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2007 and newer Chevrolet Tahoe and GMC Yukon
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I think they are just being a little too colloquial and simply mean that they will try to determine whether adjustments can be made to get V4 to work right. Clearly, they cannot make that determination over the phone.
tidester, host
Your milage is normal. I was getting around 13.8 when I bought mine. Up until 3000 miles, the best i saw on highway were 19 at optimal spds like 60mph. Also, you have to BABY it to get good gas numbers. No driving over 2000 rpms. Also, most areas are using 10% ethanol in gas. This will result in worse milage b/c ethanol has fewer BTUs. ie less efficient just burns cleaner. The axle ratio you have could make a diff too. Not sure.. The mileage I reported above in my last posting was new to me. It improved when I hit 3000 miles. These #s are only obtainable when criusing on flat road. Don't expect them around town. Basically meaning stop and go driving. Expect your 13.8 or less around town. Yep, I'm impressed by the mileage I get on hwy. But they should be forced to get on TV and explain to everyone that their fuel managment system is a joke. When I didn't see it come on during the test drive, I was told that I had to drive it longer on the hwy to see it come on. HA.. that man should be fired.
I suspect that if you can 'fool' it then it can be tuned or reprogrammed. After I get to the dealership, I suspect I already know their answer, I will report back here. I am willing to be the squeeky wheel, but if I do have to go the GM route it I will need the support of a lot of other drivers. I have found through other venues that grass roots movements against big companies DO work. If we can garner enough support e CAN grab media attention and get the numbers that were promised to us.
After I get back from the dealership I will make my private email address available to everyone to see how much support we really have.
http://www.chevrolet.com/pop/tahoe/2007/vortec5300_en.jsp
Good luck!
"The powerful 32-bit engine control computer triggers cylinder deactivation based on inputs from vehicle sensors —making deactivation virtually undetectable." Either the sensors are sending the wrong info or the programming is not correct for info being fed in.
There are a lot of complaints coming in from all over the country on this matter. GM better stand up and take care of business on ths one.
I specifically justified the ability to upgrade based on the fuel savings. At almost 3.00 per gallon every MPG counts. If GM advertises that they can make this easier on me by running this beefy V8 on just 4 cylinders during cruising then I expect them to live up to that promise. It's all about getting what they sold me.
If I sold you a ticket to Rio and when the plane landed you were in Alaska wouldn't you be upset. Sure, both areas have outstanding beauty and are really nice vacation spots, but you paid for a beach vacation not a glacier one. I want my beach vacation, and so should everyone else.
Both forms of tech are separate developments. While the hybrid system can work with the AFM engines though- the hybrid part is the transmission. And both have had their own development / production schedules. The production of one hasn't caused the other to slip in scheduled release either.
So stop kidding people that you were waiting for one of those "hybrid" Tahoes. Because if you really were you would know that they are and always have been due up in roughly a year..
Seems that GM is holding back. I suspect that the margin in the hybrids is a little lower and the costs to recoup the re-machining of the Arlington plant exceeds what they have invested in infrastructure at this time due to lagging sales of full sized SUV's. That's only my theory, but it would make sense. My theory would suggest that they are trying to use the coolness of the new Tahoe to drive sales to the point that they wold not have to recoup costs but could actually pay cash for the remachining (is that word?).
But to sum up, the hybrid will not be out this year or next. The only thing I see changing that would be if Ford released one before then. Even with the hybrid, if it performs like the current fuel managed units the electric motors would hardly ever kick in resulting in just as poor gas milage as we are experiencing now. The fuel management system must be corrected for any of these technologies to work and be effective.
but I did expect more than I am getting. has anyone had the reprograming yet that may help the MPG? :lemon:
Chrome 22" rims look great on the 07s. There aren't any major hardware changes to make. The tire pressure sensors need to be reused with the new tires. Realize that the new wheels and tires will change most of your calculations on your d.i.c.. Most dealers I have talked to cant correct the readings but some aftermarket programmers can. It also depends on the tire size you go with as to how off the readings will be, like speedometer wise. I don't know how to post pics in this forum but you can email me and I will reply with some.
Collins
Other than the exhaust, I think my other advantage may be that I now have 6700 miles on mine. I have noticed that I have been able to drive more and more "spirited" and have been getting better and better milage as the miles have clicked off on the odometer.
Just some food for thought.
I too have noticed some improvement as I drive further, but still nowhere where it should be.
Thanks for the information. BTW: did you happen to watch how much the V4 became active while you were cruising? This is the part that I am furious about.
jmaynard,
With the cruise set at 69 it was spending a lot of time in V-4, I would say it was somewhere between 70-80 percent of the time. With the cruise set at 74 and the light head wind, it was spending notably less time - probably more around 20-30%.
Hope that helps!
I have 4.10's in mine (it is a 4x4 as well).
Hope that helps!
so in those coasting-in-gear situations, it won't matter if the ignition is in "4" or "8" mode at that time - because there is no fuel to burn. V0 mode!
This is why the V4 mode is so important. Even while coasting you are using fuel, 2 times as much if the engine is in V8 mode! :surprise:
All I see is v4 coming on when no accelleration is underway. The individual seeing V4 coming on during cruise control is only seeing V4 come on when the computer is not accellerating. The engine is idle at this time. When V4 is on during engine idle, that minimum amount of fuel pumped into the cylinder to keep it idling is still being pumped into all 8 cylinders.
