tasdisr

Interesting article on CNN money about buyers shifting away from V-8 engines in luxury cars. Hope the link works.

http://money.cnn.com/2008/01/29/auto...ion=2008013014

JAB00

There was a similar themed article in the NYTIME some weeks ago.

LukeaTron

I don't find that at all surprising. A twin turbo option for the RL would definitely open some peoples eyes to the car though. Hmmm, RL-S?

Storm982

twin turbo in the RL would be AMAZING!!! Better yet, supercharge that bad boy and watch it fly.

Mike_TX

You guys are a hoot. You somehow think a V-8 magically gets terrible mileage and a V-6 automatically gets good mileage ... and then talk about twin turbos. Geez. A turbocharged engine sucks fuel at a more rapid rate than a normally-aspirated one, and a supercharger is even worse. Period, the end.

And my current Lexus LS460 (with a 380 hp V-8 ... 5.4 sec. 0-60) gets virtually identical mileage to my old RL (290 hp V-6 ... 7.1 sec. 0-60). It's all about engine design and transmission/gearing.

And if you want V-8 power out of a V-6, you're probably going to get WORSE gas mileage than the V-8. Why? Because of physics. If you get "x" horsepower out of 6 cylinders, they're going to have to work harder (produce more energy per cylinder, which takes more fuel) than an 8-cylinder making the same horsepower. At best, you'll get the same mileage, but it's not likely.

I just get crazy every time someone repeats the silly misinformation that a killer high-hp V-6 is somehow going to get better mileage than a V-8. Keep on dreamin'

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LukeaTron

Whoa, whoa, whoa. I certainly wasn't saying, nor implying that a twin a turbo V6 would get better mileage than a V8. That part was just thrown in because of how sweet it'd be (come on, admit it).

Theoretically, a V6 producing the same power as a V8 could be more efficient. Why? Internal inertia and friction. The V8 has more moving parts and more metal surfaces moving against each other. Before you get all worked up, pay close attention to that word "theoretically". In modern practice they'd both be very similar in fuel economy.

The smaller physical dimensions and lower mass of a V6 does give the engineers more room to play though. In reality, how often do you need or want to put down more than the mid 200's of HP anyway? Yeah it's fun and nice little boost to the ego every now and then but it sure as hell isn't practical.

Chas2

a perfect real world example in the Acura family may be the turbocharged Acura RDX. Look at the real world gas mileage for that 4 cylinder engine on the RDX board

CL6

Start sticking turbos and superchargers in yer engines and your gas mileage will drop like a rock.

Mike_TX

Too late - I'm already worked up.

Nah, this seems to come up pretty regularly nowadays, and in many cases it's because a lot of the younger set haven't had much, if any, experience with V-8's. Many of them have grown up with 4-cylinders and 6-cylinders, and unfortunately operate on hearsay and bad information. That may not apply to you, but I was reacting to the general idea and not to any one person. So, I'm sorry if I offended you.

Your theory doesn't hold up, though - the additional inertia of the extra 2 cylinders is actually a benefit, and the frictional losses are overcome by the 8's additional volumetric efficiency and torque.

Detroit is delaying some planned V-8 deployment because of public perception and the need to cut expenses to try and meet the ridiculously low CAFE standards Congress laid on them. The most noteworthy was the replacement for the Northstar, and I guess I don't blame GM for not wanting to spend more money on that right now, when they are having to scramble around trying to invent new technology to meet the 35mpg fleet average.

I fully expect the CAFE standards to be relaxed or overturned completely before 2020, since the American public isn't going to want to return to the days of VW Beetles and little Civics that looked like overgrown rollerskates.

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Cocoa

iTrader: (2)

If I remember correctly, the 98' 3000gt VR4 was making 18mpg (city) and 24mpg (freeway) while making 320hp. And the 98' Cobra was stated to be doing 18 (city) and 26 (freeway), but with consumers stating it was less by about 2-4mpg (freeway), making it pretty much even with the VR4. But the catch is, that the VR4 weighed in at 3700lbs, while the stang weighed in far less.

Pretty sure the 98' stangs weigh in around 3200lbs. That's a huge difference in weight. Add those 500lbs to the stang, and let's see how gas effecient it is...

