At Last America gets it!

[GRG55]

Re: At Last America gets it!

This argument could be extended to the view that even 4-cyl engines aren't necessary. If we accept that there's been significant advances in controlling and counteracting most of the first and second order harmonics, and some vibration level is tolerable, except for the very rich and "fun loving", who apparently are more sensitive than the rest of us [poor things]...then there's lots of examples from numerous manufacturers, including Suzuki, Saab, Toyota, Peugeot, Citroen, Subaru, Daewoo, VW, and the Smart Car division of Daimler, of 3 cylinder automobile engines that work perfectly well.

But try telling that to America, where apparently size does matter...;)

Daimler’s Smart Car Proves Not So Clever in Size-Obsessed U.S.

Jan. 11 (Bloomberg) -- Daimler AG’s two-year effort to win over U.S. drivers with a thrifty, plastic-clad minicar is running out of steam, adding urgency to the German automaker’s effort to find a partner for the Smart brand.

The U.S. debut of the urban two-seater is foundering after a promising start in 2008, when North American sales propelled Smart to its first profit. With just one model, the “ForTwo,” U.S. sales plunged 41 percent to 14,600 cars last year, more than the 15 percent decline by Daimler’s Mercedes-Benz.

“Smart’s not a car in the traditional sense, it’s a high- style alternative to public transportation,”...

[GRG55]

Re: At Last America gets it!

If you want six cylinders, why not just go with a straight six?

If I ever come into some decent money again, I'm going to get me another BMW straight six cylinder. Those are sweet ! Smooth, strong, ...

Cow: Great news. Did you see this?

Official release:


The 2011 BMW 740i and 740Li Sedans


Six-Cylinder BMW Power Returns to the 7 Series in North America.

Woodcliff Lake, NJ –As an exciting example of its EfficientDynamics engineering philosophy, BMW announced the North American debut of the 7 Series with a twin-turbocharged inline-6 engine. Featuring BMW’s award-winning inline-6 engine that produces V-8 power on six-cylinder fuel consumption, the new BMW 740i and BMW 740Li achieve a remarkable balance of power, efficiency, and sporty driving dynamics. Both models will go on sale in the United States as 2011 models in Spring 2010...

...In 1977, the original BMW 7 Series was launched exclusively with inline-6 propulsion...The 733i featured a 3.2-liter inline-6 engine rated at 197 horsepower. The 733i remained on sale in America until it was replaced in 1985 by the BMW 735i Sedan. The 735i, which featured an updated inline-6 engine producing 218 horsepower from 3.4 liters...

...The 2011 BMW 740i and 740Li feature BMW’s internationally acclaimed twin-turbocharged inline-6 engine with up-rated output of 315 horsepower at 5800 rpm and 330 lb-ft of torque from 1600-4500 rpm. All-aluminum construction, High Precision direct fuel injection, Double-VANOS variable camshaft technology, and Brake Energy Regeneration are a few of the technologies used under the BMW EfficientDynamics philosophy to place the 740i and 740Li among the most powerful six-cylinder luxury sedans in the world...

And for all you 4-banger aficionados out there, for the first time since 1999 BMW is going to sell 4-cylinder cars in the USA in some new models to be introduced over the next 3 years [but they'll probably cost as much as last year's 6-cyl 3-Series ]

[flintlock]

Re: At Last America gets it!

Did you just quote yourself?

Interest in the Smart car died with the drop in gas prices. During our dance with $4 gallon gas, there was a waiting list to get one. Americans are fickle.

[ThePythonicCow]

Re: At Last America gets it!

Cow: Great news. Did you see this?

You're mean and cruel :mad:.

Here I was happily enjoying my new downsized life, saying to myself that I could enjoy life as well poor as not.

Then you show me this gorgeous hunk of car:

[GRG55]

Re: At Last America gets it!

First let me thank you and GRG55 for a fascinating discussion. GRG55, did you design engines or do vibrational analysis?. I only took the one class, though we did a pretty thorough job of analyzing the vibrations of one multi-cylinder engine. That cured me for life. We did as you describe in three dimensions - all the torques about three axes, plus the linear forces from mass accelerations in three axis. We worked in 3 student teams and the cursory analysis still took a couple weeks.

