Talk:Flat engine
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[edit] A new opinion on terminology
Here are definitions which I have always accepted"
A "V Engine" is a piston engine with two cylinder banks (therefore, at least two cylinders) sharing a common crankshaft and arranged in a "V" shape (that is, the included angle between banks is less than 180 degrees).
Note that this definition does not require opposing pistons to share a crank pin, nor does it permit a "180-degree V" engine, which is a contradiction in terms. This seems to go against the prevailing opinion on Wikipedia, but can anyone quote an authoratative source that refutes my definition? I always thought that the definition of a V engine was connected to the name - cylinders in a V shape.
A "Flat Engine" is an engine where all the cylinders lie in the horizontal plane. For common engine designs, this would be synonymous with a "horizontally opposed engine" and also a "boxer engine." The trouble, I suppose, is when one considers exotic designs that have probably never been ever manufactured and then tries to categorize them. For example, if one tried to classify an engine with a single bank of four cylinders, pointing sideways, would it be called a "flat" engine or an "inline four engine laid on its side?" Personally, I would call it the latter. For all intents and purposes, it behaves like an inline engine, so we should call it that. It would be misleading to call it a "flat" engine because the only automotive engines currently in large-scale production (at least in the US) that are called "flat" are horizontally opposed engines from Porsche and Subaru, and they all have two cylinder banks.
The same thing applies to engines with opposing pistons, sharing a combustion chamber, with two crankshafts. I fully understand these are legitimate designs, but I have never heard of them being recently produced in large quantities anywhere. If there is an inconsistancy in the terminology, we should structure the article so it is consistant with the majority of engines and the biggest engine manufacturers.
My library of engine books is currently at work. My plan is to, sooner or later, go through them to review the terminology and edit the article as necessary. In the mean time, anyone care to respond to this?
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Didn´t the original beetle had an engine like that?
- Yes. —Morven 06:29, 8 Mar 2004 (UTC)
IMHO The Ferrari Testarossa does not have a real flat, but 180°-V-Engine.--217.187.67.229 23:33, 21 Mar 2004 (UTC)
- In my understanding of things, a 180 degree V is a flat engine, but it is not a boxer engine. —Morven 06:03, 22 Mar 2004 (UTC)
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- Interesting discussion. The same discussion is currently also on the German version Diskussion:Boxermotor. But due to in German, there doesn't exists a correct translation of flat engine (it translates to Boxermotor, too), the very interesting question about the difference between a flat engine and a boxer engine is missing. I expect "flat engine" to be some more generalized term while boxer engine and 180° V engine include both a statement on the position of the crank pins and pistons on the crankshaft as already explained in the comparision between the boxer engine and 180° V engine in the first paragraph.
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- The big question now is: Shall this page become split into three: Flat engine (some kind of overview page), Boxer engine and 180° V engine? --XTaran | Talk 00:41, 25 Mar 2004 (UTC)
[edit] Clarification
In a true boxer engine, the pistons are boxing each other, which means there is one looooooong cylinder for one pair of pistons. The two piston heads are facing each other and share one common combustion chamber. These engines have two main crank-shafts, obviously. They are essentially two inline engines made into a siamese twin by merging at the head. Such engine is used in some medium battle tanks (japanese I think) and are usually of the two-stroke principle.
In a flat engine (180 degrees Vee engine) there is one separate cylinder for each piston, because the pistons are boxing away from each other. These engines have a single crankshaft, these engines are siamese twins made of two inline engines "merged by the foot", so to say. These engines are used in Porsche and some 1980's Ferraris.
- And, I'm afraid I think you have this quite wrong. The Volkswagen Beetle is an example of a boxer engine, probably the most famous yet, as are current Suburu cars and the classic BMW "knee-warmer" motorcycle. What you are describing above as a true boxer is an opposed piston engine, a completely different design to a horizontally opposed engine, which is another name for boxer engine.
- I mostly agree with the authors above. A boxer engine has (nearly) opposing pairs of cylinders, and each pair is on a pair of crank pins (big-ends) that are 180° out of phase, so that the two pistons of the pair reach TDC similtaneously.
- A V engine on the other hand has one crank pin per pair of cylinders, so if the V angle is 180° (and there's nothing to say it shouldn't be) then the two pistons will reach TDC 180° apart. This is not a boxer engine, but a 180° V engine.
