Americans losing their love for V8s

[MX793]

CUV?  Car Utility Vehicle??

Crossover SUV, the term applied to newer, more car-like, car-based SUVs like the Chevy Equinox, Toyota Highlander, Buick Enclave and Ford Edge.

[CALL_911]

That's because the name sucks, they need a gimicky name that can make the consumer think it's a new technology.  In a way, it is compared to OHC engines so they're not lying, and neither is efficiency. 

And they need lots of advertising dollar into it to make a big stink about it.. V8 with the fuel efficiency of a I4 and power of a V8.. Consumers will buy into it in no time.. you just need advertising dollars.

OHVroom!

[GoCougs]

Uh, and the MPG of a Suburban or AT-equipped GTO? Atrocious.

The Corvette is smaller than a Civic, weighs just 3,100 lbs, has 0.50:1 top gear, and a Cd under 0.30. Give the same treatment to an M3 or 911, and you'll get similar MPG (actually probably better, since those cars have MPG-friendly VVT technology).

There's no magic in pushrod technology - or any engine technology. It's really just about the numbers - all the numbers.

[Gotta-Qik-C7]

I don't think anyone is actually losing their love for it, they're just losing the desire to pay for the gas.

Bingo!

[Raza]

Uh, and the MPG of a Suburban or AT-equipped GTO? Atrocious.

The Corvette is smaller than a Civic, weighs just 3,100 lbs, has 0.50:1 top gear, and a Cd under 0.30. Give the same treatment to an M3 or 911, and you'll get similar MPG (actually probably better, since those cars have MPG-friendly VVT technology).

There's no magic in pushrod technology - or any engine technology. It's really just about the numbers - all the numbers.

The manual LS1 GTO (3700 pounds) made 29mpg.  That says to me that GM needs more than 4 forward gears in their automatic.

[GoCougs]

The manual LS1 GTO (3700 pounds) made 29mpg.  That says to me that GM needs more than 4 forward gears in their automatic.

Actually, with the new testing standard, the 2006 6sp GTO was rated at 15/23. Had it made it to the 2008 model year, it was probably pretty close to gas guzzler tax territory.

FWIW - the 2006 auto GTO was rated at 14/19, but that is largely due to the 4sp's 0.70 top gear ratio (as opposed to the 6sp's 0.50).

[Raza]

Actually, with the new testing standard, the 2006 6sp GTO was rated at 15/23. Had it made it to the 2008 model year, it was probably pretty close to gas guzzler tax territory.

FWIW - the 2006 auto GTO was rated at 14/19, but that is largely due to the 4sp's 0.70 top gear ratio (as opposed to the 6sp's 0.50).

That's why I specified LS1.  The GTO you're talking about is the LS2.  I never said anything about the LS2.

[MX793]

Actually, with the new testing standard, the 2006 6sp GTO was rated at 15/23. Had it made it to the 2008 model year, it was probably pretty close to gas guzzler tax territory.

Applicability of the gas guzzler tax is unrelated to the "window sticker" fuel economy numbers.  It is based on the unadjusted EPA numbers (upon which the window sticker numbers are also based).

[S204STi]

GoCougs: So, CougDude, I assume the figures from the articles mean that those who never should have been allowed to purchase V8-engined vehicles are now being ferreted out and punished appropriately, right?  Good.  The world is a far, far better place...

NETDUDEI don't think that was his point at all, just that V6 engines are far superior to previous generations, and in fact outperform V8s of previous decades going all the way back to the musclecar era.  I know that it hurts your pride however to realize that a V6 can make as much or more power as your precious 'Stang.

[omicron]

Dear V8s,

I still love you.

Love, Omi.

[GoCougs]

My point was that LS1 or LS2, EPA or non-EPA, put a pushrod engine in a big, heavy vehicle and it will get poor mileage. Put the same engine in a compact, light vehicle, and it will get better mileage.

The same holds for any engine - there just aren't that many examples essentially same engine being used across such drastically different platforms (i.e., 6,000 lb Escalade and 3,100 Corvette).

[S204STi]

My point was that LS1 or LS2, EPA or non-EPA, put a pushrod engine in a big, heavy vehicle and it will get poor mileage. Put the same engine in a compact, light vehicle, and it will get better mileage.

