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Chevy Tahoe/GMC Yukon Hybrid

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  • galvanggalvang Posts: 156
    In terms of “cylinder deactivation”, GM are not a bunch of incompetent bozos (though sometimes I wonder), they have pretty sophisticated design tools and test methodologies to insure long term reliability for their engines. More than likely, they have simulation super computers to determine stress areas in their engine under certain conditions. Also they probably have thermal imaging equipment to determine hot spots internally in their engine such that they can determine latent engine failures. The one area I value the most which I know GM completes is “real life” testing, where they can test their engines under the “real world” conditions (temp, load, etc). These tests usually determine a life of an engine and helps validates some of the initial simulations done by computer or determine unforeseen failures.

    I agree above, “Cylinder deactivation” is only on when the engine is in very light loading conditions (going down hill, cruising on the highway. etc). So heat being generated is pretty minimal. If the vehicle is towing or if the vehicle is accelerating, the internal engine software will activate all of the cylinders and the heat distribution in the engine will be some what even. .

    To this day I have not heard any latent catastrophic failures with the 5.3LV8 engines. I checked NHTSA and their defects website and it shows nothing. Also GM has a 100K mile powertrain warranty which covers the engine for that length of mileage. They wouldn’t guaranty the life the engine if they had some real test data that didn’t support it. If the engine fails you could always have it replaced. So I wouldn’t worry about it.

    I received official notice that GM has pushed out the Hybrid Yukon till early next year. Must be having some sort of problem. :mad:
  • stevedebistevedebi LAPosts: 3,732
    "I received official notice that GM has pushed out the Hybrid Yukon till early next year. Must be having some sort of problem."

    (The GMC site doesn't list the weight of the Yukon, but I'm guessing it is 5500 lbs or maybe more...)

    I actually wonder if the "problem" isn't that this class of vehicle is too heavy for hybridization to provide a real benefit, other than shutting down the engine when stopped. That is what happened to the hybrid pickup - no real MPG savings. Of course the pickup had the 110v electric capability which may have been useful to some owners.

    Dual mode doesn't provide as much benefit to a large and heavy vehicle; the electric motors deplete very quickly due to the large amount of weight that has to be accelerated.

    With heavy vehicles the situation degrades to the point that it would take too much battery to provide enough boost, and then one has to remember that the battery adds weight and takes up room as well. AND hybrid components are complex and expensive. Some people assume that LiIon batteries will be the answer, but I'm not convinced that the recharging/heat problems of this technology will be overcome any time soon.
  • gagricegagrice San DiegoPosts: 28,678
    Of course the pickup had the 110v electric capability which may have been useful to some owners.

    That is the only thing I miss since selling my GMC Hybrid PU. I don't think the auto-stop saved enough gas to make any difference. It may have used more as there is a debate whether starting an engine uses more gas than idling for a minute or less.
  • galvanggalvang Posts: 156
    "(The GMC site doesn't list the weight of the Yukon, but I'm guessing it is 5500 lbs or maybe more...) "
    Yea, I could not find it in the product brochure but lists 7300Ibs for the gross vehicle weight for the regular Yukon, This includes passengers.

    The "problem" at this point may be minor such as battery or Hybrid motor or some other part availability (just guessing). If GM pushes out the introduction again then you know is something more serious. Problems like this always occur during the production of these complex vehicles or other items especially for the first year. I know I work in engineering, there always issues in complex projects like these and that's why the companies pay us the big bucks to resolve them.

    I rather see GM delay the introduction and produce it right then shipping out a lemon :lemon:.

    As for the Hybrid motors, perhaps it drains those Nickel Metal Hydride batteries faster than it was meant to. Lithium Ion batts are the way to go at least for the short term until a new exotic battery comes into fruitrition. The battery designer need to be careful though as lith ion batteries, if its not designed correctly, could explode or cause severe out gassing. Hence Toshiba and Dell Notebook recalls due to the lith ion batteries. Talk of polymer batteries might be the next thing but its all in paper. For Hybrid batteries its all about power and density and lithium ion seems to fit the bill at least for now. In some cases the Lith ion batteries can provide 50 percent more power in the same volume or space as with NiMH Batts.

