Common rail vs mechanical injection

[Boss 302]

I hear you Rooster, same goes for my buddy's common rail 5.9 Cummins in his 92 Dodge pickup. It almost seems like it starts before I even turn the key.

 

[Hall00]

A '92 Dodge would definitely not come stock with a common rail

 

[Boss 302]

Hall, good catch my bad it certainly isn't. It's the mechanical setup just as it should be. DUH

 

[MHarryE]

First diesel on our farm was a 1939 TD-6 International. Injection pressure 1500 psi. Move on to my last IDI engine near that horsepower class, a Kubota L5740. Injection pressure increased all the way to 2000 psi. Remember its the pressure that breaks the fuel into droplets with higher injection pressure resulting in smaller droplets, more surface area exposed to air, and more complete combustion. I remember my dad coming in from the fields after working with that TD-6 and he would be covered with soot. Under extreme load, it made the neatest little soot circles that settled on your clothes. In his 60's dad was diagnosed with a problem most commonly related to heavy smokers, but he never smoked. I remember in his 30's and 40's and that incomplete combustion diesel smoke. My L5740, now Tier 3 emissions, was similarly a nasty smoker although it didn't make those little smoke rings. I don't have a shop manual for my L6060 so I can't tell you the injection pressure, but my M7-171 manual says variable high pressure depending on requirements but relief valve in the fuel rail limiting pressure to 36,000 psi. I will never know how much the injection pressure reduces soot because the DPF takes care of any remaining. Incidentally our first direct injection diesel tractor was a 1963 International 806 with 2000 psi injection pressure, same as the IDI Kubota L5740. In between there is Caterpillar's HEUI injectors that give about 5,400 psi at low speed low power and 23,500 psi at high speed high power - and anywhere in between based on demand.

All of these changes have been made to get better fuel economy and lower emissions. One of my friends at Cat worked for over a year sitting at a computer terminal tweaking unit injectors to get the best fuel flow and improved fuel economy when Cat got a contract to supply engines for GM trucks. He said they would get atta-boys for every fraction of a percent of fuel economy improvement as it was so important to GMC.

Applications - fluid flow at high pressure with contamination = wear. That has always been a diesel problem even with 1500 psi TD-6 engines, but materials technology was ancient back then. Limitations of improving diesel performance has always been material technology. Even with improving materials, it is easier to reduce injection system wear by filtering. I have a couple injectors sitting on my desk as a reminder of what a customer can do saving money in the short run costing money in the long run. He bought a test machine we had a customer run for 2,500 hours with no problem. Thirty hours later I got a call that the engine wouldn't start. Sent a dealer to check. The customer had replaced our filter with a will fit as one of these "buying it used, will change all the fluids and filters before putting it to work". Only thing he replaced a highly developed filter with a common brand "will fit the same mount" filter. In this case I was not going to let the customer get stuck for his mistake and paid the dealer to replace the injectors - and install the proper fuel filter. But that is how quickly systems can fail using inferior filtration. Incidentally, before selling the machine, I had the dealer perform an injector leakage test to insure the injectors still worked right after 2500 hours (this was implementing common rail in a Tier 3 engine). They were fine. It took only 30 hours using fuel in the Atlanta, Georgia, area with the incorrect filter to take out injectors.

 

[JWR]

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.

Turbos life changed entirely when they were mfrd to share pressurized lubrication with the engines. The automotive industry had to have 100K mile guarantees to compete and they were dead if the turbos failed in large numbers at low mileage. That is why newer turbos last way, way longer and are not the liability they once were. That fact of life migrated from cars to tractors in a fairly short time.

 

[LouNY]

To the best of my knowledge all turbos have always been lubed by engine oil,
especially tractor turbos.

 

[etpm]

Regarding computer and associated electronics common rail versus all mechanical fuel injection I read a study about 15 years ago about all mechanical versus all electronic power steering in Mercedes cars. I don't know if the results can be compared to fuel injection but here goes. In Mercedes cars the fully electronic power steering, which had no mechanical connection between the steering wheel and the front wheels, was more reliable up to and including catastrophic failure than mechanical power steering. I was shocked. Really. In these Mercedes cars the fully drive by wire steering was safer and more reliable than mechanical steering. Their cars with drive by wire steering were less likely to have steering problems and less likely to have a catastrophic failure than their cars with steering that had the steering wheel connected to to front wheels. I dunno If the results were because of excellent electrical components, poor mechanical components, or a combination of the two. Or if the electronics and associated components were intrinsically more reliable than mechanical ccomponents. But I was truly shocked, especially when it came to catastrophic failure, where the driver lost all control over the front wheels, and could not control the steering. Will common rail fuel injection get there? Could it already be there on some tractors?
Eric

 

[Hay Dude]

Regarding computer and associated electronics common rail versus all mechanical fuel injection I read a study about 15 years ago about all mechanical versus all electronic power steering in Mercedes cars. I don't know if the results can be compared to fuel injection but here goes. In Mercedes cars the fully electronic power steering, which had no mechanical connection between the steering wheel and the front wheels, was more reliable up to and including catastrophic failure than mechanical power steering. I was shocked. Really. In these Mercedes cars the fully drive by wire steering was safer and more reliable than mechanical steering. Their cars with drive by wire steering were less likely to have steering problems and less likely to have a catastrophic failure than their cars with steering that had the steering wheel connected to to front wheels. I dunno If the results were because of excellent electrical components, poor mechanical components, or a combination of the two. Or if the electronics and associated components were intrinsically more reliable than mechanical ccomponents. But I was truly shocked, especially when it came to catastrophic failure, where the driver lost all control over the front wheels, and could not control the steering. Will common rail fuel injection get there? Could it already be there on some tractors?
Eric

I agree with your points and I am amazed at the reliability of all steer by wire steering article you refer to.
However, with mechanical versus common rail, there’s another variable, fuel. Fuel quality affects different injection systems, pumps and different injectors differently.
Steering does not have fuel affecting it.

 

[Boss 302]

Yepper, true statement the high-pressure fuel pumps of today are shall we say finicky. Prone to grenade due to moisture, water, inferior fuel I only buy fuel from high volume stations for my powerstroke. Our local Southern States fuel has a Cetane rating of 50 which I use for all of my diesel engines.

 

[RickB]

Yepper, true statement the high-pressure fuel pumps of today are shall we say finicky. Prone to grenade due to moisture, water, inferior fuel I only buy fuel from high volume stations for my powerstroke. Our local Southern States fuel has a Cetane rating of 50 which I use for all of my diesel engines.

But how many owners of CR fuel systems base their fuel filter choices on price?