The same holds for any engine - there just aren't that many examples essentially same engine being used across such drastically different platforms (i.e., 6,000 lb Escalade and 3,100 Corvette).

I guess the closest that I could think of would be a 6.0 V8 in the Suburban vs the 6.0 V8 in the Vette.  Different engines, but similar principle.

[MX793]

I guess the closest that I could think of would be a 6.0 V8 in the Suburban vs the 6.0 V8 in the Vette.  Different engines, but similar principle.

3.5L Pushrod V6 in the Saturn Vue vs the same motor in the lighter G6.

On a related note to those who think that OHV motors are inherently more fuel efficient, the 3.6L DOHC motor in the VUE returns the same mileage (per the EPA's tests) as the 3.5L pushrod while making 35 more horsepower and 29 more lb-ft of torque (both occuring at lower RPMs in the OHC motor to boot).

[Raza]

My point was that LS1 or LS2, EPA or non-EPA, put a pushrod engine in a big, heavy vehicle and it will get poor mileage. Put the same engine in a compact, light vehicle, and it will get better mileage.

The same holds for any engine - there just aren't that many examples essentially same engine being used across such drastically different platforms (i.e., 6,000 lb Escalade and 3,100 Corvette).

29mpg is poor?

[Soup DeVille]

29mpg is poor?

Corvette is not a big, heavy vehicle.

[Raza]

Corvette is not a big, heavy vehicle.

But the GTO is.

[GoCougs]

29mpg is poor?

But with the new ratings, the 6sp LS1 is 16/26 but the AT is 15/20.

[Raza]

But with the new ratings, the 6sp LS1 is 16/26 but the AT is 15/20.

The old standards were fine.

[Nethead]

NETDUDEI don't think that was his point at all, just that V6 engines are far superior to previous generations, and in fact outperform V8s of previous decades going all the way back to the musclecar era.  I know that it hurts your pride however to realize that a V6 can make as much or more power as your precious 'Stang.

R-inge:  RingDude, you take the bait waaaaayyyy too easily!   The Nethead here is glad the Mustang will get the new 3.5 V6--be it named Twin-Force, EcoBoost, or Whatever-The-Fuck! 

But the plain, unadorned truth is that the same level of technology/engineering/development applied to a V8 of the same displacement as a V6 will be a smoother, more powerful engine than the V6.

Why is it smoother?  Engineers claim there is an inherent imbalance in V6 configurations--even those whose cylinder banks are sixty-degrees apart instead of ninety degrees apart (which is claimed to be the most suitable angle of separation for the cylinder banks of V8s). That's why some V6s use various counterbalancing gimmicks that V8s never need.
 
But more powerful?  Yes, the V8s are.  Why?  This is the best illustration I've heard, and I'll share it here:

In a boxing match between two very fit boxers, but one of the boxers is bigger than the other, the bigger boxer will win simply because he hits harder.  BUT, if both boxers are the same size, then the boxer that hits more often will win.  Translated, if two engines of the same number of cylinders share the same level of technology/engineering/development/sophistication/whatever, then the bigger displacement engine is more powerful.  But if the two engines of the same level of technology/.../sophistication are of the SAME displacement, then the one with the most cylinders produces more power because it has eight power cycles in the time that a six cylinder engine has only six power cycles at any given RPM. There are lots of variables, but we stipulated that we keep all of them the same wherever possible (camshaft lift/duration, compression ratio, ignition advance, yada yada yada...).

Basically, the manufacturers will hustle V6s because they burn fuel in their power cycles only six times in the same amount of time in which a V8 would burn fuel in their power cycles eight times.

But you get less power than you would by applying the same technology/.../sophistication to a V8.  This applies to V10s over V8s, of course, and the jury is still out over whether this applies to V12s over V10s--there is an internal drag issue that some say becomes significant with more than ten cylinders, others say the internal drag issue is still not significant until more than twelve cylinders.  Having never owned a V10 nor a V12, the Nethead here does not know that magic number of cylinders beyond which power is lessened below that produced by a same displacement engine with fewer cylinders. Some  mechanical engineer somewhere probably wrote a graduate thesis on this subject with measurements, charts, graphs, and multicolor diagrams if you google long and hard...

