At Last America gets it!

[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, ...

Bingo! That's why I think the author in the original article that Mega posted is blowing smoke about the inevitable ascension of the lowly 4 cylinder engine, no matter how many turbo chargers it has. There's a reason why your inline 6 ran so smoothly...

I'm no automobile engineer, but that doesn't agree with my recollections (probably from some BMW salesman many decades ago ) or seat-of-the-pants experience for 150,000 miles of driving (wow!)

For example (using the far more reliable methodology of searching on Google from random blog comments ) consider these comments, from http://blog.cardomain.com/2009/08/11...ich-is-better/
Or, if you prefer the Cadillac of Research, Wikipedia, consider these comments from http://en.wikipedia.org/wiki/V6_engine :

...Among other things, automotive engineers are fighting Newton's Third Law..."For every action there is an equal and opposite reaction".

In that whirling mass of pistons, connecting rods and crankshaft throws, there are a multiplicity of forces and reactions underway at all times. Pistons moving back and forth along the direction of the cylinder bore cause the engine block to try to move in the opposite direction [the equal and opposite reaction]. The mass of the connecting rods is not only moving along the direction of the cylinder bore [like the pistons] but also laterally within the cylinder bore, which creates a lateral rocking motion of the engine block. It just so happens that an inline-6 physical configuration matches the phasing of the pistons along the crankshaft thus eliminating the single biggest contribution to secondary harmonic vibration in a reciprocating engine.

Superimposed on all this motion is the instantaneous torsional loads [and reactions] transmitted to the crank with each ignition event. An inline-4 cylinder, 4-stroke engine fires once for each half-revolution [180 degree rotation] of the crankshaft. That means that each combustion cycle is roughly coincident with the reversal of direction, and re-acceleration from zero linear velocity, of all four of the pistons and connecting rods in the engine. That is why it is almost impossible to eliminate the infamous "shake" associated with inline 4 engines. For a given engine size, more cylinders result in a smoother distribution of torsional loads for each engine rotation.

Similar to BMW today, Jaguar developed its reputation around its superb inline-6 [no longer in production]. It was even smoother than your BMW because Jaguar chose to use "Prince of Darkness" Lucas electrics in its cars so half the time the engine wouldn't start, and the other half of the time it wouldn't keep running, especially in the rain. Talk about a perfectly vibration-free car....:rolleyes:

I have a large displacement [4.5 litre] inline-6 in my Toyota Land Bruiser that runs like a turbine, and is imo smoother than the V-8 version of the same vehicle.

As before, I think Hyundai's decision to limit the new Sonata to only 4 cylinder engines is going to be interesting to watch to see how the market reacts.

[ThePythonicCow]

Re: At Last America gets it!

As before, I think Hyundai's decision to limit the new Sonata to only 4 cylinder engines is going to be interesting to watch to see how the market reacts.

My current car is a Hyundai 4 banger. It's a pleasure to drive; no BMW six, but better than most anything else I've owned.

For Hyundai's market, especially if gas prices go up again, keeping their fleet MPG low could be more beneficial to them than having the kind of engine that would cause GRG55 or myself to drool compulsively.

[GRG55]

Re: At Last America gets it!

No, No.....Totally aware it was a Buick V8, although a lot of extra R+D had to be done. I had Janspeed headers & Holly 6 barrel carb on mine.............It eat the local Ford 2 litre Pinto engined car everytime...........Sadly i had to sell because of running cost & Rust caught up with it............3 mnoths latter i was on the front page of the Liverpool Echo having been crash (At Warp speed) thought (I joke not) 5 gardens & took out 3 other cars!!!

Mike

Mike: You do surprise me at times...another former hot rodder, in Blighty of all places. Two thumbs up, guv'nor :cool:

[ThePythonicCow]

Re: At Last America gets it!

From http://wardsautoworld.com/ar/auto_hy...gen/index.html

Hyundai Forgoes V-6 for Next-Gen Sonata
Christie Schweinsberg
Ward's AutoWorld, Sep 1, 2009 12:00 PM

Hyundai Motor America will not offer a V-6 engine in its next-generation Sonata midsize sedan, which goes on sale in the U.S. early next year, Ward's learns.

The new Sonata, instead, will have an upgraded version of Hyundai's 4-cyl. Theta engine with gasoline-direct injection, making Hyundai the first auto maker in the 4-cyl. midsize-sedan segment with standard GDI.

The GDI 4-cyl. in the '11 Sonata, expected to be unveiled in January at the Detroit auto show, will boast improved horsepower and fuel economy. The '09 Sonata achieves 175 hp and 22/32 mpg city/highway (11/7 L/100 km).

