I'm new to diesels (have owned my 1st for almost a year); however, I'm not new to gasoline trucks, cars or motorcycles. I have a few questions regarding diesel injection timing.

Can someone please help me fill in the blanks:

Typically the injectors in a diesel engine fire during "___ degrees BTDC and ___ degrees ATDC".

**I realize many parameters affect the actual timing and the timing directly affects performance.** I just want a real basic, general idea about the degree range at which the injectors will operate.

What I'm hoping to gain from this is a better understanding of the basic timing structure for diesel engines and then taylor it to a more specific application, i.e. our CTD's later in this discussion.

Thanks,
Eric

 

Injection timing has gotten way more complex with the introduction of the common rail system.

With the old systems, the injection timing was similar to gas in that the injection pump supplied one "shot" of fuel per cycle. This was very loud and less efficient.

With common rail engines, and the 610's more so, you can have up to 5 injection events. Pilot injection, that gets the burn going smoothly for less noise. 3 main injection events, and even post injection that helps burn off the unburnt fuel going out the exhaust port.

So now we have terms such as: Pilot SOI (start of injection) to Main SOI distance (in crank angle). 1st main soi to 2nd main soi and so on down the line.

This increased control of the injection event(s) allow for greater control of the combustion process yielding decreased emmissions, improved BSFC, and decreased noise. This type of control is why you have to have fuel systems capable of 20,000+psi. With five events, you have to open and close the injector much faster than the old injection pumps could supply.

Definitely not complete but might get you going.

 

EXCELLENT! Keep the info coming!

I know several injection events compicate things and I understand why they are valuable. I'm looking for a rough idea of when these injection events are applied (in crankshaft degrees) if that information is not proprietarty or somehow patented.

I'm not trying to build a box, I'm just curious.

MORE MORE!

 

from some of my school notes, a typical pilot injection will start/happen at ±25°BTDC and lasts 5° and the main fuel shot happens at ±0°(TDC) and lasts ±20°... that can all be adjusted by the ECM and if it is using more than the 2 shots, they can happen later than the 20°ATDC

 

WOW, talk about wasted fuel, that shot @20 deg ATDC can't be creating much hp.

 

nickleinonen,

What school did you go to, where, did you like it? Thanks for th info, that's exactly what I was looking for.

another question... it may be a stupid one. Do the injectors on our CTD's protrude into the cylinder at all?

Thanks guys excellent info!

Eric

 

What is BSFC

Eric

 

Waaay tooooo much information. I thought diesels were suppose to be a much simpler design than those darn gas engines I used to tear up. I expected a big cylinder, a head, valves that do their thing and a nozzle pumping in fuel when it was time to burn it.

If I keep reading this thread I might actually learn something.

 

Brake Specific Fuel Consumption - typically measured as grams of fuel consumed per brake horsepower hour produced.

Rusty

 

! That's the point. Great posts guys, I'm learning a lot. But I need MORE! MORE!

I know these injectors are electromechanical. Being the nerd-geek that I am, I often wonder how these things function. I have a very basic understanding of the components contained within the injector. I believe they are as follows (PLEASE chime in if I missed something, or am just plain stupid).

1. Housing - provides the port for fuel to pass into the cylinder.
2. Pintle - the "needle" that moves within the housing and seals agiant the housing until forced to move and inject fuel.
3. Coil assembly - electrical component which applies force to the pintle
4. Seals, o-rings, etc....

It seem unreal to me that electromachanical components can open an injector with 26,000 PSI behind the injector pintle. SO I thought there could be two ways to do this.

1. I would think the injector pintle has such a small surface area in contact with the high pressure fuel (up to 26,000 PSI on the back side of the injector) that the injector pintle does not require much force to get it to move and open the port. Am I on the right track?

2. Does anyone know how much power these things draw (or current and voltage levels would be good).

3. Does the pintle move in a verticle direction or do they get torqued/pushed to the side to expose an opening?

MORE MORE!

Eric

 

right now i am in school at centennial college in toronto ontario canada for my level 3 program for my heavy equipment apptentice program. ±8 weeks from now i should be a licenced HD mechanic if i can pass the testing... the school is ok... i'd like to see more lab time than we get now, but there is so much theory to cover there isn't too much time to spend in the lab. the engine lab is pretty well equipped with newer and older engines [they have brand new ISBe and ISX engines ] to learn on, but i never work on anything that small at work... the smallest engine i work on is just over 7,700 CI [12 cylinder - 645ci x 12] and largest being near 13,000 CI [20 cylinder 645ci x 20]

 

wow sissy motors huh?

Are these huge diesels for backup or striaght power generation?

eric

 

locomotive prime mover diesel engines... all they do is spin a generator/alternator and some accessories... them little 12's make 1200 hp and the 20's make 3600hp... we've got some others too, 16's with 710ci per hole making 4300hp and our GE loco's make 4500hp on the engine [i am not really sure on the engine size for the ge's, but they are somewhere in the 10,000-12,000ci range]

GE's are 4 cycle engines, the others are EMD's, 2 cycle engines...

some pictures from work

 

Whoa, 4500 HP from a piston engine! Nice. I'm amazed to see a piston engine get into those numbers.

I'm in the power gen. industry, hydroelectric generation end. We see a lot of diesel backup generators for our powerplants. It's good I know a little bit more about them.

It's amazing the scale of things, our biggest hydroelectric generators (Grand Coulee, WA) are around 826 MW (826 mega-Watts) which translates to 1,107,684 HP - however, HP numbers are not typically used to describe power output or levels in our industry. The size of these things and the turbine shaft to withstand the power - !

Eric

 

Would that be cn or cp? I want to say cn but I think cp's logo starts out the same....