The Future of GM Powertrains

[Flybrian]

GM Goes Green
Company expands its green lineup in future

20XX Saturn Hybrid Sketch by Burns
Link to Original Article @ AutoWeek | Published 07/31/07, 11:37 am et

General Motors is poised to meet growing consumer demand for cleaner engines with better fuel economy.

Under Tom Stephens, group vice president of global powertrain, GM has been working on several hybrid powertrains; a number of clean-running, fuel-saving diesel engines; fuel cells; six-speed transmissions, and other advanced technologies.

GM starts rolling out the new products this year. Here's a look at GM's upcoming powertrains:

Hybrids:

By this time next year, GM says, it will have eight hybrid models on the road using three systems. GM also aims to put a plug-in hybrid on the road in 2010. Here's what GM has announced so far.

• The 2008 Saturn Vue and Aura and Chevrolet Malibu will be available with a mild hybrid belt-alternator system that yields a fuel economy gain of 15 to 20 percent. The system likely will add $2,000 to the sticker price.
  
  A mild hybrid turns off the gasoline engine when the vehicle is not moving, as happens at a stoplight. The engine quickly restarts when the driver releases the brake pedal. The electric motor provides a slight boost under heavy acceleration but does not drive the vehicle at low speeds.
  
  
• The 2008 Vue also will be available with a front-drive version of GM's Two Mode hybrid powertrain. Fuel economy of 40 mpg on the highway is expected; the Two Mode hybrid Vue will debut later in the model year. GM is expected to deploy the Two Mode hybrid a year or so later in mid-sized fwd vehicles with V-6 engines.
  
  
• This fall, GM will offer the 2008 Chevrolet Tahoe and GMC Yukon with what many experts consider one of the industry's most advanced hybrid systems. A 25 percent boost in fuel economy is expected, along with an industry first for a hybrid: The vehicle will be able to tow heavy loads. The 2009 Cadillac Escalade will offer the same feature.
  
  The hybrid system has a 320-hp, 6.0-liter V-8 and a four-speed automatic transmission that has two electric motors. The motors propel the vehicle from a stop to 20 mph. The engine incorporates cylinder deactivation, and the vehicle body has aluminum panels to reduce weight.
  
  
• If lithium ion batteries are ready for production in three years, look for GM to roll out plug-in hybrid versions of the Saturn Vue and Aura and possibly the Chevrolet Volt. It is unclear whether GM will use the Volt name for a specific model or incorporate the new technology into an existing model, such as the Malibu.

This powertrain uses an electric motor and a gasoline engine; the electric motor drives the wheels. A turbocharged, 1.0-liter, three-cylinder engine recharges the batteries when needed.

Also, the battery pack can be plugged into a conventional wall outlet for recharging. GM expects a six-hour recharge time.

The system is intended to propel a vehicle 40 miles on a single charge, meaning it could function as a pure electric vehicle for some commuters, using no gasoline.

During a drive longer than 40 miles, the gasoline engine cycles on and off to keep the battery pack charged.

GM estimates the Volt would deliver the equivalent of about 150 mpg during a 60-mile daily commute.

Diesel Engines:

GM plans a range of diesel engines for its U.S. cars and trucks.

This month, GM announced the purchase of a 50 percent stake in Italian diesel maker VM Motori from Penske Corp., giving the automaker more diesel technology and new engine-manufacturing capacity.

Cadillac and Saturn will lead the way for GM's return to diesels in cars. GM Vice Chairman Bob Lutz says that the 2.9-liter V-6 GM is developing with VM Motori for the European version of the Cadillac CTS also will be offered in several U.S. vehicles. A GM source says that engine will be available in the next-generation Aura and in the CTS, probably for the 2010 model year.

GM will offer its new 310-hp, 4.5-liter, turbodiesel V-8 in the Hummer H2 and in light-duty versions of the Chevrolet Silverado and GMC Sierra pickups in the 2010 calendar year. The engine should deliver a fuel economy gain of 25 to 30 percent over the current 5.7-liter gasoline engine.

Fuel Cells:

The latest fuel cell stack that GM is preparing for production fits in the same space as a four-cylinder engine.

In May, GM, transferred 500 engineers from its fuel cell research center near Rochester, N.Y., to the company's tech center near Detroit.

These engineers are responsible for developing the technology that will enable GM to mass produce fuel cell vehicles.

This fall, GM will test its fuel cell technology in a fleet of 100 hydrogen-powered Chevrolet Equinox cross-overs. GM hopes to have its fuel cell powertrain ready for mass production by 2010.

The key advantage of a fuel cell is emissions. It takes the automobile out of the emissions debate - the fuel cell emits warm air and water vapor.

Hi-Tech Features:

Variable valve timing, turbocharging and direct injection are starting to appear in GM vehicles. These features boost performance, reduce emissions and can improve fuel economy.

