engine mechanical schematic

[HBrannon]

i'm trying to locate a schematic for the third gen engine. my searches are tuning up nil. i don't believe there is a throttle plate on these engines, but i don't know how the air is metered either. the wastegate limits the max delta p, and the turbo's ability to generate boost is based on the right foot. it has been my understanding that my right foot merely controls the amount of fuel supplied to the cylinder (via the lift pump). so i speed up with more fuel, i slow down with less fuel. any help would be appreciated. thanks brannon.

 

[JApol]

The right foot determines how much fuel is being injected into the cylenders. When the fuel burns the air expands, as that air is being pushed out the exhaust system it expands again in the turbo thus spinning the turbine. As the compressor wheel turns it creates pressure. As pressure in the intake system builds a sensors sends a signal that is relative to the boost level. When the boost resches a certain level the ECM will open the waste gate allowing some of the hot exhaust gasses to bypass the turbine wheel, this makes the turbine wheel spin slower thus lowering boost.



What regulates the amount of air is how much boost there is at the time that the intake valve is open and how long its open for.

 

[cerberusiam]

i'm trying to locate a schematic for the third gen engine. my searches are tuning up nil. i don't believe there is a throttle plate on these engines, but i don't know how the air is metered either. the wastegate limits the max delta p, and the turbo's ability to generate boost is based on the right foot. it has been my understanding that my right foot merely controls the amount of fuel supplied to the cylinder (via the lift pump). so i speed up with more fuel, i slow down with less fuel. any help would be appreciated. thanks brannon.

Air is not metered in a diesel application. The engine receives a full air charge on every cycle. No throttle plate.



Fuel is metered based on APPS position to give the rpm needed to do what you ask it. Fuel is also metered on what boost pressures are reading. More boost equals more fuel to keep the combustion on stoichiometric lean side. The ECU contains fuel maps to regulate injection duration and timing based on mulitple inputs; rpm, APPS, air intake temp to name a few.



The fuel is delivered to the injectors by the rail which is pressurized by the injection pump. The lift pump in this case supplys the low pressure side of the injection pump to prevent fuel starvation.



The waste gate on the turbo is really a safety valve to keep the pressures in a realm that will allow the maximum performance for the maximum amount of time.



You are correct about your right foot. It not only controls speed, but, is a major contributor to overall economy also.





That help?

 

[HBrannon]

thanks for the quick replies. what happens when i'm rolling along at idle and go to WOT. does the engine go into a fuel rich condition prior to increased boost? an engine can accelerate in a fuel rich state, just not efficiently. there's no variable valve timing, so the valves have the same duration regardless, and cannot manipulate the amount of air going into the cylinder.



Cerberusiam, you mentioned injection timing. does the 5. 9L have multiple injection events? i know that the 6. 7L has some additional injection events on the exhaust stroke to aid the DPF in generating heat, and decrease fuel mileage.

thanks again,

Brannon

 

[rbattelle]

Air is not metered in a diesel application. The engine receives a full air charge on every cycle. No throttle plate.

From what I've read the Duramax and the Powerstroke engines actually have throttle plates!! Wacky, isn't it?

thanks for the quick replies. what happens when i'm rolling along at idle and go to WOT. does the engine go into a fuel rich condition prior to increased boost?

This is a great question. I believe on the electronic-controlled trucks with a MAP sensor the fuel metering is a function of boost (as cerberusiam points out), so mashing the throttle won't produce a massive rich condition. That's why there's very little smoke on these engines when you do that (assuming no fueling box is present).



The non-electronic engines (P7100 trucks) don't meter fuel flow as a function of MAP, so if you mash the pedal on those you get a ton of black smoke (rich condition) until the boost comes up. Right? I'm not sure about VP-44 trucks... they are electronically controlled, but I don't know whether they use a MAP sensor.

does the 5. 9L have multiple injection events?

Yes, the HPCR trucks do. All of them. 2003-2004 trucks have 2 injection events, 2004. 5-2006 trucks have 3, and I think 2006-up trucks have up to 5.



Ryan

 

[Wayne M.]

I believe the newer engines have throttle bodies to help manage EGR flow and little to do with the actual engine speed as we would think. I think the Liberty CRD has a throttle body as well.

 

[Semicrazy]

Wayne is correct, the newer engines have a throttle plate to manage EGR and to speed up engine warm up to help cold engine emissions.