Common rail vs mechanical injection

[jyoutz]

Interesting that the "efficiency" myth continues after the whole dieselgate thing.

High pressure common rail is not any more efficient than mechanical. The injector nozzles determine the maximum flow and pattern.

However, the Teir 4 version if that tractor will seem more efficient as it utilizes a turbo. By under tuning and requiring the turbo to activate for full power there is a perception of fuel economy.... at a significant parts and maintenance costs when something fails.

So if you want to pay a few dollars less to refill the tank and a few hundreds more maintaining, that would be the version.

There has been very little advancement in diesel efficiency in the last 50 years other than a rotary diesel engine that was released a year or two ago (half size, same power density).

I have had lots of diesel motors, and never a turbo failure.

 

[jyoutz]

Turbo rebuild is 500+ plus all of the piping, so around 1k.

Turbos are killed faster when shutdown hot. Idle for half an hour so they cool down kills any savings.

Average turbo life is measured in 100s of hours before the bearings wear out.

Will never buy a turbo diesel again.

Nobody idles a diesel turbo for 30 minutes prior to shutting down. Less than 5 minutes is good. I’ve had several diesel turbo trucks and cars with hundreds of thousands of miles on them. Never a turbo failure.

 

[Hay Dude]

Glad all your diesel turbos are good. Have one turbo gas engine, will be the last turbo I own.

If I want extra I'll stick with a supercharger, at least they are reliable and perform on demand.

You better rethink that. Super chargers are virtually unavailable on tractors and vehicles. They absolutely can fail and they are parasitic on power

 

[RickB]

I'm betting a newer common rail tractor with DPF, doesn't get as good fuel economy as a non common rail DPF tractor.

No betting required. Nebraska tractor tests have HP hours per gallon as a measure of efficiency. OECD tests have similar data.

 

[jyoutz]

But they aren't as fuel efficient as newer diesels without emissions.
Cummins 5.9 without DPF gets better mileage than the newer 6.7 with DPF

I'm betting a newer common rail tractor with DPF, doesn't get as good fuel economy as a non common rail DPF tractor.

My 5.9 Cummins gets about the same mpg as the newer 6.7 with dpf, but the 6.7 puts out more hp and torque.

 

[rScotty]

Interesting that the "efficiency" myth continues after the whole dieselgate thing.

High pressure common rail is not any more efficient than mechanical. The injector nozzles determine the maximum flow and pattern.

However, the Teir 4 version if that tractor will seem more efficient as it utilizes a turbo. By under tuning and requiring the turbo to activate for full power there is a perception of fuel economy.... at a significant parts and maintenance costs when something fails.

So if you want to pay a few dollars less to refill the tank and a few hundreds more maintaining, that would be the version.

There has been very little advancement in diesel efficiency in the last 50 years other than a rotary diesel engine that was released a year or two ago (half size, same power density).

I disagree. Common rail & computer control is much more efficient. If you study up on it you may change your mind.

Just think about how much advantage the higher injection pressures of the electronic injectors gives by providing better fuel vaporization. When the fuel burns better it allows for direct injection and less fuel used. That's the definition of efficiency.

That said, the only failures we've had with our diesel tractors and trucks in the last 25 years all involved common rail systems and electronics.
rScotty

 

[CausticUrbanCoast]

I disagree. Common rail & computer control is much more efficient. If you study up on it you may change your mind.

Just think about how much advantage the higher injection pressures of the electronic injectors gives by providing better fuel vaporization. When the fuel burns better it allows for direct injection and less fuel used. That's the definition of efficiency.

That said, the only failures we've had with our diesel tractors and trucks in the last 25 years all involved common rail systems and electronics.
rScotty

Higher pressure allows higher pressure injectors which allow them to open and close faster. Higher pressure injectors have larger nozzles to deliver more fuel because they open and close faster. Hydraulic and electrical control allow injector solenoids to open and close faster and are also timeing advanced based on load - so they are variable timed injectors.

On pressurized rails with electronic or hydraulic injectors, the diesel compression is lowered from the normal 21->23:1 ratio incase there is a miss. Most mechanical diesels have been running at 21 through 23:1 for almost the last century. (Theoretical maximum is 25:1).

I never disagreed that higher volume injectors could be used more efficiently than lower volume. I only compared apples to apples - the same size injectors will yeild the same maximum power no matter what the source injector pump or fuel rail provides.

It is the same for two engine blocks with domed or dished pistons, the fuel supply does not mater as long as it is adequate for the application.

 

[dirttoys]

Then you are lucky, after the third one I sent it to the scrap yard.

I don't have standing to take a position on this (other than taking the opportunity to high jack an interesting thread).

1. I know a lot of gear is turbo'd.

2. Other folks (me) have had crappy experience with different tech, turbo in this case. I had two late 80 early 90 cars ford, and Nisan both had turbo failures prior to 100k. Now I know they are probably poor representations of heavy equipment, and modern equipment, but, I do buy normally aspired equipment exclusively now, so the bias stuck right or wrong.

3. Those to get to this Assuming you don't live at high altitude. What is the upside of a turbo in a fairly low use 60 or 70 horse tractor? I understand in applications that need more power with less displacement/weight, but I always wish my tractor was heavier not lighter. I am always grateful for easier access, simpler engines. But, I am old and still willing to learn, my next purchase will probably be a replacement skid (bobcat 773) and in addition to tires vs tracks, will be deciding normal aspire vs turbo.

In order, thanks in advance for the opinions, sorry if this is too much of a hi-jack, and it is a genuine question, not trying to fuel a fuss, honestly don't see the upside.

Best,

ed

 

[kenmac]

My 5.9 Cummins gets about the same mpg as the newer 6.7 with dpf, but the 6.7 puts out more hp and torque.

compared to people I know with 6.7, I get about 5 more miles to the gallon with my 5.9

 

[jyoutz]

I don't have standing to take a position on this (other than taking the opportunity to high jack an interesting thread).

1. I know a lot of gear is turbo'd.

2. Other folks (me) have had crappy experience with different tech, turbo in this case. I had two late 80 early 90 cars ford, and Nisan both had turbo failures prior to 100k. Now I know they are probably poor representations of heavy equipment, and modern equipment, but, I do buy normally aspired equipment exclusively now, so the bias stuck right or wrong.

3. Those to get to this Assuming you don't live at high altitude. What is the upside of a turbo in a fairly low use 60 or 70 horse tractor? I understand in applications that need more power with less displacement/weight, but I always wish my tractor was heavier not lighter. I am always grateful for easier access, simpler engines. But, I am old and still willing to learn, my next purchase will probably be a replacement skid (bobcat 773) and in addition to tires vs tracks, will be deciding normal aspire vs turbo.

In order, thanks in advance for the opinions, sorry if this is too much of a hi-jack, and it is a genuine question, not trying to fuel a fuss, honestly don't see the upside.

Best,

ed

I’m no authority on this topic, but it seems like most people I know who have had turbo issues were on gasser engines. I have never had issues with my diesel turbos. There are so many diesel turbo trucks in service that it seems like failures are uncommon on diesel motors.