Engines such as the one in the Pontiac Solstice GXP point the way to the future for GM. That engine is a 260-hp, turbocharged 2.0-liter with direct fuel injection that gets 22 mpg city/31 mpg highway compared with the Solstice's 177-hp, 2.4-liter base engine, which is rated at 20 mpg city/28 highway.

GM's next gasoline direct-injection engine is scheduled for production this fall in the 2008 Cadillac CTS and STS.

The 3.6-liter V-6 cranks out 300 hp and is expected to deliver around 27 mpg on the highway. Direct injection improves performance and reduces emissions, especially on cold starts, according to Ameer Haider, GM's assistant chief engineer for the engine.

GM expects to be producing as many as 200,000 direct-injection engines by the 2010 model year.

6-Speed Automatics:

This year, GM launched the six-speed, fwd automatic transmission it co-developed with Ford Motor Co. Last year, GM rolled out its new six-speed rear-drive transmission in SUVs and other trucks. Both transmissions contribute to a 5 percent increase in fuel economy over the four-speed transmissions they replaced.

[Drew Dowdell]

2 issues:

1. How does someone make an 80mpg, 640hp, 932 mile range Mini-cooper, yet GM struggles to bring a 40mpg Malibu to market?

2. Cadillac should have offered the base CTS with a direct injected 2.8 litre that puts out the same HP as the current 3.6 but offers better mileage.

[loki]

...

GM will offer its new 310-hp, 4.5-liter, turbodiesel V-8 in the Hummer H2 and in light-duty versions of the Chevrolet Silverado and GMC Sierra pickups in the 2010 calendar year. The engine should deliver a fuel economy gain of 25 to 30 percent over the current 5.7-liter gasoline engine.

...

The 3.6-liter V-6 cranks out 300 hp and is expected to deliver around 27 mpg on the highway.

current 5.7L ?!! it's been what, 2 or 3 years since that's been made. should compare it to the 5.3 or 6.0

forgot to say it runs on regular, no need for "premium"

2 issues:

1. How does someone make an 80mpg, 640hp, 932 mile range Mini-cooper, yet GM struggles to bring a 40mpg Malibu to market?

2. Cadillac should have offered the base CTS with a direct injected 2.8 litre that puts out the same HP as the current 3.6 but offers better mileage.

curious about #1. i don't doubt it, but where's a link?

#2...hm. that would be nice for ..oh wait, i think replacing the 3.8L in the lacrosse with the 2.8DI, and maybe any places the 3.5L needs to leave, when/if it happens would be a better idea. cadillac needs that image that they don't compromise for performance/price/luxury, while it'd be good for CAFE ideas, they don't need that, yet.

[Drew Dowdell]

curious about #1. i don't doubt it, but where's a link?

Boogie woogie woogie

Edited August 2, 2007 by Oldsmoboi

[Northstar]

2 issues:

1. How does someone make an 80mpg, 640hp, 932 mile range Mini-cooper, yet GM struggles to bring a 40mpg Malibu to market?

2. Cadillac should have offered the base CTS with a direct injected 2.8 litre that puts out the same HP as the current 3.6 but offers better mileage.

1) Because the Mini weighs 2500lbs and the Malibu weighs 3600. Fuel economy has a lot to do with weight and less to do with horsepower. The Mini Cooper probably also has a ridiculously tall top gear to achieve that mileage.

2) Cost. The 2.8 DI would cost about the same as the 3.6 DI. It's the same block, same components, just smaller heads and cylinders. The 3.6 non-DI has to be cheaper than a 2.8 DI. Also note that the 2.8 gets the same mileage as the 3.6 in the current CTS, so I'm not so sure the 2.8 DI would get that much better mileage. Again, mileage has more to do with weight than power. If you put an LS7 in a go-cart, it'd probably get 200 MPG because it only has to rev to 2000 rpm to make it go 500 MPH in 6th gear.

[Drew Dowdell]

1) Because the Mini weighs 2500lbs and the Malibu weighs 3600. Fuel economy has a lot to do with weight and less to do with horsepower. The Mini Cooper probably also has a ridiculously tall top gear to achieve that mileage.

2) Cost. The 2.8 DI would cost about the same as the 3.6 DI. It's the same block, same components, just smaller heads and cylinders. The 3.6 non-DI has to be cheaper than a 2.8 DI. Also note that the 2.8 gets the same mileage as the 3.6 in the current CTS, so I'm not so sure the 2.8 DI would get that much better mileage. Again, mileage has more to do with weight than power. If you put an LS7 in a go-cart, it'd probably get 200 MPG because it only has to rev to 2000 rpm to make it go 500 MPH in 6th gear.

1. The Mini cooper has no gears at all. The electric motors are in the hubs of the wheels. Each wheel is a 160hp electric motor.

2. Image. Put a different gearbox in it, tune it for efficiency over power and have a 5-series size car that gets 30mpg+

[Northstar]

1. The Mini cooper has no gears at all. The electric motors are in the hubs of the wheels. Each wheel is a 160hp electric motor.