[SVT666]

My point was that LS1 or LS2, EPA or non-EPA, put a pushrod engine in a big, heavy vehicle and it will get poor mileage. Put the same engine in a compact, light vehicle, and it will get better mileage.

The same holds for any engine - there just aren't that many examples essentially same engine being used across such drastically different platforms (i.e., 6,000 lb Escalade and 3,100 Corvette).

Ford's 4.6L V8 is used in everything from a F-150, to the Explorer, to the Mustang, to the Town Car, and in numerous little lightweight cars by independent manufacturers.  The Nissan 3.5L V6 is used in the X-Terra and the Altima.  There are numerous examples of engines being used in a big heavy vehicle and also a lighter and smaller car.

[r0tor]

Uh, and the MPG of a Suburban or AT-equipped GTO? Atrocious.

The Corvette is smaller than a Civic, weighs just 3,100 lbs, has 0.50:1 top gear, and a Cd under 0.30. Give the same treatment to an M3 or 911, and you'll get similar MPG (actually probably better, since those cars have MPG-friendly VVT technology).

There's no magic in pushrod technology - or any engine technology. It's really just about the numbers - all the numbers.

very true... on our trip to the outer banks our trailblazer SS with the LS2 made 14mpg highway

[GoCougs]

Ford's 4.6L V8 is used in everything from a F-150, to the Explorer, to the Mustang, to the Town Car, and in numerous little lightweight cars by independent manufacturers.  The Nissan 3.5L V6 is used in the X-Terra and the Altima.  There are numerous examples of engines being used in a big heavy vehicle and also a lighter and smaller car.

But those examples don't even come close to the disparity between the Escalade and Corvette.

The closest is the Mustang GT/Explorer V8 as both use the 3-valve 4.6L. The Mustang is way bigger and quite a bit heavier than the Corvette, and the Explorer is smaller and lighter than the Escalade.

[MX793]

R-inge:  RingDude, you take the bait waaaaayyyy too easily!   The Nethead here is glad the Mustang will get the new 3.5 V6--be it named Twin-Force, EcoBoost, or Whatever-The-Fuck! 

But the plain, unadorned truth is that the same level of technology/engineering/development applied to a V8 of the same displacement as a V6 will be a smoother, more powerful engine than the V6.

Smoother, sure.  Power powerful?  Not necessarily.

Why is it smoother?  Engineers claim there is an inherent imbalance in V6 configurations--even those whose cylinder banks are sixty-degrees apart instead of ninety degrees apart (which is claimed to be the most suitable angle of separation for the cylinder banks of V8s). That's why some V6s use various counterbalancing gimmicks that V8s never need.

No engineer who knows anything about engines will tell you that a V6 is inherently balanced.  Inline 6s are balanced, V6s are not.  A V6 will require a counterbalance shaft to run smoothly.  The optimal cylinder bank angle for a V6 is either 60 or 90 degrees, although a 90 degree bank angle requires a certain crankshaft configuration.

As far as V8s go, only a 90 degree cross-plane has any inherent balance.  However, this comes at the price of an uneven firing order (the source of its lopey sound) and heavy crankshaft counterweights which sap responsiveness.  V8 engines used in racing (and in road-going Ferraris) are of the flat-plane type, which is not balanced even with a 90 degree bank angle (which is optimal from the standpoint of even firing).  They suffer from the same imbalance as the inline-4, a vibration that occurs at a frequency that is 2x the engine RPM due to an imbalance in momentum of the piston pairs in each cylinder bank.  Because vibrational smoothness takes a back seat to power (so long as the vibration isn't severe enough to break motor mounts), counterbalance shafts are typically left off on racing motors.
 