    GM needs to get hot and release the hybrids.
  • kdhspyderkdhspyder Posts: 7,160
    If the EPA numbers are accurate and I'd guess that they are then the 2-Modes are actually better for the country than say a Hybrid Camry or Hybrid Civic.!!!

    The T/Y 2Ms save more fuel than either of these two 'classic' hybrids.

    My alternate viewpoint, assuming that the 2Ms work as described, is that all BoF SUVs should have the 2-Mode system installed mandatorily. Doing this will save our country far more fuel than any other single step other than banning SUVs altogether, which will not happen barring some obscene fuel shortage.

    Yes hybrid components are complex and expensive to replace but reliability across the board has increased dramatically. Hybrids are among the most reliable vehicles at every manufacturer. Prius, Escape, Civic all are good bets not to leave you in a lurch.
  • chadxchadx Posts: 153
    "The way it stays round is this,,there is holes drilled around the round cylinder which pass coolant or antifreeze through, thus evenly cooling the round cylinder bore that the piston lives in... In the chevy v8 the cylinders are set up in two rows of four. If you shut off 2 or 4 of these cylinders these cylinders will become unround or oval shape because of the heat that will be transfored from the cylinders that are working and creating a lot of heat. "

    I really don't see how this could be an issue. The engine is still water cooled and all cooling channels still get the same amount of coolant flowed through them whether they are firing or de-activated. The heat build-up / differences between cylinders will not be significant enough to make things out of tolerances. Look how much air cooled engines expand and contract without issues. Since this is a water cooled engine, it's true that the tolerances will be tighter, but then, the operating heat range is smaller as well, with or without deactivated cylinders.

    Plus, like other have said, they are de-activated for very short time periods and if the 'brain' is deactivating them, it means you are on a very low power situation so the other cylinders are likely barely working at all. Basically in a coasting or idling work mode rather than a "make power" mode like when accellerating. At which time, all cyclinders will be working anyway. This technology has been around for quite a while (in everything from 4 stroke auto engines to two stroke outboard boat motors) so it's nothing new. No doom and gloom needed.
  • stevedebistevedebi LAPosts: 3,732
    "As for the Hybrid motors, perhaps it drains those Nickel Metal Hydride batteries faster than it was meant to. Lithium Ion batts are the way to go at least for the short term until a new exotic battery comes into fruitrition. The battery designer need to be careful though as lith ion batteries, if its not designed correctly, could explode or cause severe out gassing. "

    Since Toyota has abandoned LiIon for the 2009 Prius Refresh, I would be shocked if GM solved the problems inherent with current LiIon batteries.
  • stevedebistevedebi LAPosts: 3,732
    "I could not find it in the product brochure but lists 7300Ibs for the gross vehicle weight for the regular Yukon, This includes passengers."

    Ford was originally going to put a hybrid powertrain in the Explorer. They halted the concept because it turned out that they could achieve the same MPG increase with a 6 speed transmission. A Ford Explorer is probably 2000 lbs lighter than a Yukon at full load.

    The point is that it takes a lot of energy to push that kind of mass up to speed, and I don't think that a 3 ton gas/electric hybrid is necessarily going to provide enough MPG savings and/or power.
  • kdhspyderkdhspyder Posts: 7,160
    The numbers may be small and not as exciting as 45-55 mpg like for some others but both GM hybrids save more fuel for the country than say a hybrid Civic does over an ICE Civic. In addition if the pricing is at a $4000 premium for the hybrid over the ICE then it's also cost effective for the owner.

    Both of these are significant accomplishments.
  • stevedebistevedebi LAPosts: 3,732
    "The numbers may be small and not as exciting as 45-55 mpg like for some others but both GM hybrids save more fuel for the country than say a hybrid Civic does over an ICE Civic. In addition if the pricing is at a $4000 premium for the hybrid over the ICE then it's also cost effective for the owner.