2. Image. Put a different gearbox in it, tune it for efficiency over power and have a 5-series size car that gets 30mpg+

1. Well in that case how can you compare a basically totally electric vehicle to a gas powered one?

2. What gearbox do you suggest? What do you actually want in this 2.8 DI engine? First you say make it have the same power as the current 3.6 and better mileage. That would require 92 HP/L, or 7+ HP/L more than the 3.6 DI makes. That means you have to had some higher-performing part elsewhere, which usually doesn't lead to better mileage. Then you say you want it tuned for mileage so that it gets 30MPG. Well, which do you want? A 2.8 DI would make 235HP on paper (based on the same HP/L as the 3.6) and I see no reason why it would get any more than 1 MPG more than the 3.6 DI. The CTS is a heavy vehicle at ~4000 pounds and unless you go with a hybrid powertrain I don't think you're going to find many 4000lb vehicles with 260HP that get 30MPG without a hybrid system.

[smk4565]

2 issues:

1. How does someone make an 80mpg, 640hp, 932 mile range Mini-cooper, yet GM struggles to bring a 40mpg Malibu to market?

2. Cadillac should have offered the base CTS with a direct injected 2.8 litre that puts out the same HP as the current 3.6 but offers better mileage.

Point 1 is funny.

I totally agree with #2. I had a big problem with the base engine from the beginning. If the optional engine gets better mileage and more power, what is the point of even having the other engine. Every single GM 4 and 6 cylinder should be a DOHC direct injection engine by 2010. They could get 250 hp from a 2.8 DI V6 and probably gotten an extra 2 mpg over the 3.6 liter. Gas mileage is more important to some people than horsepower.

The Volt could be GM's most important car ever. I really hope they offer a luxury interior as well as the base. There are many people that gas mileage matters a lot to, but 45-60 year olds probably will want a nice interior, and not something like a college student drives.

Personally I am waiting for the Ultra V8, I want to see how good that is. Better be good, BMW is working on a twin-turbo DI V8 to go with the twin-turbo six. The six makes 300 hp, the V8 is rumored to be 408 or even more.

[Drew Dowdell]

1. Well in that case how can you compare a basically totally electric vehicle to a gas powered one?

2. What gearbox do you suggest? What do you actually want in this 2.8 DI engine? First you say make it have the same power as the current 3.6 and better mileage. That would require 92 HP/L, or 7+ HP/L more than the 3.6 DI makes. That means you have to had some higher-performing part elsewhere, which usually doesn't lead to better mileage. Then you say you want it tuned for mileage so that it gets 30MPG. Well, which do you want? A 2.8 DI would make 235HP on paper (based on the same HP/L as the 3.6) and I see no reason why it would get any more than 1 MPG more than the 3.6 DI. The CTS is a heavy vehicle at ~4000 pounds and unless you go with a hybrid powertrain I don't think you're going to find many 4000lb vehicles with 260HP that get 30MPG without a hybrid system.

1. Volt? The mini cooper has a small V2 petrol engine to recharge the batteries. But still, even if you had just two wheels with electric motors, you'd have a car with 320 horsepower and amazingly high MPG.

2. a. I'd suggest a gearbox with a really tall overdrive with a 2.8 litre tuned to make as much of it's torque as possible in the low RPM range so it can loaf around 1700 rpm at 70mph in 6th gear.

b. CTS base is 3800lbs

c. Toyota Avalon

[emh]

1. How does someone make an 80mpg, 640hp, 932 mile range Mini-cooper, yet GM struggles to bring a 40mpg Malibu to market?

The link you posted goes to a 78kW (~104hp) 200 mile range Mini for $50k. What am I missing?

[Drew Dowdell]

The link you posted goes to a 78kW (~104hp) 200 mile range Mini for $50k. What am I missing?

The part where I post the correct link. Sorry... fixed now to the correct article.

[emh]

I totally agree with #2. I had a big problem with the base engine from the beginning. If the optional engine gets better mileage and more power, what is the point of even having the other engine.

Uh... it's cheaper.

The Volt could be GM's most important car ever. I really hope they offer a luxury interior as well as the base. There are many people that gas mileage matters a lot to, but 45-60 year olds probably will want a nice interior, and not something like a college student drives.

There's no point trying to offer a luxury interior in the same car "a college student drives". I'd much rather see the technology adapted to existing cars in different market segments. Edited August 2, 2007 by emh

[emh]

The part where I post the correct link. Sorry... fixed now to the correct article.

I see... thanks for the link. But you can't really compare a one-off technology demonstration to a production vehicle. A much more compelling case would be to argue why GM doesn't have a competitor to the likes of the Tesla roadster (0-60 in 4s and energy efficiency equivalent to 135mpg according to Wikipedia -- yes that great source of absolutely accurate information). Of course, this applies to all major manufacturers, not just GM.

[dado]

Any news on ultra V8? In which car will be put, will it have FI,etc.

