Talk:Straight-five engine

Crank Angles

Reading the article it's not apparent what the crankshaft of a straight-5 looks like.

I recall having it described by someone once as being like that of a 4 - except there's an extra middle crank sticking out sideways. This would imply an uneven fire engine, probably with crank angles of 0, 151, 255, 151, 0 (with #1 at TDC #2 is close to, but not at, BDC and #3 is close to, but not quite, half way). The firing times are then 151, 104, 104, 151, 208 with a 1 4 3 5 2 order.

However everything I've found while looking into this implies that straight-5 engines always use crank angles of 0, 72, 144, 216, 288 - and no attempt made to achieve any kind of dynamic balance at all, although even firing is acheived, probably with a firing order 1 3 5 2 4 and a power stroke every 144 degrees.

I don't know anyone who owns a straight 5, but could those of you who have seen the crank please note here what engine and what it was like? Thanks Number774 (talk) 21:58, 25 March 2013 (UTC)

Aha, so this is a "strawman" :) I have never seen an inline 5 crank, but the firing order on my Mercedes was indeed 1-3-5-2-4. This will indicate that the crank throws are advanced 72 degrees sequentially. I had to google the VW engine to find out about the 1-2-4-5-3 firing order. This will indicate that the VW crank is different from the Mercedes. I dont have knowledge of other I5 engines, but a Volvo one sounds significantly different from a VW or Mercedes. This could be due to the exhast system being different.

--83.191.149.201 (talk) 21:13, 29 March 2013 (UTC)

By closer inspection I have found myself to remember wrong regarding the firing sequence of my old Mercedes. I was sure and it also seemed the most logical as 1-3-5-2-4 would be the firing order of a 5-cylinder radial engine. And if you draw a diagram it will become a perfect pentagram. But there is perhaps a logic to it, if you read 1-2-4-5-3 backwards it will become the same, only 2 and 4 switched places. It is perhaps done to break the pattern and counteract bad harmonics, perhaps the rocking tendency I mentioned in the article.

--83.191.149.201 (talk) 21:55, 29 March 2013 (UTC)

I have seen a large stationary two-stroke diesel with the crank arranged like a conventional four plus one at an angle Designengineer (talk) 18:01, 11 September 2014 (UTC)

I have edited out "Unlike other engine configurations, the inline-five's sound can be approximated by doubling the cylinders" as it's impossible to ascribe any meaning to it. Designengineer (talk) 18:08, 11 September 2014 (UTC)

Sound

marking this for heavy revisal, the information in this section has little to do with the 5 cilinder and more to do with acoustics in general. --2601:248:C100:1C45:18FC:31DD:2FC8:3732 (talk) 07:55, 28 February 2016 (UTC)

Smoothness

I feel this whole paragraph is too wordy and it needs some serious pruning to become more concise. Arrivisto (talk) 13:27, 31 May 2017 (UTC)

Fueling

The premise of this section is nonsensical. Were it actually true that "the length of the inlet manifold between the carburetor varies too greatly ... for reliable and consistent fuel delivery", then it would be even more true of carburetted straight-six engines (of which there are many successful examples) and caburetted straight-eights and v-twelves. (of which there were several)

It may well be true that nobody ever built a successful straight-five engine with a carburettor, and that one such engine was unsuccessful, but I don't think there's any fundamental reason why this configuration couldn't have been viable.

Nor does there seem to be anything inherently problematic about a carburettor feeding an odd number of cylinders. The naturally-aspirated carburetted Corvair engine had one carburettor supplying three cylinders through a distinctly-asymmetrical manifold, with the carburettor located far from its center. Drcampbell (talk) 07:32, 4 December 2018 (UTC)

The problem of fitting carburettors to cylinder numbers is mostly about asymmetry. Some carburettors, more than others, have a strongly asymmetric mixture distribution across their outlet port. This is mostly a problem for single choke carburettors, such as SU, where one choke has to cope for all flow rates, compared to sequential choke designs where the range of flow rate per choke is rather less. So it's often possible to fit these carburettors to two or three cylinders, but their orientation also has to be the right way round for each grouping. For Webers there's the problem that the similarly-bodied multi-choke (DCOE or IDA) and sequential-choke designs had their throttle spindles 90° apart, so that the manifold design changes a lot between them, to avoid the asymmetrical mixture going preferentially to one cylinder. Tuning such a setup for racing, and swapping the "production" sequential choke to a twin-choke could need a whole new manifold.

For 5-cylinder engines, 5 is a prime number and so it's impractical to split the cylinders 2 & 3 between two carbs. It would be near impossible to tune such a setup and get equal cylinder performance. So that's either one carb of five throttle bodies. As injection was well established by the advent of the inline 5 cylinder engine, and was easier to set up than carbs, it just became the obvious choice. Andy Dingley (talk) 11:51, 4 December 2018 (UTC)

"This fueling issue was never present in diesel engines (except the Volvo D5) which..." Except the Volvo D5, what is meant by this? Does this refer to the problems with the fuel injectors of the very early examples? That's nothing inherent of fuelling, just a quality problem. Jeroen74 (talk) 17:45, 26 September 2021 (UTC)