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Old 08-03-2007, 07:32 AM   #1
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Is GM getting smart?

The new GMT900 pickups are nice looking, but GM really didn't have FE in mind when they selected powertrains.

Finally, a year after their introduction, they're offering the old 4.3 liter V6 option. Now, if they would just add a cam phaser and cylinder deactivation from its V8's to the V6, along with a manually tranny, I could dump my Ford P.O.S. for a truck that gets 25 mpg.

I should start another contest to see if GM ever does it.
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Old 08-03-2007, 12:30 PM   #2
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Quote:
Originally Posted by Sludgy View Post
The new GMT900 pickups are nice looking, but GM really didn't have FE in mind when they selected powertrains.

Finally, a year after their introduction, they're offering the old 4.3 liter V6 option. Now, if they would just add a cam phaser and cylinder deactivation from its V8's to the V6, along with a manually tranny, I could dump my Ford P.O.S. for a truck that gets 25 mpg.

I should start another contest to see if GM ever does it.

4.3s are awesome engines. I like your idea for the cam phaser, cylinder deactivation, and manual tranny. That would be a truck I'd like to own as well.
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Old 08-03-2007, 11:44 PM   #3
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what do you do that you need a full size for? i have a 2.2L 5speed s-10 that gets 28mpg around where i drive (alot 55mph highway)...no aero mods whatsoever.(a bed toneau cover could add 1-2 mpg). even the 4.3L s-10s are getting mid 20's or so.
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Old 08-04-2007, 02:58 AM   #4
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what is a cam phaser? something having to do with variable cam timing? What if you dropped in a cam that has a low end power band and call it a day? Like a RV cam.
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Old 08-04-2007, 07:04 AM   #5
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Very few people who drive trucks actually need them. Most people just want them and find excuses to buy them. My own opinion is that the guy in the shiny F-350 doesn't really need a truck. If he really needed the truck, it wouldn't be all shiny. It would be doing truck stuff.

For the 2 or 3 times a year I need to haul stuff, it's a LOT more economical to rent a U-Haul, and save on gas the rest of the year.

As for GM getting smarter, I think they are. I have a few friends who work for them, and I don't want run my mouth about stuff I shouldn't, so I'll just say that they are working on things to make their engines more efficient.

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Old 08-04-2007, 07:23 AM   #6
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The 4.8L in a regular cab can get into the mid 20s stock, and has almost 100HP and 100TQ more than the 4.3L. The 4.3L is old technology, it's the same engine they've been running since the late 80s. With the right engine, drivetrain and computer mods, a 4.8 in a regular cab could get into the low 30s. A friend of my dad had a 4.8 in a 99 that got a rock solid 25MPG, and it had the mechanical fan up front. This is the engine I was going to install in my S15 before GM announced their new 4.5L diesel. Sometimes GM gets it right, but then other times...

GM's cylinder shutdown is one place where they are NOT smart. It's activated by OIL PRESSURE. That's right, it depends on the quality of oil used and how dedicated the owner is to keeping the oil changed. Two years into China-Mart brand oil changes every 6 months, the passages that control the cylinder deactivation are going to be full of gunk, and the system will fall flat on its face and the system will be blamed for it, because "that's the same way I've always changed my oil and I never had a problem." Or, wait till the engine has 100K or more miles on it and the oil pump starts getting weak. The system depends on the computer being able to shut down 4 cylinders at the exact same time to run seamlessly, all it'll take is a little gunk to block one cylinder's control port or not enough pressure not quite shutting everything down to kill the system, and shortly after the engine from harmonic distortions. I think they are going to wind up having to shut the programs down on the engines when people start bringing them back with complaints.

I just don't think they will be able to work out the bugs on a multidisplacement system until they perfect electronic valves. Of course, when they do this they will solve many of the problems of the internal combustion engine. Imagine having an engine that accelerates like a dragster on WOT, yet sips fuel at cruise because the "cam profile" is determined by load on the engine and throttle position, not by an unchanging, heavy chunk of steel going through the engine. With electric valves, a multidisplacement system might be able to fire as few as 2 cylinders on a V8 to maintain speed since you won't be limited to a specific valve event as you are with a camshaft. Electric valves are a dream come true for me.
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Old 08-04-2007, 08:21 AM   #7
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The 3.9L V6 in the new Impala has cylinder deactivation, thery should transplant it into the GMT900....

Quote:
Originally Posted by Sludgy View Post
The new GMT900 pickups are nice looking, but GM really didn't have FE in mind when they selected powertrains.

Finally, a year after their introduction, they're offering the old 4.3 liter V6 option. Now, if they would just add a cam phaser and cylinder deactivation from its V8's to the V6, along with a manually tranny, I could dump my Ford P.O.S. for a truck that gets 25 mpg.

I should start another contest to see if GM ever does it.
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Old 08-04-2007, 08:23 AM   #8
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GM's cylinder shutdown is one place where they are NOT smart. It's activated by OIL PRESSURE.
Do you mean it's controlled by oil pressure, or actuated by it? Honda's VTEC has been using oil actuated, computer controlled mechanisims since 1990. While comparing Honda and GM engineering-wise is like apples and oranges, using oil pressure for mechanism control isn't an inherently bad design.
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Old 08-04-2007, 08:44 AM   #9
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Under low load, the resulting low oil pressure collapses the lifters which keeps the valves from opening, thus deactivating half the cylinders.

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Do you mean it's controlled by oil pressure, or actuated by it? Honda's VTEC has been using oil actuated, computer controlled mechanisims since 1990. While comparing Honda and GM engineering-wise is like apples and oranges, using oil pressure for mechanism control isn't an inherently bad design.
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Old 08-04-2007, 12:24 PM   #10
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my dad had an 81 ford f150 with the 300 inline-6, 2.73 rear end, the HE package and OD, it was a 2wd stepside and got 25 mpg.. in a full sized half ton, in 1981.

so don't give me all this need modern (read: expesive) technology stuff to get halfway decent fuel milage in a truck

light-duty diesels would be nice though

Jeff
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