# Diesel Engines **URL:** \ **Category:** Factual Questions\ **Created:** [January 4, 2008, 4:26am UTC](https://boards.straightdope.com/t/diesel-engines/432236 "2008-01-04T04:26:07Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [January 4, 2008, 8:40pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/21 "2008-01-04T20:40:44Z")
[QUOTE=Balthisar] Just for the record, European diesels were just as bad as American diesels back when the Americans were playing around with the idea. The difference is, the Europeans didn’t give up. Current European and American diesels are still relatively dirty. Newer generations of American diesels will be vastly cleaner than European diesels, though. [/QUOTE] Right. Because American gasoline engines are so much better than European ones… :rolleyes: Also, to answer the question, diesel cycle engines _do_ produce more particulate emissions (and nitrogen oxides), and do smell a little worse (subjective, of course). In Europe, diesel fuel is subsidized much more heavily than gasoline, which is as much if not more of a consideration that whatever GM may have done to destroy the US diesel market. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [January 4, 2008, 10:03pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/22 "2008-01-04T22:03:51Z")
[QUOTE=Really Not All That Bright] In Europe, diesel fuel is subsidized much more heavily than gasoline [/QUOTE] I think this is true, provided “subsidized much more heavily” = “subject to lower taxes”. ---
**Author:** ![Myglaren](https://avatars.discourse-cdn.com/v4/letter/m/f1d935/32.png) [@Myglaren](https://boards.straightdope.com/u/Myglaren)\ **Post date:** [January 4, 2008, 10:24pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/23 "2008-01-04T22:24:31Z")
I can’t find a cite but recall that about a year ago “Top Gear” showed a Renault Formula 1 Diesel. ---
**Author:** ![Throatwarbler\_Mangrove](https://avatars.discourse-cdn.com/v4/letter/t/8c91f0/32.png) [@Throatwarbler\_Mangrove](https://boards.straightdope.com/u/Throatwarbler_Mangrove)\ **Post date:** [January 4, 2008, 11:08pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/24 "2008-01-04T23:08:17Z")
You are thinking of either [this one](http://en.wikipedia.org/wiki/Peugeot_908) or [this one](http://en.wikipedia.org/wiki/Audi_R10%5B/url). Both appeared on TG IIRC. ---
**Author:** ![Myglaren](https://avatars.discourse-cdn.com/v4/letter/m/f1d935/32.png) [@Myglaren](https://boards.straightdope.com/u/Myglaren)\ **Post date:** [January 5, 2008, 12:18am UTC](https://boards.straightdope.com/t/diesel-engines/432236/25 "2008-01-05T00:18:19Z")
No, neither of those, it was definitely a Renault. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [January 5, 2008, 1:19am UTC](https://boards.straightdope.com/t/diesel-engines/432236/26 "2008-01-05T01:19:48Z")
[QUOTE=Xema] I think this is true, provided “subsidized much more heavily” = “subject to lower taxes”. [/QUOTE] Ahem. Yes, that’s what I meant. :smack: ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [January 5, 2008, 2:33am UTC](https://boards.straightdope.com/t/diesel-engines/432236/27 "2008-01-05T02:33:09Z")
[QUOTE=Really Not All That Bright] Right. Because American gasoline engines are so much better than European ones… :rolleyes: [/QUOTE] Not sure what the rolling eyes are for. Everyone’s gasoline engines are about the same now, when talking mass market. Everyone’s gasoline engines back before the emphasis on diesel passenger vehicle engines were also about the same (mass market). Don’t forget that small engines and diesels are a response to gasoline pricing pressures. In the US, there was an oil embargo. In Europe, there were high taxes on gasoline but not diesel. Eventually the American gasoline prices got reasonable again, but that never happened in Europe. The love of diesel in Europe is entirely market driven due to fuel costs. Consequently the market demanded better and better diesel engines. There wasn’t the same market incentive in the USA, and so it was easier and cheaper just to give up diesel development for the USA market. Both GM and Ford have excellent, well regarded diesels in Europe today (they’re just not clean enough for the USA). In the USA, though, we didn’t revert to purely big V8’s and large-displacement V6’s due to CAFE. That was regulation driven, not market driven (cheap gas). Of course the Europeans _also_ got good, small-displacement gas motors too, because not everyone wants diesel. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [January 5, 2008, 4:50am UTC](https://boards.straightdope.com/t/diesel-engines/432236/28 "2008-01-05T04:50:46Z")