But more powerful?  Yes, the V8s are.  Why?  This is the best illustration I've heard, and I'll share it here:

In a boxing match between two very fit boxers, but one of the boxers is bigger than the other, the bigger boxer will win simply because he hits harder.  BUT, if both boxers are the same size, then the boxer that hits more often will win.  Translated, if two engines of the same number of cylinders share the same level of technology/engineering/development/sophistication/whatever, then the bigger displacement engine is more powerful.  But if the two engines of the same level of technology/.../sophistication are of the SAME displacement, then the one with the most cylinders produces more power because it has eight power cycles in the time that a six cylinder engine has only six power cycles at any given RPM. There are lots of variables, but we stipulated that we keep all of them the same wherever possible (camshaft lift/duration, compression ratio, ignition advance, yada yada yada...).

Basically, the manufacturers will hustle V6s because they burn fuel in their power cycles only six times in the same amount of time in which a V8 would burn fuel in their power cycles eight times.

But you get less power than you would by applying the same technology/.../sophistication to a V8.  This applies to V10s over V8s, of course, and the jury is still out over whether this applies to V12s over V10s--there is an internal drag issue that some say becomes significant with more than ten cylinders, others say the internal drag issue is still not significant until more than twelve cylinders.  Having never owned a V10 nor a V12, the Nethead here does not know that magic number of cylinders beyond which power is lessened below that produced by a same displacement engine with fewer cylinders. Some  mechanical engineer somewhere probably wrote a graduate thesis on this subject with measurements, charts, graphs, and multicolor diagrams if you google long and hard...

This is absolutely incorrect.  More power cycles per rotation does not equate more power, all else being equal.  Smoothness, yes, but not more power.  Why?  Because while the V6 has 3 bangs per rotation versus the same sized V8's 4, each bang in the V8 is weaker than that of the V6.  When it's added up, so long as the key parameters are indeed equivalent, the power will be the same. 

If two engines have the same displacement and are operating with the same volumetric efficiency and at the same RPM, they will be making the same amount of power.  Doesn't matter how many cylinders either has.  Power is strictly a function of the rate at which you can burn fuel, which is a function of how much air the engine can pump, which is a function of displacement and volumetric efficiency.

[Nethead]

MX793:  MXDude, the Nethead here agrees with your thorough and informative reply--proof yet again that the MXDude always engages his brain before he engages the keyboard!

Well, except for this:
"Because while the V6 has 3 bangs per rotation versus the same sized V8's 4, each bang in the V8 is weaker than that of the V6.  When it's added up, so long as the key parameters are indeed equivalent, the power will be the same."

As you are well aware, a V8 with the same total displacement as a V6 obviously has less displacement per cylinder--at a displacement of 240 cubic inches, for example, a V6 has six cylinders of forty cubic inches each whereas a V8 has eight cylinders of thirty cubic inches each.  Power output of the 240 CID V6 exceeds the power output of the 240 CID V8 only if each of the V6's six larger cylinders puts out more than 33.33 percent more power than each of the V8's eight smaller cylinders (in order to fully offset the V8's two additional power cycles per unit of time at a given RPM). 

At an identical level of development of each engine, the 33.33 percent larger individual cylinders of the V6 will not put out 33.33 percent more power per cylinder than the individual cylinders of the V8. Combustion is like that . To get 33.33 percent more power from a cylinder (or a collection of cylinders), you have to increase it's displacement by more than 33.33 percent.  There's probably a table and graphs somewhere illustrating this uneven ratio between power and displacement when the level of development of the engine does not change.  I suppose the reason--merely speculating here--is that the combustion of fuel in a cylinder produces a whopping amount of expansion, so much so that there is an excess of expansion whether a cylinder displaces volume X or volume 1.3333 X, and that excess of expansion would continue except that it has to be released as the piston approaches Bottom Dead Center or it would be fighting against the power cycles of other cylinders in the engine once the piston passes BDC. 'Seems to me that the excess expansion produces more pressure (which is what produces the power) in volume X than it would in the roomier volume 1.3333 X, so there's the root reason--even though there's an offset due to the need to maintain optimal fuel/air ratios to get the best combustion (the combustion that produces the greatest expansion, and thus the greatest pressure).

