Talk:Detroit Diesel Series 71

24V-71
The article lists the 24V-71 as making far more power per cylinder than the smaller versions, is that correct? It seems unlikely that the specific output is 75hp per cylinder while the other versions reach at most 40hp per cylinder. Totensiebush (talk) 17:56, 15 June 2015 (UTC)
 * Any power you like, just set the blower gearing how you want and then live with the resultant reliability.
 * AIUI, there's no V24 71 series. For a very brief period in the mid-90s, Detroit and MTU were playing catch-up in the "who's got the biggest" stakes. Detroit's response was to bolt things together until it was a V24, then wind up the boost until it was greater output than the comparable MTU. Only a handful were built, and not since. Andy Dingley (talk) 18:51, 15 June 2015 (UTC)

71 cubic-inch cylinder
What are the bore and stroke of the Standard GMC 71 c.i. cylinder? Thanks in advance.


 * The cylinder bore of the 71 series is 4-1/4" (107.95 mm) and the stroke length is 5" (127 mm). WikiPro1981X (talk) 03:00, 16 August 2010 (UTC)

Single Cyliner 1-71 engine applications
I would like to see proof that the 1-71 was used only as a marine engine. I have seen a generator set that use the 1-71. Until then I am going to delete that entry. I have also added the 1-71 to the features list as well as displacement per cylinder. I have also changed the minimum horsepower to 15 as the 1-71 I have seen was rated at 15 horsepower. Thaddeusw 03:45, 21 March 2007 (UTC)

Role of Roots Blower
From the article:

"All versions were supercharged."

The term supercharged is incorrect.

The role of the blower on this (or any other 2 cycle Diesel) is to produce scavenging airflow. This is not supercharging, as the blower's capacity is carefully matched to the engine displacement so that a slight amount of positive air pressure is produced in the cylinders during the scavenging phase. This is done to prevent exhaust backflow into the blower, which could result in damage due to contaminants being introduced.

BDD 05:58, 17 June 2007 (UTC)


 * From a pure dictionary definition, "supercharge" is the correct term. Though I agree, "pressure charge" might be more accurate.  The definition appropriate to this case is "to provide air at greater than atmospheric pressure".


 * You are perfectly correct in the role the blower plays in the operation of a two cycle diesel, but the statement that the -71 series were all supercharged is linguistically and grammatically correct. The fact that a Roots blower can be (and often is) used to create considerably more than atmospheric pressure, doesn't mean that using "not much more than" atmospheric pressure isn't supercharging.


 * Bagheera 22:22, 10 July 2007 (UTC)

"...but the statement that the -71 series were all supercharged is linguistically and grammatically correct..."

Huh??? I'm not sure which version of English you use, but in my version supercharging refers to the mechanical elevation of cylinder pressure above atmospheric for the purpose of increasing engine power output. The scavenging role played by the blower on any two cycle engine does not result in any such effect. The blower's role is to purge the cylinder of combustion gasses and replace them with air. The slight pressure applied by the blower is a "protective mechanism" intended to prevent spent combustion gasses from getting into the fresh air side of the engine and possibly causing damage. Please get your facts straight! —Preceding unsigned comment added by Bigdumbdinosaur (talk • contribs) 06:23, August 28, 2007 (UTC)


 * Actually, my facts are quite straight. As is my use of the word "supercharge".  Please check any of the available on-line dictionaries and you will find the definition, as I indicated above.  While I agree the more common usage of the term is for increasing horsepower, that doesn't make the usage of the term here incorrect.  We agree on the use of pressure charging in a two stroke diesel.  The only reason I dug into the article there was because the previous explanation was a bit garbled. The only point of contention is the term "supercharger" - and considering how many -71 Roots blowers have found their way onto the top of Chevy Small Blocks, it's hard NOT to use the term in reference to them!


 * To clarify though, here is the definition as sourced from dictionary.com - full link http://dictionary.reference.com/search?q=supercharge&x=0&y=0

Dictionary.com Unabridged (v 1.1) - Cite This Source - Share This su·per·charge     /ˈsupərˌtʃɑrdʒ/ Pronunciation Key - Show Spelled Pronunciation[soo-per-chahrj] Pronunciation Key - Show IPA Pronunciation –verb (used with object), -charged, -charg·ing. 1.	to charge with an abundant or excessive amount, as of energy, emotion, or tension. 2.	to supply air to (an internal-combustion engine) at greater than atmospheric pressure. 3.	pressurize (def. 3).


