Petrol vs Deisel

[Cpl Carrot]

Can some kind grog please explain to me (in words of one or less syllable) the advantages and disadvantages of using a petrol engine over a deisel. The only thing I know is that deisel's don't ignite as easy as petrols but don't know why.

Thanks in advance and the rest

Cpl Carrot

[Brian]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Cpl Carrot:

Can some kind grog please explain to me (in words of one or less syllable) the advantages and disadvantages of using a petrol engine over a deisel. The only thing I know is that deisel's don't ignite as easy as petrols but don't know why.

<HR></BLOCKQUOTE>

Basically, the flashpoint of petrol is much lower than dieso. Petrol engines are easier to maintain but the fuel is more volatile and hence dangerous in a battlefield environment.

Diesel engines offer better economy and higher torque generally at lower RPM than do petrol ones. They also tend to be simpler to build but more difficult to develop to high horsepower.

Diesel engines tend to be more tolerant of vary fuel quality than most petrol engines as well.

All combatants used at various times, engines of both types. The Matilda II had two diesel engines. The M4 Sherman had varients with both diesel and petrol engines (and of various types). The Russians exclusively used, because the poor qualities of their fuels for the most part, diesels in tanks. The Germans experimented with diesels but tended to prefer petrol engines.

[Michlos]

On a little side note: During my service we utilized some russian MTLBs for troop transport. These puppies would run on basically anything that was flamable (we DID try a wide variety of different liquids.)

The APC would only do about 50 km/h in standard mode but after some of our techs worked a little with it they could get it to reach speeds around 100 km/h. Of course then it required better kinds of fuel

[PJungnitsch]

Big gas engines tend to run hot, go through a lot of fuel, and don't last very long.

Diesels tend to run cooler, are MUCH easier on fuel, and can last almost forever with proper care. The downside of extra weight is generally not a problem in machines that are heavy to begin with.

Heavy equipment from trucks to bulldozers to earthmovers is all diesel now. Diesels are hugely better for heavy slow machines in the same way as gas engines are hugely better for light fast machines like motorcycles.

[Cpl Carrot]

Thanks again for your replies. Now I may be wrong (quite likely) but does the diesel not require electrics to work (ie sparkplugs and the like) and can therefore work submerged or something, as long as the air intake is above water of course?

[Stixx]

Well no you couldn't exactly run them under water (I don't think). They still have altinators which are electrical and charge the batterys. The batteries are needed to run electrical equipment but i'd say tanks have some sort of back up.

Still you need electricity to warm up the fuel and turn the starter motor. Diesels have Glow Plugs instead of spark plugs.

Petrol engines are ignited by spark plugs which actually set the fuel alight.

Diesel engines ignite fuel by compression, but glow plugs warm up the fuel so that it ignites easier under compression.

Hope that helps.

[Wesreidau]

Hey, Carrot, this the same Carrot from Warbirds?

Well it's dyna (dynamo) here!

drop me a line you lazy bastard

1249731

And i'll whoop your behind at CM?

PeterNZ

[killa in manilla]

Deisel engines use something called a glow plug, instead of a spark plug, which is used in petrol engines. THe difference is that the glow plug minimally heats the air coming into the engine, the majority of heat to ignite the fuel is created when the air is compressed very fast and very hard. This compression is intended to heat the air to over 700 degrees f. Often times in cold areas, most often in WWII on the eastern front, the air would be too cold and the compression of the air would not cause sufficient heating, therefore the deisel would not ignite, and the engine would not start. In situations like this, it was necessary to use a specially designed starter to heat the air, and because these were few and far between, it would sometimes take hours just to start a small company of armor or transport.

The advantage of deisel over petrol is taht first, they get much better mileage, and therefore can go farther on each gallon. Also a deisel engine has far fewer moving parts, and therefore requires less maintenance.

[Subvet]

Another good thing about diesel engines is that they produce less carbon monoxide than a gas engine.

[Bruno Weiss]

Now now, it ain't gas. It's petrol. Just like it ain't aluminum, it's aluminium. Or, it isn't crevass, it's crevasse. Only thing bothers me, is I keep wondering what would make a wicket, sticky?