Even in these "keep-everything-the-same-as-much-as-possible" hypothetical engines, the V8 will have more moving parts and thus generate more internal friction, but things like piston rings will be necessarily smaller so they will not generate as much friction as the rings in the V6, so there is some offset here.  Computing these frictional variances would be tough to do accurately, but the point is moot since the additional friction of the V8's "extra" pieces is more than offset by the extra two power cycles per unit of time at the same RPM.  If power cycles didn't more than offset an engine's total internal friction, the crankshaft would never be turned at all!  A V12 displacing 240 cubic inches is a collection of twelve cylinders of twenty cubic inches each, and it will probably produce more power at an equal level of development as the 240 CID V6 as well as the 240 CID V8.  Same reason, different engine--but I say "probably produce more power" because of those theories that there is a diminishing return beyond a certain number of cylinders (see the earlier posting).

That concludes today's Combustion 101 Lecture and Conjecture, class.  The midterm will be next Friday, so I hope you took good notes.  Babes --I mean Ladies--see me in my office after class for several very interesting extra credit projects you are encouraged to participate in  

[sportyaccordy]

The only way I could see two equal sized motors w/different cylinder counts not making the same power (assuming the same manifold efficiencies, cam specs, redlines etc) is the higher losses coming from a higher cylinder count. With more valvetrain to open and close, and more friction from more surface area that comes with more cylinders it's plausible that more cylinders would make less power for a given displacement.

On the other end low cylinder counts = big vibrations in large displacements, especially for 4 and under. But there's really no reason to make a V8 over a V6 in the 3-4L displacement range.

[ChrisV]

Except that there have been some excellent V8s in that displacement range, from Ferrari's 2 to 3.6 liter variety, to the BMW 3 and 4 liter V8s and the Lexus 4 liter unit.

[dinkeldorf]

Cool thread, interesting info on the existential 6 vs 8 debate. Isn't the real issue here that traverse engine installs, front drive / AWD are the norm for costs sake and this points towards V6s?

I've owned I4s, Turbo I5s, V6s, I6s and vicariously flat 4s and V8s and to be honest for me the numbers are more important than the number of pots.

That article is a dumbed-down sound bite of the automotive market place trends with a nice alarmist headline.

And woeful grammar: "fuel prices now more expensive than ever". My six year old reads better than that.

[sportyaccordy]

Except that there have been some excellent V8s in that displacement range, from Ferrari's 2 to 3.6 liter variety, to the BMW 3 and 4 liter V8s and the Lexus 4 liter unit.

4L is on the extreme end for a V6. That's like a 2.7L L4.

And Ferarri's V8s are a special case... super duper big bores = better breathing; plus they're not very fuel efficient. I'm not saying great engines with those parameters aren't possible, but I think the best compromise between smoothness and efficiency in that displacement range comes in a V6

[MX793]

MX793:  MXDude, the Nethead here agrees with your thorough and informative reply--proof yet again that the MXDude always engages his brain before he engages the keyboard!

Well, except for this:
"Because while the V6 has 3 bangs per rotation versus the same sized V8's 4, each bang in the V8 is weaker than that of the V6.  When it's added up, so long as the key parameters are indeed equivalent, the power will be the same."

As you are well aware, a V8 with the same total displacement as a V6 obviously has less displacement per cylinder--at a displacement of 240 cubic inches, for example, a V6 has six cylinders of forty cubic inches each whereas a V8 has eight cylinders of thirty cubic inches each.  Power output of the 240 CID V6 exceeds the power output of the 240 CID V8 only if each of the V6's six larger cylinders puts out more than 33.33 percent more power than each of the V8's eight smaller cylinders (in order to fully offset the V8's two additional power cycles per unit of time at a given RPM). 

At an identical level of development of each engine, the 33.33 percent larger individual cylinders of the V6 will not put out 33.33 percent more power per cylinder than the individual cylinders of the V8. Combustion is like that . To get 33.33 percent more power from a cylinder (or a collection of cylinders), you have to increase it's displacement by more than 33.33 percent. 

If I have two cylinders with identical compression ratios and volumetric efficiencies operating at the same air/fuel mixture and the same burn efficiency (percent of unburned fuel), the larger will generate more mechanical work, and if cycling at the same rate, more power.  Always. 

The trick is getting all of those parameters equal.  For example, as pistons get bigger, particularly the bore, getting even and complete burn in the combustion chamber becomes more difficult, and this can eat into power output.  Not something I'd expect to play much of a part when comparing 6 pots to 8s of the same displacement, but a consideration if you're comparing a 5.0L twin or I4 to a V10 or 12.

