Tech Preview: GM Two-Mode Hybrid Pickups

[HoosierRon]

Originally Posted by joemac

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.

The Tahoe hybrid gets 21/22 mpg does it not? Use the 2.9L V-6 diesel (which has tons of low end torque), and you will increase mileage by 33%. That puts you at 28/29. The Tahoe hybrid is reportedly going to be sold in the low $40's. So with the diesel, you would still be under $50,000. You can spend over $47,000 on an LTZ right now.

If you drive 18,000 miles per year, you will save 415 gallons of gas a year compare to a current 2WD Tahoe. If gas is $3.00 a gallon, you will save $12,000 in 10 years.

Economics aside, people will want to do this to reduce our consumption of foreign oil. GM should want to do it to increase its CAFE.

[jomo]

Originally Posted by MechEng

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.

Agreed. I don't think that either system should be called a CVT at all, as they are not truly CVTs. People like the previous poster get confused when you call it a CVT and try to connect it with the belt-driven systems of the past. Call it an Electronically Variable Transmission or something else, but the CVT term has a lot of baggage, especially as Ford and GM both retired their real CVTs because of problems and as Chrysler and Nissan are still deploying true CVTs.

[PhishPhood]

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?

By your first sentence you don't understand what the most modern ECVT system means and this is probably what HEVguy was indicating. An ECVT like the 2-Modes and the HSD system don't use any belts. The original ones in the Gen1 Prius and the current Nissans do use belts but that was the old fashioned method. The most current mechanical method uses sets of planetary gears to Vary the gear settings in a Continuous range which is nearly infinite. It's done electronically but it's not done with belts.

[boynton6spd]

I must have missed it...

[b4z]

No Tahoe is going to get 29mpg(rated) on the hwy.
There is just too much frontal area.
No matter what engine you put in it.
But if you somehow got the weight down to 4,000 lbs
and put the most efficient drive train possible, AND
cruised at 55mph, it is possible.
My SRX will pull 30mpg at 50-55mph, but it has less frontal area.
The 1 advantage the Tahoe will have is the 6 speed, my V6 has the 5 speed w/ .75 overdrive and 3.73 gears.

[Olds88]

Originally Posted by HoosierRon

The Tahoe hybrid gets 21/22 mpg does it not? Use the 2.9L V-6 diesel (which has tons of low end torque), and you will increase mileage by 33%. That puts you at 28/29. The Tahoe hybrid is reportedly going to be sold in the low $40's. So with the diesel, you would still be under $50,000. You can spend over $47,000 on an LTZ right now.

If you drive 18,000 miles per year, you will save 415 gallons of gas a year compare to a current 2WD Tahoe. If gas is $3.00 a gallon, you will save $12,000 in 10 years.

Economics aside, people will want to do this to reduce our consumption of foreign oil. GM should want to do it to increase its CAFE.

How bout the 4.5L Diesel? A engine more appropriately sized to this vehicle. 250hp is not adequate for a Tahoe.

[b4z]

250hp should be plenty for a Tahoe if it has the normal turbocharged diesel torque whichI imagine would be at least 500ftlbs

[Gm786]

Definitely an amazing piece of technology. The new Chevy Tahoe/GMC Yukon hybrid SUVs should sell very well for GM. Can't wait to see what else GM has in store for their other vehicles.

[joemac]

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.

All the same R&D, certification, tooling, production costs would still be incurred. With low volume the end cost of the vehicle would go even higher yet.

[Z28x]

How about a hybrid Diesel with GMs 2.9L V6 instead of the 4.5L V8?

[joemac]

Originally Posted by HoosierRon

The Tahoe hybrid gets 21/22 mpg does it not? Use the 2.9L V-6 diesel (which has tons of low end torque), and you will increase mileage by 33%. That puts you at 28/29. The Tahoe hybrid is reportedly going to be sold in the low $40's. So with the diesel, you would still be under $50,000. You can spend over $47,000 on an LTZ right now.

If you drive 18,000 miles per year, you will save 415 gallons of gas a year compare to a current 2WD Tahoe. If gas is $3.00 a gallon, you will save $12,000 in 10 years.

Economics aside, people will want to do this to reduce our consumption of foreign oil. GM should want to do it to increase its CAFE.

250HP in a 5300lb give or take truck would likely be a slug. Torque is nice but HP indicates that while there is good torque isn't only for a short time. HP basically being derived from torque over time (rpm).

Where does the diesel 33% mileage increase over the existing hybrid come from? I just don't see it, thinking that it will reach a point of diminishing returns as with the Tahoe’s wind signature and weight; it's still punching a huge hole in the air and carrying a considerable amount of heft. Not to mention the diesel will add more weight over the gasser. If the 2 mode only gets 10% better highway, roughly 1mpg, adding the diesel nets it an additional 8mpg increase? Hard to realize that has possible. Call me doubtful on this one for a 250HP slug with mileage stated 28/29 at an under $50k price.

[KingElvis]

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?

Thanks for clarification.

Now another question: Does this have a torque converter? When you look a the powertrain page, it lists ratios as "Infinity to X" and it does appear that it uses super low gearing and electric power to take off from a stop - that would explain why the towing rating is lower too.

Enlighten me if you can - I've never quite understood how it works and GM doesn't seem eager to explain it.

[MelvinJ]

Originally Posted by KingElvis

Thanks for clarification.

Now another question: Does this have a torque converter? When you look a the powertrain page, it lists ratios as "Infinity to X" and it does appear that it uses super low gearing and electric power to take off from a stop - that would explain why the towing rating is lower too.

Enlighten me if you can - I've never quite understood how it works and GM doesn't seem eager to explain it.

From the article quoted here:

At low speeds (Mode 1), the first electric motor, which also replaces the torque converter, silently drives the truck off the batteries up to 32-mph, and as far as one to two-miles, depending on charge levels.

[PA Dweller]

About time they gave this truck the two mode option, should help sales when gas prices go up. BTW, will this truck be able to act like a generator for powered equipment like the last one?

[chakis24]

Originally Posted by joemac

All the same R&D, certification, tooling, production costs would still be incurred. With low volume the end cost of the vehicle would go even higher yet.

most of its there since its mated to the gas engine. shouldnt be that much moreto mate it with the new 4.5L. simply split the cost between both hybrids then, along with chrysler and bmw