Cocoa

iTrader: (2)

My friend with his boosted em1 gets the same miles per tank as he did when it was stock. He's only putting down 230whp though (stock interior and all), but you get the point. I understand what you're trying to state. I just don't agree with it 100% because of certain variables that can easily change that.

visuelz

It pisses me off how people made fun of the RL, because it was a V6 and that it wasn't going to be able to compete. Right when Honda decides to make a bigger engine, the consumers change their mind. Damn to all those people!

LaZyPiGgY

I'm with Mike_TX, design of the engine ultimately affects its efficiency. Not sure if many people notice but a lot of the domestic car manufacturers are using a Multi-Displacement System to turn a V8 into using only 4 cylinders and achieving good gas mileage, comparable to the RL's except they have at least 350hp and 350 lb/ft on tap should they need it.

Mike_TX

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TampaRLX-SH

Don't forget to include vehicle weight, transmission gears & ratios, tires, fuel delivery system type, fuel type, etc, etc, etc.

Power and cylinder numbers mean squat unless it integrates well this the rest of the vehicle.

Unless of course you wish to commute soley upon your engine block.

LaZyPiGgY

+those things too!

Mike_TX

Well, not to argue (really), but my '08 LS460 weighs in about 4,250 lbs., whereas my '06 RL was about 4,000 IIRC. The LS has 90 hp more than the RL, and is a V-8. I got about 18/26 city/hwy with the RLl and I'm so far getting 18.5/27 city/hwy with the LS. It should improve with some miles ... my RL sure did.

Now, the LS has an 8-spd AT and no AWD. It also has a combination Direct-injection/Port-injection system, but no cylinder deactivation. These things give it an advantage over the RL in mileage, but the additional weight kinda offsets some of that advantage. So the LS isn't getting any free ride, and it's doing as well as the smaller V-6 in the RL.

As far as the Mustang is concerned, it's older tech, and not really trying to be economical.

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LukeaTron

Every example of those cars that shut off cylinders thus far have proven to be shite. They don't offer any significant advantage at the cost of an unduly complex system that is prone to trouble. Adjustable cams, particularly the timing have proven far simpler and more effective. Add in the direct injection and you've got a winning combo. The only advantage of the cylinder banking is that it's easy to explain and Joe Beercan laps it up even though it barely does anything for the actual mileage.

Mike, an V8, particularly a 45 degree V8 is about as optimally arranged as you can get a 4 cycle engine to be with possible exception of a radial engine which is ridiculously too cumbersome for automotive use. Any boxer engine with a cylinder count divisible by 4 gets the same benefit but with anymore than 4 cylinders they get cumbersome in size. This all down to the natural counterbalancing of engines of these configurations which will always be perfect.

I do have to disagree with your claim of volumetric efficiency though. A 1 cylinder engine is as volumetrically efficient as you can get. On a per unit area of cylinder wall basis (the main contributor of friction is the snugly fit rings sliding up and down the cylinder), the less cylinders for a given displacement will always win. Coming in at number two in the friction game is journal bearings. Again, less cylinders, less journals, less friction. Friction eats up a huge portion of the energy harvested from the moving pistons. I don't know for sure but I'd be surprised if there's anything that takes more of it away (inside the engine anyway, once you hit the transmission the inertia of the drive line takes over).

All of this is but academic posturing though because as far application goes, your observations hold very well. Torque sells a lot of cars and I don't think that's going to change any time soon since the mileage of the most efficient V6s and that of the most efficient V8s (with comparable power output) is barely different at all.

Cocoa

iTrader: (2)

I was jsut trying to chim in with the old tech. Who knows what they can really do now if they put the money into it...I guess we'll have to wait and see with the future hybrids...

CL6

Ok, if you add it yourself and want to tinker and make other mods, maybe... but generally not if you are a car maker.

iforyou

iTrader: (1)

LS460 is pretty much as efficient as the RL, but the reasons are quite obvious.

-New engine design, J35 is old
-Direct Injection
-dual VVT-i
-8spd
-RWD

The extra 70kg (~4%) that the LS carries becomes negligible. Direct injection alone, according to Mitsubishi, can reduce fuel consumption by 20-35%, while increasing output by 10%. Then factor in the 3 extra gear ratios and the lack of AWD, it's not surprising that the LS460 is that efficient.

