Take a look...

http://www.digitalcorvettes.com/corvette-photos/data/703/Corvette-LS9.jpg

It's a C/N. Really just talking about some sort of damper, probably something to do with engine mount or drivetrain mount as the wording appears. Is it the DOHC wording that hits you? Because I see it as GD OHC meaning nothing new.

Edit: Thanks 555. :D

Sad thing is, even though those engines are proven technology and do work very well, inch for inch, our 2.5 N/A makes greater power per volume.

But the big ol american pushrods are torque heaven. :)

It's a 6.0 DOHC, not the 7.0, and the DOHC was just a rumor.

What would the GD refer to if it were just GD OHC? I liked watching the C6Rs run by the DB9s in traffic in Sebring using the torque even though the DB9s had top end speed. Don't foget the 427 GT40 at LeMans won the race and the index of efficiency. Anyways it will be interesting to see what GM comes up with.

nothing wrong with torque, it moves the world. And like them or hate them (I hate them in modern cars) pushrods and GM are married for a very long time. The specific output of the LS7 is pretty crappy. 7 liters...500HP... blah blah.. no biggie. Far from amazing. As much as I am unimpressed with the LS7, you have a to appreciate the way the Corvette package works. They take a dinosaur motor with ancient tech, and exploit its characteristics very well.

And whether you hate the pushrods or not, johnei's point cant be disputed... those vettes do really well against any other GT1 car. It will be a great fight all year with the astons.... which are one of the most beautiful cars I have seen in the ALMS in as long as I can remember..


SCRAPPYDO

I've never really understood the concern about specific output--how is it really relevant? I haven't looked at the numbers, but I would be willing to bet that the C6 Z06 probably has a similar EPA rating as an S2000 (one of the highest NA specific output motors) yet makes more than double the HP and creates performance numbers that put it to shame. Of course some of this is due to gearing, but so what, if it works, it works.

nothing wrong with torque, it moves the world. And like them or hate them (I hate them in modern cars) pushrods and GM are married for a very long time. The specific output of the LS7 is pretty crappy. 7 liters...500HP... blah blah.. no biggie. Far from amazing. As much as I am unimpressed with the LS7, you have a to appreciate the way the Corvette package works. They take a dinosaur motor with ancient tech, and exploit its characteristics very well.

And whether you hate the pushrods or not, johnei's point cant be disputed... those vettes do really well against any other GT1 car. It will be a great fight all year with the astons.... which are one of the most beautiful cars I have seen in the ALMS in as long as I can remember..


SCRAPPYDO
How is this a dinosaur motor? Just because it uses pushrods? Don't even compare the LS series with the old chevy small block. The similarities are few in number.

I don't understand this ridiculous obsession with hp/L. What do you gain by having a high ratio? bragging rights? You can brag all you want about it it doesn't mean anything. If the motor sucks so bad why do Mosler, Ultima, Bristol, Marcoss, etc. use the LS series? It's cheap, reliable, light, compact, makes good numbers stock, has huge potential (N/A, turbo, super), etc.

I don't mean to say that a Ferrari powerplant is crap (or any other hi-tech engine), quite the opposite, but it is no better than a LSx really, just different. Dismissing the engine becuase it is "antiquated" is just import fanboi crap.

I've never really understood the concern about specific output--how is it really relevant? I haven't looked at the numbers, but I would be willing to bet that the C6 Z06 probably has a similar EPA rating as an S2000 (one of the highest NA specific output motors) yet makes more than double the HP and creates performance numbers that put it to shame. Of course some of this is due to gearing, but so what, if it works, it works.

I would assume both cars are geared optimally.

I'm at the other end of the spectrum. I don't see what's so impressive about the S2000 motor. It has lots of "technology" but it still doesn't make any real HP or (especially) torque. It's MPG isn't that great (probably worse than a C6), and unless it's turning 9,000 RPM it can't get out of it's own way. Maybe I'll change my mind if I drive one, but I just don't get the appeal. Maybe spinning to 9,000 RPM makes it feel fast.

My NA motor makes 320hp/liter and revs to 13k rpm! BUT it is a 2-stroke, 125cc, and only makes like 18ft*lbs of torque. :)
Of course I change the ring every 3 hours and the piston every six, so uh, it's not the most reliable motor.

The similarities are few...really? Your kididng. What is the new technology other than material selection. Sure its not an aluminum casting of an 50's small block, I never said that. But aside from the electronics, its basically the same thing...It makes power the same way Smokey Yunick would have...Long stroke, big bore, lightwieght valvetrain and rotating components, fully floating pistons, yada yada. I had that all that on my small block 400. Which by the way made more HP, and More torque than LS7 with a carburator. Granted the torque curve was not nearly as level, but I could have pushed that puppy far higher if I would have used a solid lifter cam, or maybe a nice roller hydrualic..

Aside from the materials, which are fairly exotic (If you consider titanium exotic, and I still do) the layout is basically the same tech as the old schoolers. Now, I am far from an import fanboi, as I have built more small blocks than I can remember. And I like the V8 rumble. Heck I was cheering for the C6R during Sebring.

But there is nothing revolutionary about the LS7.... its just BIG. Now I can see everybody itching to say, "hold up SCRAPPYDO, its a smaller, lighter package than most, and its external dimensions are smaller..." I have never argued that, but its internal displacement is HUGE! If GM deserves any credit, its for packaging.

But even that is nothing new. I could have stroked my small block 400 to a 434cid when I was building engines with a crank kit. And I would have had a small block 434, 7.1 liter monster. In fact if can ever find a nice 1970 Z28, I will probalby build a full roller 434!

Again I will say it... the Corvette is impressive to me, the LS7 is not. Its just a bigger version of the same old V8 tech. That alone use to make me hate that engine, but as an engineer I have to appreciate its simplicity and its raw nature. Honda, BMW, Mercedes use technology to help them make HP, where GM uses size. You can kill squash a bug with an intricate press, or just use a 50lb sledge! A bullet is just a small rock thrown really fast.

I have had this argument so many times I get dizzy, but each time I learn a little more about the other perspective. As far as efficiency, you can throw out MPG figures, as the VETTE is geared to death to exploit the 7.0 liters of displacment. Its that displacement that gives you massive torque, which in tern lets you run 1200 rpm at like 60 mph, thus good mpg. Again its the package thats impressive and efficient, not the engine.

More HP out of smaller engines is impressive to a degree, but whats more impressive is more torque from less displacment... I think that takes more work. And it takes more technology to get you their, be from FI, or from crazy cam wizardry, or whatever.

Well, whatever your opinion about the vette, or LS7, or both, its always interesting to hear the other side of the argument. At least to me it is... :)

SCRAPPYDO

The similarities are few...really? Your kididng. What is the new technology other than material selection. Sure its not an aluminum casting of an 50's small block, I never said that. But aside from the electronics, its basically the same thing...It makes power the same way Smokey Yunick would have...Long stroke, big bore, lightwieght valvetrain and rotating components, fully floating pistons, yada yada. I had that all that on my small block 400. Which by the way made more HP, and More torque than LS7 with a carburator. Granted the torque curve was not nearly as level, but I could have pushed that puppy far higher if I would have used a solid lifter cam, or maybe a nice roller hydrualic..

