As I know a lot about a gas engine to be somewhat honest I know my way around a diesel but do not know the ins and outs quite as well.
In a gas engine fuel is entered when the piston is at TDC or just before and then the ignition then boom the piston goes back down repeating itself.
Now my question... With a diesel being a compression ignition engine is the fuel added while the piston is at BDC giving it time to compress the fuel? Or is it injected at TDC getting thrown into the mix when all hell is breaking loose in the cylinder?
Thanks guys. I know it seems like a dumb question, I figure its only dumb if I don't ask.

 

how's this:

 

on the vdub diesels we would advance the fuel pump a hair when replacing timing belts- the earlier fuel would spool the turbo a lil quicker.

 

For some reason YouTube isn't loading on my phone.... Figures

 

Actually, in a 4 stroke Otto- Cycle gasoline engine...the fuel charge enters the cylinder during the intake stroke (while the piston is going down), then the intake valve closes, the charge gets compressed (piston moving up) and the spark plug fires a few degrees before TDC.

Modern diesel engines are direct injected so this means the fuel enters the cylinder whenever it's commanded to do so (via the calibration programming). The subject of injection timing is somewhat mysterious since many tuners don't really like to discuss those details. Generally speaking, the term SOI is used to talk about the Start of Injection and SOC is used to discuss Start of Compression since there is a delay between the two events. Some folks even talk about Start of Electrical Injection and Start of Mechanical Injection to talk about the delay in the injector component itself. At any rate, you'll have to talk to a tuner for specifics, but I am pretty sure the fuel is injected just slightly before TDC similar to spark timing on a gasoline engine.

The Ecoboost engine is more like a diesel than a gasoline engine so it's somewhat of an oddball in regards to timing. Revolutionary technology though...I expect all gasoline engines to be direct injected before too long. There are so many advantages to direct injection that it's hard not to go with that technology.

Another type of gasoline engine that is making a comeback is the Atkinson-cycle. Originally fell out of favor since they produce very low torque but are now becoming very practical with electric-over-gas vehicles such as the Ford Focus or Fusion Energi models. Since those cars are primarily electric vehicles, the Atkinson-cycle engine is a perfect choice since torque no longer matters (electric motors have a flat torque curve). However, even those cars have a faux Atkinson engine because they use elaborate valve timing vs an eccentric crank shaft so it's a hybrid of a hybrid (so to speak...)

 

for proper flame front propagation, diesel is injected before peak cylinder pressure. simple as that.

 

That's simple enough thanks guys.