Talk:V8 engine

message: Recently  changed the following:
:Medium-weight trucks tend to use the straight-6 configuration since it is simpler and easier to maintain, and because the straight-6 is an inherently balanced layout which can be scaled up to any size necessary. Large V8s are found in the larger truck and industrial equipment lines.
to:
:Trucks tend to use the straight-6 configuration since it is more economical, and have the potential for more torque for a given displacement. The straight-6 is an inherently balanced layout which can be scaled up to any size necessary, but despite of this V8s are found in large truck and industrial equipment lines, as well as in small to medium duty trucks. Having the potential for more hp than the 6 cylinder engine, the V8 may outrun it until the weight of load and steepness of hill combined exceeds a certain limit that may not exist in real life, while still maintaining good economy due to that its working cycle has no negative torque.
I reverted it with the comment "Revert good faith edit. Your reasoning doesn't always follow. Why does an inline-6 have more torque? Why does a V8 have a limit that doesn't exist in real life?" RP left the following comment on my talk page:
:Because a 6 cylinder engine will have bigger cylinders and/or longer stroke than a V8 with the same displacement. 1 cylinder engines have the biggest possible torque potential for any given displacement. The more cylinders an engine has, the bigger the potential for much hp, simply because it can turn faster. The limit may not exist in real life simply because trucks dont normally have that heavy loads and when they dont the engine with more hp at that rpm range gets on top of the hill first. Why do you think this is a product of "own reason" ?
I have shifted his comment here so that others can point out any flaws in either of our arguments.
Simple one first. I said "your reasoning" because the changes were not self evident and had no supporting references. A 6 will indeed have bigger cylinders for the same total capacity, which is balanced by the V8 having more cylinders. Torque should be the same. Why would one big cylinder have more torque than several smaller cylinders totalling to the same capacity? Assuming the same total capacity, why would more cylinders help an engine turn faster? An 8 cylinder would have a shorter stroke and smaller pistons (assuming bore/stroke ratio is kept the same), which would allow higher revs, but the better balance of the inline-6 also allows higher revs. The smaller V8 piston also puts a restriction on valve size, which would limit it compared to a 6 cylinder. So the upper limit is not a straight forward comparison to make and would rely on specifics on each engine (journal size, bore, stroke, valve size, valve lift, cam timing, induction, fuel and many other details). By negative torque I assume you mean small periods of time in the engine cycle when pumping losses and frictional losses are higher than the instantaneous torque produced by any currently firing cylinder. This depends very much on the burn time of a particular engine and depends on far more variables than just the number of cylinders. I don't necessarily think that you are wrong. But neither do I automatically assume you are correct. It must be either self evident or having supporting references so that laymen can follow without just taking your word (or WP's word) for it. Comments?  Stepho  talk  06:04, 13 October 2018 (UTC)
replies: text: While I neither agree or disagree with the above (some of it is above my head), it neither obvious, not referenced. Anything that is not obvious must be referenced, otherwise it can be deleted. Which does mean that many of the current statements that you find objectionable can be deleted if you think they are likely to be wrong, or tagged with  if you think they are likely to be right. The onus to find a suitable reference is on the editor who wants something to stay. Note also that the reference can't just be somebody stating an opinion. WP lives or dies by being able to support what it asserts. I offer https://books.google.com.au/books?id=DoYaRsNFlEYC&pg=PA46&lpg=PA46 as a starting point.  Stepho  talk  22:49, 18 October 2018 (UTC)
replies: text: Agree with Stepho, and in essence:  TL:DR - source please.  Chaheel Riens (talk) 11:46, 19 October 2018 (UTC)
replies: text: AFAIK both MAN and Mercedes have dropped their V8 (and V6 in the latter case) truck diesels in favour of straight-6 engines, leaving Scania as the only big (European) player with a V8 option.  Renault did offer the option of a Mack V8 in the Magnum but I don’t believe they sold many and they stuck to I6s when the T was introduced. Mr Larrington (talk) 17:51, 12 October 2021 (UTC)
thread_title:  v8 vs inline-6