Just right, yet wrong
#1
12-25-2007, 01:43 PM
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Just right, yet wrong
http://www.latimes.com/news/printedi...news-highway_1
Personally, I think the author was a little harsher on the concept of a hybrid SUV than merited. Also, they speculated that the hybrid part was not needed and everything could be accomplished with just a weight reduction program. Having been up close and personal with a lot Prius engineering data over the past two years, this is b*llsh*t speculation.
Bob Wilson
. . .
So, what's it like? For sheer execution, you can do nothing but throw rose petals at the thing. The engine starts instantly -- as you would too if you were goosed with a 300-volt battery pack -- and falls into a serene idle. Once the gas engine reaches operating temperature, it will shut down during low speed/load conditions, and if you feather the accelerator just right you can make the Tahoe Hybrid sluice along at up to 30 mph in all-electric mode, just a 5,700-pound Prius. The vehicle's two honking 60 kW traction motors (wrapped around the transmission) are primarily responsible for the uptick in around-town mileage.
. . .
GM has made a fair amount of bubbles calling it a "two-mode" system, though I'm not clear even now what the two modes are. I count three: electric only; gas only; and/or gas-electric, in which the operating system constantly ciphers the fuel-saving optimum between the engine's contribution and the electric motor's. If you wanted to send a congratulatory case of beer to anybody at GM, address it to the software writers -- whose ka-jillion lines of code keep the engine, transmission, batteries and motors in a constant state of reification. Spare a six-pack for the transmission's designers, for it is the transmission -- with its three planetary gearsets, two integrated motors (with their own reduction gears) and various other hardy fitments -- that allow the Tahoe to tow 6,200 pounds, a tonnage that would fatally herniate a Toyota Highlander Hybrid.
. . .
So, what's it like? For sheer execution, you can do nothing but throw rose petals at the thing. The engine starts instantly -- as you would too if you were goosed with a 300-volt battery pack -- and falls into a serene idle. Once the gas engine reaches operating temperature, it will shut down during low speed/load conditions, and if you feather the accelerator just right you can make the Tahoe Hybrid sluice along at up to 30 mph in all-electric mode, just a 5,700-pound Prius. The vehicle's two honking 60 kW traction motors (wrapped around the transmission) are primarily responsible for the uptick in around-town mileage.
. . .
GM has made a fair amount of bubbles calling it a "two-mode" system, though I'm not clear even now what the two modes are. I count three: electric only; gas only; and/or gas-electric, in which the operating system constantly ciphers the fuel-saving optimum between the engine's contribution and the electric motor's. If you wanted to send a congratulatory case of beer to anybody at GM, address it to the software writers -- whose ka-jillion lines of code keep the engine, transmission, batteries and motors in a constant state of reification. Spare a six-pack for the transmission's designers, for it is the transmission -- with its three planetary gearsets, two integrated motors (with their own reduction gears) and various other hardy fitments -- that allow the Tahoe to tow 6,200 pounds, a tonnage that would fatally herniate a Toyota Highlander Hybrid.
. . .
Late thought: strip a gas only Tahoe so all it has is a driver seat. Take everything else out so it is a bare bones shell and loan it to the writer to do their 'mileage' testing.
IMHO, GM would be well served if they could take future authors on a test drive with a data recorder. Then after the trip, print out how much energy was conserved by the hybrid system.Bob Wilson
Last edited by bwilson4web; 12-25-2007 at 01:48 PM.
#2
12-26-2007, 09:38 AM
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Location: Chicago area
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Re: Just right, yet wrong
From the same article:
Those numbers leave me very confused. What?
Here are the relevant data points: The two-mode hybrid Tahoe returns an EPA estimated fuel economy of 21 miles per gallon in the city, 22 mpg highway; the 4x4 version gets an even 20/20, city/highway. The company and its various choristers -- such as the Green Car Journal, which recently named the Tahoe Hybrid "Green Car of the Year" -- are pleased to point out that represents up to a 50% improvement of in-city fuel economy over the non-hybrid Tahoe.
