Talk:Flat-six engine

Corvair section isn't all that accurate.

66.56.28.232 11:22, 29 September 2007 (UTC)

Balance and Vibration

"The movement of the pistons in a horizontal engine is all in the same plane, so it creates less vibration than in a V-configuration engine; particularly one with an odd number of cylinders on each side of the engine, like a V6. Unlike the V6 but like the inline-6, the flat-6 is a fully balanced configuration which is in perfect primary and secondary balance. The three cylinders on each side of the crankcase tend to have an end-to-end rocking motion, like a pair of straight-3 engines, but in the usual boxer engine configuration, the imbalances on each side cancel each other, resulting in a perfectly smooth engine.""

That is nonsense. For starters, the terms "primary balance" and "secondary balance" have no universal definition, and whenever anyone uses these terms, it is a dead giveaway that they don't really understand anything about this stuff, and are merely regurgitating some nonsense that they read somewhere else. It is not possible for the three cylinders on one side to cancel the end-over-end rotation of the crankcase that is caused by the three cylinders on the other side. The only way that would be possible would be if there were four cylinders on each side, in which case the rocking motion is cancelled on each side independently of the other side. —Preceding unsigned comment added by Princesscheetah (talk • contribs) 18:59, 13 April 2008 (UTC)

It's not nonsense, nor does it suffer from lack of definitions. Primary imbalances tend to cause vibration at engine speed, secondary imbalances tend cause vibrations at twice engine speed, and tertiary imbalances cause vibrations at three times engine speed. Higher order balances tend to cause much less vibration than lower order balances. Hence, primary imbalances are very serious, secondary imbalances are considerably less so, and tertiary imbalances not much of a concern at all. Straight-3 engines have a primary imbalance that causes an end-to-end rocking motion at engine speed that is very annoying unless canceled by a balancing shaft. Straight-4 engines are in primary balance but have a secondary up-and-down vibration at twice engine speed that only needs balance shafts in the larger displacements.

Now, a flat-6 configuration consists of two straight-3 engines laying on their side and connected to the same crankshaft. In the horizontally-opposed or boxer configuration, the two halves are mirror images of each other and the directly opposing pistons are moving toward each other or away from each other at the same time. So, while one three-cylinder bank is trying to rock clockwise, the other other bank is trying to rock counterclockwise, and the two motions cancel each other. Hence the engine is in perfect primary balance. Straight-3 engines have no secondary imbalances, so all you are left with is an intrinsic tertiary vibration caused by the fact there are only three cylinders firing per crankshaft revolution, and as I said, tertiary vibrations are not much of a problem.

Flat-8 engines would be even better, because in the boxer configuration the secondary vibrations of the two straight-4 banks will cancel each other, there are no tertiary vibrations, and all you are left with is an intrinsic quaternary vibration which should be insignificant. But nobody has a problem with the tertiary vibrations of the flat-6 (which are themselves very expensive to build), so nobody bothers with flat-8s. They are sometimes used in racing engines, but racers are not concerned with a few vibrations, so they usually use the non-boxer or 180° V8 layout in which opposing pistons share crank journals. In this case the two banks reinforce rather than cancel the secondary imbalances, and the engine has a rather nasty side-to-side vibration at twice crankshaft speed. They just use lots of lock washers, secure all the fasteners very well, and hope the engine doesn't shake the car to pieces at high speed.RockyMtnGuy (talk) 02:45, 14 April 2008 (UTC)

Corvair

There seems to be a bit of controversy over whether the early Corvair had handling problems. I can offer the following excerpts from the John DeLorean/Patrick Wright book On a Clear Day You Can See General Motors. DeLorean was a vice president of GM at the time:

• "...These problems with the Corvair were well documented inside GM's Engineering Staff long before the Corvair ever was offered for sale. Frank Winchell, now vice-president of Engineering, but then an engineer at Chevy, flipped over one of the first prototypes on the GM test track in Milford, Michigan..."
• "...The questionable safety of the car caused a massive internal fight among GM's engineers ... One side of the argument was Chevrolet's then General Manager, Ed Cole... On the other side was a wide assortment of top-flight engineers..."
• "...Albert Roller, who worked for me in Pontiac's Advanced Engineering section, tested the car and pleaded with me not to use it at Pontiac. Roller had been an engineer with Mercedes-Benz before joining GM, and he said that Mercedes had tested similarly designed rear-engine, swing-axle cars and had found them far too unsafe to build..."
• "...The son of Cal Verner, general manager of the Cadillac Division, was killed in a Corvair ...The son of Cy Osborne, an executive vice-president in the 1960s, was critically injured in a Corvair and suffered irreparable brain damage. Bunkie Knudsen's niece was brutally injured in a Corvair..."
• "...When Knudsen took over the reins of Chevrolet in 1961, he insisted that he was given corporate authorization to install a stabilizing bar in the rear to counteract the natural tendencies of the Corvair to flip off the road. The cost of the change would be about $15 a car...
• " ... Bunkie put a stabilizing bar on the Corvair in the 1964 models. The next year a completely new and safer independent suspension designed by Frank Winchell was put on the Corvair. And it became one of the safest cars on the road.....