[QUOTE=Throatwarbler Mangrove] … and because diesel engines use direct injection, it is less sensitive to knock than a gasoline engine (I’m not 100% certain on the technical details of the last bit, maybe someone else can explain it). [/QUOTE] With a spark ignition (gasoline) engine, all the fuel is already in the cylinder when the spark ignites it. If the pressure exceeds some amount (depending on a LOT of variables) it detonates, causing a knocking sound. For non-gearhaeds, “knock” in this context means a rattling sound, nothing like knuckles on a hardwood door. A compression ignition (Diesel) engine, as you point out, uses direct injection. Ideally the fuel burns instantly as it is injected, and the burning rate is limited by the injection rate. What spoils this ideal is that there is a delay between the start of injection, and when the fuel first ignites. All the fuel that has been injected to that point then detonates, creating the characteristic diesel rattle (knock) sound. This IS detonation, but only of a small amount of fuel. While you can hear it, it doesn’t do the damage that full charge of fuel in a gasoline engine detonating does. Some modern Diesels inject a small initial “priming” charge, pause, then inject the main charge. Only the priming charge detonates, greatly reducing the noise. Beyond that mentioned above, Diesel engines do not detonate, regardless of cylinder pressure. Insanely “bombed” sport pulling tractors have run 200+psi of boost (multi stage turbocharging) with pure oxygen injection. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [January 5, 2008, 1:55pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/29 "2008-01-05T13:55:59Z")
[QUOTE=Kevbo] A compression ignition (Diesel) engine, as you point out, uses direct injection. Ideally the fuel burns instantly as it is injected… [/quote] Not \*instantly. \* Did you forget about the compression stroke? [repeat]Injection…compression…ignition…exhaust…[/repeat] ---
**Author:** ![smithsb](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smithsb/32/12107_2.png) [@smithsb](https://boards.straightdope.com/u/smithsb)\ **Post date:** [January 5, 2008, 2:21pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/30 "2008-01-05T14:21:38Z")
In so far as relative performance goes, I should point out that Audi has won the last two 24 Hours of Le Mans with a diesel powered race car. Maximum power might have been down slightly from previous race cars but the torque, simplicity, and fuel mileage gave the R10 a big advantage. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [January 5, 2008, 2:48pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/31 "2008-01-05T14:48:27Z")
[QUOTE=Musicat] Not \*instantly. \* Did you forget about the compression stroke? [repeat]Injection…compression…ignition…exhaust…[/repeat] [/QUOTE] The only thing being compressed is air. Fuel is then injected at the end of the compression stroke. > [@Wiki](#): > > Unlike a gasoline engine, which draws an air/fuel mixture into the cylinder during the intake stroke, the diesel aspirates air alone. Following intake, the cylinder is sealed and the air charge is highly compressed to heat it to the temperature required for ignition. [Cite.](http://en.wikipedia.org/wiki/Diesel_engine#How_diesel_engines_work) ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [January 5, 2008, 2:54pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/32 "2008-01-05T14:54:10Z")
Direct injection, mentioned in the post above, presented challenges along the way. It’s always been tough to master direct injection, and the successful progress of Diesel engines has a strong correlation to the ability to manage direct injection. Reliability issues have been solved (mostly), and with computer aided everything, the precision is now there consistently. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [January 5, 2008, 3:39pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/33 "2008-01-05T15:39:43Z")
[QUOTE=DesertDog] > [@Wiki](#): > > Unlike a gasoline engine, which draws an air/fuel mixture into the cylinder during the intake stroke, the diesel aspirates air alone. Following intake, the cylinder is sealed and the air charge is highly compressed to heat it to the temperature required for ignition. The only thing being compressed is air. Fuel is then injected at the end of the compression stroke. [Cite.](http://en.wikipedia.org/wiki/Diesel_engine#How_diesel_engines_work) [/QUOTE] I sit corrected. 🙂 ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [January 5, 2008, 4:32pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/34 "2008-01-05T16:32:10Z")