- It seems agreed that a boxer engine is a type of flat engine. But is a 180° V engine another type of flat engine, or is the boxer the only type? Some authors definitely say it's not, but I'm not impressed. Many other knowledgable writers describe the Ferrari Berlinetta Boxer and Ferrari Testarossa engines as being flat 12 configuration (but nobody AFAIK calls them boxer).
- I'm inclined to think that the attempt to say that 180° V engines aren't really flat engines is overly pedantic (which is not uncommon among motoring writers IMO). It might also stem from the difficulty in translating between English and German; It seems that there is no term in German for flat engine apart from Boxermotor, which of course means boxer engine. Andrewa 13:22, 27 September 2005 (UTC)
- A Flat engine is an engine that lies flat, regardless of whether it is a "180deg V engine" or a horizontally opposed engine. A boxer engine is a completely different thing with two pairs of crankshafts and pistons facing each other. A horizontally opposed engine is an engine which has on crank pin per piston with the pistons facing left, right, left, right etc. The pistons in a horizontally opposed engine move towards each other then away from each other and so on. A 180 degree V engine has two pistons per crank pin and move together in unison.
I hope that clears it up for you
[edit] Another attempt at standardising terminology
There seems no consistency across Wikipedia on this at present.
A summary of the issues:
[edit] V engine
In a V engine, do the corresponding cylinders necessarily share a single crank pin?
In a V engine, can the angle between the cylinder banks be 180°?
If yes in both cases (as I suspect) then all is well.
But if no to the first and yes to the second then we have a problem, in that all flat engines would then become 180° V engines, which I don't think is the case.
[edit] Boxer engine
In a boxer engine, do the pistons in corresponding cylinders necessarily reach top dead centre similtaneously?
If yes (as I suspect) then there is a translation problem between German and English, in that the German boxermotor would mean flat engine in English, but the obvious translation of boxer engine would be wrong, as in English boxer engine means something more specific.
If no, then perhaps there is such a thing as an engine that is both a boxer engine and a V engine.
[edit] Flat engine
This seems relatively straightforward and general. However the term is defined, any boxer engine is also a flat engine. If there is such a thing as a 180° V engine, then it is also a flat engine.
Comments? Andrewa 12:54, 26 October 2005 (UTC)
The Fiat 500 Giardiniera (1960-1976) uses an in-line air-cooled twin lying flat under the rear floor. Deconstruction 21:39, 8 February 2006 (UTC)
[edit] Cleanup needed
I would like to edit this page and clear up the misinformation and confusion. Here are a few points:
1. A "flat engine" comprises two types: a horizontally-opposed engine (boxer), and the non-boxer type (that the article calls 180 degree V). American car magazines such as Road & Track refer to both boxer and non-boxer types of flat engines as flat engines.
2. It is not a distinguishing characteristic of V engines that the crank pin is shared. A five-minute search on Google can confirm this. It may be true that all currently-produced flat "180 degree V" engines have this characteristic, but I doubt it's a requirement.
3. This sentence from the article is ambiguous: "Flat engines with more than eight cylinders are most commonly V engines." Does it mean "180 degree V engines" (i.e. non-boxer type) or does it mean V engines with some angle (e.g. 60 degree or 90 degree)?
4. It seems that the true distinguishing characteristic of boxer vs. non-boxer type of flat engines is the "horizontally-opposed" nature of them. If we can get agreement on this item, we'll be closer to a consensus.
It would be nice to gain consensus on this topic so that we can clean up this article.
Erikvcl 23:33, 29 January 2007 (UTC)
[edit] Two definitions
If there are two definitions of a V-engine then we should explain that, and then we should just be clear which one we are using in each case. This article and the V-engine article are very confusing. --Gbleem 20:16, 22 August 2007 (UTC)
[edit] Standardising
I copied information from the wikipedia page on 180 V engines to further show the difference between, a V engine and a "boxer" flat engine. This also helps the articles be inline with each other in content. —Preceding unsigned comment added by Lossy (talk • contribs) 14:14, 23 October 2007 (UTC)
[edit] Engine Deficiencies
A mechanic recently explained to me several deficiencies in this engine. These include the oil pooling on one side of the engine and the combustion of the gas, which is injected into the cylinder, occurring primarily on one side of the piston. This results in a slight impact of the piston on the cylinder wall on ever power stroke. Eventually, this causes a decrease in engine life as the piston tends to go through the cylinder wall. I don't even know where to obtain professional verifiable sources for this but would welcome anyone expanding on this or finding sources for this.
Andrew M. (talk) 04:18, 18 January 2008 (UTC)