There's probably a table and graphs somewhere illustrating this uneven ratio between power and displacement when the level of development of the engine does not change.  I suppose the reason--merely speculating here--is that the combustion of fuel in a cylinder produces a whopping amount of expansion, so much so that there is an excess of expansion whether a cylinder displaces volume X or volume 1.3333 X, and that excess of expansion would continue except that it has to be released as the piston approaches Bottom Dead Center or it would be fighting against the power cycles of other cylinders in the engine once the piston passes BDC. 'Seems to me that the excess expansion produces more pressure (which is what produces the power) in volume X than it would in the roomier volume 1.3333 X, so there's the root reason--even though there's an offset due to the need to maintain optimal fuel/air ratios to get the best combustion (the combustion that produces the greatest expansion, and thus the greatest pressure).

The pressures in two cylinders of different sizes burning the same air/fuel ratio will be the same when the piston reaches BDC.  You're burning 33% more fuel (or adding 33% more heat, which is all the fuel really serves to do) in the V6 cylinder, but you're expanding it over 33% more volume.  It ends up a wash at the end of the combustion stroke.

And both motors have to fight against any overpressure experienced at BDC (although with the exhaust valve opening at that time, I doubt there's much fighting). 

Even in these "keep-everything-the-same-as-much-as-possible" hypothetical engines, the V8 will have more moving parts and thus generate more internal friction, but things like piston rings will be necessarily smaller so they will not generate as much friction as the rings in the V6, so there is some offset here.

Friction is entirely independant of surface area.  Small piston rings generate as much friction as larger ones when the force pressing them into the cylinder wall is equal, assuming the rings and cylinder sleeves are of the same materials. 

Computing these frictional variances would be tough to do accurately, but the point is moot since the additional friction of the V8's "extra" pieces is more than offset by the extra two power cycles per unit of time at the same RPM.  If power cycles didn't more than offset an engine's total internal friction, the crankshaft would never be turned at all!  A V12 displacing 240 cubic inches is a collection of twelve cylinders of twenty cubic inches each, and it will probably produce more power at an equal level of development as the 240 CID V6 as well as the 240 CID V8.  Same reason, different engine--but I say "probably produce more power" because of those theories that there is a diminishing return beyond a certain number of cylinders (see the earlier posting).

That concludes today's Combustion 101 Lecture and Conjecture, class.  The midterm will be next Friday, so I hope you took good notes.  Babes --I mean Ladies--see me in my office after class for several very interesting extra credit projects you are encouraged to participate in  

Again, more frequent power cycles don't in any way generate more power unless they are accompanied by an increase in fuel and air moving through the engine.  It's no different than climbing a flight of stairs two at a time rather than step by step.  When you reach the top you've performed the same amount of work.  Provided you climb the steps at the same speed regardless of how you go up, by ones or by twos, the power used is the same as well despite your power pulses coming twice as frequently when you go one by one.

Is the extreme upper envelope of a V8 higher than a V6 of the same displacement?  Probably, (and I suspect very slightly) but not because the V8 has more power strokes per revolution.  It comes down to a number of other factors that go along with having smaller pistons.  The ability to reach higher RPMs would be the one that jumps out at me.  Smaller pistons are lighter, which reduces stresses in piston/con-rod assembly at any given RPM and allows higher revs.  Likewise, smaller and lighter valves as one would find in a smaller piston are less prone to valve float.

[omicron]

Except that there have been some excellent V8s in that displacement range, from Ferrari's 2 to 3.6 liter variety, to the BMW 3 and 4 liter V8s and the Lexus 4 liter unit.

Oh, and the ubiquitous Buick/Rover 3.5 V8! Similarly, the Jaguar AJ-V8 series of 3.2, 3.5, 4.0 and 4.2 litres were quite lovely engines from what I've heard, and the Holden 253 V8 was a sound engine in its day.

Of course, the United States is quite unique when it comes to the prevalence of V8 engines in mainstream cars of the past - not just in performance or luxury models, but also in Mother's family wagon in which she trundles off to Kresge's each week.