Talk:Diesel engine

Diesel Engine Power and SIze

In the "Power and fuel economy" section, there's a paragraph saying that diesel engines have a lower power output than a petrol engine with the same size. This is not accurate. In Europe, in general, clean diesel engines do have a lower power output when compared to a same sized petrol engine. However, there are exceptions... BMW's diesel engines. The BMW N47 engine has a displacement of 2.0 L, but can deliver 204 PS. That 201 hp. There are petrol engines with the same displacement, that cannot deliver that much...

Also, I must point out the existence of diesel engines used in competition. The Audi R15 TDI (5.5L, 600 PS) and the Peugeot 908 HDi (5.5L, 730 hp) are evidence of this.

It's possible, with current engine technology, to make a similar sized petrol engine, more powerful than it's diesel counterpart. But reality demonstrates that there are diesel engines more powerful than a same-sized petrol engine (or even more powerful than larger petrol engines). —Preceding unsigned comment added by 82.155.143.227 (talk) 16:21, 22 June 2010 (UTC)

What many people do not realize is that diesel engines will develop a much higher peak torque than a petrol engine. They also generate the peak torque at a much lower RPM as well. Petrol engines typically develop about half (or less) torque than a petrol engine of equivalent horse power. So a 140HP diesel could outrun an 200+ HP petrol car. The engine weight is a bit of a problem though. The weight difference can even out the difference. Thaddeusw (talk) 23:41, 9 July 2010 (UTC)

You're completely wrong. Basically, because torque measured at engine (crankshaft) has to be demultiplied by the gearbox. Therefore, you can have a car with has a higuer engine-torque than another one, but less torque measured at the wheels because it has to demultiply itself much more due to it's engine running, for example, at lower rpm. This is why the horsepower is more important for racing: it's the same as speaking of energy output. Whether the energy is in form of torque or in form of "rpm" is completely irrelavant as long as you have a gearbox: you can transform rpm into torque and viceversa. Obviously, a more torquier engine could be more driveable in everyday situations but you are speaking about "outrunning" which assumes a race. In such a situation, you usually strech both engines to its max power ouput (rpm), making it irrelavant the horsepower (or torque) at its lower end. So no way a 140 bph diesel would outrun a 200 BHP petrol car, until it's gearbox configuration is totally screwed.

For example (the numbers are imaginary):

140 bph => 500 units of torque * 2000 rpm => 1:1 drivetraing demultiplication => 500 units of torque at the wheels (the wheels spinning at 2000 rpm) 200 bph => 300 units of torque * 6000 rpm => 1:3 drivetraing demultiplication => 900 units of torque at the wheels (the wheels spinning at 2000 rpm (6000 * 1 /3) Thus the latter outruns the former.

Look it from another perspective. Why a V12 6 litres engine outperforms a V6 3 litres? Because it burns twice the petrol (or produces twice the power) in the same space of time. Simple eh? Then, why a lot of people can't understand that you can burn more petrol in the same period of time by increasing the number of cilindres and displacement OR by burning it faster (more rpm)? I just don't get. It's the same thing yet people understands the former but not the latter....

— Preceding unsigned comment added by 37.14.162.34 (talk) 22:11, 18 March 2012 (UTC)

Why no mention of the Enfield diesel motorcycle? Surely it is worthy of note...? 86.14.187.220 (talk) 21:10, 24 April 2012 (UTC)Lancetyrell

Hydrolocking a diesel engine?? (Dubious)

The hydrolock page says that a diesel engine can get hydrolock from water in the injectors ... they don't have a reference showing where in literature that it does so (put a dubious tag on that page). Maybe it doesn't, maybe it does ..... (Personally I haven't seen this particular scenario (water in the fuel hydrolocking an engine) myself, although we did have an incident with a blown head gasket). 186.32.119.213 (talk) 16:50, 21 May 2012 (UTC)

It's quite easy to damage a diesel engine by hydrolocking it (a petrol engine will usually just stop instead), but you need to get enough volume of liquid in there to cause it. This is most commonly done by fording a river etc., and sucking water in through the air inlet.