[Drew Dowdell]

I see... thanks for the link. But you can't really compare a one-off technology demonstration to a production vehicle. A much more compelling case would be to argue why GM doesn't have a competitor to the likes of the Tesla roadster (0-60 in 4s and energy efficiency equivalent to 135mpg according to Wikipedia -- yes that great source of absolutely accurate information). Of course, this applies to all major manufacturers, not just GM.

My point is that the technology is out there. The Tesla is a great example of this also.

[Drew Dowdell]

Any news on ultra V8? In which car will be put, will it have FI,etc.

Well, I assume it's not going to be carburated....

[emh]

My point is that the technology is out there. The Tesla is a great example of this also.

I agree, but my point is that just because a technology exists doesn't mean it's commercially viable. For a good example, think about super-sonic flight -- technology that has existed for decades but isn't in use in commercial flight today (and the one historical use was a commercial failure).

[thegriffon]

Two historical uses. You're forgetting the Russians had one as well.

[dado]

Well, I assume it's not going to be carburated....

OMG..you didn't really think that by FI i meant fuel injection?? I meant forced induction-supercharger or turbocharger. Who would use carburator now??

[thegriffon]

1) Because the Mini weighs 2500lbs and the Malibu weighs 3600. Fuel economy has a lot to do with weight and less to do with horsepower. The Mini Cooper probably also has a ridiculously tall top gear to achieve that mileage.

2) Cost. The 2.8 DI would cost about the same as the 3.6 DI. It's the same block, same components, just smaller heads and cylinders. The 3.6 non-DI has to be cheaper than a 2.8 DI. Also note that the 2.8 gets the same mileage as the 3.6 in the current CTS, so I'm not so sure the 2.8 DI would get that much better mileage. Again, mileage has more to do with weight than power. If you put an LS7 in a go-cart, it'd probably get 200 MPG because it only has to rev to 2000 rpm to make it go 500 MPH in 6th gear.

Which is why BMW has quietly dropped the 2.5 L I6 in favor of a lower-output version of the 3.0 L DI engine (of course Americans get a different, non-DI 3.0 L badged 328 to match Mercedes' 3.0 L C280). GM's 2.8 exists primarily as a base for turbocharging. Expect output to keep increasing (beyond the current 280 PS) as the driveline allows increasingly higher torque and hp levels.

[Drew Dowdell]

OMG..you didn't really think that by FI i meant fuel injection?? I meant forced induction-supercharger or turbocharger. Who would use carburator now??

Myself, along with FlyBrian, OCN, Pontiac-Custom, and a few others are the smart asses of the site.

Flybrian is king smart ass though.

[dado]

Myself, along with FlyBrian, OCN, Pontiac-Custom, and a few others are the smart asses of the site.

Flybrian is king smart ass though.

good to know :lol:

[smk4565]

Uh... it's cheaper.

It is a Cadillac, "cheap" shouldn't factor in to any decisions. I didn't see Lexus going with a 6-speed auto for the Lexus LS, they brought out an 8-speed transmission, I am sure that wasn't cheap, and they don't care. Cadillac needs that attitude.

On another topic, the 2.8L V6 with DI might not make 260 hp, but I think 245 is very doable, it makes 210 now, 245 is probably a goal they can meet, they got nearly 50 more hp from the 3.6 liter, they should be able to get 35 from the smaller engine. Or make the 2.8 a 2.9 liter if need be to get it to 245 hp. Under 3 liter is good for foreign markets that limit or tax displacement. That engine could be a real winner for cars like the Malibu, Aura, next gen LaCrosse, Pontiac alpha car, etc. And maybe GM should do a light hybrid on every car. Toyota in 10 years says they will be 100% hybrid, might as well try to beat them to it.

There's no point trying to offer a luxury interior in the same car "a college student drives". I'd much rather see the technology adapted to existing cars in different market segments.

Then maybe they have to do 2 Volts. I think it will be tough to get more mature buyers to buy a Volt if the interior is like a base Cobalt. But if they make it like a $28k car interior, they will price too many people out. If they have a nice LTZ package, they could pull it off I think in one car.

[cletus8269]

weight could be an issue with the interior too though right? if the car is all electric the less it weighs the better because that could in turn determine a 100 mile trip or a longer trip. all that fancy ooh and ahh crap may just add ballast or just pull more on the batteries.

http://www.teslamotors.com/styling/cockpit/cockpit.php

Edited August 3, 2007 by cletus8269

[Drew Dowdell]

Make the Volt technology a trimline in existing vehicles.

You can buy a Chevy Malibu... or a Chevy Malibu Volt

You can buy a Buick LaCrosse... or a Buick LaCrosse Electra

You can buy a Cadillac CTS... or a Cadillac CTS - E

You can buy a GMC Yukon... or a GMC Yukon Electromotive

You can buy a Saturn Aura... or a Saturn Aura Power-line

Sorry, I couldn't come up with one for Pontiac..... but I did most of the heavy lifting here.