SCRAPPYDO

The cooling is different from the old small block, it's a distributorless system, the bottom end uses stronger materials, the intake is totally different, the heads are totally different, sodium filled exhaust valves, etc. The heads on the LS7 have better flow numbers than most aftermarket heads for gen I small blocks. To say that you could make a gen I small block with more power doesn't mean much, I'd be willing to bet a ton of money it wouldn't be as reliable or usuable as the LS7.

You're arguing that it is still old technology; but so are overhead cams, turbochargers, and superchargers. The newest technology is VVT and even that is almost 20 years old now. Obviously the technology has been refined over the years, but so has the pushrod V8.

I'm not attacking you personally, because you seem to respect all types of engines; but many people dismiss pushrod V8s because they are old.

But even that is nothing new. I could have stroked my small block 400 to a 434cid when I was building engines with a crank kit. And I would have had a small block 434, 7.1 liter monster. In fact if can ever find a nice 1970 Z28, I will probalby build a full roller 434!SCRAPPYDO

Heh, I would consider a 400ci to be a big block. What I have found interesting is that recently there have been many people building small bock (360ci) engines for the track and are beating many of the big blocks. I might have gone that route but I'm already invested in my 440.

It is awesome to think that after 30 years we are still messing with these engines.

we need to put together a pushrod bashing v. boosting thread and then put this to bed. Can't we just say that different motors have different advantages (efficiency, overall size, effective power band, cost to prduce, etc.) and then leave it to an overall test to determine the merits of a car?

we need to put together a pushrod bashing v. boosting thread and then put this to bed. Can't we just say that different motors have different advantages (efficiency, overall size, effective power band, cost to prduce, etc.) and then leave it to an overall test to determine the merits of a car?

It's been done and nothing was accomplished. It's personal taste...

And also, let's stick to the topic.

Thanks.

Again its the package thats impressive and efficient, not the engine.
And that's what so amazing about the Corvette: the package. Watch an episode of Top Gear and listen to them bash the technology used in the Corvette, but in the end it still puts up some impressive numbers. The technology used in each component may be "old," but it results in a car that has the best bang-for-the-buck on the market (IMHO). For $70k you get a car that can hang with cars that cost 2 & 3 times as much! I don't care how old the technology is, it works!
Just my $.02
-Chris

And that's what so amazing about the Corvette: the package. Watch an episode of Top Gear and listen to them bash the technology used in the Corvette, but in the end it still puts up some impressive numbers. The technology used in each component may be "old," but it results in a car that has the best bang-for-the-buck on the market (IMHO). For $70k you get a car that can hang with cars that cost 2 & 3 times as much! I don't care how old the technology is, it works!
Just my $.02
-Chris

At the bleeding-edge of performance (where 99% of the drivers out there will never get to), being able to brag about the technology is just as important as the potential performance.

Same exact thing in the excutive high-end luxury car market. Some of these cars have 500 hp, and yet are limited to 65mph roads. The abilities of these cars is less important than the technology under the hood.

Is it fairly egotistical? Yup - but that is the price of admission.

Yep, it's all about the technological bling for some people. For others, it's just about whatever works the best.

Car | Chevy C6 Z06 | Ferarri F430
========+=======================+================= ====
Engine | 500 hp "antiquated" | 490hp "cutting edge"
| 7.0L pushrod V8 | 4.3L 5v DOHC V8
Tranny | 6 speed | 6 speed clutchless
Weight | 3130lbs | 3197lbs
0-60 | 3.9s | 4.0+s
1/4 | 11.5 @ 127 | 12.6 @ 114
econ | 16/26 mpg | 11/16 mpg
price | $65K | $175k


Man those old pushrods suck.

Car | Chevy C6 Z06 | Ferarri F430
========+=======================+================= ====
Engine | 500 hp "antiquated" | 490hp "cutting edge"
| 7.0L pushrod V8 | 4.3L 5v DOHC V8
Tranny | 6 speed | 6 speed clutchless
Weight | 3130lbs | 3197lbs
0-60 | 3.9s | 4.0+s
1/4 | 11.5 @ 127 | 12.6 @ 114
econ | 16/26 mpg | 11/16 mpg
price | $65K | $175k


Man those old pushrods suck.

Haha..... Yeah, the new Z06 is a hell of a steal if you're looking for ultimate performance for the $$$...... However, that pushrod engine as you can see is about 40% larger to make the same kind of power made by the Ferrari.... So yeah, it is a little technology "edge".....

But then again.... Who actually buys a Ferrari so they can say they have a "performance" car ??? They don't cost $175k because of their performance value, so much as their social and poon-value..... :lol:

Haha..... Yeah, the new Z06 is a hell of a steal if you're looking for ultimate performance for the $$$...... However, that pushrod engine as you can see is about 40% larger to make the same kind of power made by the Ferrari.... So yeah, it is a little technology "edge".....

But then again.... Who actually buys a Ferrari so they can say they have a "performance" car ??? They don't cost $175k because of their performance value, so much as their social and poon-value..... :lol:

Actually, the Ferrari engine is about 30% larger...and heavier. Its just the empty space in the LS7 engine that is larger.

fyi - sat in a new Z06 at the Raleigh Auto show, C R A M P E D! Very tight confines for my 6'5" frame... oh and sticker read $70K MSRP (vert.)...

Didn't realize how close you are to me..

Haha..... Yeah, the new Z06 is a hell of a steal if you're looking for ultimate performance for the $$$...... However, that pushrod engine as you can see is about 40% larger to make the same kind of power made by the Ferrari.... So yeah, it is a little technology "edge".....



Actually, the Ferrari engine is about 30% larger...and heavier. Its just the empty space in the LS7 engine that is larger.


mh_WRX is right... the engine in the ferrari is heavier and larger. So to summerize:
The Z06 engine is lighter, produces more power, is more compact, has a lower CG, and is more fuel efficient (and could be even better if GM added DOD).
The ferrari engine has less displacement.

What exactly is the advantage of having less displacement? Lighter engine? Not in this case. More fuel effiecent? Nope. More drivable? Definitely not.

Is there more "tech" in the ferrari engine... possibly... is that tech paying off? It doesn't appear to.

My bad.... When I said "larger" I was referring to the displacement....

Do I think the Ferrari is worth the money??? Hells no !!!

The Z06 is definately money better spent...... However, if I had that sort of money laying around, I'd be all over the Porsche or Aston Martin action.... :banana:

But that's just me.....

Again, the fuel efficient argument for the engine is incorrect. You can say the Corvette is more fuel efficient than the F430, but thats the only argument you can make about efficiency

http://forums.nasioc.com/forums/showthread.php?t=964502

Again, the fuel efficient argument for the engine is incorrect. You can say the Corvette is more fuel efficient than the F430, but thats the only argument you can make about efficiency

What other fuel efficiency argument other than "more or less fuel efficient" is there?