Also, for the RL, Motortrend obtained 6.5s for 0-60mph, while C&D obtained 6.7s.

Ibn Rushd

Something is weird about the turbocharger vs naturally aspired thing here, although i know i'm a little late.

But if a turbocharger kicks in at say 4000RPM, (I believe the one i was looking into starts around 4500), in an RL that would rev to 6000, how many times will you actually drive it that high in the revs?

So theoretically, although a turbocharger would hurt gas mileage, it shouldn't change it much more than usual, unless you drive in those revs, right? Because otherwise the turbo isn't spooling. Obviously a supercharger would cause it to be a gas guzzler for sure, but shouldn't the turbo be more forgiving?

That's why i'm not understanding what's going on with the RDX...or is it just that it's a turbo in an SUV that's giving it problems? Or am i actually that wrong?

So i know driving it hard a turbocharger is just as bad, probably even worse, but in normal driving where you don't even touch those revs, wouldn't it keep a V6 fuel efficiency, more or less, thus becoming a bit better?

larrynimmo

turbos boost pressure through out the RPM range. It is more noticable and gives more kick in the higher RPMs.

Turbo power is there when you need it.

Mike_TX

Yep, the goal of most mfrs' turbocharged engines these days is to make the turbo kick in at the lowest possible rpm, for smooth engagement and overall driveability. One that waits until 4,000 rpm to spool up would be useful only for full-throttle bursts of power.

If you're going to get your power through turbocharging, you have to get that turbo spinning as soon as you can and stuffing air and gas into the cylinders.

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Mike_TX

We're getting too academic here, but IIRC, the smaller the combustion chamber volume, the easier it is to achieve stoiciometric efficiency. That is, it's harder to achieve and maintain an ideal gas/air mixture in a large volume than it is a smaller one.

Hence my assertion that an 8-cylinder engine tends to have better volumetric efficiency than a 6, given the same displacement, because it's divided up into smaller samples.

Even if I'm wrong, thanks for the intelligent discussion!

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CL6

If you compare a TSX and an RDX you get 20 vs. 17 City and 28 vs. 22 highway. I know the 'SH' AWD eats up maybe 1 or 2 mpg but that turbo still chomps the gas.

The RL is a teeny tiny bit more efficient than the E350 4MATIC.

http://www.fueleconomy.gov/feg/sbs.htm

LukeaTron

No, you're correct there. Enter direct injection. Have you seen the pistons on a direct injection engine? They have crazy geometry on the top that that's designed to mix the air and fuel as completely as possible. In low RPM, low throttle situations the engine switches modes to where it contains all the combustion in an air pocket in the center of the chamber. It switches to low lift, staggered opening mode that combined with the piston design causes the air to roll in the center of the combustion chamber at high velocity.

At the last fraction of second the fuel is injected into this rolling air bubble and ignited. The result is the air fuel mixture being surrounded by walls of air with no (or significantly less) fuel mixed in. The mixture in the middle is as close to stoichiometric as possible so it burns at peak efficiency. The flame front is insulated from the cylinder walls by the air around it causing less energy to be absorbed as heat by the block.

It's very cool and works really well. The technology is mostly borrowed from the diesel world, though the idea of insulating the combustion with air is a new innovation. The ability to tightly control the valve overlap is key to making it work since that's a large part of what gets the air rolling.

I love thinking about and discussing this stuff so I'm down for more whenever you want. A few years ago I came up with a completely new design for a rotary engine that I thought would be really efficient (due to the lack of any reciprocating parts) until I started doing a lot of complicated math and determined the large interface areas required would be an insurmountable hurdle. I was initially going to patent it but after those calculations it didn't seem to be worth it. The design might still work as simple but effective high positive pressure pump though.

LukeaTron

The death blow to the RDX vs the TSX in highway mileage is the much larger sectional area of the RDX. It just has to shove more air out of its way and above 60 mph or so, drag takes over as the biggest consumer of energy. The faster you go, the more predominate it becomes in a huge hurry (wind resistance rises logarithmically with speed as you approach mach 1 where it becomes absurdly more complex).