Hyundai also is nixing the V-6 option from its Tucson cross/utility vehicle.

Hyundai says 85% of the Sonata's current-model output features a 2.4L I-4. The 3.3L V-6 accounts for the remaining 15% of Sonata production.

According to Ward's data, 76% of '08 Honda Accords had 4-cyl. engines, while 90% of non-hybrid Toyota Camrys were equipped with 4-cyls.

Hyundai is not alone with its I-4 strategy. American Suzuki Motor Corp. says its new '10 Kizashi sedan also will offer only a 4-cyl.

[Red emphasis by ThePythonicCow]

With direct fuel injection, I can imagine Hyundai can get close to 200 horsepower. That's not much less than a BMW six, for less cost upfront, lighter weight, less maintenance cost and better mileage.

Ah - here we go. From http://en.wikipedia.org/wiki/Hyundai...0.94present.29

With direct injection technology this new engine will boast improved gas mileage and 201 ps (at 6300 rpm), 25.5㎏·m (at 4250 rpm). It is part of the Theta II engine lineup. Furthermore, all engines are offered with a new six-speed automatic transmission.

That's 201 horsepower. I guessed about right. That and the six speed automatic should be a pretty nice ride, actually.

[GRG55]

Re: At Last America gets it!

From http://wardsautoworld.com/ar/auto_hy...gen/index.html

[Red emphasis by ThePythonicCow]

With direct fuel injection, I can imagine Hyundai can get close to 200 horsepower. That's not much less than a BMW six, for less cost upfront, lighter weight, less maintenance cost and better mileage.

Ah - here we go. From http://en.wikipedia.org/wiki/Hyundai...0.94present.29

That's 201 horsepower. I guessed about right. That and the six speed automatic should be a pretty nice ride, actually.

Indeed. But they still won't be able to get rid of "the shake"...

As for the sales stats for the Accord and Camry [4-cyl vs 6-cyl] I wonder how much the economic situation has recently shifted those numbers in favour of the less expensive models [often the higher end accessories and trim packages from Honda and Toyota are only available on the 6 cyl versions...but I'll bet they are rethinking that strategy in these lean and mean times...]. Up where I am in Canada almost nobody ever bought a 4 cyl Accord or Camry judging by what I see on the streets [and our gasoline is more heavily taxed than the USA], but that may have changed in the past year or so.

[ThePythonicCow]

Re: At Last America gets it!

Indeed. But they still won't be able to get rid of "the shake"...

They (Hyundai 4 bangers) feel pretty smooth to me. Have you driven one?

I don't think that the problem is you can't get rid of the shake. I think that the problem is that it's difficult to calculate how to get rid of it. Hyundai (from what I recall while being in the super-high performance computing business) has one of the highest number of compute cycles per car model design of anyone in the business.

Those guys aren't using slide rules anymore.

[GRG55]

Re: At Last America gets it!

They (Hyundai 4 bangers) feel pretty smooth to me. Have you driven one?

I don't think that the problem is you can't get rid of the shake. I think that the problem is that it's difficult to calculate how to get rid of it. Hyundai (from what I recall while being in the super-high performance computing business) has one of the highest number of compute cycles per car model design of anyone in the business.

Those guys aren't using slide rules anymore.

It's not slide rules or compute cycles...it's Newton's [immutable] Laws.

Consider what I said above about re-acceleration of the mass inside all four cylinders from zero linear velocity at the same time. As long as it's a 4-cylinder, 4-cycle reciprocating engine that can't be changed.

What can be changed is the various techniques to try to isolate the passenger cabin from the effects of this, or to mitigate the effects to the highest degree possible with various dynamic balancing techniques [like the counter-rotating balancing shafts in most modern V-6 engines].

I have no doubt that Hyundai have excellent engineers and make a good product - the latter requires the former, and in the hyper-competitive world of auto marketing no company can survive without the latter. And maybe the 4-cyl engine is going to be the norm in the future. But no matter how sophisticated the engine power producing technology, people like me are unlikely to deliberately seek out a 4 cyl engine over a well built inline-6, unless we are given no other choice.

btw, I have never owned a V-6, but the one version that does intrigue is the VW VR6. Because of the configuration VW was able to replicate the optimized cylinder firing order of an inline-6.

[ThePythonicCow]

Re: At Last America gets it!

Consider what I said above about re-acceleration of the mass inside all four cylinders from zero linear velocity at the same time. As long as it's a 4-cylinder, 4-cycle reciprocating engine that can't be changed.

Something doesn't seem right in your observation.

