Talk:Flat-plane crank

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Requested correction of various articles to stop calling any flat engine a 180 degree V engine

Even within the article of V engines, it specifies within that the designation refers to the shape of the cylinders when looking at the engine end on. That, by default, means that there is no such thing as a 180 degree V engine, because by that point, there is nothing to V, it is a flat plane, if you will. 32.212.104.223 (talk) 18:39, 9 July 2017 (UTC)[reply]

The usual choices are inline and V, the former being 4 and 6 cylinder, that latter 6 or more. What would you call a non-inline engine with two banks of cylinders 180 degrees apart? Are there any made? Gah4 (talk) 05:22, 25 February 2019 (UTC)[reply]

https://en.wikipedia.org/wiki/Flat_engine Isn't 180 degree cylinders called a flat engine or boxer? Ahevle (talk) 18:09, 15 October 2019 (UTC) — Preceding unsigned comment added by Ahevle (talk • contribs) 17:58, 15 October 2019 (UTC)[reply]

"inherently much louder" is dubious

The claim that flat-plane makes for a louder engine cites a Jalopnik article that attributes the effect to higher revs and lighter parts. To the extent being louder is due to higher revs, that's not "inherently" louder (it's only louder if you take it to high RPM). The Jalopnik article claim about loudness being due to lighter parts is a stretch (read the article and see if it sounds authoritative or if the writer is speculating). Flat-plane V8s nowadays are in sports cars whose exhausts are intentionally not designed to be as quiet as possible: a greater effect than any inherent loudness due to flat-plane. I would remove the "inherently much louder" statement unless a more convincing citation is provided. Tom239 (talk) 00:20, 4 November 2018 (UTC)[reply]

My understanding (which might be wrong) is that cross plane crankshafts give less vibration (suitable for road cars) and flat plane crankshafts enable higher revs (suitable for race cars which also typically have less restrictive exhaust systems) and therefore some of the loudness is guilt by association. However, a flat plane crankshaft effectively configures the engine as 2 groups of 4 cylinders, with cylinders firing in pairs. Which means you get 4 big bangs instead of 8 smaller bangs per revolution. The total sound pressure should be the same but the peaks will be higher for a cross plane. Not sure how much of this turns into perceived loudness. Stepho talk 12:15, 5 November 2018 (UTC)[reply]

A four cylinder four cycle engine fires every 180 degrees of crank motion, so no two fire at once. A flat plane V8 has two of those 90 degrees out of phase, so one every 90 degree of crank motion. But the firing order is not optimal for lowest vibration, as pistons on the same crank position (opposing), have to be either 90 degrees or 450 degrees apart in crank motion. Well, they also have to do that for the non-flat plane, but there are more choices. Flat plane means always alternating between cylinder banks, which isn't necessary for non-flat plane. Seems to me that equalizes the pressure on the two exhaust manifolds, which should be good. Gah4 (talk) 05:29, 25 February 2019 (UTC)[reply]

rev faster?

".. this in-line configuration allows for the engine to rev much faster..."

Why? Being in-line (inline?) doesn't help the revs. Because balance weights? This really needs expert explanation. PRR (talk) 02:03, 9 June 2023 (UTC)[reply]

Image in "Details"

I think the first image in the details section is a cross plane crankshaft. (1 & 4 are at 180 degrees and 2 & 3 are at 270 degrees) 71.38.136.221 (talk) 04:58, 14 June 2023 (UTC)[reply]

Do you mean the "computer generated" image? I just checked it and it shows a crank with angles roughly 45°, 225°, 225°, 45° with each throw being 45° above or 45° below the horizontal. Which is correct for a flat-plane crank. Admittedly, it is hard to judge the angles. Stepho talk 18:13, 14 June 2023 (UTC)[reply]