TL_Captain

http://money.cnn.com/2008/01/29/auto...ion=2008013014

"New, more sophisticated V6s offer nearly the same performance with better fuel economy.
" quote from the above link.

Not sure if that statement applies to domestic junks. Some domestic V8 engines probably generate less HP than Japanese I4s and drink gas faster than MB V12.

CL6

Any Benz besides a V6 gets hit with a Gas Guzzler tax.

cs9530

OK...I have to weigh in...usually just read these forums.

I just traded my 2002 MB E430 V8 for a 2006 RL. Loved the MB but switched jobs last fall and am in the car for 3-4 hours a day at an average speed of 15 - 18 mph as confirmed by the computers in both cars.

I bought the RL for NAV, XM, mp3 and driver's seat comfort... figured fuel economy would be an added bonus. I'm shocked that the RL is giving me 16, while the MB did 18 consistantly. No idea what the EPA rating is on either car - mileage wasn't the driver for this purchase, but I'm really surprised.

As far as the driving difference, there's no comparison. The V8 far exceeds the V6 for consistant smooth power at all speeds. If you look at the same model MB in a 6 vs 8, mpg is generally not appreciably different (within 2 mpg as I recall) but drivability is dramatically better. I'll take the 8 any day and would LOVE to see Honda take that direction with the RL.

The bozos at CNN and the NYT need to let go of their trees long enough to see the light. They sound silly making such ridiculous generalizations.

B+O

Sorry for bumping this. But i had to weigh in as well.

First up is the issue about V8s declining in popularity. Their popularity has never really been key. They've never been the big sellers. Studies have shown that 85% of the Midsize car sales are six cylinder models. That means 19 out of 20 BMW 5 series will be 530s or 535s. That means that 19 out of 20 Mercedes E classes will be E320s or E350s. People seem to fail to understand this bit of trivia and it's always shocking to find out that NO a V8 car DOESN'T sell well.

But going to the whole V6 versus V8 thing. This all falls under engine load and BSFC (Brake Specific Fuel Consumption.) Without going into specifics, the harder an engine has to work the less fuel efficient it will be. The reason the V8s are seemingly less thirsty is aside effect of being shoved in a smaller car. This is not the best solution because you then have to account for extra cooling needs, reworked chassis designs and suspension upgrades.

Put them back into the cars they were ment to be in and watch their mileage fall well below the RL's mileage with comparable torque to weight ratios.

An example of this would be look at any large SUV's city MPG.

Here's the problem...I love the Flagship Acura in a big way, and i want it to stay V6, but in order to get the most out of the engine, it WILL need something in the way of forced induction...

Someone said earlier forced induction will immediately lose fuel efficiency. That's about as blinded as thinking a V6 is more fuel efficient than a V8.

With the dual stage VNT turbochargers that Honda has been known for using, even in the early Honda Legend Wing Turbo 2.0Ti, They've managed to achieve comparable fuel economy with far more power. With tuning like only Honda and Acura can do, the BSFC can be manipulated, the power brought in and fuel consumption brought down.

Excellent highway mileage is easy to achieve with VNT. When you are "off the boil" so to speak, the engine can be quite efficient. I've noticed LARGE differences in the turbocharged vehicle I drive in and out of boost. staying out of the boost on the highways will net around 26-28mpg at between 65 and 75mph. on the boost at speed around 60-80 almost always drop that down to 20-21.

I've never been, and never will be a fan of V8s in small cars. And I will never be a fan of RWD. especially when SHAWD is leagues better than both FWD and RWD.

B+O

and speaking about the fuel efficiency...

saying 2-4 mpg is a negligible amount. Think about it like this. say your car has a 20 gallon tank. (typical of the cars in this field).

Say you fill up on E at 18 gallons. You went, we'll say, 320 miles on that tank. Premium nowadays is something like 3.15 or thereabouts.

this fill up was $57.00 'cause you topped off.

Now you just pulled about 18 mpg combined, mostly city driving. An average number for most people.


Now You bought a V8. Happy it's jettisoning you everywhere much faster. You paid ten grand more for it over the V6 model but you've got the pride of ownership.