And don't give me the gearing crap. An engine not connected to gears gets exactly 0 mpg no matter what engine it is. Put the Vette engine/gears in the Ferrari and you get a more fuel efficient (and just as fast, maybe faster) Ferrari.

rmbrady no offense taken your making valid points...DOHC is not by any means the newest game in town. But it does tend to help make more HP out of a given engine than an a typical 2 valves per cylinder. The ZR1 engine was a sweet piece of work, and given the some of the same advances in materials it would be devastating today.

The things you listed are noteable differences. But I would hesitate to call it revolutionary. But by that argument not many engines are. Outside of things like VANOS (BMW) and other various trickery not too many revolutionary things have happened to our friend the Internal Combustion Engine. In fact the advent of Direct Injection is a pretty big deal in terms of evolution.

I would agree with you on your statement that my small block would not last as long. The machining on my engine would not rival that of an OEM manufacturer. Nor was my powerband as broad as the LS7... I simply did not have fuel injection or computer controlled spark timing. I only bring up my old engine because people seem to be blown away at how much power the LS7 is making, and by many peoples standards its just not that much for its displacement. Its smoothness, its ability to rev are all notable and noteworthy.

I keep hearing that the Ferrari engine weighs so much, but I have never seen that weight documented anywhere. I cannot argue that fact either way, because I have never seen any data on it. And it really does not mean that much to me to do a search on it...

jamest: I would agree, but its nice to have the external dimensions of a 283cid small block and actually have 434cid. It makes all those battles on the street that much more fun when you can tell somebody you have a 350.. :) I know its sneaky, but I was younger then...

I don't understand this ridiculous obsession with hp/L.

Just a bunch 'o Hunduh boyz on a Subie forum. ;)

um scott your missing the point, make the vette engine run at 3200 rpm at 70 mph and then see how efficient it is. Gearing has everything to do with it. And there is nothing wrong with that. GM is exploiting their advantage. Kudos to them.

If the Ferrari engine was in a vette, it would probably get better mileage than the LS7. A 4.3 liter engine at 2200 RPM gets better mileage than a 7 liter engine at 2200 rpm all other things being equal. Of course this would drastically effect performance, but we are only talking efficiency here.

I dont hate the LS7, nor do I hate V8s (I thought I covered this already). NO design can be around as long if its not pretty darn good to begin with.

I know it has to do with gearing - my point was you *have* to consider the gearing with the engine as a package. The Ferrari engine in the Vette would be slower. Likewise, the Vette gears in the Ferrari would be slower. The ability to use the Vette gears is directly a function of the LS7. You can't seperate them and talk about the fuel efficiency of the engines or gears individually. Both engines get 0 mpg without gears, and both sets of gears get 0 mpg without engines.

The LS7 (more power at lower RPMs) is directly responsible for the gears in the Vette - therefore it is more fuel efficient.

I'm not a big Vette fan - I've never owned one and probably never will. I just think it's ridiculous that people are so quick to bash the "old" technology when there isn't any "new" technology that's caught up to it yet. There are plenty of valid things to criticize GM about - the LS7 and Corvette are *not* one of those things!

What about torque?

The things you listed are noteable differences. But I would hesitate to call it revolutionary. But by that argument not many engines are. Outside of things like VANOS (BMW) and other various trickery not too many revolutionary things have happened to our friend the Internal Combustion Engine. In fact the advent of Direct Injection is a pretty big deal in terms of evolution.


What about displacement on demand? Haven't seen a DOHC engine disable cylinders yet. I have seen it done in GM V8s and DC Hemi's.

Displacement on demand was tried a long time ago by cadillac... Had very poor reliability record. I am sure todays is far better, but its a bandaid. Getting an engine running and then shutting off half its cylinders still means you have 4 pistons and 4 rods that are dead weight. Its not graceful, and I have yet to see the reliability yet.

Usually DOHC engines dont need to use DOD because they make much better use of the air/fuel they recieve (they are more efficient). However, if they wanted to...it would simply be a matter of telling the plug not to fire and the fuel not to be injected. Its not that complex to do DOD. Far from it.

scott_gun, I am hearing ya with the fact that no engine can run without gears...point taken. but my point is that the Corvette package all together is more efficienct than the Ferrari package. Not the engine. The LS7 is just a very large displacement V8. I dont hate it, just dont respect it. Like using a hammer to drive a screw. It will get the job done through brute force.

As far as which is the better air pump, the Ferrari is better. It moves more air per liter of displacment, and thus makes more HP/Liter.

But this arguement has about run its course. I have never set out to persuade anybody to not like the LS7. To each their own. I just thought I would voice my opinion that if the LS7 is the pinnacle of GM performance its pretty sad. The new Solstice engine with its DI and turbo is far more advanced.

I just don't understand how you can't respect it just for having different technology. If someone invented a new electronic screwdriver with tons of innovative technology, but it couldn't drive in a screw as well as an old-technology electronic screwdriver, would you prefer it for the sake of technology alone - despite the fact it doesn't perform as well, is heavier, uses more electricity, and is more expensive?

That's crazy!

It's pretty sad, IMO, that all these modern innovations can't create a car that touches the Vette performance wise for anywhere close to the same price. And none of them come close to matching the Vette's fuel efficiency. Other manufacturers may have the edge in driving dynamics though.

All innovation technology comes with a price... The more technology, the more it will reflect on the price. There HAS to be a legitimate reason why GM continues to use the pushrod on the Vette vs. sophisticating the engine.

Sales say that the pushrod is not an issue to the buyers... they ARE buying. So regardless of whether you agree or not, the Vette is the best bang for the buck in it's category and blows competition away. Sometimes the older technology is better and lasts longer than what's being introduced today.

I just don't understand how you can't respect it just for having different technology. If someone invented a new electronic screwdriver with tons of innovative technology, but it couldn't drive in a screw as well as an old-technology electronic screwdriver, would you prefer it for the sake of technology alone - despite the fact it doesn't perform as well, is heavier, uses more electricity, and is more expensive?
scott_gunn. This is not a parallel comparison. The exact same LS7 engine, but with more up to date technology (in the valvetrain at the very least) WOULD be more efficient. Name any engine that has had both a push rod and overhead cam varient, and in EVERY instance that I can think of the OHC version makes more power -in the same state of tune- and gives better fuel economy. This is why some of us are dissapointed with the LS7 (not the Corvette as a whole).

The engine COULD have been so much more. Is it enough? Obviously yes to match (or beat) the competition. But... a plain old ordinary screwdriver which works still doesn't impress me, or many others.

All innovation technology comes with a price... The more technology, the more it will reflect on the price. There HAS to be a legitimate reason why GM continues to use the pushrod on the Vette vs. sophisticating the engine.
As I said in a previous post I would bet the reason the pushrod is still being used by GM, is because they are not in the financial position to invest in new engine building lines. The old pushrod lines were likely modified to produce the new Vette motor. I have no proof of this, but it seems a reasonable explanation.

Sometimes the older technology is better and lasts longer than what's being introduced today.
Sometimes that is true, but I don't think so in this case. Some of the newer technologies the LS7 is missing are cheaper (neglecting the cost of new machinery), simpler, and more reliable.