Edited August 3, 2007 by Oldsmoboi

[CaddyXLR-V]

Make the Volt technology a trimline in existing vehicles.

You can buy a Chevy Malibu... or a Chevy Malibu Volt

You can buy a Buick LaCrosse... or a Buick LaCrosse Electra

You can buy a Cadillac CTS... or a Cadillac CTS - E

You can buy a GMC Yukon... or a GMC Yukon Electromotive

You can buy a Saturn Aura... or a Saturn Aura Power-line

Sorry, I couldn't come up with one for Pontiac..... but I did most of the heavy lifting here.

Pontiac Wave, or Pontiac ShockWave

[AAS]

Pontiac Wave, or Pontiac ShockWave

Pontiac Buzzzz!

I can imagine the commercial now...

guy 1: Hey! What's with all the buzzz?

guy 2: It's a Pontiac!!!

(though lame, this sounds much funnier in my head and doesn't seem to translate well in text...)

[bcs296]

The hybrid system has a 320-hp, 6.0-liter V-8 and a four-speed automatic transmission

Damn, I just threw up in my mouth a little...

[Drew Dowdell]

Damn, I just threw up in my mouth a little...

it's not just a 4-speed auto..... it's 4 fixed gears plus 2 electric CVTs.

This transmission really needs a new name so people can get off this 4-speed rant.

[thegriffon]

Not two electric CVTs, two electric motors in conjunction with the planetary gear sets combine to form one electro-mechanical CVT. When you have an infinitely variable transmission adding extra fixed-gear sets is pointless.

[thegriffon]

NEW APPLICATIONS: CHEVROLET TAHOE, GMC YUKON

The 2-Mode transmission’s case size is nearly the same as the GM 6-speed rear wheel drive transmission, minimizing the impact to vehicle packaging.

ALL-NEW DESIGN FOR REAR- AND ALL-WHEEL DRIVE

The 2 Mode Hybrid Transmission (M99) is available in both two and four-wheel drive configurations. The M99 can mate with a BorgWarner 4485 transfer case, which was developed with GM Powertrain for uplevel, full-size trucks. This transfer case features an open planetary differential. Traction control and wheel slip monitoring are performed by the stability and anti-lock braking systems.

The 2-Mode Hybrid Transmission contains two electric motors, 3 planetary gear sets, and 4 wet-plate clutches. The hybrid transmission can operate in multiple modes including propelling the vehicle electrically with the combustion engine off. Two continuous ratio modes of operation are attained with the electric motors, one with the combustion engine supplying torque, and the other with the other with an electric motor supplying torque. Since the continuous ratio ability is attained with one of the electric motors, these modes are described as Electrically Variable Transmission modes or “EVT” modes. Three 300 volt A/C cables are connected to each of the two motors, these cables attach to the transmission housing via a rigid conduit around the transmission and are connected to the an inverter which drives the motors.

Four fixed ratios of 3.7:1, 1.7:1, 1.0:1 and 0.7:1 may be chosen for balancing performance and fuel economy. The fixed ratios also let the transmission save battery power that would otherwise be used to control range of the variable ratios to keep the engine in its optimal rev range. Fixed ratios also allow overdrive, for faster overall total speed of the vehicle. Fixed gear changes are accomplished with clutch-to-clutch control, where an oncoming clutch is engaged and an “offgoing” clutch is released in a precise manner to achieve the ratio change. The first-to-second upshift, however, is a freewheeling action, where the second gear clutch engages while the first gear one-way clutch spins freely. This allows a greater degree of smoothness at lower vehicle speeds.

MATCHED TO 6.0L V8 AFM AND VVT V8

The two-mode hybrid is mated to an optimized gasoline/flex-fuel engine, which takes advantage of AFM cylinder deactivation, optimized late intake valve closing (LIVC) to reduce pumping losses, flex-fuel usage for operation on 85 percent ethanol bio-fuel, as well as variable valve timing (VVT).

ENGINE OFF OPERATION

With engine off operation, additional features were added to the main case to minimize noise vibration and harshness. Additional ribbing has been designed to the main case while structure has been added to the input housing enabling the mounting of the electric motors.

In typical operation an acceleration will be initiated with the engine off and utilize only electrical power. As the acceleration continues, the electric motors will simultaneously propel the vehicle and start the engine. With the engine running the control system will blend the electrical energy with the engine energy operating in the most efficient range to maximize fuel economy.

In a 2-mode system, one electric motor controls the speed ratio using the sun gear of a planetary gearset as the input from the gasoline combustion engine and a second motor generates electricity to power the first motor, or to supply torque to the output shaft. The hybrid design therefore has two power sources, the gasoline/ethanol combustion engine and the electric motor, and either can supply torque independently to the output shaft and final drive.

An externally mounted oil pump supplies oil pressure for the hydraulic clutches, and for cooling the electric motors with the combustion engine running or turned off.