When I was a bicyclist, I didn't feel any particular 're-acceleration' shock at the top or bottom of the stroke. On a bicycle, one's two legs are rather like pistons in an inline two cylinder engine. I could spin the cranks at (my memory is fading here) up to a 120 RPM cadence. I've been up to 60 MPH (down a nice hill) on a ten speed on my own power. It's all nice and smooth (unless you wipe out.)

The dynamics feel to me to be more like those of a pendulum, which as we know from old clocks can swing back and forth with an efficient gentle smoothness for hours, even days, on end. But it's been too long since physics classes for me to readily work this out properly.

I am sure that there are imbalances to work out, but the one you describe doesn't seem right. A problem I would expect with any four cycle engine having four or fewer cylinders is that there must be dead zones when none of the cylinders is doing any pushing. In a four cycle engine, each cylinder is only actively powering for something less than one fourth of the time. This is going to make getting a smooth torque on the drive shaft impossible. The power must pulse. However sufficiently high RPM's would put the frequency of that pulse above anything you'd notice, other than as part of the sweet sound of a fine engine.

Now in an old John Deere farm tractor (a classic two cylinder, four stroke engine) pulling a load ... then you notice that pulsing power for sure.

[tofu2u2]

Re: At Last America gets it!

The article is actually predicting the demise of the V-6.

OMG! SAY IT ISN'T SO!! This is the end of the world . . .

[thriftyandboringinohio]

Re: At Last America gets it!

Something doesn't seem right in your observation.

When I was a bicyclist, I didn't feel any particular 're-acceleration' shock at the top or bottom of the stroke. On a bicycle, one's two legs are rather like pistons in an inline two cylinder engine. I could spin the cranks at (my memory is fading here) up to a 120 RPM cadence. I've been up to 60 MPH (down a nice hill) on a ten speed on my own power. It's all nice and smooth (unless you wipe out.)

The dynamics feel to me to be more like those of a pendulum, which as we know from old clocks can swing back and forth with an efficient gentle smoothness for hours, even days, on end. But it's been too long since physics classes for me to readily work this out properly.

I am sure that there are imbalances to work out, but the one you describe doesn't seem right. A problem I would expect with any four cycle engine having four or fewer cylinders is that there must be dead zones when none of the cylinders is doing any pushing. In a four cycle engine, each cylinder is only actively powering for something less than one fourth of the time. This is going to make getting a smooth torque on the drive shaft impossible. The power must pulse. However sufficiently high RPM's would put the frequency of that pulse above anything you'd notice, other than as part of the sweet sound of a fine engine.

Now in an old John Deere farm tractor (a classic two cylinder, four stroke engine) pulling a load ... then you notice that pulsing power for sure.

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.

[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...

Hmmm. Apparently one can use the internet to hide that one is a Cow, but apparently not that one is a Mechanical Engineer...it shows that much does it? Please don't tell the neighbours...they might stop inviting me to their parties.

Actually my first degree is in Mech Eng., but I went to work in the oil patch as a summer student because it paid better than anything else I could find [that was legal]. However, I was fortunate to have a truly gifted researcher and inventor in the field of vibration control systems as a professor. And yes, that was in the days when we still used slipsticks. I passed the series of interviews and was offered a job with General Motors on graduation, but decided that since I wasn't a GMI graduate my chances of a decent career were limited [every single interview that counted was conducted by a GMI alumnus -what did that say?]. Besides the oil patch paid better at the time and were willing to fund the formalities of a petroleum engineering education.

The oil patch summer student pay was also enough to fund my hot rod habit. I have never designed an engine. Everything I know about engines I learned from taking them apart, modifying them, running them competitively on weekends, breaking them, and re-building them again...hopefully better [& sometimes so I could get to class on Monday morning]. A mis-spent youth indeed.

My favourite car of all was an inline-6 powered Datsun 240Z that I used for gymkhana events on the weekends during my college years. One of my brothers is a machinist so I had access to the lathes and other equipment in his shop, where the two of us experimented and made a variety of custom suspension components to eventually create a formidably competitive car. The engine internals and other stuff came from Pete Brock's BRE, and F.A.R. Performance in Mountain View, CA. This was the heyday of Datsun racing in SCCA when John Morton, Bob Sharp and Walter Maas were beating the best that Porsche, Triumph and Toyota could field. Properly set up, the 240Z was a wonderfully competitive and versatile car and I spent a lot of hours both in it, and under it [wrenches in hand] back in those days. It's too bad the damn thing eventually rusted away on me.

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...

