Tech Preview: GM Two-Mode Hybrid Pickups

[91 s-10baja]

Tech Preview: GM Two-Mode Hybrid Pickups
By: Mike Levine Posted: 10-18-07 00:00 PT

© 2007 PickupTruck.com

If the discontinued GMT 800 Chevrolet Silverado Hybrid was a 'mild' hybrid, then the new GMT 900 Two-Mode Hybrid must be a jalapeno.
I recently drove the 2008 Chevrolet Tahoe Hybrid to get a full size, SUV-flavored preview of the 2009 Silverado Two-Mode pickup. The next-gen Silverado Hybrid is expected to go on sale a year from now.
General Motors co-developed Two-Mode Hybrid technology with Daimler|Chrysler and BMW. It's more capable and versatile than the parallel hybrid technology it replaces.
http://www.pickuptruck.com/html/stor...ode/page1.html

[unkillsam]

So 4-mode hybrids are coming within the next decade?

[DuSpinnst]

Originally Posted by unkillsam

So 4-mode hybrids are coming within the next decade?

4-mode would just be adding two other EVT ranges.

Probably spliting the current modes in half and tweaking the running variables in each.

AHS-R(WD) should start development in 2009. Current Two-Mode is AHS-T(ruck), and AHS-C(omfort).

AHS-F(WD) is a separate program (see 2009 VUE)

[MechEng]

Intresting read I found the end of the article most intresting.

"And don't get hopes up for a diesel hybrid either. Mr. White explained that hybrids and diesels are independently expensive powertrains to produce. Combining the two would likely not yield high enough fuel economy improvements to make it economically worthwhile to offer a diesel-electric Two-Mode Hybrid truck.

So what comes after the Two-Mode Hybrid? It could eventually be a serial hybrid pickup, like the Chevy Volt or what entrepreneur Ian Wright proposes. But that's a long way off. According to Mr. Lutz, look for Four Mode Hybrids next, which will add extra modes to more efficiently run the truck in a wider array of driving conditions."

[HEVguy]

This article is, overall, a nice summary of the 2-mode offering from GM. It is unfortunate that the author is WRONG in his overall summary of the system, toward the beginning. The 2-mode IS a 'CVT' in the SAME sense as the Prius is a 'CVT.' They are both ECVTs, which the author does correctly state later in the article. I guess GM is afraid of saying there is a CVT in a truck, because of the CVTs historical problems with torque capability and reliability. HOWEVER, they need to stop fretting, just say it like it is. So what if it is an ECVT with 4 'fixed' modes. If your afraid of any CVT doubts, play up how this advanced CVT is completely different from any other CVTs out on the market,... AND emphasize its truck-like capability and durability! Problem (or made up problem) solved, and confusion over as well!!!

[HEVguy]

I agree, the 4-mode is an interesting proposition,... as long as it adds even more system efficiency and only incrementally to cost, I'd say bring it on!

As far as not offering a hybrid diesel, I understand their point from a financial perspective,... HOWEVER if they can get a noticeably higher fuel economy with this combination,... like the Prius currently does compared to all other available hybrids, but in this case in the truck segment, then this may be worth the extra costs by making GM the clear leader in heavy hybrid technology/offerings. Like Lutz has said before, they have to consider the PR / free advertising / media fan boy behavior that would ensue from a kick-a$$, highest fuel economy, AND high torque/towing diesel hybrid. I am not saying that it definitely makes sense, but hopefully they are at least studying the costs vs. benefits seriously.

[unkillsam]

Originally Posted by HEVguy

I agree, the 4-mode is an interesting proposition,... as long as it adds even more system efficiency and only incrementally to cost, I'd say bring it on!

As far as not offering a hybrid diesel, I understand their point from a financial perspective,... HOWEVER if they can get a noticeably higher fuel economy with this combination,... like the Prius currently does compared to all other available hybrids, but in this case in the truck segment, then this may be worth the extra costs by making GM the clear leader in heavy hybrid technology/offerings. Like Lutz has said before, they have to consider the PR / free advertising / media fan boy behavior that would ensue from a kick-a$$, highest fuel economy, AND high torque/towing diesel hybrid. I am not saying that it definitely makes sense, but hopefully they are at least studying the costs vs. benefits seriously.

20/21 or whatever it is that the Tahoe is rated at is higher then any other full-size SUV. What more do you want?

The amount of money it would cost to get a Tahoe to 30 mpg would gain some sales from people who want a big, guilty free vehicle.

But such a vehicle would likely cost more then $50,000.00

[jomo]

Originally Posted by HEVguy

This article is, overall, a nice summary of the 2-mode offering from GM. It is unfortunate that the author is WRONG in his overall summary of the system, toward the beginning. The 2-mode IS a 'CVT' in the SAME sense as the Prius is a 'CVT.' They are both ECVTs, which the author does correctly state later in the article. I guess GM is afraid of saying there is a CVT in a truck, because of the CVTs historical problems with torque capability and reliability. HOWEVER, they need to stop fretting, just say it like it is. So what if it is an ECVT with 4 'fixed' modes. If your afraid of any CVT doubts, play up how this advanced CVT is completely different from any other CVTs out on the market,... AND emphasize its truck-like capability and durability! Problem (or made up problem) solved, and confusion over as well!!!

