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Discussion Starter #1
A couple of interesting points for people on this subject, and yes, I bring it up because I like debate.

Wholly unscientific, just observations of various cars, HP, and milage.

2006 Vette (pushrod) 6.0l V8 400 Flywheel HP, 18-28 MPG
2005 Mustang GT 4.6l OHC V8 300 FHP, 17-25 MPG
2005 Honda S2000 2.2l DOHC I4 240 FHP, 20-25 MPG

I find it interesting GM has made a pushrod motor the least thirsty and most powerful engine of the group. :hmm:
 

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I think there are wayyyy to many other factors to figure in than just the valvetrain config. Particulary the horsepower per liter, gearing, and rpm range. The cars posted, I think its comparing apples to oranges:poke:
 

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One could easily say that the Honda S2000 engine is more efficient then the vettes as it is making over 1/3 of the HP while only using a little more than 1/4 or the displacement...while attaining similar MPG#'s:idunno: Lots of different ways to look at this one, very interesting topic...

back to the old addage no replacement for displacment are we?:p
 

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The 6 liter vette produces 33% more hp than the mustang which has 33% smaller displacement. I don't see the difference. :idunno:
 

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All good points so far.

Also of note, the vette turns almost NO rpms at speed on the highway. Not sure about the torquey C6, but my old man's C5 will turn 1600 or so at 73-75... Thats nothing, its barely idling...

Of course, it can get away with gearing like that because the engine is such a stonking stump puller!
 

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Thinking about it, I don't think OHC makes much of a difference compared to pushrod, it does the same thing in a different way, I guess the tiny difference between them would have to do with which has the least drag and the weight of the reciprocating parts
 

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Mattress said:
Thinking about it, I don't think OHC makes much of a difference compared to pushrod, it does the same thing in a different way, I guess the tiny difference between them would have to do with which has the least drag and the weight of the reciprocating parts

Except for one big difference: THe OHV motor in the 'Vette has only 2 valves per cylinder.

Lots of other things to consider here, and ccwilli3 touched on a major one: RPM's. But more specifically, the way that the EPA (or in EnerGuide in Canada) conducts mileage testing. Cruising at 60Mph the Corvette motor is barely above idle, and the first to fourth skipshift is also used in the cycle. This is the same reason the EPA reports 60mpg for the Prius while owners typically get around 40. THe testing favors cars with lots of low-end torque.

In real-world driving I suspect the S2000 owner would see quite a bit better mileage compared to the corvette owner.

Technically, the corvette motor is a lower performance engine compared to an S2000, with half the horsepower per litre of displacement. It is debatable as to which method is better to obtain more power; more cc's or more RPM's.

This isn't very scientific, but would a 2.0 litre motor cruising at 5400RPM use basically as much fuel as a 6.0l motor cruising at 1800RPM?

It's a good debate.
 

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Something I forgot:

I don't think GM is clinging on to the pushrod design for all-out performance. The design has a major advangage in its size; pushrods allow for compact cylinder heads and valve covers, allowing them to stuff the motor in a very small space ie under the low-profile hood of a corvette.

I read an article several months back which had a good argument about engine efficiency. Rather than simply measuring horsepower per displacement, what about horsepower per total external volume and weight of the engine. WHen you look at it this way, the motor in the corvette is far more efficient than your average HO cammer.
 

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Minor tangent....:p

As the manufacturing guys will tell you, one of the major advantages to OHC lies in the engine assembly flow...with an OHC, the head comes into the stream with the valves already set. Time the cams...done...

Meanwhile a pushrod motor assembly line has a bottleneck at the machine where the valves are set...

Aside from the differing performance aspects, one of the major drivers for OHC adoption is a manufacturing related one...much in the same way that FWD was foisted onto us... :twocents:
 

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Discussion Starter #12
phobiaphobe said:
In real-world driving I suspect the S2000 owner would see quite a bit better mileage compared to the corvette owner.
While it's still new, we've got about 800 mi on ours now, most of it from a long highway roadtrip last weekend. We see 23-25 MPG. It is turning around 4000 RPM at 70. I'd guess Vette owners would've seen similar numbers in similar conditions.