TOWING CAPABILITY INCREASED

Under higher load drive cycles the control system will directly clutch the engine through the transmission, effectively locking the first electric motor between its input and output, enabling full V8 engine torque with electric motor assist torque.

FUEL EFFICIENCY DRAMATICALLY INCREASED

With these systems all working in concert, the fuel efficiency of the vehicles, the Tahoe and Yukon, is expected to achieve approximately 25 percent better fuel efficiency. While these current 6.0L V-8 applications are rated from 15 to 16 mpg on the EPA city cycle and from 20 to 22 mpg on the EPA highway cycle, with the EVT the fuel efficiency is expected to achieve approximately 18 to 20 mpg on the EPA city cycle and up to 25 to 26 mpg on the EPA highway cycle.

INCREASED PERFORMANCE

Combined engine and transmission output is 369 bhp and 380 lb ft of torque, with 310 bhp and 340 lb ft coming from the 6.0L V8 Gen IV gasoline engine. The 2 Mode Hybrid transmission adds the equivalent of the balance of the output, and in addition it increases the time the engine can remain at peak power during acceleration. The fixed gear ratios are designed to let the most power be used over the most useful vehicle speeds.

Overview

Model year 2008 interim is the debut of the two-mode M99 electrically variable hybrid transmission. It was developed from the years of experience GM has gained from designing large passenger buses with single-mode hybrid drive systems.

Electrically Variable Transmissions (EVT) have been used since the 1930s, and are most prevalent in locomotives. These are one-mode operations, with the combustion engine driving a generator which powers electric motors at the wheels. This requires very large electric motors to enable variable speed ranges.

GM began building passenger buses with two-mode EVTs, the first mode using an input-split EVT mode and the second being a compound-split EVT mode and production began in 2003. The two-mode systems reduce the size of the electric motors necessary, allowing them to be used in smaller vehicles.

In addition, to optimize the size of the electric motors for a private passenger vehicle, the 2 Mode RWD Hybrid Transmission uses four fixed ratios, added with the addition of two additional planetary gearsets. The fixed ratios in addition to the EVT continuously variable ratios were developed for the full-size SUVs to improve fuel efficiency and meet all requirements for acceleration, towing, top speed, driveline refinement, and emissions.

Locking the first motor keeps the output shaft operating at the same speed as the input shaft, which is called “input-split” mode. This is a single-mode system such as is used on the commercial vehicles. For passenger vehicles it can have high fuel efficiency or high power, but not both. That is why the two-mode, or “compound-split”, system with two electric motors was developed for the Tahoe and Yukon.

The clutches in the 2-mode EVT are wet hydraulic clutches, similar to those in a conventional automatic transmission, and require a pump to activate, however unlike a conventional automatic transmission, the pump is independent from the torque supplied by the gasoline combustion engine.

The fixed ratios are operated by synchronous “clutch-on, clutch-off” timing, which allows smooth shift events between modes of fixed and variable ratio operation. The fixed ratios were added to the EVT design to allow superior towing capability without requiring larger electric motors. This required two additional clutches and two additional planetary gearsets, which with the electric motors can be packaged inside a case that fits in the existing platform package of the Tahoe/Yukon application.

In layman’s terms, the 2-Mode EVT can be thought of like two transmissions connected inline: One transmission is continuously variable by way of using an electric motor to vary ratios, and the other is a conventional stepped-ratio transmission. The fixed gears take over when power demand from the combustion engine is higher than the electric motor’s ability to maintain a ratio.

The fixed gears are used in high-load situations. When the fixed gears are in use, the electric motors then can generate electricity rather than consume it, or they can also be used to add torque to the output shaft for better performance. Coasting and braking also allow the electric motors to generate electricity.

Low maintenance

DEXRON® VI is used as a lubricant and to cool the electric motors. For normal use there is no fluid change scheduled. DEXRON® VI was developed to have a more consistent viscosity profile; a more consistent shift performance in extreme conditions; and less degradation over time. Internal GM tests have demonstrated DEXRON® VI delivers more than twice the durability and stability in friction tests compared to existing fluids.

The 2008i 2 Mode RWD Hybrid Transmission (M99) is produced in Baltimore, Maryland.

[Satty]

Sorry, I couldn't come up with one for Pontiac..... but I did most of the heavy lifting here.

Pontiac probably wont be around in 4 years anyways.

[4gm]

Noticeably absent from the article was talk of any 4 cylinder disel or small displacement 4 cylinder with direct injection.

[dwightlooi]

OK... I went and drove a Saturn Aura 3.6 over the weekend. Here are the conclusions.