Say you're now getting about about 285 miles to the tank filling up on E, 18 gallons at 3.15 for premium.

You lost 2mpg not a big deal, but overall you lost 35miles to the tank. The average driver consumes a tank of gas every week or every 7 to ten days. Given the number seven because you may have a long commute. You've lost 140miles worth of gas. over the course of the year you've lost 1680 miles. At 16mpg you've lost 300+ dollars just in fuel. Not mention the price of ownership which in most cases is at the very minimum 100 dollars a month, insurance rates, and more expensive maintenance like more oil required, more parts for basic tuneups, different filters, etc.

It's a significant difference that can add up.

B+O

Can't edit my post... typing too fast without thinking...

Meant 17 out of every 20 E-classes and 5 Series.

Mike_TX

Well, you're close. According to BMW's numbers, about 20% of 5-series sold in the U.S. are V-8's. I didn't bother to check M-B's numbers, but they're probably not far off that.

What you have to consider, though, are a lot of complex things - one is that BMW's 6's are very lively engines, and many people would take a 530 or 535 over a V-8 for that reason. Then there's cost considerations ... many folks want the BMW experience, but frankly can't make themselves fork over $50-60k for a 545. Then there's production quotas, which make the V-8 cars a little harder to even get. And so on.

But more than anything, "mid-size cars" as a category includes American and Japanese-made cars, most of which aren't even offered with a V-8. That sort of skews the numbers, and makes your generalization too broad.

If you could remove all the barriers of cost and availability, etc., I wonder how many people would choose a V-8 over a 6 ... IOW, just turn 'em loose in the candy store and watch 'em go for the 8's.

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Mike_TX

Really? I didn't see any gas guzzler tax on my 380hp V-8 Lexus LS460 ... wonder why the Benz engines are so inefficient?

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mondo540

Interesting discussion...I've always been a v-8 person myself... have a couple muscle car comparisons to share...

Back in the day I had a '95 camaro z28, 6 spd, 275 HP. Got consistent 18-19 mpg mixed. Long freeway drives got 28-30 mpg. That 6th gear kept the car at 1500-1700 rpm at 70 plus. Old pushrod technology where gearing makes a big diff.

Also had an '03 Mustang Cobra. Supercharged v8, 390 hp., 6 spd. Never, ever got above 18mpg. 6th gear had the car spinning much higher rpms, I believe around 2500-2700 or so. And power dropped a lot on hot days. Heat soak. Superchargers make a LOT of heat.

v8 options seem to be about $4-8K more, depending on premium brand. And the people I see buying (leasing) some of these cars are stretching a lot to have even the base model...everyone wants a BMW, it seems....will be interesting to see how the current state of economy and housing affects all that.

FWIW.

B+O

When i said Mid-Sized, i was refering to mostly Luxury name brands. the Class that the Acura RL plays in.

Going specifically by numbers, that's still only 20% of a niche market for BMW...which, if you look at total sales of these cars per year isn't even 100,000 units. More like 40,000 at best. world wide.

Other manufacturers will have a higher 6 cylinder ratio like Mercedes' E-Class which in 2004 did a 84:16 split, If I recall correctly. That along with their sales have been slipping up to 2006. They're still selling approximately 25% more than BMW's share though.

All that said, the vast majority of the market doesn't want a V8. Either they don't want it, or they can't afford it.

Either way, the V8 doesn't sell off the shelves like people make it seem. The only thing required is power, and if your standard engine is powerful enough to push everyone out of the way, then Super Kudos.

I'd like to see a Twin Turbo charged RL before Lincoln drops their Twin Turbo MK-whatever.

B+O

remember i'm not including Germany's Fleet purchases as you know 5s and 3s make a large portion of those figures world wide too.

dwboston

The whole V-8 thing may be moot in the next 10 years or so due to environmental regulations and CAFE standards. The insurance companies are also beginning to gravitate towards horsepower limitations, arguing that there are correlations between higher HP and higher insurance losses. And we all know that lobbying by big corporations trumps consumer needs or wants most of the time in this country. I'm just shocked it took this long to become an issue. See linked article below from the WSJ online (via Yahoo).

http://finance.yahoo.com/insurance/a...on-Horsepower?