I think Big Elm has a good point, despite what we would LIKE to see with the production of the LS7, there is more to it than what meets the surface. Can GM continue to sell pushrod V8's. Sure they can and probably will. Unless they mainstream the production of the Northstar and invest some time and money in it. There is so much we dont know about the inner world of GM

brandon: I wholehearted agree that you got my point.

There is a technology gap. GM cant just keep making the vette engine bigger to compete with the rest of the world. Eventually they are going to have to incorporate some 'more evolved valvetrains'. American cars are often refered to as the knuckle draggers of the automotive world because of the 'SEEMING' lack of any innovation.

I would like to think of the vette as the premier american sports car. The best of the best of what this country can produce in style, technology, performance and feel. Well we got the performance down. NO questions about that. But its embarrasing that the best we can produce is a big, burly V8. I admire its simplicity and its effectiveness...but I do yearn that we are not really pushing the envelope. I want the vette to be a WOW car and leave the rest of the world in a 'how did those yanks do that!' mode.

The vette just does not do that for me. They have a proven equation that works, but are only taking baby steps to improve it. The 911 has gone from baby 4 banger that is rear wheel drive to turbo 6 cylinder AWD all the while improving the package. Its honorable to keep the heart of the car true to its heritage, but not at the expense of progress.

I like the vette, I just want it to be a flagship of more than just performance. I would like it to dazzle the world with its whole package. I can always hope.

You might like the LS9 then

I know it has to do with gearing - my point was you *have* to consider the gearing with the engine as a package. The Ferrari engine in the Vette would be slower. Likewise, the Vette gears in the Ferrari would be slower. The ability to use the Vette gears is directly a function of the LS7. You can't seperate them and talk about the fuel efficiency of the engines or gears individually. Both engines get 0 mpg without gears, and both sets of gears get 0 mpg without engines. (snip)


Not entirely true. You could measure them both using brake specific fuel consumption - a grams/bhp-hr kind of thing. I'm used to seeing efficiency maps this way.

um scott your missing the point, make the vette engine run at 3200 rpm at 70 mph and then see how efficient it is. Gearing has everything to do with it. And there is nothing wrong with that. GM is exploiting their advantage. Kudos to them.

If the Ferrari engine was in a vette, it would probably get better mileage than the LS7. A 4.3 liter engine at 2200 RPM gets better mileage than a 7 liter engine at 2200 rpm all other things being equal. Of course this would drastically effect performance, but we are only talking efficiency here.


Again - this isn't necessarily true (although it likely is). There are lots of games you can play with these sorts of things (Atkinson cycling, lightweight engine components, variable displacement - although that is somewhat cheating :)), but a 4.3L doesn't have to be more efficient OR get better mileage at the same engine speed.


Usually DOHC engines dont need to use DOD because they make much better use of the air/fuel they recieve (they are more efficient). However, if they wanted to...it would simply be a matter of telling the plug not to fire and the fuel not to be injected. Its not that complex to do DOD. Far from it.

Mercedes S-Class had cylinder deactivation on their OHC engines in the late 90s early 00s - but it is harder to do it on OHC engines than pushrod engines, that's for sure.

well put

As I said in a previous post I would bet the reason the pushrod is still being used by GM, is because they are not in the financial position to invest in new engine building lines. The old pushrod lines were likely modified to produce the new Vette motor. I have no proof of this, but it seems a reasonable explanation.

Uh...Northstar?

Hypothetical question: Is the rotary more high tech than overhead cam? Since it's "newer technology", it must be right? Or is it just a different way to build an engine?

BTW, One of the things not mentioned but worth noting is that it's going to be hard for any DOHC V8 to beat the pushrod V8's mileage. The big torquey V8 can idle down the freeway, while the smaller, OHC V8 engine must turn higher RPM. Higher RPM = Higher Friction = Worse MPG. The OHC engine also has the frictional losses associated with 4 cams vs. 1 cam and 32 valves vs. 16, and that big fat chain connecting everything. You can get around a lot of these losses by building an inline engine (2 cams instead of 4, and a much shorter chain) but packaging becomes an issue after you have more than 4 cylinders. Finally, remember that in other countries, vehicles are taxed by engine displacement, penalizing larger engines (whether they are more efficient or not). This isn't going to be an issue for a Ferrari owner, but BMW owner...perhaps.

There's really an ideal engine combination for any given car. The Pushrod V8 is ideal for the Corvette. The DOHC is suited to the Ferrari. The Boxer engine is ideal for a symetrical AWD layout. A rotary works well in a flyweight RX7. Are any of them better than the other? Maybe, maybe not, but if the package works well, who cares?

Uh...Northstar?
Um... ZR1? Your point being? Although I suppose you didn't see my posts in the other thread, and I hate posting the same thing over and over. The Northstar engine was designed before GM's latest financial woes. Hence money for the new line wasn't as big an issue. Also, it is entirely possible the Northstar motor is being produced on the old ZR1's (I think it was the LT5) line. This line would be lower volume and incapable of producing both Corvette and Northstar engines (just speculating here).

Hypothetical question: Is the rotary more high tech than overhead cam? Since it's "newer technology", it must be right? Or is it just a different way to build an engine?
Perhaps we should modify our statements to read "better technology".


BTW, One of the things not mentioned but worth noting is that it's going to be hard for any DOHC V8 to beat the pushrod V8's mileage. The big torquey V8 can idle down the freeway, while the smaller, OHC V8 engine must turn higher RPM. Higher RPM = Higher Friction = Worse MPG. The OHC engine also has the frictional losses associated with 4 cams vs. 1 cam and 32 valves vs. 16, and that big fat chain connecting everything. You can get around a lot of these losses by building an inline engine (2 cams instead of 4, and a much shorter chain) but packaging becomes an issue after you have more than 4 cylinders.
Sorry, but it has been mentioned and I disagree with you. The LT7 with the exact same bottom end, and a properly designed OHC WOULD get better mileage. I really don't think this is even debateable. OHC engines don't have to turn any faster than pushrod ones, it's all in the tuning with the cams. However, pushrod engines CAN'T turn as fast as OHC engines can (a big disadvantage). Frictional losses in a piston engine are very low (contrary to popular belief). All the studies I've ever seen in my career put these losses at less than 2% overall. The "big fat chain" in an OHC cam engine travels the same direction all the time. It's the CHANGE in direction the riders, pushrods, lifters etc. have to make which is one of the reasons the pushrod system is less efficient. Plus the pusrod still has a chain (just not as big).

The Pushrod V8 is ideal for the Corvette. The DOHC is suited to the Ferrari.
I'm sorry, but I have to ask you why that would be the case? We're not talking entirely different engine layouts for packaging reasons here. We're not saying the LT7 is a BAD engine. We're just saying it could have been much more.

Also, it is entirely possible the Northstar motor is being produced on the old ZR1's (I think it was the LT5) line. This line would be lower volume and incapable of producing both Corvette and Northstar engines (just speculating here).

The Northstar engine is definitely not being produced on the LT5's old line. I know you were speculating, but there is no way this is possible. The LT5 wasn't produced by GM. It was subcontracted out to Mercury Marine, where it was assembled by hand. The reason that GM stopped subcontracting labor to Mercury Marine was because Mercury Marine was not a union establishment. Also, just a side note, the LT5 was designed primarily by Lotus Engineering for GM.

