prius

3) Regenerative braking like in Toyota drive train

4) New rechargeable Lithium-ion batteries battery from A123Systems. 10X longer life, 5X power gains and dramatically faster charge time (5 minutes).

5) Use new thin as film solar panels to capture solar energy

6) Super capacitors to quickly capture energy
From using brakes to recharge batteries while driving
And while it is on parking help to capture solar energy.

7) Plug-in capabilities
World's First 150 MPG Plug-In Prius


I think that if the fork-tongued environmental air heads would consider the cost to replace the batteries on the Toyota and other "standard" hybrids, and would think through what would happen to the lead and the acids when they are recycled, they would see that their utopian ideas regarding power generation are not as well developed as they thought.

Of course, they'd have to remove the foil hats to pick up on anything logical first...


That is the one big question when do the first set of batteries gona die?

We have been hearing 100k miles maybe 150k. Both the cars we own now are well beyond those numbers so if they had been hybrids and sold into used car lots.....


What hybrids are using lead-acid batteries? If you are referring to the various "garage shop" experiments to create PHEVs from Prius's using lead acid batteries, it's not relevent.

NIMH and Lithium batteries are highly recycleable.

Sure, the first set of batteries may expire before your engine does (and the jury is still out on that - keep in mind that most hybrid makers have a longer warranty on their batteries than their engines). I believe about the worst-case scenario for replacement now is about $3000. Those costs will come down significantly by the time most people hit that point.

Furthermore, you have to figure in the reductions in maintenance costs. What about the 2 full brake jobs (say, conservatively, $600/ea) you're likely to spare yourself during that same time? Brake wear is SIGNIFICANTLY reduced due to the regenerative braking.


Standard lead-acid car batteries too, have been a cost effective, environmentally sound, recycling industry for decades, Memilio probably knows but choses to deny for the purpose of partisan argumentation.

Angelo, GM's corporate charter should be revoked. This corporation's effect upon the US economy should not be determined solely by their profit motive. GM manipulates the transportation market in monopolistic fashion. Not only does GM deny the American people a product that determines essential economic security, GM frivolously wastes public funds researching technology GM knows to be fraudulent.

GM's invisible hand of the free market stabbed a knife in America's back. What city will the neo-cons destroy next? New York, New Orleans... Perhaps they'll pull the rug out from under the entire country, let all hell break loose, then retreat to their secluded, self-contained enclaves, and the nearby Big Box warehouse converts into a detention center?

!! DIE GM, DIE !!


Is Rome burning? When gas hits >$3gal and stays there, then more people will buy cars and trucks that get better gas mileage. SUV sales in this country are way down from a few years ago. Or maybe we should just leave things up the U.S. Gov’t to fix? I don’t think so! Last time I checked, European socialism doesn’t work. People are can buy FFV and hybrid type cars on the market right now. Anyway, Bio-fuels will continue to replace oil on an increasing basis as time goes on. A Hybrid vehicle that can run on bio-fuels will be built in the near future and this will help the country become more energy independent. Hey Artie, time to take your meds!

Tim Russell

Point missed by many a GM hater here (BTW I have no love for GM myself)

This system can probably fit most of the cars that use that same engine and they will sell probably a million of them. Humm a million cars getting another 5 Mpg, do the math, it's a good thing but the total tree hugging, twits that think that a few hundred thousand full hybrids will save us all people just gotta put it down.

Now what if all automakers moved all accessorys to electric power and added start/stop/mild assist to their cars. Think of the millions of gallons of fuel saved at a much smaller cost than full hybrids.

I say let the consumer decide, full hybrids, no hybrid, diesel, mild hybrid etc. Now where's my mild hybrid diesel car.


A couple of points here, first there is no single best solution for all driving needs. Full hybrids do well in urban drive cycles not because electric power is more efficient (the electric system efficiency is actually very poor) but because the petroleum based engine can be downsized by relying on the electric power for the high energy requirements of accelerations and making the steady state operation of the petro. engine more efficient. For rural/highway driving this efficiency scenario is much less impressive (here a hybrid diesel is generally best). In terms of accessory drive components (AC, PS...) any of these that require near continuous operation are generally less efficient when driven by electric power. The reason for making them electric powered is more a strategy of allowing initial operation and/or operation at a stop (engine off). Plug-in power is not a simple answer either you are typically just trading burning coal instead of gasoline. Unless you are wired to a wind generator (that would be cool). Solar on the car sounds good but the power generated vs. the cost of the system is not a really good trade-off unless the vehicle spends a lot of time parked and is not driven long distances (notice you wouldn't be burning much gas in that scenario either).
One last thing. Where did this left wing wacko concept of GM is all about profit but Toyota is just trying to do the right thing for the customer and environment come from? Toyota is a company that has grown to be a dominant force in the auto industry due to a long term strategy of steady increase in market share and PROFIT!!! Substantially in the form of U.S. trade deficit dollars. Wanting to see the demise of American Industry is wishing for the demise of the standard of living you inherited from people who didn't think like you.


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Jack Daniels

The writer who wishes GM to die is a moron. It's hard to reason with such a person because they know it all.

Jack Daniels

The writer who wishes GM to die is a moron. It's hard to reason with such a person because they know it all.


There's no reason to plug in a hybrid vehicle to charge the on-board batteries. Use air-induction throught the vehicle's hood, to provide an on-board battery charging system.

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