So, I think we can conclude from this that GM knew there were handling problems with the early Corvair, and that they were relatively easy to fix. It's just that GM was too cheap to spend $15 on a stabilizer bar. It also has been said that the NHTSA in 1972 gave the Corvair a clean bill of health, needs to be qualified. What the NHTSA said was, The 1960-63 Corvair compares favorably with contemporary vehicles used in the tests, which is setting the bar very low because the contemporary vehicles included the Ford Falcon, Volkswagen Beetle and Renault Dauphine, none of which was known for inspired handling. The Dauphine was known as the "widow maker" in some circles. RockyMtnGuy (talk) 21:53, 1 August 2008 (UTC)

Are the handling problems of the Chevrolet Corvair and the development of the suspension of the Porsche 911 really relevant to an article on the Flat-6 engine? Respectfully, SamBlob (talk) 15:56, 27 December 2008 (UTC)

Well, given that these were two of the most prominent applications of the flat-6 configuration, I thought so. Otherwise it's nothing but Subarus and light aircraft.RockyMtnGuy (talk) 17:00, 27 December 2008 (UTC)

I'm not sure the extent to which the use of flat-6 engines was a factor in these areas. These analyses seem to be more relevant to rear-engine, rear-wheel drive layout than to flat-6 engines. Respectfully, SamBlob (talk) 03:08, 28 December 2008 (UTC)

The article on rear-engine, rear-wheel drive layout says almost nothing about the handling issues of R-R cars, of which the Corvair and Porsche are two classic examples. In fact a lot of it is just plain wrong. It's pretty sad from an engineering standpoint and doesn't discuss the intrinsic problems of oversteer and rear suspension geometry in the R-R layout. The flat-6 article is better in that it provides some useful information and examples. There aren't many examples of the flat-6 engine, other than Porsche, Subaru, and Corvair, and if you delete them, there's not much left, whereas other engine articles have vast numbers of automobiles cited. The problem is not that the flat-6 article has too much information, it is that the R-R has too little, and a lot of it is pretty nebulous from an engineering perspective. RockyMtnGuy (talk) 21:40, 28 December 2008 (UTC)

Actually, part of the problem with this article is that it has too much information unrelated to the flat-6 engine, just as the problem with the RR layout article is that it does not have this information. I would like to move this info to the RR layout article, but I would rather have some citations for this info first. Do you know where I can find any references to cite? Respectfully, SamBlob (talk) 02:22, 29 December 2008 (UTC)

Well, the classic book on the Corvair is Ralph Nader's book, Unsafe at Any Speed - not exactly an unbiased reference. And also John DeLorean's book On a Clear Day You Can See General Motors, also not unbiased. Neither one of these dwells long on engineering theory. Most of my information came from working at my father's garage and talking to Corvair owners, but in the Wikipedia world that would be considered WP:Original research. The factory manual for the Corvair specified odd things like underinflating the front tires to 14 psi, so we knew something was up, but GM didn't explain why (a bass-ackward method of reducing understeer - and they weren't kidding, if you inflated all four tires to the same pressure, a Corvair was likely to spin out on corners and go into the ditch facing backwards). As for Porsche, there have been a zillion articles in car magazines about them, but all of mine have gone into the recycling bin. Porsche is the only major manufacturer still building cars this way, and I think they consider the theory of the configuration part of their intellectual property.RockyMtnGuy (talk) 16:27, 29 December 2008 (UTC)

Yet the ultimate question is still avoided: what in blazes does all of the talk about the safety aspect of the Corvair have to do with an entry specifically focused on the flat-6 engine? It should be in an entry specific for the Corvair, not here. As for HOW any rear-engined car will handle...until you've actually experienced sudden trailing-throttle oversteer, all discussions are moot. From first-hand experience, it is NOT fun (put most mildly), though with subsequent episodes it does get a tad less shocking. It definitely pays to have a change of undershorts, assuming of course you actually survive the encounter (either the sheetmetal carnage or the heart attack).