What about displacement on demand? Haven't seen a DOHC engine disable cylinders yet. I have seen it done in GM V8s and DC Hemi's.

Not a DOHC, but Honda has a SOHC system on their Odyssey vans that do DOD (they call it VCM).

But it'd be nice to have a discussion about the Vette without people saying, "pushrod, bah." I don't think it matters to the end user what type of technology is being used inside of the engine when you have 500hp at your beck and call.

If you could take an engine like the LS7, make it OHC, and it would be superior, how come there aren't any such engines around? There has to be a valid reason that no other manufacturer is making such an engine.

Not a DOHC, but Honda has a SOHC system on their Odyssey vans that do DOD (they call it VCM).

But it'd be nice to have a discussion about the Vette without people saying, "pushrod, bah." I don't think it matters to the end user what type of technology is being used inside of the engine when you have 500hp at your beck and call.

I am pretty sure one of the Accord engines has DoD also. Maybe it's the same one you are thinking of, but I thought it was a DOHC.

If you could take an engine like the LS7, make it OHC, and it would be superior, how come there aren't any such engines around?
Ahhh! And there's the rub! It is most likely because other manufacturers believe (and I would suggest correctly so) that:

a) 7L is more than they need to do the job;
b) 7L is too large a displacement for only 8 cylinders (in a track performance engine);

There has to be a valid reason that no other manufacturer is making such an engine.
I believe THIS is a very key question! Because I don't know of any other manufacturers that are making 7+ liter, 8 cylinder performance motors period... pushrod or otherwise. So, why aren't they? It's not as if it's a difficult design to pursue. The question then becomes; are all the other performance engine builders stupid, or was GM trying to save some manufacturing costs? I suppose if we see some more large displacement pushrod motors in the next few years... but I doubt we will.

^^^ you touch upon the point that I have been saying for YEARS now... if OHV engines are "better" then why is it that EVERY other car manufacturer has given up on the design besides Detroit?

I think some people can make the case for the fact that OHV engines tend to have more torque (ofcourse that might be because they tend to be larger, and ofcourse a larger engine will usually have more torque) so it is a good engine for a truck. But if that was the case, then why do the full-size Japanese pickups use OHC designs? They are clean-sheet designs, so if an OHV engine was better, I would totaly have expected them to go that route.

And honestly, I don't really consider this argument to be about the Vette - the engine in that car is fantastic.

^^^ you touch upon the point that I have been saying for YEARS now... if OHV engines are "better" then why is it that EVERY other car manufacturer has given up on the design besides Detroit?

I think some people can make the case for the fact that OHV engines tend to have more torque (ofcourse that might be because they tend to be larger, and ofcourse a larger engine will usually have more torque) so it is a good engine for a truck. But if that was the case, then why do the full-size Japanese pickups use OHC designs? They are clean-sheet designs, so if an OHV engine was better, I would totaly have expected them to go that route.

And honestly, I don't really consider this argument to be about the Vette - the engine in that car is fantastic.
Exactly! Although I should point out that an OHC engine is also OHV (over head valve). There are/were some engines that did not use over head valves, and use a prechamber instead. However, many people do commonly refer to pushrod motors as OHV.

I don't quite understand what you mean by this not being about the Vette engine though, as this motor (as you refered to it) is an OHV.

I don't quite understand what you mean by this not being about the Vette engine though, as this motor (as you refered to it) is an OHV.

I just mean that the engine in teh Vette is admittedly a great engine, no matter what the technology inside of it is... I have a MUCH bigger issue with the other pushrod designs out there that might make decent hp and decent mileage, but are exactly that... decent, and nothing more. For the largest automaker in the world to keep it's title as #1, it can't jsut make "decent" anything.

I am pretty sure one of the Accord engines has DoD also. Maybe it's the same one you are thinking of, but I thought it was a DOHC.

You're right - the Accord Hybrid has DoD, but it is also a SOHC, I believe.

The GM trucks, in general, have more power and better fuel efficiency than similar Tundras and Nissans. At least they did a couple of years ago when I was shopping for trucks (ended up with an Avalanche).

If there is one thing the domestics are good at, it's V8s.

You're right - the Accord Hybrid has DoD, but it is also a SOHC, I believe.

Yup, your right, it is a SOHC design:
http://www.caranddriver.com/article.asp?section_id=3&article_id=8779&page_number=4

The 2997cc V-6 has a system to deactivate all the valves on the rear bank. It's programmed to shrink back to three-cylinder operation below 3500 rpm when cruising or coasting, and the others don't come alive even for mild acceleration. Instead, the electric motor readily and seamlessly kicks in to help. Only at higher revs, or if the battery is down, or if significant acceleration is ordered, will all six cylinders join in. One staffer thought he could feel some rough running on three, but most of us could not. This feature is highly successful, effectively cutting consumption in half when the green glows.

60 mph: 6.7
EPA city driving: 30 mpg
EPA highway driving: 37 mpg
C/D-observed: 26 mpg

I think there are a few reasons why GM has stuck with pushrods, vs. going all out with 4-valve-per cylinder, OHC designs, and most of it is cost. It's just cheaper for them to keep using the same old designs that they've had for years and years and years. And cost is what drives that company more than pretty much anything else.

Even their "newest" engines, like the 3500 V6, is nothing more than an old, wheezy 3400 punched out a little more. Same with the "new" 3.9L in the Malibu SS.

As for fuel economy, I can tell you this much from daily observation running all kinds of different cars on a dynamometer: the only reason GM engines manage even "decent" MPG numbers is through the gearing in their transmissions. At speed, they will be turning much lower RPM than competing Japanese engines of similar size and/or power. And yet the Japanese still usually manage better or equal fuel economy and power/performance. Does that mean that the pushrod design and its ability to "idle down the freeway" is therefore more efficient? Doesn't look like it.

Somewhere (I don't remember where, but probably Car & Driver) I read that one of the reasons that the Japanese (and Europeans) use smaller displacement engines that spin faster, is that smaller engines (or maybe it was engines in general; I forget at the moment) are actually more efficient while under load. Try that with an old pushrod design and you will just be wasting fuel, since revving them up usually gets you nowhere.

Don't get me wrong, I'm not a GM-hater per se, nor do I think that the pushrod design is inherently flawed; it has its uses. I'm sure the Corvette motor is marvellous. I like the Supercharged 3800-series; fantastically fat torque curve. It's just that if the "old-school" pushrod engine design was so great, then why isn't GM selling more cars? Why are they falling from their position as #1-selling automaker?

I know there's more to it than engine tech, but it's an indicator. I think it all comes down to cost. They cheap out on engines, interiors, R&D (why make something new, when the same-old-same-old will do), and spend on marketing and funding rebates. Makes no sense to me.

As an aside, can't really complain about their transmissions; you can tell where the budget for the greasy bits went.

Um... ZR1? Your point being? Although I suppose you didn't see my posts in the other thread, and I hate posting the same thing over and over. The Northstar engine was designed before GM's latest financial woes. Hence money for the new line wasn't as big an issue. Also, it is entirely possible the Northstar motor is being produced on the old ZR1's (I think it was the LT5) line. This line would be lower volume and incapable of producing both Corvette and Northstar engines (just speculating here).

