Fuelly Forums - Is GM getting smart?

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Quote:

Originally Posted by Telco (Post 66805)

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. :D

A 4.8 liter GM getting mid '20s for FE is ludicrous at normal speeds. My son had a 4.8 in a 2wd Chevy and it got 18 mpg tops. And check the EPA ratings for the GMT900s......Are you telling me that your relatives are hypermiling?

Quote:

Originally Posted by vt420 (Post 66827)

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

I absolutely agree that old tech can get good FE. But just try to get 2.73 axles in any new truck today. The salesman will look at you like you're from Mars.

I've been deploring the lack of FE trucks at Gassavers for as long as I've been posting. I don't care whether it's old tech, new tech, or unobtanium.

GM could build a FE Sierra from its own parts bin, equipped with a 2.73 to 3.23 axle, 15" wheels instead of those ridiculous 17's, electric power steering, water pump and fan, manual tranny and a 3.9 liter V6. It would get 25 EPA mpg without breathing hard. With gas over $3, ya gotta wonder why they don't.

yeah, that ford had plenty of power with the 300, that was a really nice motor.

if you could get an FE tuned version of the 4.2 inline6 in the chevy with a 5 (or better yet 6) speed trans and a fairly tall readend (the 3.08 8.5 inch 10-bolt comes to mind) with a t56 in 2nd od (6th gear) and 235/70-15s about 65 mph would only be 1200 rpm and i think you could build enough torque with a FE/lowend cammed 4.2 to pull that out of the freeway, you would just have to not use 6th on slower roads, but you would have a second overdrive that was less tall to use the rest of the time

Jeff

Quote:

Originally Posted by Sludgy (Post 66846)

2.73 seems awefully low for a fullsize pickup that'll probably be used for hauling quite a load or trailer. They really just need a 5 or 6 speed so you can more correctly control revs at speed.

Quote:

Originally Posted by Telco (Post 66805)

I haven't read anything about it (to know if they're even trying or close), but I too saw the merits of the electric valves years ago and have been waiting eagerly. I've even thought about attempting it myself a few times but really don't have the time or money.

Other added benefits, you no longer need to pump oil into the head, there will be nothing to lube up there. I think I read the main place oil gets heat sheered is the head because of temperatures there and the lack of fluid (much less resevoir up there compared to the oil pan), so this should instantly increase the milage you can get from regular oil between changes.

Also we can finally get an efficient cylinder shutdown. Displacement on demand isn't much different than just killing the injectors to half the cylinders, during compression you're still stressing and losing energy you won't regain with ignition. With electric valves you can just make the intake open during every downstroke (assuming sequential injection so you would only be drawing fresh air) and open the exhaust valve on every upstroke, while the injector or cylinder is 'off'. This would drastically decrease how much energy an engine draws when not igniting.

I work on the LS4 engine in the W cars. We have never had a problem with the lifters clogging due to oil breakdown. The oil pump is a higher displacement pump then normal to compensate for the new style lifters. When tested for durability the ecm is used to calculate needed oil changes. I know on our Buick that means 6500 miles. With todays oils even cheap ones this should not be a big problem. One of our engineers drove a Buick Lacrosse Super from Michigan to D.C. and he is no light footed driver and recorded 27.8 MPG not bad for 300 hp and as heavy as it is! I think most of us could see over 30MPG. I hope since my pay check is directly affected by GM's programs and with their 100,000 mile warranty in place, having them clog or shorten the life span of the engine won't be true. Remember that Chrysler also has a similar system, so does Ford I think?

Forgot to add that all of these systems default to max. number of cylinders they have.

Quote:

Originally Posted by Telco (Post 66805)

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...
:D

I was talking about "supposed" 1/2 ton diesels which are coming in '09 with a cousin who works for Ford in their advanced planning area. I had read that Ford, GM, and Dodge were introducing small diesels in their light trucks starting in '09. Well....he sees designs out to 2013 right now, and they don't have any diesel on the docket in that time period. Obviously this doesn't say anything about GM or Chrysler, but if one of the 3 were introducing a 30+ MPG truck, you'd think the other two would be right there as well. I think this whole small diesel rumor is just that....a rumor. I asked my cousin why they weren't already building small diesels, as they would sell more of them than they could make if the price was not much more than a gas truck. He said they did many surveys,and there is no customer demand. Well...if there isn't an oil exec. standing behind the curtain of that decision I'd be shocked...
Spence

Quote:

Originally Posted by Spencyg (Post 68144)

He said they did many surveys,and there is no customer demand. Well...if there isn't an oil exec. standing behind the curtain of that decision I'd be shocked...
Spence

I'm pretty sure that oil companies make money on diesel sales too. Otherwise they'd register the diesel sales as some sort of "charity" thing, and take a write-off...

The survey question was probably written like :
If you could have paid $3,000 more and gotten a diesel with the exact same performance and 3 mpg more, would you have?
And so people said no.

Quote:

Originally Posted by Spencyg (Post 68144)

He said they did many surveys,and there is no customer demand.

Yeah, there was no customer demand for the EV-1, either. :rolleyes:

Rick

Every single time I read the title of this thread:
"Is GM getting smart?"

I think
"Doubtful."

Every time...