Talk:Detroit Diesel Series 71

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[edit] 71 cubic-inch cylinder

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

[edit] 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)

[edit] 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)

[edit] 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)