As for Porsche: they are stubborn; they build the 911 this way because it's become a tradition that Porsche enthusiasts--yes, like me--continually demand, as if it's some sort of pent-up need for maintaining company and engineering heritage from the 356, if not earlier with Dr. Porsche's prior creation, the VW Beetle. The 911's long-standing history--and the years of experience and knowledge gained refining the tech--makes them money; that's the ultimate root for the stubborn tenacity with maintaining the flat-6 and rear engine location. Yet Porsche's been dumbing-down their current downmarket mid-engined cars--the Boxster and Cayman--through lesser engine performance just to keep the 911 at the top of their sports car food chain, which should tell you something about the ultimate limitations of the rear-engine configuration. But as fun as this is to banter about, none of this has not a bit to do with the actual flat-6 engine configuration. Personally I think a 'rethink' needs to happen with the tone of this particular Wiki article. Notations on the Corvair and Porsche 911 (and Boxster/Cayman) should remain, but only in regards to their use of a flat-6, not in where the engine is actually located.Monoblocks (talk) 15:45, 6 May 2009 (UTC)

The normal procedure is to put a link to a main articles with a short summary into the particular article in question - which I just added. There are only three significant examples of the flat-6 layout in automobiles, so if you don't put in any detail about them, you end up with a rather short article. In the case of the Corvair, you kind of wonder what GM was thinking when they put a flat-6 into it, because it's a rather expensive engine layout for what was supposed to be an economy car, and they compromised the design badly to get the price down. In the case of the Porsche, it's an example of inspired marketing using product differentiation. They're able to charge a much higher price for it because it's different from anything else. Also, there's no real reason for using a flat-6 other than in the longitudinal rear-engine rear drive or front engine front drive configurations that Porsche and Subaru use.RockyMtnGuy (talk) 03:02, 8 May 2009 (UTC)

Subaru

This sentence is broken -- or should be: "Subaru offers flat-6s as optional or standard engines on its larger models, starting with the ER-27 in the Subaru XT6, the EG-33 in the SVX, and the EZ series currently used in the Legacy, Outback, and B9 Tribeca SUV which features a Porsche/Subaru designed and German manufactured, Active Valve Control System (AVCS) and Variable Valve Lift (VVL) system, that further enhances high range power and smoothness at idle."173.57.26.9 (talk) 22:18, 8 September 2009 (UTC)

Suspension and handling issues removed

The suspension and handling issues of the Chevrolet Corvair and the Porsche 911 have finally been removed from this article after years of being the bulk of the article. To do this, the "Corvair", "Porsche" and "Subaru" sections have been replaced by an "Automotive use" section that condenses the issues of placing the wide flat-six engine into an automotive layout and minimizes discussion of the handling problems of the available layouts.

The "Automotive use" section has been placed after the "Aircraft engines" section as the latter is the more prominent use of the flat-six engine.

Sincerely, SamBlob (talk) 16:20, 30 January 2010 (UTC)

Subaru innovation? I think not.

"Subaru, an automobile manufacturer with a history of making aircraft engines, has developed a front-engine configuration for use with its flat engines. The engine is mounted longitudinally ahead of the front axle and the transmission is mounted longitudinally behind the front axle. Although this layout is intrinsically more expensive to manufacture, less compact, and less space efficient for front wheel drive than a transverse V6, it allows the addition of four-wheel drive by taking power off both the front and back ends of the transmission, since the transmission is located between the front and rear axles. As a result of this unique layout, Subaru now specializes in all-wheel drive vehicles."

On most of its automobiles, Audi as well uses a Longitudinal all wheel drive layout (as well as for most of its front wheel drive cars) with the engine in front of the axle, it almost seems like sensationalist propaganda to say that Subaru pioneered the usage of an opposed layout engine in front of the axles (as well as all wheel drive in a longitudinal layout with the engine in front of the front Axle), as Lancia and Citroën both had cars of a similar layout before Subaru. Another qualm that I have with this section is that it is not like placing the transmission in that layout magically made it suitable for all wheel drive, instead, it was likely re-engineered for that usage (I highly doubt they just "slapped on" a normal transaxle and arrived at all wheel drive, like the article might seem to imply). The power for the front wheels, as well, is not coming directly from the front of the transaxle, rather it is coming from the sides of it, otherwise, where would the engine be attached? The layout Subaru is not unique, and this section seems poorly, and not factually written. Pastorboy0 (talk) 06:07, 2 November 2010 (UTC)

