[wagspe208]

I know engines...well race, gas and alcohol anyway.
New to diesels. I understand them more or less...fuel, into chamber, ignites due to temp/pressure.
Question is terminology. The duramax is called a "direct injection" by many. Aren't all diesel engines direct injection? I think a common rail high presure is more correct.
These injectors are triggered electronically. (hence the common rail), and wiring to injectors.
Older diesels had individual lines running from the injector pump.? Timing was controlled by literally turning the pump? Correct?
Please help me out on a few terms here.
Also, what sort of timing do our duramaxes use? Stock? with programmers?
Thanks
Steve

 

[DURAtotheMAX]

I understand your confusion because it confused me for a while to until I saw many different pictures and cutaways of it...

A direct injection diesel has the injector "directly" in the combustion chamber of the cylinder. An Indirect injection engine has a separate little "pre-combustion" chamber thats connected to the main cylinder by a short little passage. The explosion happens in the little pre-chamber and then travels into the cylinder.

At least thats how I interperated the various things ive read, I could be wrong...

ben

 

[ziadmax]

That's how it was explained to me as well.

 

[Idle_Chatter]

That's exactly how it is on the 6.5TD engine. The injector shoots into a small chamber in the head and the ignited fuel enters the cylinder and piston bowl out of a slot opening from the pre injection chamber.

 

[wagspe208]

I see. I have seen "indirect injection" heads in my shop then. Those little steel cups are hard as hell. Can't cut them, need to be ground.
Steve

 

[erniew]

That is exactly the difference, alot of automotive diesel have pre-combustion chambers. The reason it is done this way is to reduce the noise, now with the electronically controlled sysems they can achieve this through up to 5 injection sequences.

 

[wagspe208]

so, are the injectors pulsed by pcm? Put another way, do the injectors pulse with every cylinder compression stroke, or are they simply "on" for a period of time with each stropke?
Does that make sense? Late here.
Wags

 

[malibu795]

so, are the injectors pulsed by pcm? Put another way, do the injectors pulse with every cylinder compression stroke, or are they simply "on" for a period of time with each stropke?
Does that make sense? Late here.
Wags

the ECM turns each injector when the cylinder is ready to fire. unlike the batch fire the the gas engine do. iirc the dmax has a trigger/crank wheel that tells the ecm whaat postion the crank is at and it(ecm) can tell when the next piston is ready to be fired.

unlike the gas efi/sfei which either fire bank to bank or odd and even cylinders

 

[rock_shoes]

With a 6.2 everything is mechanical. When line pressure reaches a certain point the injector opens up and pulses.

 

[Idle_Chatter]

With a 6.2 everything is mechanical. When line pressure reaches a certain point the injector opens up and pulses.

Yep, 6.2 and 6.5 have a mechanical pump that has eight individual plungers timed to the cylinders/pistons. As the piston comes up, that injector's plunger is pressurizing the injection line and injector until it "pops" and injects.

 

[wagspe208]

I understand they are controlled by the ecm. Is the injector on, then for so many milliseconds, then off until next compression stroke, or is the injector pulsed so many times for each compression stroke?
Wags
doesn't really matter, just wanted to know

 

[malibu795]

I understand they are controlled by the ecm. Is the injector on, then for so many milliseconds, then off until next compression stroke, or is the injector pulsed so many times for each compression stroke?
Wags
doesn't really matter, just wanted to know

the highlighted part is correct

 

[Lennox69]

now ,this is what i think so don't shoot...just my two rusty cents.....the direct injection which is at full cylinder pressure requires higher pressures, benefits are better distrubution of diesel to cylinder,burns better,but one bad draw back its expose to all the carbon crap from the burn that causes all injector to wear out. indirect injection (old school diease) has a mini chamber build like of the main cylinder ,therfor the pressure on the injector are less and the injector is not expose to great corbon deposits,draw back is noise and lack of power.

 

[rock_shoes]

Also the direct injection diesels with computer controlled injection get to have multiple injection events instead of one as with the old school indirect injection. Those multiple events make it possible to optimize the burn and are much more friendly for use with a turbo. One of the biggest reasons for the drastic increase in power over the last 5-10 years without much of a drop in fuel economy. It's also one of the reasons new injectors cost a mint compared to say 6.2/6.5 injectors.

 

[Idle_Chatter]

I understand they are controlled by the ecm. Is the injector on, then for so many milliseconds, then off until next compression stroke, or is the injector pulsed so many times for each compression stroke?
Wags
doesn't really matter, just wanted to know

Injectors are operated by solenoids controlled by the ECM. The injector is fed from a high pressure common rail that is continuously pressurized by the injection pump. At the correct timing and for the correct duration the ECM energizes the solenoid which lifts a plunger off an internal ball and allows high pressure fuel to flow to the injector needle and tip and inject. This allows very precise and variable computer controlled injection for both timing and volume. The HPCR system also allows "pilot injection" which makes a small early shot of fuel to start combustion in the cylinder just prior to the main shot. This is why the HPCR Dodges and Duramaxes (and any other diesel using the Bosch system) doesn't "rattle" like older diesels. High rpm doesn't allow sufficient TDC time to make two shots, so pilot injection cuts out and there will be a brief period of "diesel rattle". Basically, there is only one main injection shot and the pilot shot, no pulsations.

 

[Idle_Chatter]

now ,this is what i think so don't shoot...just my two rusty cents.....the direct injection which is at full cylinder pressure requires higher pressures, benefits are better distrubution of diesel to cylinder,burns better,but one bad draw back its expose to all the carbon crap from the burn that causes all injector to wear out. indirect injection (old school diease) has a mini chamber build like of the main cylinder ,therfor the pressure on the injector are less and the injector is not expose to great corbon deposits,draw back is noise and lack of power.

Close, but indirect doesn't have any less pressure than direct. They are both part of the cylinder and exposed to full cylinder pressure. They have to be, because cylinder pressure (and temperature) is what ignites the fuel and makes the whole thing work.

 

[wagspe208]

Man, now there are some answers. That's what I was curious about. The multiple shots per cycle thing.
Thanks
Wags

 

[malibu795]

Close, but indirect doesn't have any less pressure than direct. They are both part of the cylinder and exposed to full cylinder pressure. They have to be, because cylinder pressure (and temperature) is what ignites the fuel and makes the whole thing work.

and indirect injectors lift about 3000-5000 psi the IDI system iirc is less than 10k system verses the 23-26k that the CR diesel are at.

 

[Idle_Chatter]

and indirect injectors lift about 3000-5000 psi the IDI system iirc is less than 10k system verses the 23-26k that the CR diesel are at.

Yes but he said "cylinder pressure" not injection pressure.

 

[38388]

wow , there is some smart dudes on here !:cool2:
Tim