[Skipper]

Of course, glow plugs are only needed at startup, and there are 101 ways to start a diesel without using them.

Modern diesels are easier to maintain, exactly because they do away with electrical ignition.

[Subvet]

Right Skipper! I ran a big 12 cylinder Fairbanks-Morse diesel in the navy. That sucker didn't have any glow plugs and didn't need any electicity to start. A bit of compressed air, some diesel fuel, and 24 pistons 8 1/8" in diameter is all she needed.

[Hon John Howard MP LLB]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Bruno Weiss:

Now now, it ain't gas. It's petrol. Just like it ain't aluminum, it's aluminium. Or, it isn't crevass, it's crevasse. Only thing bothers me, is I keep wondering what would make a wicket, sticky?<HR></BLOCKQUOTE>

The Don (may he rest in peace) would have said moisture but having the greaest spin bowler in the world (av wickets per match or runs per wicket) in Clarrie would not have mattered...

[Cpl Carrot]

<BLOCKQUOTE>quote:</font><HR>Originally posted by PeterNZer:

Hey, Carrot, this the same Carrot from Warbirds?

Well it's dyna (dynamo) here!

drop me a line you lazy bastard

1249731

And i'll whoop your behind at CM?

PeterNZ<HR></BLOCKQUOTE>

Well I'm not and if you go around talking like that then I'm not surprised he has not replied to you.

[Gyrene]

The problem with Diesels in cold weather has nothing to do with the temperature of the air being taken in (The colder the better, as far as internal combustion engines are concerned), but it has everything to do with the fact that Diesel fuel has the nasty tendency to turn to jelly in very cold weather.

We had a nice diesel vs petrol discussion a little while back.

Gyrene

[Subvet]

Both gas and diesel engines will have problems with oil freezing up if something isn't done to prevent it. You always have the lube oil, no matter which fuel you use. Aren't there additives you can put into the diesel fuel to minimize this problem?

[PJungnitsch]

<BLOCKQUOTE>quote:</font><HR>The problem with Diesels in cold weather has nothing to do with the temperature of the air being taken in (The colder the better, as far as internal combustion engines are concerned), but it has everything to do with the fact that Diesel fuel has the nasty tendency to turn to jelly in very cold weather.<HR></BLOCKQUOTE>

Here in the 'Great White North' anyway, diesel gelling is relatively easy to sort out. Special winter fuel or additives to regular summer fuel all work (I think during WWII the Soviets got good at adding the right amount of gasoline or kerosene to the diesel to lighten it up.)

The big problem I'm assuming is diesel engines rely on the heat of compression to start them off, and that is just not as reliable or hot as an electric spark. For industrial engines here in the winter glow plugs themselves are marginal, therefore ether cans are everywhere.

Plus when they are going they are much slower to get up to operating temperature, hence all the idling diesels rattling around town all winter. Big truck engines especially are usually not shut off, but idle all night long outside motels and truckstops.

One of the disadvantages mentioned of the T-34 is that it took much longer to get it warmed up and going in the winter than German tanks that used gasoline engines.

[killa in manilla]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Gyrene:

The problem with Diesels in cold weather has nothing to do with the temperature of the air being taken in (The colder the better, as far as internal combustion engines are concerned), but it has everything to do with the fact that Diesel fuel has the nasty tendency to turn to jelly in very cold weather.

Gyrene<HR></BLOCKQUOTE>

not true Gyrene, it has everything to do with the temperature of air being taken in, because Deisel engines have no spark plug to ignite the fuel, a combination of what is called a glow plug, and the rapid compression of air is intended to heat the air to over 700 degrees F. if the origional air is very cold, <0 F. than those two actions will not be enought to heat the air and therefore start the engine

[killa in manilla]

but in addition the fuel does turn to jelly, but that is a different and unrelated problem. If the air was to be able to become hot enough, than the jelly would instantly turn to liquid and by the second turnover it would ignite

[Skipper]

> Right Skipper! I ran a big 12 cylinder

> Fairbanks-Morse diesel in the navy.

...

