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Originally Posted by fedezyl
...that's what they did in the early days of formula one, until they ran into the problem of weight and space..
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Are you quite sure? Going by this theory, modern Formula One teams, even though they're allowed 3.0 liters, should be making 2-2.5 liter engines...because that would make them smaller and lighter. And a reduction in stroke would make revs easier.
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Originally Posted by fedezyl
Then came overhead camshafts, and double overhead camshafts, again a compact light design...
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Compact and light? Take a look at this picture. The one on the right is actually marginally
larger in displacement than the one on the left.
Take a look at the size of the heads:
Here's a popular conversion for the Datsun 240Z. On the left, a small-block Chevy. On the right, the DOHC from the "smaller" (in displacement) Infiniti 4.5 liter V8. Which one looks more compact to you?
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Originally Posted by fedezyl
Then came overhead camshafts, and double overhead camshafts, again a compact light design that allowed for an easy an simple change on valve phasing thus again helping the engine breathe, try doing that on a pushrod design....., also the DOHC design allows for variable valve timing and lift, thus again keeping size, and weight under control while again improving engine breathing making it even more efficient.
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Hmm...Ok.
"The LZ8 3900 will be the first GM overhead valve engine to use variable valve timing, and it will be GM’s first V-6 to use DOD."
http://www.auto-report.net/index.html?gmpt05.html
This is partially correct. It will be the first GM OHV
production engine to use variable valve timing. The XV16 had it too.
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Originally Posted by fedezyl
yes, they think having a big V-8 is fast and powerful, when in the end a 3.6 liter engine can get almost as much power as the V-8, I think the Corvette is never going to be as good as a sports car, because of the many design compromises, the thing is, what is cheap is cheap for a reason....
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I don't think you understand how cheap it really is. A Chevy LS6 is about $6-7K. And makes 405 hp and about an equal amount of torque. A standard, normally aspirated Porsche flat-6 is $20K. We're not even talking about GT3 engines here. And makes nowhere near that kind of power or torque. Porsche's 996 Turbo is right on the mark for power and torque. But oh, dear. It's $40K...And sure as hell isn't as cheap to service.
You have to ask yourself: Why is Porsche's engines continuing to increase in displacement? How large was the original Porsche flat-6? How large is the 997 C4S engine? By the same token, recall that the original BMW M3 had a 2.3-liter inline-4. It's gone from an I-4 to an I-6. Next up is a V8. Same with with the M5, except it's a level up from the M3.
What all of you guys are forgetting about is that
peak hp doesn't matter as much as the
way that power is delivered, its effective powerband, the shape of its torque curve, and the area under the curves. Take a look at these two modified engines:
One is a turbocharged I-6. The other a naturally aspirated V10. They both put out about 640-650 RWHP. But does hp=hp? Not necessarily. Look at the area under the curves. Which do you think would have better throttle response? Which do you think would make a better street engine, ie. which is more driveable?
These are ALL considerations into why GM chooses to use pushrods (which it says saves them $2.7B a year). In the case of the Corvette, not only is it cheap to build, it's cheap to service, it's durable, less complex (compared to a DOHC design), and it offers the instant throttle response owners look for. On top of that, they can afford to use a lazy overdrive 6th gear: the Z06/C6 basically does with 5 forward gears what many of its competitors do with 6. And that lazy 6th gear means better fuel economy. The Z06 is about as fuel efficient as a standard 996.