GM's new V-8

[Guest]

For modern vehicle buyers, here's one for debate- what do you think of the new V-8 coming out(first for GM trucks & SUV's, others later I'm sure) that will run on just 4 cylinders in normal driving? Wasn't this tried once before with disastrous results??(on Cadillacs) Wouldn't going back to dual carburetors be better??(ha ha) Another thing, this will be aluminum, not cast iron. That reminds me of the Chevy Vega or the 1978-79 Olds diesel & the warpage problem

[Guest]

I think that with modern technology an engine can run on four cylinders. With todays fast computers it should be much better than the system that came out 20 years ago.<P>Aluminum engines are better and they are necessary in order to reduce the weight. The most common cause of head gasket failure is on iron engines with aluminum heads. They have trouble with head gaskets because the metals expand at different rates.

[Guest]

also one of the main problems with the caddy motor was that it had a hard time running on the 6 cylinder configuration. the 4-8 configuration is not too hard to manage.the caddy motors have done this for a few years now. when those engines run out of coolant, they already alternate the spark on its cylinders to use the unburned fuel charge to cool the engine (i know how many time does an engine run out of coolant. but i remember an ad and a subsiquent article on how this works). GM needs to have their 8.1 liter motor run in this 4-8 config so that it can get some form of normal gas milage. it now get 8-10 mpg. i for one hope that it works. this is not the most bizzarre thing that i have heard. Saab has developed a variable compression engine . <P> <P>john

[Guest elk93001]

I was under the impression that fuel was cut off to the cylinders not firing. The engine only pumps air in as a way to cool the engine.

[NTX5467]

A recent article on GM's move to improve the fuel economy on utility vehicles mentioned the "cylinder kill" strategy. It was mentioned that the technology and equipment are now much better than with the Cadillac system of earlier years.<P>I have also noticed that the limp-in mode in the event of coolant loss has been expanded to some other GM engines now also.<P>As crude as that earlier high-tech Cadillac stuff was, it kept the EPA at bay long enough for the newer engines to come online with better fuel economy and for the newer bodies to get into production for them.<P>I suspect the new systems will work much better than the old ones ever could.<P>NTX5467

[Guest]

you guys are right. i was talking about the limp in mode of the caddies. the GM engines with the 8-4 mode will shut down the cylinder<BR>(i.e. no fuel) to get the better fuel economy. there us a cool article in this weeks autoweek about it. there is also some other cool things to get better fuel economy in these big trucks. also these new engines will be in production in 2004 silverados/sierras and SUV's<P>john

[Gene Brink]

Given the computer contols on engines today doing this should be fairly easy. Programmed 4 cyl operation would merely require cutting off injectors and spark to given cylinders. (Spark should be shut off too as one would not want the top of the piston to be the best ground for the ignition spark. If that happens it does not take too long to arc a hole in a piston top as I learned with a very nice running '54 322 with 34 thousand miles on it in 1964.)<P>Heck, computer systems on cars today would even permit a good 8/6/4 configuration like Cadillac tried previously.<P>Gene