Lead image

It is annoying that the image that leads this topic is of a motorcycle engine. Most people would think of a Porsche engine when "flat six" is mentioned. What gives? 02sbxstr (talk) 00:21, 13 December 2012 (UTC)

That's easy: the photo of the Valkyrie engine is the lead image because it's a lot easier to see the Valkyrie engine and identify it as a flat-6 that it is to see a Porsche flat-6 installed in a Porsche. Unless I'm mistaken, it's almost impossible to see a Boxster or Cayman engine once it's installed in the car. Sincerely, SamBlob (talk) 15:19, 15 September 2013 (UTC)

A flat six is not a boxer engine

The term "boxer" is normally applied only to a flat-four, each piston representing a boxer's glove. A flat six is not a boxer engine - human boxers do not have three hands! Arrivisto (talk) 10:42, 2 September 2014 (UTC)

The term boxer engine can be applied to any horizontally opposed engine with an even number of pistons where the pairs of pistons appear to jab at each other like the gloves of boxers. The number of pistons is irrelevant and boxers have been built with from 2 to 16 pistons. The Ferrari Berlinetta Boxer was technically not a boxer - not because it had 12 cylinders but because it was really a 180 degree V - the pairs of pistons shared the same crankshaft journal rather than being opposed. A V-12 can be balanced at a 60, 120, or 180 V degree angle. However the Porsche and Subaru flat sixes are true boxers. See Subaru Boxer Engine Comparison RockyMtnGuy (talk) 21:27, 2 September 2014 (UTC)

I acknowledge that common usage now has it that any horizontally opposed engine may, for the sake of convenience, be called a boxer, but my earlier point was that, strictly speaking, a "boxer' is a flat-four, for the reasons given above. Arrivisto (talk) 12:29, 3 September 2014 (UTC)

The origins of the term "boxer" are unclear and it probably should be classified as slang or jargon, but some motorcycle enthusiasts argue that a "boxer" has only two cylinders and that a flat-4 is not properly a boxer. From motorcycles.about.com:

definition

Boxer engines are two-cylinder powerplants with horizontally-opposed cylinders, and the name derives from the fact that the pistons move in an outward "punching" motion, and the cylinder heads protrude on either side of the bike. BMW motorcycles are among the best known manufacturers-- especially with their so-called older "airhead" powerplants-- for their boxer engine configurations.

The BMW airhead boxer flat twin engine definitely has seniority over the flat four - it was introduced in 1923. RockyMtnGuy (talk) 16:36, 3 September 2014 (UTC)

"...some motorcycle enthusiasts argue that a "boxer" has only two cylinders and that a flat-4 is not properly a boxer." As a biker myself, I feel entitled to point out that motorcycle enthusiasts are not necessarily the best authorities on etymology! Arrivisto (talk) 10:07, 4 September 2014 (UTC)

I was merely trying to point out where the term "boxer" probably originated, even if it was tattooed and leather clad chain laden people whose knuckles drag on the ground when they walk. However, BMW refers to their flat twins as "boxers", while Porsche and Subaru refer to their flat sixes as "boxers", so I am disinclined to disagree with the manufacturers. I don't like the term "boxer" anyway, I prefer "flat" or "horizontally opposed" myself. RockyMtnGuy (talk) 21:33, 5 September 2014 (UTC)

F6 or H6

Is there any consensus between which is used in articles? Spacecowboy420 (talk) 08:27, 23 August 2016 (UTC)

Both are somewhat ambiguous. "F6" is ambiguous because Ford has a series of inline six engines it calls "F6", ostensibly for "Force 6", but Honda has a flat-6 motorcycle engine it calls an "F6". Subaru calls its flat-6 engines "H6", but an "H engine" is usually considered to be a pair of flat engines stacked together with the two crankshafts geared to a common output shaft in an "H" configuration. An "H6" in this configuration is infeasible (Two flat-3s geared together?) but H4's, H8's, H16's and H24's have been built. The H4 configuration for motorcycles is interesting because it consists of two horizontally opposed boxer twins stacked together, which is the most vibration-free configuration possible for a four cylinder engine.RockyMtnGuy (talk) 17:03, 23 August 2016 (UTC)

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Rocking couple

'Also, when used in a boxer configuration, a flat-six engine does not have the rocking couple that is present on flat-four engines.'

The [2] reference points to an article that disagrees:

'A flat (“180-degree V”) engine, such as a Subaru four-cylinder, also can be perfectly balanced. To counter the rotational and reciprocating forces, the cylinders in one bank move in exact opposition to those of the other, thereby completely canceling the forces created by each.'

Can I correct this? Derekburgess (talk) 15:26, 14 June 2021 (UTC)