The 3.6 liter (LY7) is OK at lower engine speeds (<3000~4000 rpms). But it get's rather coarse at 5000~6500. Yes, I have pretty high standards as to what "coarse" is, but let's just say that it is coarser than the VQ35 (Nissan/Infiniti) which isn't exactly known for upper end refinement and significantly coarser than the Honda C30/C32 engines (Accord-V6/Acura-3.2TL). It is similar in smoothness to the Mazda/Ford 3.0 liter (Duratec30/MZI) in the upper end, but more refined under 4000 rpm. The engine note is an uninspiring blah-blah with a granular rush toward the redline - a combination of an argicultural groan with a rather plastic sounding moan when pushed. Too much low frequency sounds filtering through, no metallic rasp or whirls. I'll say that is below average for a 60 degree V6 of a rather modest 85.6mm stroke. On a 1 to 10 scale for refinement -- if the BMW M52 Inline-6 (E36 2.5 liter) is a 9.5, the Mazda K-series 2.5 liter V-6 is an 8, the Honda C30 is a 7, my Audi 2.7T (2001 S4) is a 6.5 and the Nissan/Infiniti VQ35 (Altima/G35/Murano/350Z/you name it) is a 5 -- I'll rate the LY6 at a 4.

The 6T70 automatic was however very well implemented. Shifts very well and very smoothly. The lock-up clutch stays locked more than I am used to which is actually very encouraging. Shift speed is about as good as the Aisin TF60SC (VW-Audi 6A - traverse) which is very decent, but the box is actually smoother in lower gear transitions. Fantastic. This is definitely a solid 9 in my book.

I think GM needs to do three things --

(1) Put as balance shaft-in -- yes, you can even on a 60 degree engine although it is not normally done. The shaft will turn at crank speed and quell 1st order end-to-end rocking forces of the 60 degree layout.

(2) Increase the stiffness of the block with additional Iso-grids or webbings in the castings with the explicit purpose increasing the resonance frequency of the block. Higher frequencies sound metallic -- lower frequencies sound agricultural and/or plasticky.

(3) Re-tune Quiet Tuning measures to reduce low frequency sound passage and increase higher frequency sound passage.

Why do all of these? Well, why bother to make a DOHC VVT V6 only to have it sound little better than the 12v push rodder? This engine may cut it as a Saturn or Pontiac mill, but if it is to power Caddys (albiet with a bump in output due to DI) it'll need to shape up. Otherwise, they should take the easy route and de-stroke the 4.2 liter Vortec 4200 Inline-6 (LL8) from 102mm to 88mm to produce a 3.6 liter mill which is naturally vibration free and which already has a very nice metallic whirl to it even in 4.2 liter form.

[Drew Dowdell]

I'm curious as to what "agricultural" sounds like.

I noticed with the 3.6 in my CTS that it noticeably smoothed out as it ages. For the first 10,000 miles or so, you're right, it's still a bit 3800 sounding. Now that I'm around 42,000 it's smooth like butta...

[dwightlooi]

I'm curious as to what "agricultural" sounds like.

I noticed with the 3.6 in my CTS that it noticeably smoothed out as it ages. For the first 10,000 miles or so, you're right, it's still a bit 3800 sounding. Now that I'm around 42,000 it's smooth like butta...

It sounds a little gritty. Sort of like tire noise over concrete freeways. The sound is a mixture of low and mid frequencies. And, as I said, there is just a lot of these low and mid frequency "groans" and basically no high frequency, turbine like, whirls, or metallic rasps like some other engines. It isn't horrible, just uninspiring.

Maybe... its just that you got used to it and didn't notice as much.

[loki]

Noticeably absent from the article was talk of any 4 cylinder disel or small displacement 4 cylinder with direct injection.

maybe for the next ~3-4 years the 2.0L turbo will be the only DI'ed 4, and hopefully gm does a 4 diesel to compete against honda and others, at least in something like the aveo. for 4 cylinders i'd hope something like the 1.8 or 2.0L could be DI w/o a turbo for base engines and a 2.4 DI for a sportier model for the delta size cars

[dwightlooi]

maybe for the next ~3-4 years the 2.0L turbo will be the only DI'ed 4, and hopefully gm does a 4 diesel to compete against honda and others, at least in something like the aveo. for 4 cylinders i'd hope something like the 1.8 or 2.0L could be DI w/o a turbo for base engines and a 2.4 DI for a sportier model for the delta size cars

I am all for greater use of the LNF (2.0L DI Turbo). In fact I think GM should simply eliminate the 3.6 liter engine in smaller car applications and simply use the LNF. It is more refined sounding, it is more economical, it is lighter, it is more "tunable" as far as enthusiasts are concerned, it has a fatter torque band and it is easier to work on and fix. It sounds wonderful too, especially at 1500~2500 rpm in a parking lot where it makes a very neat whistling sound as the turbo spools gently on low load. 260hp / 260 lb-ft is basically equal or to the 3.6 VVT.

The 2.0 liter I4 is better in just about every measure compared to the 3.6 VVT except for the fact that some buyers are simply stuck on the V6 badging that a 6-cylinder engine will allow for.

Edited August 12, 2007 by dwightlooi

[thegriffon]

Noticeably absent from the article was talk of any 4 cylinder disel or small displacement 4 cylinder with direct injection.