    Both of these are significant accomplishments."

    I understand your point, but I will wait to see what MPG the vehicles get in actual useage. The same point was made about the Sierra Hybrid P/U, and it was dismal in actual performance. If the difference is 1 MPG that is not a "whole lot of fuel saved for the country"... :surprise:
  • chadxchadx Posts: 153
    "If the difference is 1 MPG that is not a "whole lot of fuel saved for the country"

    Actually, it is when you are talking about such low mileage vehicles. It's more about percentage increase and number of gallons saved and not mpg increase.

    If real world numbers in a vehicle improve it from 15mpg to 16.5mpg, that is a real world increase of 10%.

    Toyota camry (I4 engine) is rated at 31 hwy vs Toy. Cam. Hybrid rated at 38 hwy (I don't know what the real world numbers are). That is a about a 23% increase.

    However (and it's a big however), look at the number of gallons of gas burned over 15,000 miles in a year.

    Changing from 15mpg (1,000 gallons) to 16.5mpg (909 gallons) saves 91 gallons a year.

    Changing from 31mpg (483 gallons) to 38mpg (394 gallons) saves only 89 gallons a year.

    What this shows is the planet would be way better off focusing on getting an extra 1 or 2 mpg out of the worst gas mileage vehicles rather than getting more mileage out of already high mileage vehicles. If they got the same 23% mileage improvement on the trucks, the difference would be even more obvious. Now you'd save 187 gallons a year.

    Of course, ideally, everyone would change the type/class of vehicle they drive to a smaller and inherently better mileage class, but if that is not going to happen, the real "world saving" differences will be seen improving the gas guzzlers and not the gas sippers.

    This has all been outlined before, but it was worth repeating because it is not an obvious train of thought. It's really all about using less gallons of gas a year. Improving the worst of the worst will prove far easier (and have a far larger impact) than improving the best of the best.
  • kdhspyderkdhspyder Posts: 7,160
    What this shows is the planet would be way better off focusing on getting an extra 1 or 2 mpg out of the worst gas mileage vehicles rather than getting more mileage out of already high mileage vehicles. If they got the same 23% mileage improvement on the trucks, the difference would be even more obvious. Now you'd save 187 gallons a year.

    Yes, agreed. This should be our first order of business as a tion, actually 2nd IMHO.

    1st.. Every government vehicle Federal or State must be either a hybrid or diesel.
    2nd. Every BoF SUV must use the 2-Mode or similar technology
    3rd. Every truck must be a diesel
    4th. Within 7 yrs all the older technology vehicles must be off the road.
  • galvanggalvang Posts: 156
    1st.. Every government vehicle Federal or State must be either a hybrid or diesel.
    2nd. Every BoF SUV must use the 2-Mode or similar technology
    3rd. Every truck must be a diesel
    4th. Within 7 yrs all the older technology vehicles must be off the road.


    Wait a minute, some people may call that communism. I don't. Agreed, something is got to be done. Above may be some crucial steps. You might want to include some of the tougher CAFE standards which the auto companies are against.

    Every bit counts for the larger gas-a-hog trucks or SUVs whether we save 1 mpg or more. With gas prices in some areas in CA hitting close to $5,00 a gallon and slated to go higher every bit counts. A good time to overfill your air in the tires by a few pounds to add some extra MPG on your vehicle. That seems to work well for me.

    Saw a good show in CNBC "Street Signs" ;) along with Brian Williams during NBC Nightly News. They were broadcasting out from a Chrysler MFG plant in Detroit. The Chrysler plant was spitting out trucks every minute or so. The plant was somewhat automated with robotics, looked pretty amazing on TV. Just curious, why didn't CNBC/NBC visit the GM plant where the Hybrids are being built?? Perhaps no cameras or news reporters allowed?? Too bad. Other than that, the shows were well produced.

    Pardon my ignorance, but what does BoF stand for? Yea, I know I've been living in the west coast too long.
  • kdhspyderkdhspyder Posts: 7,160
    BoF is = Body on Frame.