#3
12-26-2007, 11:23 AM
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Re: Just right, yet wrong
From www.fueleconomy.gov:
combined - vehicle
21 - Tahoe hybrid
14 - Tahoe gas, 6.2L
---
7 - difference in MPG
7/14 = 50% better mileage
So let us say you are importing 'guest workers' and need 8 seats for 15 guests. With the regular Tahoe, it would cost $3,470 per year for 15,000 miles. The hybrid Tahoe would only cost $2,142 per year. You'll be ahead $1,328 each year but there is more to save.
With the longer range, you can do more of the trips using inexpensive, Mexican gasoline. This allows dropping off the 'guests' much further North of the border and picking them up further south.
Bob Wilson
combined - vehicle
21 - Tahoe hybrid
14 - Tahoe gas, 6.2L
---
7 - difference in MPG
7/14 = 50% better mileage
So let us say you are importing 'guest workers' and need 8 seats for 15 guests. With the regular Tahoe, it would cost $3,470 per year for 15,000 miles. The hybrid Tahoe would only cost $2,142 per year. You'll be ahead $1,328 each year but there is more to save.
With the longer range, you can do more of the trips using inexpensive, Mexican gasoline. This allows dropping off the 'guests' much further North of the border and picking them up further south.
Bob Wilson
#4
12-26-2007, 07:34 PM
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Join Date: Sep 2005
Location: New Orleans
Posts: 521
Re: Just right, yet wrong
It is quite a vehicle. I would bet the 21 mpg city is real life possible,and I know folks who get an honest 23mpg hy with 5.3 Suburbans,so I would bet the 22 mpg can be bettered-maybe 25 mpg at 60 mph on level ground.Older Suburbans(1998 2wd 200,000 miles- worn tires-42 psi) can get 19+ mpg on short city trips, if you shut the motor off at redlights.Without cutting the motor 14.5 mpg is about it-even when driven carefully-P&G etc.This is with a warm motor of course.
The H Yukon is a niche vehicle.I think GM has decided all the huge SUVs will be niche vehicles, not volume sellers.This might be behind the announced increase in prices.Seems crazy for a corp that is losing market share to raise prices, but I bet they raise them on Suburbans/Tahoes/Yukons etc.Once they clean out current inventories,they will build fewer, but sell them for more.The $55000 they want for the Hybrid Yukon clearly makes it a niche vehicle.No middle income need apply.Folks of average means won't be buying a "normal" Tahoe as their primary vehicle-not with $140 fillups.
Very nice vehicle, but not for me-not for $60000 OTD.
Charlie
The H Yukon is a niche vehicle.I think GM has decided all the huge SUVs will be niche vehicles, not volume sellers.This might be behind the announced increase in prices.Seems crazy for a corp that is losing market share to raise prices, but I bet they raise them on Suburbans/Tahoes/Yukons etc.Once they clean out current inventories,they will build fewer, but sell them for more.The $55000 they want for the Hybrid Yukon clearly makes it a niche vehicle.No middle income need apply.Folks of average means won't be buying a "normal" Tahoe as their primary vehicle-not with $140 fillups.
Very nice vehicle, but not for me-not for $60000 OTD.
Charlie
#5
12-27-2007, 03:41 PM
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Re: Just right, yet wrong
Ah, I was confused by the bit about the 4x4 being 20/20. 20 to 21 doesn't seem like a 50% jump, you see, and that 14 mpg figure wasn't actually mentioned anywhere in the article. I suppose it's just the kind of thing that irks me about certain types of journalism- numbers thrown around out of context and needing a translator to understand the jargon or a textbook to tell whether the information presented is reasonable, ridiculous, misleading or even faked. Thanks for the clarification, Bob. (though all the random slams in your explanation about undocumented immigrants seemed a bit unnecessary and OT)
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