Ok Mick8y, a vroum, vroum, vroum ? Might even be called a chug if slow
So which is it yours does Bert?
Is it a hanging back and then quick catchup.
Diesels are a bit prone to fuelling and throttle dependency - the quantities of fuel being injected are often so minute, and the way the charge is ignited and burns all being so dependent on spray pattern and timing, its perhaps not always what to do
The mechanical injection pump is a real marvel of modern engineering, that gives such good control over the engine's whole operating range can be taken for granted.
The slightest thing wrong though, the minutest leak or air bubble in an injector pipe, slight wear in the pump, can sometimes make an engine a different beast. Magic they work at all...
================================
Here's an out-take from a Sir Harry Ricardo lecture that reflects on that magic:
Let us imagine ourselves inside the cylinder of a Diesel engine, seated confortably on the top of the piston, at or about the end of the compression stroke. We are in complete darkness, the atmosphere is a trifle oppressive, for the shade temperature is well over 500C, and the atmosphere is very dense. Also it is very draughty, such that in reality we would be blown off our perch and hurled about like autumn leaves in a gale.
Suddenly, above our heads a valve is opened and a rainstorm of fuel begins to descend. In fact, the velocity of droplets approaches much more nearly that of rifle bullets than of raindrops! For a while nothing startling happens, the rain continues to fall, the darkness remains intense. Then suddenly, away to our right a brilliant gleam of light appears, moving swiftly and purposefully; in an instant, this is followed by a myriad others all around us, some large and some small, until on all sides of us the space is filled with with a merry blaze of moving lights; from time to time the smaller lights wink and go out while the larger ones develop fiery tails like comets; occasionally these strike the walls of the cylinder but being surrounded with an envelope of burning vapour they merely bounce off like drops of water spilt on a red hot plate.
Right overhead all is darkness still, the rainstorm continues and the heat is becoming intense; now we shall see that a change is taking place. Many of the smaller lights around us have gone out, but new ones are beginning to appear, more overhead, and to form themselves into definite streams shooting rapidly downwards or outwards from the direction of the injector nozzles. Looking around again, we see that the lights around are growing yellower; they no longer move in definite directions but appear to be drifting listlessly hither and thither; here and there they are crowding together on dense nebulae and these are burning now with a sickly smoky flame, half suffocated for want of oxygen.
Now we are attracted by a dazzle overhead, and looking up, we see that what at first was a cold rain falling through utter darkness has given place to a cascade of fire as from a rocket. For a little while this continues, then ceases abruptly as the fuel valve closes. Above and all around us are still some lingering fireballs, now trailing long trails of sparks and smoke and wandering aimlessly in search of the last dregs of oxygen which will consume them finally and set their souls at rest.
So ends the scene, or rather my conception of the scene, and I will ask you to realise that what has taken me nearly five minutes to describe may all be enacted in one five-hundredth of a second, or even less.
Sir Harry Ricardo lecturing to the Royal Society, 23 November 1931
(76 years ago tonight)
===========================================================
(posted in Syncro 23rd Nov, 2007) so will be 79 years very soon... the father of the high-speed diesel engine some would say, as well as father of many others. Today the firm still carrying his name remains at the forefront of research, development and dissemination of knowledge to the World's engine and motor manufacturers, as it was back then. He made significant contributions to both WW 1 (the engine for the first British tanks) and WW II (a list would be too long here).
If you run a VW TD diesel, then Sir Harry's genius is alive in your cylinder head, its Indirect Injection Pre-chamber was developed at Shoreham-on-Sea, during the mid 30's (patented as Comet). Ricardos are still there, at Shoreham.
.