> and 24 pistons 8 1/8" in diameter

In ships it's a separate story, by the way. I for one wouldn't want the iron genny on my boat to work on petrol. Not even if it's half a price of a diesel. It's too dangerous in a small boat.

[Hanns]

I've worked with some diesel engines both in the military and civilian world. Diesels produce much more torque than gas engines but are much more limited in max RPMs thus less Horsepower. In cold weather a mixture of 20:1 diesel/gas or kerosene thins out the fuel enough so that it doesn't gel and won't damage the injectors. In the Army the Deuce and a halfs used a pretty anemic inline six that was multifuel capable. It had an electric tank mounted primer pump and an engine driven injector pump. A primary, secondary and final fuel filter and two oil filters. It could and would run on anything that was burnable but really seemed to like JP-8 fuel! Seemed to have about twice the grunt when running jetfuel. The Bradleys had a nice Cummins VTA-903T600 diesel. 903 cubic inche V-8 with 600 HP. Too bad the governor was set to a max speed of 42 mph. The newer M113A3s we started getting when I got out had a V-6 Detroit Diesel with a turbo and supercharger. Talk about get up and go on a light vehicle! Plus they had a steering yoke instead of the lateral sticks which was nice. Point being that the US military learned at least one lesson in WWII and most if not all of the vehicles are diesel now. Thanks Rudolph

[PJungnitsch]

<BLOCKQUOTE>quote:</font><HR>Right Skipper! I ran a big 12 cylinder Fairbanks-Morse diesel in the navy. That sucker didn't have any glow plugs and didn't need any electicity to start. A bit of compressed air, some diesel fuel, and 24 pistons 8 1/8" in diameter is all she needed.<HR></BLOCKQUOTE>

I helped overhaul (more like wash the parts for) a big diesel Belarus tractor engine once when I was still in school. V-12 with pistons like paint cans. The rumor was that the tanks ran the same engine.

Really interesting, apart from the size of the thing. Nothing was really balanced or shimmed inside, the philosophy seemed to be just make it a huge size and turn it slow, it would make the power needed and everything would hold together.

[Gyrene]

<BLOCKQUOTE>quote:</font><HR>not true Gyrene, it has everything to do with the temperature of air being taken in, because Deisel engines have no spark plug to ignite the fuel, a combination of what is called a glow plug, and the rapid compression of air is intended to heat the air to over 700 degrees F. if the origional air is very cold, <HR></BLOCKQUOTE>

Very cold intake air might have some effect on diesel compression ignition, but even a 60 degree variation in intake air temperature is not much compared to the 600+ variation between air temperature at BTC & TDC.

Cylinder Head Temperature is also a factor in this, the relatively small mass of air entering the cylinder is far easier to heat up (And 20:1 compression will heat it up regardless of outside temperature) the the much larger mass of the Cylinder Head, which is counted on to provide part of the heat required for combustion during normal operation (CHT being as high as 200 degrees F in some engines).

Until the cylinder head reaches normal operating temperature the glow plug will be required.

Of course this will take much longer in very cold weather.

Gyrene

[MikeyD]

The big air-cooled V12 diesels in the post-WWII M60 series tanks (perhaps to be seen in CM5?) look suspiciously similar to diesels on wartime Japanese tanks. I've never seen this mentioned in print but I bet the U.S. tech guys ventually 'borrowed' the air-cooled V diesel concept after doing tests on captured Japanese equipment.

[Slapdragon]

<BLOCKQUOTE>quote:</font><HR>Originally posted by MikeyD:

The big air-cooled V12 diesels in the post-WWII M60 series tanks (perhaps to be seen in CM5?) look suspiciously similar to diesels on wartime Japanese tanks. I've never seen this mentioned in print but I bet the U.S. tech guys ventually 'borrowed' the air-cooled V diesel concept after doing tests on captured Japanese equipment.<HR></BLOCKQUOTE>

Actually they are a progression on the large air cooled designs of WW2. By this time tank engines were no longer stock units but designed specificallyu for the tanks they sat in, so the designs were changing rapidly, but the engine basics came about in WW2.