Cow, I think your personal experience on a bicycle was misleading due to slow speed both rotationally and linearly. Your legs aren't going fast enough for the dynamic forces to be noticable. A couple hundred RPM is pretty fast pedaling, but still pretty low linear leg velocity and acceleration. As a car buff, recall that 2,000 RPM is a modest tach reading. The linear acceleration forces GRG55 calls out are real and important.

In a 4 stroke car engine at 3000 rpm, typical linear piston velocities are about 16 m/s, or 36 mph. Seems like no big deal, until you look at time. The piston goes from top-dead-center to bottom-dead-center in a half revolution. That's zero up to speed and back to zero in a half rev. At 3000 RPM, you get only 1/6000 minute to accelerate and decelerate, or 1/12000 minute to accelerate., or 0.005 sec. Five miliseconds to go from zero to 35MPH results in big acceleration forces.

To your thought about dead zones, that is certainly true That's why expensive cars tend to have more cylinders. In terms of consistant non-pulsing torque, for a given displacement a 12 cyl is smoother than an 8 cyl is smoother than a 6 cy...

And GRG55, as I recall from that class, it was not only those parts reversing motion that caused important forces, but also the force couples creating torsional moments - a rising piston one place and a falling piston at another, separated by a distance along the crank or off center by two crank throw distances, all times 3 or 4 couples along the crank shaft length tending not only to roll about the crankshaft, but also to pitch in another axis and to yaw in a third axis. The complete set of forces and moments is pretty large, and all are separted by phase-angle relationships and all are sinusoidal (as Cow points out, "like a pendulum"). Being sinusoidal, the whole messy model is well suited to Fourier analysis to account for the addings and cancellings. Certainly not my cup of tea, too theoretical and too much numerical anaysis for me.

My earlier comment about vees being inherently smoother is true, but as you both remind me, overly simplistic in the modern word. We had no rotating balance shafts in engine vibrations 101.:rolleyes: Still, certain geomerties do have inherent advantages. In a vee, many of the forces naturally cancel each other, that's why it's so popular when packaging space isn't an issue. But great companies make world-class engines in many forms, and all the great ones are smooth as silk.

I cerainly bow to both of you as experienced, real-world car buffs. I promise to never again try to give either of you advice about car engines!
Thanks for the insights.

When I saw this article this evening I couldn't help but resurrect this decidedly non-economic, non-political thread. My all time favourite engine configuration may not be headed for the scrap heap of history after all


FEB 20, 2015 @ 2:36 PM

Why the straight-six engine is making a comeback

The accountants want fewer cylinders. The engineers want smooth engines. The compromise? A good straight six. Let us explain.

The V8 engine has long ruled the world of luxury cars, thanks to glass-smooth grunt and a delicious howl under duress. But tightening fuel-economy regulations are encouraging the use of smaller piston counts, and on the standardized tests that automakers use for fuel-efficiency ratings, the average downsized, turbocharged V6 uses less fuel than an equally powerful V8. That may seem win-win, but don't be won over. Engineers don't fantasize about V6s—accountants do. The V6 layout has proliferated because it "packages well," a sexless industry term that's code for "easy to cram into a variety of engine compartments."

It's also incredibly easy to build a V6 from an existing V8. Jaguar, for example, doesn't even bother changing the outside dimensions of its block. The company's V6, available in every new Jag sold in the U.S., is simply its V8 with shorter cylinder heads and balancing weights on the crankshaft where the last two piston throws should be.

It works, but not without compromises. Like all V8-derived V6s, Jaguar's has a 90-degree angle between its cylinder banks. That works well for a V8, but it's the wrong angle for a six, because it means the engine will fire at uneven intervals, and odd-fire engines run rough and make terrible noises. A V6 will fire at perfectly spaced intervals (read: smoothly) with its banks splayed to 120 degrees, but that's too wide to fit in most cars. Halving that angle keeps the even firing order and, with a couple of crank counterweights, it allows for smooth running. Toyota's ubiquitous 3.5-liter V-6 is a 60, and it's as creamy as they come.