A certain % of chevy's consumers don't understand this and are going to be satisfied with just seeing V4 mode show up on thier console. Chevy isn't dumb and they obviously know this. Maybe their sales force don't know this, but engineers and decision makers at Chevy do. They are satisfied with this. This was their intention. This was their quick fix to quickly coerce people into feeling comfortable buying a large SUV when gas prices are so high. They know what they are doing and it is 100% intentional. They know that if a concumer does catch on, they will be stuck with the Tahoe and drive it long enough until they feel comfortable selling it. To Chevy, its a sale and on paper its a sale. That's all they care about. If american companies were out to make the best vehicle possible they'd be building them with the reliability of Nissan and Toyota. They all have the same engineers with the same capabilities.
This is confusing for many as they may think that the engine does nothing on deceleration. This is not the case. This is one of the reasons that hybrids are so attractive. They use the deceleration to generate electricity to store in the batteries thereby taking energy from braking from what is usually wasted in heat(brakes) and/or fuel(combustion engine autos).
To have a real V0 mode auto whould be the most attractive and efficient. This could be done by making a hybrid that used braking force to generate electricity stored in batteries which would run an electric motor that would work under light load saving the gasoline engine for high load. None of the hybrids made now are as efficient as they could be. The most efficient would run the air conditioner and car in heavy traffic, stop lights, cruising and stop and go situations thereby saving fuel for only heavy demand situations. This formula has been being used by diesel electric locomotives and ships for years. Battery technology is the key. Batteries are heavy, expensive and wear out. To get enough capacity with weight constraints for autos has just become possible in the last few years.
I have done some long trips and the Tahoe/DOD system works very well on the highway with almost 19mpg. For short trips with a/c it is getting around 12.5mpg. This was to be or should have been expected. The engine is 5.3 liters with 300HP. That's a big motor. I have been babying the accelerator. I don't think I've floored it since I bought it. In comparison, my 2004 Land Rover Discovery with a 4.6 liter engine was getting 11mpg in short trip driving. So I will take the 12.5mpg any day.
Hopefully, GM will release a software upgrade that will improve the V4 mode operating efficency. I do believe that it could stay on more. Especially during highway crusing. Just be happy you didn't buy an Escalade or a Denali which have the 6.0/6.2 liter engines. I imagine they are only getting 10mpg or less in the city!
I just wnet and looked on the Escalade and Yukon sites. Evidently, Escalade/Yukon owners are not as budget conscious as us Tahoe owners. No threads about gas mileage. Maybe they're just so awful that they don't want to think about it!
Check out the burned up Denali in the thread on Yukons! Wonder what went wrong with that one?
Don't accept that because they hand you all this power YOU are responsible for improper engineering and YOU should pay for it. This problem CAN be fixed and GM needs to step up to the plate. Please help by complaining. You have nothing to lose and everything to gain. I promise, they don't kow you well enough to hate you for complaining and the savings that you could recieve would go staight back into your bank account.
It seems that GM could do that when the car was brought in for service. An example would be: Tahoe comes in for service and they download version 2.XX of DOD firmware to the car which addresses issues in V4/V8 mode.
This seems like a logical step to expect. Maybe GM is not that advanced, but it would seem that they already have the capability and the Vortec DOD is in a continual state of fine-tuning.
I already called customer service and formally asked about the possibility that a newer firmware could be downloaded at the dealership to address these issues, but I am not sure that it will be heard by the responsible parties.
Thanks for raising a red flag where you are. Hopefully others will follow. I will be on the lookout for other 07 owners so that I can spread the 'love' to them.
You are absolutly right. Someone will come up with an aftermarket chip or program, but if you are like myself, you wouldn't want to invalidate the warranty by installing one. I also leased my ehicle and the lease states no after market parts be installed.
I agree that they should be able to do it when brougt in for service, the only problem is there is not a newer version available from GM. As far as they are concerned, noone is complaining so there must not be a problem.
V4 mode comes on when coasting. Maybe a little when cruising at 60mph.
The 2007s are a lot nicer than the old ones, I just wish the mileage would be as advertised. It really irks me that we took a step backwards, mileage wise, from our 2002 Yukon XL.
The dealer service department tells me there are no codes, so there is nothing they can do.
What number at GM are you calling to complain? I will certainly give them a call.
Thanks.
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I think the above reference was to reprogramming the engine computer, not the NAV system. But that NAV reprogram kit looks pretty cool.
This will allow you to play a video on the front screen as well as programing the Nav while moving.
I'm interested in this mod but don't want to be the first!!!
http://autos.aol.com/article/hybrid/hub/_a/flex-fuel-fallacy/2006081513330999000- 1
Maybe we can get AOL involved to do an article on their AFM fallacy
Biggest issue currently is that most ethanol plants use the kernal of corn to make it. The next generation of ethanol plants will use the stalk, or grass, or other plant materials that are typically waste products today.
this is the way fuel-injected vehicles have operated for at least 20 years - i not aware of *any* exceptions and would be awfully surprised if this new Tahoe is an exception.
it would be counterproductive and wasteful for the ECM to pump any fuel during foot-off-gas/deceleration, as long as RPM is ~1000 or more.