Uhm... no. The GM system is NOT a CVT. There are no belts. There are no Discs squeezing on a belt. The GM system is a standard Automatic transmission with some funky input modes. If GM is shying away from calling the transmission a CVT, then they are entirely justified. It's not. Not in the traditional sense. The traditional CVT has a lot of issues related to parasitic losses and expensive oil/operating fluid. Since hydraulic pressure on a set of disks is what causes the belt in the CVT to change ratios, a lot of the engine's power is lost in just operating the mechanism. Also, this operating fluid is more expensive than regular transmission fluid and has, historically, had a poorer operating temperature range. In contrast, the GM system uses conventional planetary gear sets with a set of electric motors embedded amongst them, and it is this set of motors that creates the "variability" of the ratios. Completely different than a true CVT and far more robust than hydraulic pressure on pairs of disks squeezing a drive belt. Why should GM call their transmission something it isn't when that something has negative connotations?

[chakis24]

Originally Posted by unkillsam

20/21 or whatever it is that the Tahoe is rated at is higher then any other full-size SUV. What more do you want?

The amount of money it would cost to get a Tahoe to 30 mpg would gain some sales from people who want a big, guilty free vehicle.

But such a vehicle would likely cost more then $50,000.00

why not make it specail order? im shure there would be people willing to pay. have the technology there, but only build them as necessary. if they can special order the hummer, they can do it with this.

[MechEng]

Originally Posted by jomo

Uhm... no. The GM system is NOT a CVT. There are no belts. There are no Discs squeezing on a belt. The GM system is a standard Automatic transmission with some funky input modes. If GM is shying away from calling the transmission a CVT, then they are entirely justified. It's not. Not in the traditional sense. The traditional CVT has a lot of issues related to parasitic losses and expensive oil/operating fluid. Since hydraulic pressure on a set of disks is what causes the belt in the CVT to change ratios, a lot of the engine's power is lost in just operating the mechanism. Also, this operating fluid is more expensive than regular transmission fluid and has, historically, had a poorer operating temperature range. In contrast, the GM system uses conventional planetary gear sets with a set of electric motors embedded amongst them, and it is this set of motors that creates the "variability" of the ratios. Completely different than a true CVT and far more robust than hydraulic pressure on pairs of disks squeezing a drive belt. Why should GM call their transmission something it isn't when that something has negative connotations?

Then by your definition the Toyota HSD system dosn't use a CVT either. Yes the GM two mode has 4 fixed gear ratio's but the electric motors allow the system to run like a CVT and allow the ICE to run at near constant RPM's.

[joemac]

Originally Posted by unkillsam

20/21 or whatever it is that the Tahoe is rated at is higher then any other full-size SUV. What more do you want?

The amount of money it would cost to get a Tahoe to 30 mpg would gain some sales from people who want a big, guilty free vehicle.

But such a vehicle would likely cost more then $50,000.00

Agreed.... the initial gains are relatively cheap. But to get a Tahoe in plus 30mpg territory, your talking major modifications and weight shed.

Sum the cost of the Hybrid option $6k?, plus the diesel $6k. Plus all the other necessary changes to shed a great amount of weight, aluminum frame, aluminum suspension components, carbon fiber panels, etc etc etc. Your looking at $18+k before you actually put the car around it. An average LT Tahoe runs what 35 to 40k?

You'd have to have seriously deep pockets and death chills come over you when you insert a gas pump into your vehicle for something like this to become viable.

Won't even mention the financial aspect as $18k will buy a lot of gas even at say $4 a gallon.

[Slideways]

Originally Posted by unkillsam

20/21 or whatever it is that the Tahoe is rated at is higher then any other full-size SUV. What more do you want?

The amount of money it would cost to get a Tahoe to 30 mpg would gain some sales from people who want a big, guilty free vehicle.

But such a vehicle would likely cost more then $50,000.00

I see your point, but then again, an LTZ Tahoe CAN cost $50,000. Just out of curiousity, I would like to see the theoretical sticker price of a diesel 2-mode.

[01cavalier]

The GM system would use the fixed gears for towing and highway driving. On the highway it woudl be more effecient to use the fixed gear. For city driving and normal acceleration it would operate more like a CVT, so in the way it operates, it is both. While operating in a fixed gear, the motors for the CVT would generate electrity or if needed it would provide additional torque, helping to keep the engine in 4-cylinder operation or at least help it perform better while having less of an impact on fuel economy.

[unkillsam]

Originally Posted by chakis24

why not make it specail order? im shure there would be people willing to pay. have the technology there, but only build them as necessary. if they can special order the hummer, they can do it with this.

Even if you make it special order you still have to tool up to actually build it not to mention design costs.

Say that you spend 100 million bucks doing that.

In order to keep costs reasonable to the consumer you only charge $5,000 over cost instead of $10,000 like on reg Suv's.

You only sell 1,000 units

Your profit is $50,000,000

It does not pay for the intial costs.

[unkillsam]

Originally Posted by Slideways

I see your point, but then again, an LTZ Tahoe CAN cost $50,000. Just out of curiousity, I would like to see the theoretical sticker price of a diesel 2-mode.

Yes but you would not be getting the luxury options on the hybrid that you do on the LTZ

LTZ plus diesel hybrid would probably run over $60,000.00