But a 60-degree six negates the economic advantage of basing the engine off an existing V8. So luxury brands tend to stick with the 90-degree architecture and apply various tricks to make it work for a V6. The big one is using split, offset crankpins. These are impossible to fully understand without a physics degree and a stiff drink, but in essence, they slightly offset opposing pistons, forcing them to move in such a way that the engine fires evenly. But these are difficult to engineer and expensive to manufacture. Plus, the 90-degree V6 usually has an engine-driven balance shaft to prevent the whole complicated mess from vibrating itself apart. All of this adds expense, hurts efficiency, and requires royalty payments to Rube Goldberg.

That complexity, however, masks the problem instead of solving it. The mass of the pistons moving up and down in an internal combustion engine creates enormous forces, which cause the engine to vibrate. The most effective way to reduce that vibration is to use the force of one piston to cancel out the force of another; in other words, as piston A moves in one direction (up), piston B moves in the exact opposite direction (down) at exactly the same time. But that's only possible for engines with an even number of pistons in a single plane, like an inline-four-cylinder. When you have an odd number of cylinders, as with an inline-three, the force moving in one direction (say, up) is almost always imbalanced compared with the force moving in the opposite direction (down). This makes the engine rock back and forth. Now think about a V6, which is essentially two three-cylinder engines joined at the crank—it's like having a pair of amped-up pit bulls on a shared leash. And that typically means a whole lot of unpleasant mechanical noise, to boot.

You can avoid the drama by arranging the pistons in one line. A straight-six doesn't need split crankpins, balance shafts, or big counterweights, because each of its cylinders has a twin that's doing the opposite thing, at the same time and in the same plane, canceling out the other's forces. That lack of internal dissonance gives the same perfect balance as a V12. There's a reason museum-piece marques like Rolls-Royce, Mercedes-Benz, Jaguar, Aston Martin, and Alfa Romeo earned their reputations with inline-sixes.

At the moment, BMW remains the sole champion of the straight-six. Munich engineers admit that they regularly develop and test prototype V6s, per internal policy, but say the results don't come close to meeting company noise and harshness standards. Mercedes-Benz must not have such stringent benchmarks. Once renowned for its silken inline-sixes, Stuttgart phased out those engines and began building V6s out of its V8s during the dark, cost-cutting days of the marque's DaimlerChrysler ownership. As the sting of that failed merger continues to fade, so will the company's coarse, complex, 90-degree V6, which is being retired in favor of a 60-degree unit. This stopgap engine, which fits into the vee-focused packaging of Mercedes's current lineup, is noticeably smoother than the 90-degree unit, but its exhaust still sounds like Fran Drescher on Spanish fly—not the voice you want your luxury car to sing with.

That's likely one reason Mercedes is rumored to be developing a new family of inline-sixes. And because accountants, not engineers, usually run the show these days, you can be sure there's an economic incentive as well. As tightening fuel-economy standards encourage four- and six-cylinder engines where sixes and eights once lived, an inline layout becomes the norm and it makes financial sense to develop a modular family of inline-threes, fours, and sixes. Add the straight-six's other cost-savings (half as many cylinder heads, camshafts, and turbos), and suddenly, tougher emissions mandates have the unintended consequence of unifying the dreams of engineers and bean counters alike. It's a dream aligned in one straight line.

Jason Cammisa is a senior editor at Road & Track. He crams easily into very few engine compartments.

[Southernguy]

Re: At Last America gets it!

No way: the future is electric cars

[GRG55]

Re: At Last America gets it!

No way: the future is electric cars

Yes, through the years there have always been a few people that think that. My bet is natural gas derivatives will dominate over electrics as the preferred displacement for crude oil based transport fuels.

[jk]

Re: At Last America gets it!

i have owned a good number of subarus, which use boxer engines. i know porsche also uses one, but in the modern era, those 2 appear to be it. the flat boxers are balanced and give the car a lower center of gravity. i've got to ask why flat, boxer engines never became more popular?

[GRG55]

Re: At Last America gets it!

i have owned a good number of subarus, which use boxer engines. i know porsche also uses one, but in the modern era, those 2 appear to be it. the flat boxers are balanced and give the car a lower center of gravity. i've got to ask why flat, boxer engines never became more popular?

We did chat about the Subaru engine earlier in this thread:

http://www.itulip.com/forums/showthr...026#post143026

The horizontally opposed engine is an excellent configuration for air cooling. Its original versions for automotive use designed by Dr. Porche for the Volkswagen, its brief life within General Motors powering the Corvair and its ongoing production to this day for light aircraft by Lycoming and Continental are testament to that.