Why do you come in so matter of factly when you don't even know the facts?


Sorry, but it has been mentioned and I disagree with you. The LT7 with the exact same bottom end, and a properly designed OHC WOULD get better mileage. I really don't think this is even debateable. OHC engines don't have to turn any faster than pushrod ones, it's all in the tuning with the cams. However, pushrod engines CAN'T turn as fast as OHC engines can (a big disadvantage). Frictional losses in a piston engine are very low (contrary to popular belief). All the studies I've ever seen in my career put these losses at less than 2% overall. The "big fat chain" in an OHC cam engine travels the same direction all the time. It's the CHANGE in direction the riders, pushrods, lifters etc. have to make which is one of the reasons the pushrod system is less efficient. Plus the pusrod still has a chain (just not as big).


I'll agree with you when you show me a DOHC V8 car that has a better HP/MPG ratio.

I think there are a few reasons why GM has stuck with pushrods, vs. going all out with 4-valve-per cylinder, OHC designs, and most of it is cost. It's just cheaper for them to keep using the same old designs that they've had for years and years and years. And cost is what drives that company more than pretty much anything else.

Even their "newest" engines, like the 3500 V6, is nothing more than an old, wheezy 3400 punched out a little more. Same with the "new" 3.9L in the Malibu SS.

Absolutely - they have decided that this design can be made cost effectively for them - don't forget how much commonality there is between the small block in the trucks and in the GTO and in the SSR, Corvette, etc. They are getting big-time economies of scale out of this. They have built some nice engines (the DOHC engines in the newer Cadillacs - the "high feature" V-6, or the 4.2 I-6 in the Trailblazers) - don't ask me why they don't apply them more broadly. That could consume a whole new thread.


As for fuel economy, I can tell you this much from daily observation running all kinds of different cars on a dynamometer: the only reason GM engines manage even "decent" MPG numbers is through the gearing in their transmissions. At speed, they will be turning much lower RPM than competing Japanese engines of similar size and/or power. And yet the Japanese still usually manage better or equal fuel economy and power/performance. Does that mean that the pushrod design and its ability to "idle down the freeway" is therefore more efficient? Doesn't look like it.

Somewhere (I don't remember where, but probably Car & Driver) I read that one of the reasons that the Japanese (and Europeans) use smaller displacement engines that spin faster, is that smaller engines (or maybe it was engines in general; I forget at the moment) are actually more efficient while under load. Try that with an old pushrod design and you will just be wasting fuel, since revving them up usually gets you nowhere.


I snipped the bits about why they are getting hammered domestically - I agree with you. The parts above, I think, are oversimplifying. A big reason the Japanese and Euros started out chasing a "more-from-less" approach has to do with taxation and its structure in those countries. Engines are typically taxed on displacement - so you have a market force to drive you toward more power from smaller engines through turbocharging, revs, breathing, whatever. There is no such carrot in the US - so if the customer wants 300hp, the only requirement is to get there in the cheapest fashion possible - and cheapest includes warranty costs, part stocking, etc - so a nice, common, V-8 engine with no bells and whistles is a good (dare I say - best?) way to get there. The Corvette then gives them budget to hot-rod and exotic up that engine.

Oh - yeah, the other point about the smaller engines and efficiency - typically the smaller displacement engine will have lower pumping losses at part throttle, but due to the smaller displacement will require being worked harder. This is why GM gears the V-8s the way they do as well - you want to get that engine as close to wide-open throttle (unthrottled) as possible, to get your efficiency up. One way to do this is engine downsizing (the Japanese method) the other is to gear the engine super tall so that you can run it near WOT (the American method).

Why do you come in so matter of factly when you don't even know the facts?
Because it's what makes the most sense. Give me an alternate possibility, and I'll listen to it.

I'll agree with you when you show me a DOHC V8 car that has a better HP/MPG ratio.

Ahem. Your wish is my command! (I can't believe none of us have looked for this sooner. ENTER... the 1990 Corvette (quite applicable don't you think). BOTH versions are 5.7L V8s, a similar weight, same body style, and are manual transmissions. However, one of them is wider and uses larger tires (read less aerodynamic and more rolling resistance). I'll let you guess which one.

Corvette 2dr Coupe, Base model (MT):
5.7L V8 (pushrods)
245hp@4000rpm, 345ft-lbs@3200rpm
16mpg/25mpg, city/hwy

Corvette 2dr Coupe, ZR1 (MT):
5.7L V8 (aluminum, DOHC)
380hp@6200rpm, 370ft-lbs@4500rpm
17mpg/26mpg, city/hwy

So there you have it. 55% more hp, 7% more torque, and better fuel mileage. The HP/MPG ratios would be 9.8 and 14.61 respectively, based on hwy mileage. However I would argue that this ratio is useless, even though it proves my point. I would also point out the base moter might not have been in the same state of tune. Regardless, it's what you asked for. Information came from edmunds.

Do you agree with me yet?

BTW, I hadn't realized the LT5 was the same displacement as the pushrod version. It looksas though GM may have been doing a little experiment of thier own at the time.

I think one of the factors (not the reason but one possible reason) is that of Marketing. There are very few performance car makers that are out to make inexpensive products and so most go for the expensive high tech route.
I also think most manufacturers are in a similar position as GM in terms of existing in house know how and existing investments in certain technologies. A company like BMW or Honda has a background producing small engines with overhead cams. Now what happens when they need a 500 hp 5.0L + engine in an expensive performance car? Do they go for a clean sheet design or do they stick with what they have a lot of experience with and is appropriate for what people perceive the company to represent (ie one with high tech products).
I think that's why you see some companies doing a physically large big displacement dohc performance engine when a physically smaller larger displacement pushrod engine could do the trick. It is in their background and it is approved by the Marketing Dept.

hp/L is so irrelevent. So what? If the larger displacement engine doesn't give up weight, package size, or fuel economy, who cares if it takes more displacement? It's completely irrelevent to any worthwhile end goal.

I don't understand why anyone gives the *slightest* crap about HP/L. It means nothing.

Only in the markets where you get penalized (taxed) on displacement.

As some fodder for this discussion - an old link that compares the DOHC ford vs. the old pushrod 302.

http://www.vorshlag.com/pictures/motor-4.6-4V-004.jpg

Because it's what makes the most sense. Give me an alternate possibility, and I'll listen to it.

In the case of the corvette, Dave Hill (Chief Engineer) originally wanted to put the northstar in it, but couldn't fit it under the low hoodline. After the powertrain guys said they could do equal or better with the pushrod engine, they agreed to keep that engine. You can read about it in "All Corvettes are Red", a very interesting book in it's own right that really showed how disfunctional GM was (and is).


Ahem. Your wish is my command! (I can't believe none of us have looked for this sooner. ENTER... the 1990 Corvette (quite applicable don't you think). BOTH versions are 5.7L V8s, a similar weight, same body style, and are manual transmissions. However, one of them is wider and uses larger tires (read less aerodynamic and more rolling resistance). I'll let you guess which one.

