Amazing, Chevy builds a 330 HP engine with 28mpg Options

[Hawktel]

So the new Impalla that chevy has released has a option for a 330 HP V8 with 28 highway fuel consumption.

Thats amazing. Just amazing. I wonder how far fuel efficency can be pushed?

[jniemeier]

We call them ETC's: Electronic Throttle Control, and no, that won't work. For one, you can't put an ETC into a 500deg C exhaust stream. Well, you could, but it wouldn't live long. Why do you think this would work better? Doing it in the valvetrain is the closest to the combustion chamber we're trying to control and by far the most mechanically simple (engineers would say, "elegant") solution. There's no need to think up anything else.
Individual throttles implies you're using individual intake runners. Very expensive and won't fit for a V type engine. V engines like plenum's and a single throttle cuz it helps even out the flow balance to the cylinders, fits better, and of course is lots cheaper. Racing engines may have seperate runners, but keep in mind they are optimized around a very narrow rpm band.

Cylinder filling: I don't think you caught what I wrote before. You need to seperate the idea of quality of combustion from the amount of mixture in there. To have acceptable emissions, you need to keep the mixture at 14.7 to 1 air/fuel ratio. Period. After that, the AMOUNT of 14.7:1 mixture we get in there is the thing that directly controls the torque that cylinder makes. At Wide Open Throttle (WOT), less restriction to air flowing in, more mixture in the cylinder, max torque. At idle, tons of restriction past the throttle, little mixture inside, low torque. In both cases, the mixture is always 14.7 to 1. It takes a while to digest that fact. So, things like the ease of initiating the burn, and the combustion 'efficiency' are the same in both cases. The power generated is drastically different of course, so the heat loss to the wall is different, sure, but the efficiency is the same. Engines are most efficient at WOT not because they burn better, but because they don't waste work pulling air past the nearly closed throttle at low loads.
Answer to paragraph #3: Number 1 and 2 are both good, although I think number 1 is the easiest and likely the larger improvement, at least for big V8's. With a 914 engine pushing the car at 70 mph, you can't be lowering the revs too much can you? But, when Chevy was trying to avoid the gas guzzler tax on the Vette inspite of increasing hp to 400 (and now 500!), they went to gearing that left it turning what, 1600 at 70? Something like that. IF you have the torque, that's the easiest way to go. By now, I hope you agree that Number 3, increased filling, is simply a method to increase torque, not improve efficiency, BUT, you can use your increased torque to drive taller gearing, and THAT is option Number 1, the best option. So, 3 is just an enabler for 1. Got it?

Now, since you're such an inquisitive guy, here's my advice I hope you take on board: Go to a used book store (or probably Amazon) and buy a copy of "Internal Combustion Engines and Air Pollution" by Obert. That's the one used in most engineering schools and is the all time classic. Every engine designer in the country has a copy in his office. Read the whole thing. It's actually not that hard to read. I'm sure you will get a ton out of it.
(IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif) Jim N.