Technically, the corvette motor is a lower performance engine compared to an S2000, with half the horsepower per litre of displacement. It is debatable as to which method is better to obtain more power; more cc's or more RPM's.
Yes, I've been looking at this motor from a fairly scientific standpoint (piston speeds, hp/l, which is about 110 for the S2000, 67 for the Vette) and am still mazed at what Honda did with the motor. It achieves literal race car performance, and it's first scheduled tune up is at 105,000 miles. It is truly a statement by Honda, the "Performance First" company. But, who cares. I don't buy cars to brag about my hp per liter to people.

As a consumer I don't care what makes the car go. I want to know my average milage, and feel my car take off when I press the gas. If the General gives me a car with more CI's, but it still gets good milage, and turns less RPM, I don't care.

G-Force, I actually think it's a pretty good comparison. The Vette and the Stang are about the same weight. The S2000 is much lighter, which should of course help it in the milage game.

I read an article several months back which had a good argument about engine efficiency. Rather than simply measuring horsepower per displacement, what about horsepower per total external volume and weight of the engine. WHen you look at it this way, the motor in the corvette is far more efficient than your average HO cammer.
YES! The S2000 motor is HUGE for a four cylinder. I can only guess at the reasons (needed room for the VTEC cam wizardry, tall deck block for long rods, etc etc) but it is very obvious.

It's a good debate.
:thumb: I think so.
 

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Discussion Starter #13 (Edited)
EDDIE110171 said:
The 6 liter vette produces 33% more hp than the mustang which has 33% smaller displacement. I don't see the difference. :idunno:

The Mustang makes 100 less hp, and it gets WORSE milage. :thumbd: Ford! (BTW, it's 25% less)
 

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luvtolean said:
... The S2000 motor is HUGE for a four cylinder. I can only guess at the reasons (needed room for the VTEC cam wizardry, tall deck block for long rods, etc etc) but it is very obvious.



:thumb: I think so.

One of the disadvantages of Hondas DOHC VTEC is its bulk; they actually use rocker arms and shafts, which makes for a very tall and wide cylinder head.
 

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Discussion Starter #15 (Edited)
Yeah. It's a pretty sophisticated car. If I was a betting man, I'd bet Honda makes VERY little money on each car sold.

Over on S2KI they do have links to statements by Honda officials that the car does make money. :idunno: Creative accounting or fact? :hmm:
 

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with an LS1 6spd equipped C5, my old man's routinely gets 31-33 mpg on the highway. It makes me sick...

My acura RSX Type S (a 200HP/2L engine) will normally get me 27-28 mpg in mixed city driving. It sees 8000rpm at just about every stoplight... I don't htink thats half bad considering how I beat on it all the time! On the highway, it'll still net maybe 31. No ways as impressive as the C5...
 

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They probably had to sell tens of thousands of them to break even with their developmental fixed costs. Now that its been on the market a while they probably make a bit of dough.

They're also making money financing and leasing them ;)
 

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ccwilli3 said:
with an LS1 6spd equipped C5, my old man's routinely gets 31-33 mpg on the highway. It makes me sick...

My acura RSX Type S (a 200HP/2L engine) will normally get me 27-28 mpg in mixed city driving. It sees 8000rpm at just about every stoplight... I don't htink thats half bad considering how I beat on it all the time! On the highway, it'll still net maybe 31. No ways as impressive as the C5...
Just curious; how much oil does your motor use?
 

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Discussion Starter #19
ccwilli3 said:
with an LS1 6spd equipped C5, my old man's routinely gets 31-33 mpg on the highway. It makes me sick...
:nod:

I wonder if part of it has to do with the fuel injectors. I don't know what ratings they have, but the S2000 (and type S) must have HUGE injectors to feed these things up at 8k. The Vette is much more relaxed, has a lower hp/l meaning it's far less stressed, so they can use smaller injectors.

Smaller injectors are much easier to control at low RPM, and thus tend to be more efficient.
 

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Discussion Starter #20 (Edited)
phobiaphobe said:
They're also making money financing and leasing them ;)
Yeah, but our total lease payments, and residual value, are still well below sticker! :D

(Yes, I'm still proud of our deal. ;) )
 
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