Corvette 2dr Coupe, Base model (MT):
5.7L V8 (pushrods)
245hp@4000rpm, 345ft-lbs@3200rpm
16mpg/25mpg, city/hwy

Corvette 2dr Coupe, ZR1 (MT):
5.7L V8 (aluminum, DOHC)
380hp@6200rpm, 370ft-lbs@4500rpm
17mpg/26mpg, city/hwy

So there you have it. 55% more hp, 7% more torque, and better fuel mileage. The HP/MPG ratios would be 9.8 and 14.61 respectively, based on hwy mileage. However I would argue that this ratio is useless, even though it proves my point. I would also point out the base moter might not have been in the same state of tune. Regardless, it's what you asked for. Information came from edmunds.

Do you agree with me yet?

BTW, I hadn't realized the LT5 was the same displacement as the pushrod version. It looksas though GM may have been doing a little experiment of thier own at the time.

No, because you've only shown me a DOHC V8 that gets the same mileage as the current Z06 engine, but with 100 fewer horsepower and 100 fewer foot lbs of torque. Moreover, the ZR1 was also only marginally quicker than the 97 base corvette, despite costing nearly twice as much.

Incidentally, you'll be interested to know that the ZR1 motor was required to have the same bore spacing that the pushrod engine did, for really no apparent reason other than the management wanted it that way. Ultimately, this ended up reducing the performance of the engine.

But in the end, it doesn't matter. GM could release an 8 liter pushrod V8 with 700 HP, 700ft lbs of torque that got 40MPG on the highway and people would still say "Jeez, how lame are they for using pushrods."

But in the end, it doesn't matter. GM could release an 8 liter pushrod V8 with 700 HP, 700ft lbs of torque that got 40MPG on the highway and people would still say "Jeez, how lame are they for using pushrods."

Forget about the imaginary 700hp 7L engine, and how about making competitive family sedans... you know, the ones that actually bring in profits?!? :lol: :lol:

Your probably right. Sad to say, but I think thats a true statement. Although the 40 mpg would be impressive. Would be some crazy gearing.

All I am saying its 2006, GM just needs to get with the 90's. GM can keep putting pushrods in the vette, just dont tout the corvette as the flagship of American Performance when the best we can do is bigger is better.

In the case of the corvette, Dave Hill (Chief Engineer) originally wanted to put the northstar in it, but couldn't fit it under the low hoodline. After the powertrain guys said they could do equal or better with the pushrod engine, they agreed to keep that engine. You can read about it in "All Corvettes are Red", a very interesting book in it's own right that really showed how disfunctional GM was (and is).
One thing I've learned reading all these books over the years, is not to believe statements like this. I have a shelf full of books on Lotus, which all conflict with one another. I have a very hard time believeing that if the lines had the capacity to supply Nothstar engines for the Vette, that they would choose to design a whole new engine rather than redesign the hood. Especially given GM's financial situation. Plus, in the last thread on this subject I think someone debunked this claim.


No, because you've only shown me a DOHC V8 that gets the same mileage as the current Z06 engine, but with 100 fewer horsepower and 100 fewer foot lbs of torque. Moreover, the ZR1 was also only marginally quicker than the 97 base corvette, despite costing nearly twice as much.

Incidentally, you'll be interested to know that the ZR1 motor was required to have the same bore spacing that the pushrod engine did, for really no apparent reason other than the management wanted it that way. Ultimately, this ended up reducing the performance of the engine.
I gave you the proof you asked for, and now you've changed the rules. So what can I say. You're now saying I'm wrong because a 16 year old engine which is only 80% the displacement makes less power. Give me a break. With the same HP/L, a ZR1 motor of 7L would make 467hp (only 33 hp less from a 16 year old design). And OBVIOUSLY it would get better mileage because of gearing. Believe what you like. I've made my case regarding valvetrains, and the engineers at virtually all the other car companies on the planet, and what I was taught in school (engineering) agree with me.

If you want to convince ME otherwise, please provide an example of two engines (any number of cylinders, or displacement) which support your case. All I ask is that they both be the SAME vintage, displacement, configuration, # of cylinders etc., like the Corvette example I gave above (or the Lotus Elan and old school Mini in a previous thread).

With the same HP/L, a ZR1 motor of 7L would make 467hp (only 33 hp less from a 16 year old design). And OBVIOUSLY it would get better mileage because of gearing. Believe what you like. I've made my case regarding valvetrains, and the engineers at virtually all the other car companies on the planet, and what I was taught in school (engineering) agree with me.

So, OBVIOUSLY, why don't the other competitive 500HP (let alone 400HP or 300HP) OHC V8 cars get way better mileage than the Z06 - the only >400HP car to avoid the gas guzzler tax? Don't thow "gearing" out there like GM is the only company that gears their cars for optimal fuel economy.

Uh Oh. Better pull those engineering books back out.

http://www.emoticore.com/smilies/sign0023.gif

regardless of what's under the hood... the Corvette is one kick@ss performance value and an awesome car that does what it was designed to do very well.

You make a good point, why dont other car companies gear the snot out of their cars like GM does. When I go through the short list of must have vehicles with >= 400 HP, I cant think of one of them that gear the hell out of their cars. Lets think about that. There has to be a reason!

Well all the cars in europe usually have displacement taxes upon them, so making smaller engines is just about mandatory (VERY few 6-7 liter monsters across the pond). Smaller engines usually dont produce the torque that large engines can, and killer overdrive ratios are just not possible. So that rules out Europe, Japan, and the UK. They had to learn to produce higher efficiency engines that are smaller. Hmmm suppose that means that we have to look in our own back yard.

Lets see.

We have no such displacement tax here, so we can fall back on what we like, bigger = better :rolleyes: . The high HP cars we have are the HEMI monsters...but they have to tote around an additional 1200 lbs, and that just kills mileage. Plus Dodge has never had better mileage than GM. I mean the SRT8 Dodge Ram is a poster child for waste.

So the vette is a bit of an enigma. A very good package. But the engine can only be called efficient in this particular package . I would bring to this argument that if the 400 HP vette engine is so efficient, then why does it get only 16/21 in the GTO (vs 18/28 in the vette)? Same engine. The difference is two fold. Weight and Gearing.

I cannot think of another car off the top of my head that weighs only ~3100 lbs and has 400 HP. So I resubmit, the vette engine is not that efficient, the Corvette package is. Again bravo to GM to use very simple guidelines that have been true since cars had been around. Light weight, big engine equals blazing performance (just ask a guy named Shelby). You dont need any gizmos if you can build a light car. Just ask the Elise guys. Weight kills. Less weight allows a car to be geared even higher.

GM deserves credit for the vette package. It was a well architected project. And I will argue with anybody who says different. It just could be better if a more efficient technology combined with the large displacement would be used. But then again, maybe then it would not be a vette....

:devil:
SCRAPPYDO

regardless of what's under the hood... the Corvette is one kick@ss performance value and an awesome car that does what it was designed to do very well.
I don't think there has been a single post in this thread to the contrary.

I don't think there has been a single post in this thread to the contrary.

The point is that this arguing has gotten far off topic.