[QUOTE=633squadron] Railroad “diesel” locomotives are actually diesel-electrics: the diesel engine powers an electric generator which then feeds current to motors at each drive wheel. The generators don’t run at high speed but their torque requirements are enormous. Of course, electricity is used because you can turn an electric motor under load. [/QUOTE] That’s true generally. However, diesel-hydraulic units are becoming more common, especially for higher-speed, lower-load rail applications such as DMU (Diesel Multiple Unit) passenger rail cars. Diesel-hydraulic is also used widely in Japan, for some reason. ---
**Author:** ![Pushkin](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@Pushkin](https://boards.straightdope.com/u/Pushkin)\ **Post date:** [January 5, 2008, 5:16pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/35 "2008-01-05T17:16:49Z")
[QUOTE=dolphinboy] I own two hybrids and when I was in Germany last month they thought it was strange that anybody would buy a hybrid when diesels are cheaper and better (older technology). I don’t think any car company has been successful selling hybrids iagainst diesels n Europe [/QUOTE] I saw a few figures published in the motoring section of The Times some months back and hybrids beat diesels (just about) in city driving, so I suppose if you rarely venture beyond the suburbs, they’re worth it. Although IIRC Peugeot are working on a diesel hybrid. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [January 5, 2008, 5:16pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/36 "2008-01-05T17:16:59Z")
[QUOTE=TheLoadedDog] That’s true generally. However, diesel-hydraulic units are becoming more common, especially for higher-speed, lower-load rail applications such as DMU (Diesel Multiple Unit) passenger rail cars. Diesel-hydraulic is also used widely in Japan, for some reason. [/QUOTE] In the U.S. Krauss-Maffei tried out their line of German diesel-hydraulics and they quickly fell out of favor due to reliability issues. [Story](http://en.wikipedia.org/wiki/Diesel-hydraulic#Diesel-hydraulic) here (scan to the bottom of the paragraph). There are some industrial diesel-hydraulics puttering around on this continent but inless there have been some really recent developments, no main-line that I know of. In Germany, on the other hand, they are quite popular, easily outnumbering diesel-electrics. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [January 6, 2008, 3:08am UTC](https://boards.straightdope.com/t/diesel-engines/432236/37 "2008-01-06T03:08:13Z")
There are gasoline direct injection engines. Ford will be releasing them very soon in North America (in the automotive world, that means within 3 years). It’s a huge fuel savings, without some of the other disadvantages of diesel. Of course, there are new diesels coming out, too, clean ones, as I mentioned above. ---
**Author:** ![Sockmunkey](https://avatars.discourse-cdn.com/v4/letter/s/f17d59/32.png) [@Sockmunkey](https://boards.straightdope.com/u/Sockmunkey)\ **Post date:** [January 6, 2008, 4:42pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/38 "2008-01-06T16:42:50Z")
What about the two-stroke diesel? How common are they? Don’t they have the kind of weight/power ratio to outperform gasoline? ---
**Author:** ![Throatwarbler\_Mangrove](https://avatars.discourse-cdn.com/v4/letter/t/8c91f0/32.png) [@Throatwarbler\_Mangrove](https://boards.straightdope.com/u/Throatwarbler_Mangrove)\ **Post date:** [January 6, 2008, 5:16pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/39 "2008-01-06T17:16:47Z")
Heh, that’s bully for Ford. Mitsubishi started selling GDI engines in 1995, BMW, GM and Audi off the top of my head are offering them right now. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [January 6, 2008, 9:31pm UTC](https://boards.straightdope.com/t/diesel-engines/432236/40 "2008-01-06T21:31:20Z")
[QUOTE=Throatwarbler Mangrove] Heh, that’s bully for Ford. Mitsubishi started selling GDI engines in 1995, BMW, GM and Audi off the top of my head are offering them right now. [/QUOTE] I wasn’t meaning to say, “hey, good job, Ford.” Only to say, they exist, in light of this being mentioned as an advantage in diesel. They already exist in Europe from Ford, by the way. I believe the North American versions will be turbo only, too. [Previous page](https://boards.straightdope.com/t/diesel-engines/432236.md?page=1) [Next page](https://boards.straightdope.com/t/diesel-engines/432236.md?page=3)