Already in the pipeline. the cost for a 4-cylinder diesel in the US may be excessive, but see the long version of GM Europe's EcoFlex release for news on small engine developments, stop-start systems etc. There is also GM's version of what Daimler is calling Diesotto, but don't expect them to do what Mercedes will and offer it in a large luxury car (S 220 1.8 L Turbo). Edited August 12, 2007 by thegriffon

[thegriffon]

I am all for greater use of the LNF (2.0L DI Turbo). In fact I think GM should simply eliminate the 3.6 liter engine in smaller car applications and simply use the LNF. It is more refined sounding, it is more economical, it is lighter, it is more "tunable" as far as enthusiasts are concerned, it has a fatter torque band and it is easier to work on and fix. It sounds wonderful too, especially at 1500~2500 rpm in a parking lot where it makes a very neat whistling sound as the turbo spools gently on low load. 260hp / 260 lb-ft is basically equal or to the 3.6 VVT.

The 2.0 liter I4 is better in just about every measure compared to the 3.6 VVT except for the fact that some buyers are simply stuck on the V6 badging that a 6-cylinder engine will allow for.

Except that the 3.6 is already 270+ and even 300+ in DI form. Of course the 2.8 Turbo will soon be 300+ as well, but that is just as if not more expensive to produce.

[dwightlooi]

Except that the 3.6 is already 270+ and even 300+ in DI form. Of course the 2.8 Turbo will soon be 300+ as well, but that is just as if not more expensive to produce.

Well, the 3.6 VVT ranges in output from 240 to 275 hp in port injected form and 304 in DI form. The 2.0 LNF I4 is 260hp in its 1st iteration. You can get between 200 or 300 hp out of the LNF easily depending on how much turbo lag you want to put up with. I'll say that the output of the two engine families are essentially equal.

The big difference is that the LNF is:-

(1) More economical when driven gently because of its smaller displacement, 2/3 as many cylinders and half as many cylinder heads.

(2) Has superior torque characteristics - 260 lb-ft from 2500 rpm vs a torque peak in the 4000~5200 range for the 3.6.

(3) Its lighter and slimmer than a 3.6 liter.

(4) Is smoother and more refined sounding than the 3.6 (surprisingly enough).

[thegriffon]

Looking further out, an 8-speed auto is almost certain, there being not only numerous patents, but a trademark as well.

GM also has innumerable patents for dual-clutch planetary transmissions, several for 7-speed dual-clutch counter-shaft transmissions (traditional DCTs), one for a hybrid planetary/countershaft DCT, and even a triple-clutch countershaft transmission (requiring less space and fewer gearsets)!! According to union documents a 7-speed DCT will be offered in the Corvette and undoubtedly other rwd cars.

A basic search for 9- and 10-speed transmission patents registered by any company uncovers a handful for each—one each for both types by Eaton, and several more for both types by … General Motors. These seem to be primarily for medium-duty trucks and with the sale of Allison are not being further developed at present. No-one else seems to have similar patents in the US, but a more exhaustive search could uncover more.

As for engines, GM has several recent patents for multi-stage valve-lift mechanisms (switchable cam lobe systems like Mazda's SVT and Honda's VTEC), but with three stages instead of the standard two; and several more for electro-hydraulic valve actuation. According to suppliers developing such systems, unnamed manufacturers will offer engines with these active valve systems from 2009.

Oh yeah, a DI engine with flex-fuel capability also seems on the cards.

[dwightlooi]

A C-VVL system like this can work on a cam-in-block engine like the LS3 or L99...

by basically changing the rocker ratio from say 1.3:1 to 1.73:1 continuously...

Edited August 31, 2008 by dwightlooi

[ZL-1]

Looking further out, an 8-speed auto is almost certain, there being not only numerous patents, but a trademark as well.

GM also has innumerable patents for dual-clutch planetary transmissions, several for 7-speed dual-clutch counter-shaft transmissions (traditional DCTs), one for a hybrid planetary/countershaft DCT, and even a triple-clutch countershaft transmission (requiring less space and fewer gearsets)!! According to union documents a 7-speed DCT will be offered in the Corvette and undoubtedly other rwd cars.

A basic search for 9- and 10-speed transmission patents registered by any company uncovers a handful for each—one each for both types by Eaton, and several more for both types by … General Motors. These seem to be primarily for medium-duty trucks and with the sale of Allison are not being further developed at present. No-one else seems to have similar patents in the US, but a more exhaustive search could uncover more.

As for engines, GM has several recent patents for multi-stage valve-lift mechanisms (switchable cam lobe systems like Mazda's SVT and Honda's VTEC), but with three stages instead of the standard two; and several more for electro-hydraulic valve actuation. According to suppliers developing such systems, unnamed manufacturers will offer engines with these active valve systems from 2009.

Oh yeah, a DI engine with flex-fuel capability also seems on the cards.

The issue is then how to bring this stuff to market before the competition does it. In other words, money (or lack of it) and management willing to risk making a few bad bets along the way.

Edited August 31, 2008 by ZL-1