Well I'm glad that you're the one that brought up force couples...I considered including the issue of moments when drafting the earlier post, but only for a moment [groan] and thought the better of it.... I was also going to point out the sinusoidal vs non-sinusoidal dilemma that arises when trying to use counterweights and counter-rotating balance shafts to control vibration - unfortunately the forces acting on the piston are not sinusoidal [even though the motion is], but the countering forces from the motion of counterweights and balance shafts are sinusoidal...so the countering effect is imperfect. One more reason for my bias in favour of the natural primary balance of an inline-6 engine - although the force couples on such a long crankshaft are not to be trifled with I will admit.

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.

I'm not much of a motorcycle guy, but it's pretty clear that the popularity of 4-stroke vee-twins in that application is an indication that the vibration issues of a vee configuration are manageable, even with only two cylinders. Honda in particular has done some creative engineering, including using offset crank pins on its series of narrow angle vee engines to deal with the balance issues of having a less than 90 deg included angle.

I would be greatly disappointed if you chose not to give of your advice and expertise on car engines or anything else, and I would encourage you to please reconsider.

[jk]

Re: At Last America gets it!

so now, grg, let's hear your thoughts on my car's engine: i drive a manual transmission subaru turbo legacy - 2500 cc, turbocharged, 4 cyl BOXER engine, car-and-driver tested at 5.6sec 0-60 iirc. [maybe it was 5.7, i'm not sure.] i'm not an engineer, but i recall something about balancing the movements/vibrations on the two sides of the engine, and a lower center of gravity. just askin'.

[GRG55]

Re: At Last America gets it!

so now, grg, let's hear your thoughts on my car's engine: i drive a manual transmission subaru turbo legacy - 2500 cc, turbocharged, 4 cyl BOXER engine, car-and-driver tested at 5.6sec 0-60 iirc. [maybe it was 5.7, i'm not sure.] i'm not an engineer, but i recall something about balancing the movements/vibrations on the two sides of the engine, and a lower center of gravity. just askin'.

Gawd, we've really started something here, haven't we...:eek:

The boxer configuration is actually a pretty interesting way to build an engine. My experiences with them have been restricted to the air cooled versions in my '68 VW Beetle [which, of course, I modified, overstressed, broke and fixed several times] and the Lycoming in the Piper I used to own [which, for obvious reasons, I treated with the utmost of respect and care, and was rewarded with several hundred hours of trouble free operation before I sold it ].

Naturally the opposing cylinder layout does a nice job of cancelling the kinetic energy of the pistons [the only 4-cyl configuration that does that], but two things happen in this configuration. First the cylinders on each side of the crankcase cannot be directly opposite each other, because the connecting rods have to be offset from each other where they connect to the crankshaft throw. That means the engine tries to rotate back and forth [yaw] about a vertical axis that runs through its centre of mass. Second, the lateral forces from the connecting rods and connecting pins [from the side to side motion of the connecting rod in the cylinder] create a moment with a significant arm length because the cylinders are on opposite sides of the crank, unlike an in-line engine [which has the same problem but a smaller moment arm]...the resulting motion is a rocking of the engine about its longitudinal axis.

BMW motorcycles, light aircraft powered by Lycoming or Continental engines [which is the vast majority of them], and VW/Porsche use the boxer layout mostly because it facilitates air cooling of the cylinders. Your Subaru is water cooled, so I am honestly not sure why Fuji Heavy Industries settled on that configuration for an automobile. There are few other non-air cooled examples of a boxer configuration [the Ferarri Berlinetta Boxer with its flat-12 engine is the only other one that comes immediately to mind].

Interestingly, the Subaru engine is one of the more popular auto engine conversions for experimental light aircraft - probably because of the compact packaging fits inside a conventional cowling [and its reputation for reliability and durability].

[flintlock]

Re: At Last America gets it!

Is this the Road & Track forum?

Truth is, 4 cyl engines these days are both strong and smooth enough for any practical car use. Anything more is just for the fun factor. I suspect the worse the economy, the more people can learn to live without the "fun".

Back in the 80s I had a Porsche 944 Turbo that at 2.5L put out about 280hp when chipped (and still got 22 mpg city and about 30 on the hwy). That was considered at the time as almost unheard of for a 4 cyl. Now a Subaru would smoke its doors off. That car had counter rotating balance shafts and other technical enhancements to reduce vibration. It still was a bit rough at idle. I suspect they have come a long way in reducing vibration since then.

[GRG55]

Re: At Last America gets it!

Is this the Road & Track forum?

Truth is, 4 cyl engines these days are both strong and smooth enough for any practical car use. Anything more is just for the fun factor. I suspect the worse the economy, the more people can learn to live without the "fun". ...

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.