But if the engine is water cooled this configuration would appear to have few advantages. It is more expensive to produce than a comparable displacement in-line 4 or 6 cylinder engine (two heads, two camshafts, a more complex exhaust system joining from opposite sides of the engine, etc), and is more difficult to package in a small vehicle where engine bay space competes with passenger compartment volume (the boxer 4 is virtually impossible to package in the transverse FWD arrangement pioneered by Sir Alec Issigonis in the original BMC 'Mini', and much copied since).

There is much speculation as to why Subaru has persisted with the horizontally opposed configuration. The AWD drivetrains that Subaru has become famous for take advantage of the fact that the longitudinally aligned crankshaft in the engine forces the transmission to be located between the front and rear axles, facilitating driving both. There are also some that believe this style of engine has something to do with Subaru's lineage back to Nakajima Aircraft, one of Japan's two largest aircraft manufacturers during WWII (although back then the engines were mostly radials).

[jk]

Re: At Last America gets it!

We did chat about the Subaru engine earlier in this thread:

http://www.itulip.com/forums/showthr...026#post143026

The horizontally opposed engine is an excellent configuration for air cooling. Its original versions for automotive use designed by Dr. Porche for the Volkswagen, its brief life within General Motors powering the Corvair and its ongoing production to this day for light aircraft by Lycoming and Continental are testament to that.

But if the engine is water cooled this configuration would appear to have few advantages. It is more expensive to produce than a comparable displacement in-line 4 or 6 cylinder engine (two heads, two camshafts, a more complex exhaust system joining from opposite sides of the engine, etc), and is more difficult to package in a small vehicle where engine bay space competes with passenger compartment volume (the boxer 4 is virtually impossible to package in the transverse FWD arrangement pioneered by Sir Alec Issigonis in the original BMC 'Mini', and much copied since).

There is much speculation as to why Subaru has persisted with the horizontally opposed configuration. The AWD drivetrains that Subaru has become famous for take advantage of the fact that the longitudinally aligned crankshaft in the engine forces the transmission to be located between the front and rear axles, facilitating driving both. There are also some that believe this style of engine has something to do with Subaru's lineage back to Nakajima Aircraft, one of Japan's two largest aircraft manufacturers during WWII (although back then the engines were mostly radials).

i'm impressed that you remembered we'd already had an exchange about this. it's testimony to either your retention of gearhead discussions, or my declining powers of memory.

re non-aircooled flat boxers, i just looked at wikipedia and see that bmw flat boxer motorcycle engines went from air cooled to oil cooled to water cooled.

[santafe2]

Re: At Last America gets it!

i have owned a good number of subarus, which use boxer engines. i know porsche also uses one, but in the modern era, those 2 appear to be it. the flat boxers are balanced and give the car a lower center of gravity. i've got to ask why flat, boxer engines never became more popular?

Living in the Southern Rockies we've been fans of Subaru for a long while now. It seems like every other car in Santa Fe is some make and model of Subaru. The older ones often have 10-20 bumper stickers all over the back of the car admonishing one to be a peaceful, environmentally aware Buddhist, (not, I believe, just a plain vanilla Buddhist).

I may have mentioned this before but I swapped out the 4-cylinder VW water-boxer 2.1 for a Subaru 3.0 engine in my Vanagon Westy about 4 years ago. What a great difference that made. Not the least of the benefits is that it always starts.

And it doesn't look like Subaru is going away any time soon. They grew sales in the US from 336,000 to over 500,000 in the last 2 years and their year-to-date sales are up 30%. The big winter might have something to do with that.

[GRG55]

Re: At Last America gets it!

i'm impressed that you remembered we'd already had an exchange about this. it's testimony to either your retention of gearhead discussions, or my declining powers of memory.

re non-aircooled flat boxers, i just looked at wikipedia and see that bmw flat boxer motorcycle engines went from air cooled to oil cooled to water cooled.