You make a good point, why dont other car companies gear the snot out of their cars like GM does. When I go through the short list of must have vehicles with >= 400 HP, I cant think of one of them that gear the hell out of their cars. Lets think about that. There has to be a reason!

Viper? It's geared to hit 300+ mph, and does 2000rpm at 100mph in 6th.

I cannot think of another car off the top of my head that weighs only ~3100 lbs and has 400 HP.

There's quite a few exotic cars that weigh the same or less, and put out the same or more hp... McLaren F1 (2550/650), Porsche Carerra GT (3050, 605), Saleen S7 (2900/750), Enzo (3000/650), F430 (3200/498), Lamborghini Gallardo (3150/520), Koengigesgesggenesnes (2600/800)...

well I was thinking more mainstream... haha
Those cars are not built with gas mileage in mind...

The Corvette is not built with fuel economy in mind either. It is totally performance oriented. GM is targeting class leading speed and acceleration when choosing gears for the Vette. The gearing is a function of the pushrod's torque delivery. It wouldn't make sense to have shorter gears. The gas mileage is a nice benefit, but there is no way in hell the Vette engineers decided to sacrifice performance for gas mileage. I don't buy it.

THe vette is a mass produced car for the masses. You bet your house that it was built with fuel economy in mind. The first 5 gears are all out performance gears and the 6th is an overdrive. It would take about 10 minutes to think of that. You can have your cake in and eat it too. GM has been doing this for years. The last gen camaro firebird had a standard 4 speed performance manual, with 2 extra over drive gears, for mpg. NO secret what worked well there, worked for the vette.

the vette would be even faster with lower gearing, with traction control activated it would be a bullet. Dont confuse the power of being able to market 28 hwy miles per gallon in this day of 2.90/gallon fuel.

Yes, 6th being an overdrive gear for fuel economy makes sense. I know that and should have clarified. The rest of the gears are chosen to match the characteristics of the engine and to provide class leading acceleration. The important point to note is that none of the DOHC engines making similar power (that could fit in a small car) can have such tall gears.

Actually I checked, and the 2005 Z06 has two overdrives. Fifth gear being 0.80ish, and 6th being 0.50ish. No doubt the torque of the engine helps make these possible. In fact the last model Z06 was drag limited in 4th gear to its top speed. Meaning you could not max out 4th, and put it in 5th and accelerate. They were put there for mileage reasons, not performance. So the gears were chosen for performance and mileage. Good package if you ask me.

Keep in mind its not the pushrod nature that makes this kind of torque possible, its the 7 liters of displacement. If you make a DOHC engine from 7 liters of displacement it would rack up far more than 500/500, and leave its pushrod sibling way behind. I would rather have that an a couple of extra bulges in the hood anyday.

So the vette is a bit of an enigma. A very good package. But the engine can only be called efficient in this particular package . I would bring to this argument that if the 400 HP vette engine is so efficient, then why does it get only 16/21 in the GTO (vs 18/28 in the vette)? Same engine. The difference is two fold. Weight and Gearing.


SCRAPPYDO

Sorry, you're wrong. Corvette has a 3.42 rear end with a 0.5 6th. Viper has a 3.07 rear with a 0.5 6th. GTO has 3.46 rear with 0.5 6th. Corvette gets 18/28, GTO gets 17/25, and Viper gets 12/20. The Viper should get great numbers with a 3.07 rear end, but doesn't. On the other hand it is quite impressive they get the acceleration they do with such a low(numerically) rear end.

Look at the Ferrari F430. The acceleration numbers that it posts are due in large part to its gearing. The thing has a 4.30 rear end and a 3.29 first gear. A 4.30 rear is drag racing type stuff. So if we are going to dismiss the corvette's numbers through gearing, then we must also dismiss many exoctics performance as a result of gearing, and not actual performance of the car.

The GTO I looked at did not get 17/25. I used the EPA cited mileage on the GTO(auto) from the EPA website.

Wait, let me check Pontiacs website..

http://www.pontiac.com/gto/index.jsp

seems they are 16/21 too...interesting. Whats your source exaclty?

I fail to see where I am wrong. The viper is also a huge pushrod engine, in a heavier car. 12/20 does not seem hard to believe to me. Why would its acceleration be hard to believe. Its playing the same game as the vette. Huge engine, mega torque. The Z06 engine is just better than the vipers. Its no doubt a better designed engine to make more power form less displacement.

So I am wrong because a heavier car with a bigger engine gets worse mileage than lighter car with a smaller engine. Very strange.

I am really not understanding why people thing that GM has some sort of mystical power with the LS7. Its just a large V8 and nothing more. Its geared low and the car is light. There is no other magic to the car. Put the 400 HP version in the GTO and the car sufferes in efficiency due to its weight. No big mystery. The vette is not magic, its just a tried and true combination of light weight and big torque. It works.

I never said that the Ferrari did not use gearing to its advantage. Just as GM used it for both performance and efficiency, Ferrari exploits its high reving nature of its cars by using really high gears. Faster acceleration insues. Just Ferrari did not put a killer overdrive in it to get great mileage. Probably because they just dont care. But your right, they do get their performance through gearing. If you cant make 500 ft-lbs of torque at idle, you need to rev that puppy.

The GTO I looked at did not get 17/25. I used the EPA cited mileage on the GTO(auto) from the EPA website.

Wait, let me check Pontiacs website..

http://www.pontiac.com/gto/index.jsp

seems they are 16/21 too...interesting. Whats your source exaclty?

I fail to see where I am wrong. The viper is also a huge pushrod engine, in a heavier car. 12/20 does not seem hard to believe to me. Why would its acceleration be hard to believe. Its playing the same game as the vette. Huge engine, mega torque. The Z06 engine is just better than the vipers. Its no doubt a better designed engine to make more power form less displacement.




I was comparing the numbers on the GTO with a manual transmission. If you want to compare it to the auto, then you have to take into account that the final drive ratio of the auto corvette is much lower(numerically) than the manual, which is why the auto mpg numbers are close to the manuals. But when looking at the two manual transmission cars, which have the same transmissions and very similar rear end ratios, the mpg numbers are very similar. The LS1/2 is just as "efficeint" in the GTO as it is in the Corvette. As far as the Viper being heavier, I agree, but the difference is not as drastic as the difference between corvette and the GTO; and the Viper is geared even more for better MPG(3.07).

As far as the Viper goes, I thought the acceleration numbers were impressive because when compared to the corvette it is heavier, has same HP, a bit more TQ, and a crippling 3.07 rear end ratio yet still accelerates as fast.

You're saying that the Ferrari would get just as good numbers as the corvette if it was geared the same, or saying the same thing a different way, the corvette would perform even better if it was geared like the Ferrari.

Given the choice between a 7L OHV and a 4.3L DOHC, the bigger engine seems to be the better package in today's world, in performance/cost/efficiency/size. I am in no way saying that a 7L DOHC would not be the best, but that is not what we are talking about.

http://www.emoticore.com/smilies/sign0018.gif It's obvious you guys have stretched it enough. Though your debates are entertaining, they have completely geared away from this thread.

Let's get back to the LS9.