    This is what most SUVs are, a body on a truck ladder frame.

    OTOH the newer lighter and more fuel efficient vehicles are Crossovers. These are similar or even larger inside but they use a unibody construction like a car does.

    The first Crossover was the RAV4 back in 95. The first large volume Crossover was the Lexus RX300 which was an SUV body on a Camry frame. Instead of getting 15-16 mpg most crossovers get 20-23 mpg.
  • galvanggalvang Posts: 156
    BoF, Sounds like my kind of SUV.

    Truck frame vs the crossover unibody construction.
    Ala, Ford Exploder Vs. Buick Enclave. Got it thanks.

    The Yukon is BoF.
  • kdhspyderkdhspyder Posts: 7,160
    Actually the BOFs are probably dinosaurs. Ford has announced already that the next Exploder will be a crossover. The lambdas are far more capable as people movers and more fuel efficient than either the TrailBlazer or Envoy. I also read that Nissan is replacing the Pathfinder as a crossover also.

    This will leave..
    Tahoe, Yukon, Escalade, Suburban, Expedition, Aspen/Durango, Sequoia, 4Runner, FJ, Armada, Xterra
  • I have been a Suburban buyer for a long time. I have a 93 Suburban that gets about 12 mpg around town. It only has 88,000 miles. I am irritated with how GM has screwed up the inside of the suburban where you can't remove or fold the seats down to create a 4x8 area to carry stuff. My daughter and son-in-law have wanted a Suburban for about a year. She brought over a Consumers Report magazine with the auto ratings. It made me ill looking at the ratings on the Yukon, Tahoe, Suburban and Yukon XL. The Yukon and Tahoe got worse than the full size.
    My daughter and son-in-law are leaning now to a Dodge Caravan. I believe the oil companies have the auto manufacturers by the hand and dancing into record profits. The little bit of extra mileage they are getting makes it not worth the while to buy the expensive junk. If I was to buy a new car it would be a Toyota Prius just to make the oil companies eat their high priced gas.
  • Retail prices for the new Tahoe/Yukon Hybrids are officially announced. I found this on Detroit News:

    GM said the Chevrolet Tahoe Hybrid's suggested retail price would be $50,490 (two-wheel drive) and $53,295 (four-wheel drive), while the GMC Yukon Hybrid would be $50,945 (2WD); and $53,755 (4WD).

    Those prices include a $900 destination charge and pending IRS approval, could be eligible for a federal tax credit.


    All I can say is WOWSA!! You can drive a LONG way for the 10K premium people. So much for the theory that they were going to almost cost the same. This officially means I will be looking elsewhere for my next vehicle. I'm not getting into a vehicle that STARTS out costing the same as the first condo we ever owned. Sorry but I just don't see the value everyone.
  • gagricegagrice San DiegoPosts: 28,678
    I have been a Suburban buyer for a long time. I have a 93 Suburban

    I'm with you. My 1998, last of the good Suburbans, was a very well built vehicle. The new stuff is tinny crap with plastic bumpers. Much of it was forced onto the automakers by lame government regulations. I should have never sold my 98 Suburban. It was 7 years old, trouble free with only 45k miles. I bought a 2005 GMC hybrid PU that was built out of tin foil. The new ones are even tinnier. The only thing my Suburban needed was a small diesel engine to be the perfect vehicle. I think the EPA, automakers and the oil companies are tied together. They keep adding more devices to clean the air a tiny bit more and never worry about the MPG. We keep buying as much oil, have lots more stuff to replace on the vehicles and the EPA has bragging rights on the infinitesimal amount they cleaned up the exhaust.

    All three win and the consumer gets the big shaft.
  • galvanggalvang Posts: 156
    I saw that. I was very disapointed by those numbers. I've seen other numbers at around mid-40ish which would have been acceptable. At these prices sounds like Audi may win my business after all. I tried with GM, buy american, but looks like they are being unreasonable at these prices. Could it be because of the current gas prices being high that they will command an added premium to their hybrid?? Possibly so. If that will too bad not going here.
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