Without looking up the article I would venture a guess that three things drove that shift: a) As engine displacement and hp increased using air as the heat transfer medium became problematic; b) Emissions requirements in some jurisdictions, may be driving the need for a more stable engine operating range than widely fluctuating ambient air temperatures at surface will allow; c) fuel efficiency is much more difficult to optimize in an air cooled engine, again because of the wide range of the heat transfer rates under different ambient temperature conditions. (As an aside, air cooled aircraft engines have some major advantages over air cooled automobiles - on any given day air temperatures a few thousand feet above ground tend to be more stable than temperatures across the surface, and once airborne the vehicle is always in motion so there is always flow through the cylinder fins.)

One of my friends rides one of the newer, larger BMW bikes (I think it's an R1600?) and I noted it has one of those beautifully smooth in-line 6 cylinder engines (maybe the Bimmer cycleworks is borrowing engineering from the auto plants?).

[cbr]

Re: At Last America gets it!

Of all the irresponsible bs. That article is absurd. While it is true that if all you want to do is put around getting groceries, a normally aspirated modern 4 banger is fine, the reality is it is not a better package than a v8. Frankly, a nice 200 hp na 4 banger would be pretty efficient in a 2000 lb car. But the problem is almost nobody makes a grocery getter in the us that weighs less than 3500 lbs now. So cars are getting fatter faster than motors getting more efficient.

Also, the time is money concept is lost on people when they talk cars. Unless you make less than than the US minimum wage, your time is worth much more than a few mpg difference you get by putting around, and if you understand that now you're flogging that 200 hp 4 banger to hell just getting around at a reasonable pace. Its no longer getting good gas mileage and its not going to last long either.

If you put a turbo on it, now you have added many expensive, heavy moving parts at extremely high temps and rpms, and your durability goes way down. To survive, it has to run a rich mixture as well, driving down fuel efficiency whenever you are in the boost.

Further, to get the needed performance per cubic inches out of the small displacement motors, you are seeing 2ohc, big intakes and exhaust, which makes those motors as wide and often as heavy, and more expensive than an ls series gm v8 pushrod motor.

Which is why your 3300lb corvette with a massive frontal area and huge tires, and a 500 hp 7 liter v8 still gets 30 mpg cruising - and will last 300,000 miles. Because to make cruising speed it only needs to turn 1400 rpm.

And by the way, that gm v8 only weighs 390 lbs. The motor is physically no larger or heavier than the 4 banger in a honda s2000 or mazda miata. In fact there is a large ls swap community putting those motors in cars designed for 4 cyl engines and generally the only weight added is in stronger drivetrain to handle to increased power.

Basically, take any mass production vehicle on the planet and put that aluminum pushrod v8 in it and it is a better car.

Cases in point: my 30 year old stock vette will get 31 mpg at 65 mph, and 22 at 95. My 640 hp 2008 vette will get 20 at 95...never cruised at 65. When it was stock at 500 rwhp it got about 28 at 65. My miata sized cobra with a v8 humorously got 37mpg at 65 with almost 500 hp.

My last 3 4 cylinder rental cars got worse mpg than these larger, equally heavy vettes, because i was flogging the living shit out of them trying to maintain a reasonable pace - which would be sleepwalking for the v8's.

The main drivers for the trend toward 4 cylinder displacement limited vehicles are taxes and regulations, and irrational incentives.

It is true that if all you want is less than a tenth of a g of accelleration and a 50 mph cruising speed, you can be slightly more efficient with a smaller motor. Except that you are wasting incredible amounts of time. It is also true that if you were really looking for efficiency youd put the most modern efficient 4 banger in a mid 1980's civic wagon which weighed anout 1900 lbs and has a tiny frontsl area. But no one is making such a car which only adds to the hypocritical absurdity of it all.

Ignorant people write articles like this trying to make themselves feel better, and satisfy some anti detroit sentiments, but that doesnt make them right or rational.

It is also true that a small displacement, harder working 4 cyl makes slightly less emissions at certain hp loads than a smoothely idling v8 at the same low hp load. But as i sit here through the longest, coldest winters in history reading about all the fraudulent political bs around the carbon debate, i really couldnt give less of shit about that.

And frankly i never see those low hp loads. With my driving requirements, i am in the efficiency range of my v8's and probably generate less emissions than the 4 cylinder i would be flogging far beyond its most efficient range of hp.



ps - apologize for the poor writing skills - on an iphone and cant see very well to type, see what i typed, or proof read


rant over. Thx for listening.