If you fill the fuel tank with water, you will spray a tiny quantity of it in through the injectors. A _tiny_ quantity. Not a hope of being enough to hydrolock it. This is no more likely to hydrolock an engine with water than it is to hydraulically lock it with diesel fuel, if you turn the engine over cold and it isn't firing. There's not enough injected on each cycle, and remaining fuel or water is flushed out by the airflow fast enough to not build up appreciably.

As WP is not a reliable source, I've once again removed this addition. The fact that it's mentioned, uncited, at another article is no reason to propagate such an error. Andy Dingley (talk) 17:17, 21 May 2012 (UTC)

Images

Can someone revert the page to this revision. The "crosshead" link in the image needs to be changed to "Trunk piston", but the changing of the images sure was an improvement. 91.182.208.93 (talk) 13:09, 21 August 2012 (UTC)

Why? What advantage is conveyed?

Today you discovered the word "crosshead". You didn't learn what it means (you thought you did, you were wrong), but that didn't stop you spraying it across a number of WP articles. Now you think that adding "trunk piston" to a caption of an early MAN engine is useful. Why? What extra knowledge does this convey? Why is the trunk piston (which is, to be blunt, common as muck in IC engines) relevant to this particular engine? Andy Dingley (talk) 13:21, 21 August 2012 (UTC)

Compressor(s) needed for compression ignition

I was wondering whether a single turbocharger would be sufficient to create a high enough compression ratio/heat to ignite the fuel injected in the cylinder. The way I understand it, the compression ratio of a turbocharger is 2,5 X 10 (compression ratio of piston) = 25 (which should be high enough as we read in the article that "compression ratio is typically between 15:1 and 22:1 resulting in 40-bar (4.0 MPa; 580 psi) pressure compared to 8 to 14 bars (0.80 to 1.4 MPa) (about 200 psi) in the petrol engine. This high compression heats the air to 550 °C (1,022 °F)"

Am I correct to multiply the compression ratio's (rather than adding them up) ? And am I indeed correct in that a single turbocharger together with the action of the piston is sufficient to get allow the fuel to ignite (I'm not entirely sure as I read that Rudolph Diesel used a three-stage compressor (so basically 3 compressors) ?

If a single turbocharger isn't sufficient, let me know what needs to be added to allow the ignition to occur (ie add a screw compressor ?, or a mere Roots compressor, ...) 91.182.143.149 (talk) 07:27, 8 September 2012 (UTC)

I was wondering whether a single turbocharger would be sufficient to create a high enough compression ratio/heat to ignite the fuel injected in the cylinder.

That's called a gas turbine. If you abandon the piston, you can use a continuous combustion process (see Brayton cycle), where the cycle is spread out over space, not over time.

I have no idea if it's practical to reach auto-ignition temperatures for sensible fuels using this type of compressor. I 1) doubt it, and 2) very much doubt that it's worth it. If you have continuous combustion, then you can use a propagating flame front for ignition, you don't have to re-light on each stroke. Andy Dingley (talk) 08:15, 8 September 2012 (UTC)

history

this article does not mention herbert akroyd stuart who patented a compression ignition engine in 1890 and the first prototype was produced in 1891, these engines used an antechamber, the forerunner of the pre-combustion chamber and were the ancestors of the indirect injection engine but were not called diesels, as that is the name of the german, rudolf diesel, they were called 'heavy oil engines'.

Akroyd Stuart is already covered on WP and should certainly be part of the diesel timeline, as an oil engine, even if not a diesel, Diesel cycle, or compression-ignition engine. Andy Dingley (talk) 22:52, 8 October 2012 (UTC)

I've just removed a para on Akroyd Stuart from the lead. Coverage of his engine should:

• Make it clear that it's an oil engine, but not a Diesel cycle or compression-ignition engine.
• Not place comparisons with other things, outside the main scope, into the lead.

Andy Dingley (talk) 09:18, 12 October 2012 (UTC)

it is a 4 stroke engine the prototype was built in 1892, its not called a diesel engine because the bloke's name isn't diesel, and the engine runs on the diesel cycle, and is the predecessor of the indirect injection diesel engine, it's called a heavy oil engine, because the fuel wasn't called diesel, a vaporiser is used as to allow for a more moderate degree of compression , Diesel's only patentable idea was to increase the pressure.