 * Please note there's no reference to the reason the air's provided at greater than atmospheric pressure. Just that it is.  So, yes, my usage is correct for American English.


 * Cheers
 * Bagheera 18:22, 27 September 2007 (UTC)

BDD. I reverted your last edit in the main article. I realize you don't like the term, but supercharger is used correctly in the article. While a mild overpressure doesn't meet your personal definition of "supercharge" as I've shown from the dictionary example, it is used correctly.

Cheers Bagheera (talk) 03:15, 18 November 2007 (UTC)


 * Well, it appears obvious, BDD, that you have no interest in actually discussing your point. I have removed your irrelevant and pretty much inappropriate comment from the body of the article, and left your edit intact.  If you wish to discuss how the article should read, that's what the talk page is for.  Including your personal (and inaccurate: see definition of the term in question above) opinion of the word usage in the body of the article, isn't really appropriate.  I don't care enough about the phrase to get into a revert cycle with you, but you could at least make your point on the edits in the appropriate venue.


 * Cheers
 * Bagheera (talk) 01:37, 20 November 2007 (UTC)

Bagheera,

Using the word "supercharged" is still incorrect regardless of what you think; the "definition" you provided is inaccurate. "Supercharging" in the context of combustion engines refers to forcing an air or air:fuel charge (key word) into the engine which is greater than what the engine is capable of taking in w/o assistance. i.e. "supercharging" means "raising the volumetric efficiency of the engine to greater than 1.0." In the case of the Detroit two-strokes, the engine cannot run w/o the Roots blower, therefore the blower itself defines the base volumetric efficiency of the engine. Adding turbo(s) to the engine prior to the Roots blower then makes the engine supercharged.

While I'm at it, the article uses "positive displacement" incorrectly as well. Roots blowers are considered "postitive displacement" because they are simple air "pumps" and not "compressors," i.e. they just push air. Lysholm and centrifugal are examples of compressors. Jz78817 (talk) 19:13, 27 December 2007 (UTC)

I've just had a look at my DD parts books, and they clearly refer to the "blower", not the "supercharger". islandeagle 17 December 2008 —Preceding undated comment was added at 00:34, 18 December 2008 (UTC).

4-71
The restored 1946 Coast Guard Motor lifeboat CG36500 (www.CG36500.org) has a Detroit Diesel 4-71 engine that was completed on November 20th, 1948! The engine has been rebuilt at least once and is in excellent operating condition.24.91.205.56 (talk) 14:08, 26 April 2008 (UTC)

Number of cylinder heads on V-12
The statement "The three largest V units used multiple cylinder heads per bank to keep the head size and weight to manageable proportions, the V-12 and V-24 using two and four heads from the inline six cylinder model" in the article doesn't make any sense. If the V-12 used cylinder heads from an inline-6, it would only be one per bank, not multiple cylinder heads per bank.PerDaniel (talk) 17:49, 21 August 2011 (UTC)
 * So what? The V16 & V24 had multiple heads per bank, the V12 had one per bank. The wording isn't particular confusing. Andy Dingley (talk) 19:48, 21 August 2011 (UTC)
 * So the first half of the sentence is wrong; the "three largest V units" did *not* use "multiple cylinder heads per bank" -- only the two largest (the V-16 and V-24) did. That's not only confusing, it's erroneous.  (The second half of the sentence, which states that the V-12 used two heads from the inline 6, is of course correct.) 64.81.73.35 (talk) 04:08, 30 December 2011 (UTC)

V32

 * 1) I read somewhere there was a 32 cylinder engine for a short while. Perhaps this is part of the aforementioned race with MTU?
 * 2) (On the other hand I don't know how this could work because MTU engines were much larger. To my knowledge the 396 series were the smallest engines at that time (there was a 331 series for tanks only). 396 is the displacement in centilitres per cylinder (= 3.96 litres(cyl) and they had 6 to 12 cylinders and turbocharging at an early time.)--Wolle1303 (talk) 19:30, 11 February 2020 (UTC)