[cbr]

Re: At Last America gets it!

Ahhh. Somehow i missed page 2-

It is true that a 4 and even v6 has fundamental vibration issues. They also 'hit' the drivetrain and tires harder at any given horsepower level. In practice these issues can be reduced to a 'no problem' situation. However, one requirement for solving these issues is added weight - which works against packaging, performance, cost and efficiency.

Its a big issue for 4's. The straight 6 not so much. Drive an old m3 or datsun 240 and theyre good, smooth engines. V6's tend to be a bit rougher.

Bottom line, packaging, weight, overall power and efficiency, durability, and cost are what define a good motor. And in cars of todays size and weight, the gm pushrod v8 has no equal.

Bottom line, i have seen and driven a lot of gm ls v8 swap cars - porsche 911's and boxsters, bmw e36 m3's, mazda miatas and rx7's, and old datsun 260z's. It is absolutely incredible how much better each of those cars became. The ls v8 added about 50 lbs to the 2100 lb miata, but dropped weight in the datsun and bmw. It was dead even in the boxster. It dropped weight in the air cooled 911's but the water cooling system netted about +20.

The old 911 and miata in particular cracked me up. Literally 3 times the horsepower and better fuel efficiency in a motor not significantly different in size or weight than the original 4 or flat 6.

The 911 almost got me killed. It was at a track day run by the porsche club and i was destroying the entire field in a pretty non descript, quiet v8 swap car. It was no contest. Modern gt2's and 3's. Older turbos. Guys with $200k cup motors. Obliterated. By a students car with a bone stock ls3 in it. They all came over and asked about the car thinking it was a high dollar twin turbo sleeper - and when they found out it was a v8 swap there was a huge range of reactions. Some looked like they wanted to cry. Some got mad and wanted to kick us out. Some were just baffled and gawked. Some thought it was the coolest thing ever. Bottom line, you can spend $100k trying to wring out 500 reliable hp in a flat six porsche motor, or you can go buy a $6k ls3 brand new and a $6k swap kit and make 500 hp and more torque out of a bone stock chevy pushrod v8 that weighs less and will last longer snd get better gas mileage. And by the way is smaller in the critical dimensions and in many ways fits the bay better than the stock motor - which is a very wide flat 6.

[shiny!]

Re: At Last America gets it!

I'm really enjoying your comments, cbr, and written on an iPhone, yet! Thanks for taking the time to educate me. I want to ask all you gearheads for your opinion and this seems as good a thread as any:

I have a 2012 Hyundai Accent hatchback, purchased new and totally paid-for. Have put 34,000 miles on it in light city driving, about 75% on the freeways. Runs like a top. Totally reliable. It averages 33mpg. It's pretty safe for a little car; 2012 was the year they started making the frames with a stronger steel alloy like they use in Mercedes and BMW. It has 4-wheel disc brakes, side airbags and electronic stability control.

What I cannot stand is the poor visibility from the giant A and C pillars. Changing lanes to the right and backing up are nightmares. Even with extra mirrors I just can't seem to get used to it. I bought it because I wanted a reliable, cheap car with high mpg because I was expecting high gasoline prices. But the high cost of insurance and annual registration have eaten up any savings on gasoline.

It handles and brakes very well but I still miss the smooth ride of a Crown Vic. I never appreciated how great the visibility was out of those things until I got this new style car. Other drivers give you more respect when you drive a CV! They're big, cheap tanks that run forever. Parts and repairs are cheap. I always got about 20mpg in mine.

After reading about EJ's wife's collision, I've been wanting a bigger, safer car. But reading the crash safety reports, the Crown Vics have a lot of poor and marginal ratings, not even as good as my Accent. Terrible side impact rating! Yet the car is in the top ten for low mortality per million on the road. Why is that? Is it safer than the Accent, or not?

Would I be crazy to sell my car and buy a used, low-mileage CV or Grand Marquis in its place? From a financial standpoint I could pocket about $4000-$5000 in change. Without paying for collision and comprehensive anymore, and with lower annual car registration, I could also save about $50 per month to go towards extra money at the pump.

Is this a dumb idea? What are your thoughts?