Common Rail Diesels - Experience

[RaymondR]

Originally Posted by Jim Cate

You have previously posted this fuel pressure number (180,000 psi). While the rail pressures are indeed high, I think a value around 30,000 psi is normal. The issues of handling 180,000 psi are daunting to say the least!

Jim

As an old oil driller I'm fairly familiar with stuff plumbed for 10,000 psi working pressure and have tested stuff to 20,000 psi but I don't want to be in the same state as anything which operates at 180,000 psi.

[Shaneesprit]

Originally Posted by Jim Cate

You have previously posted this fuel pressure number (180,000 psi). While the rail pressures are indeed high, I think a value around 30,000 psi is normal. The issues of handling 180,000 psi are daunting to say the least!

Jim

Because it’s a real number - I will see if I can find a screen grab might take a while.
Although anything over 10bar is considered a risk, the DNV insisted on pipe in pipe above that from memory. an old Mechanical Engine only uses 3 or 4000PSI and no real fuel line pressure, so you can crack the injector pipes to bleed the fuel.
If an Engineer does that on a Common Rail he deserves to be fired or at least disciplined. There are a few engines where this is possible and I have known it happen luckily he is still alive and has all of his fingers.

[Dieseldude]

Will the people who like electronic engine controls still like them when the government gets the ability to shut down your engine? This is being proposed under the guise of stopping intoxicated drivers. But it is open to much abuse. Following is a link to a story about it. But just search "vehicle kill switch" and the story can be confirmed from many sources. The prospect of the government shutting down your vehicle or boat should scare you enough to maintain you old mechanically controlled boat or vehicle engine for life.

https://headlineusa.com/bill-would-g...-all-new-cars/

[Josh.]

No major dramas with the new common rail engines. Main advantages are fuel economy, reduced emisions (as it can be more tightly controled) and in many cases better performance. Most of it is regulation driving it, not because they are substanially better.

As pointed out, you NEED clean fuel or you will cause substanial engine damage.
Strongly recommended you get a fuel polishing system in place if you are even considering doing anything half exotic.

Normally something dumb like a dead fuel pump or failed alternator which slowly drains the battery will bite you over a dead ECU. Parts then can become a problem. I have not personally encounted or know anyone that had a high pressure line fail in both marine & automotive enviroments.

If you have a reliable current engine I wouldn't be immeditely jumping on an upgrade.

[Jim Cate]

Originally Posted by Shaneesprit

Because it’s a real number - I will see if I can find a screen grab might take a while.
Although anything over 10bar is considered a risk, the DNV insisted on pipe in pipe above that from memory. an old Mechanical Engine only uses 3 or 4000PSI and no real fuel line pressure, so you can crack the injector pipes to bleed the fuel.
If an Engineer does that on a Common Rail he deserves to be fired or at least disciplined. There are a few engines where this is possible and I have known it happen luckily he is still alive and has all of his fingers.

One of many citations of common rail pressures, from Wikipedia:

"Common rail direct fuel injection is a direct fuel injection system built around a high-pressure (over 2,000 bar or 200 MPa or 29,000 psi) fuel rail feeding solenoid valves".

Jim

[chris95040]

Originally Posted by Jim Cate

One of many citations of common rail pressures, from Wikipedia:



"Common rail direct fuel injection is a direct fuel injection system built around a high-pressure (over 2,000 bar or 200 MPa or 29,000 psi) fuel rail feeding solenoid valves".



Jim

Wow thats a lot of pressure.

Why doesn't the fuel combust at that pressure, before ever even reaching the cylinder? No air? Surely there is some...

[RaymondR]

The extreme pressures allow much greater atomization of the fuel being injected which provides a massive increase in the surface area of the droplets exposed to the oxygen in the air which provides a better burn up of the fuel hence less particulate pollution and better fuel consumption.

[Dieseldude]

Originally Posted by chris95040

Wow thats a lot of pressure.

Why doesn't the fuel combust at that pressure, before ever even reaching the cylinder? No air? Surely there is some...

Correct. Diesel fuel must be mixed with sufficient air to burn. This brings up the problem of leaking high pressure fuel lines. A tiny leak can release fuel in the form of a fine mist into the air. A spark or hot surface can ignite this and cause an engine room fire or explosion. Large diesel engines have double wall fuel lines to contain any leak. Any leaked fuel drains to a small tank with a float switch that trips and alarm to warn of the leak.

[Allied39]

Originally Posted by zstine

It's not just you RaymondR. It's the thousands of other boaters too. Every person makes a small difference and we all need to work together... ah **** it! Screw the kids, burn your dirty oil!

LOL!!! Love it!

[Jim Cate]

Wow thats a lot of pressure.

Indeed it is, but a factor of six lower that the figure posted by Shaneespirit in#104 (180,000 psi). Such a pressure would be an engineering nightmare to safely handle and I thought it worth a fact check.

Jim

[RaymondR]

Originally Posted by Allied39

LOL!!! Love it!

A few statistics which might put things back into proportion.

The Emma Maersk, a large container ship, burns 6,280 litres per hour of filthy bunker fluid which must be heated to 140 degrees celcius to get the stuff out of the fuel tanks and into the engine and it's engines operate for about 7,000 hours per year carrying containers around the oceans of the world. The containers are not primarily filled with anything of enduring value and the Emma Maersk is only one of a large fleet of similar vessels.

If every yachty in the world changed their engine to common rail diesels it would probably not reduce the overall annual environmental damage by more than that caused in a few hours by the Emma Maersk and thousands of perfectly good engines would need to be scrapped.

If your boat has a good reliable mechanical fuel pump diesel leave it in there until it is worn out and then change it, it is the environmentally responsible thing to do.

[Dieseldude]

Originally Posted by RaymondR

A few statistics which might put things back into proportion.

The Emma Maersk, a large container ship, burns 6,280 litres per hour of filthy bunker fluid which must be heated to 140 degrees celcius to get the stuff out of the fuel tanks and into the engine and it's engines operate for about 7,000 hours per year carrying containers around the oceans of the world. The containers are not primarily filled with anything of enduring value and the Emma Maersk is only one of a large fleet of similar vessels.

If every yachty in the world changed their engine to common rail diesels it would probably not reduce the overall annual environmental damage by more than that caused in a few hours by the Emma Maersk and thousands of perfectly good engines would need to be scrapped.

If your boat has a good reliable mechanical fuel pump diesel leave it in there until it is worn out and then change it, it is the environmentally responsible thing to do.

Stack that up against the CO2 produced by vulcanos, and the emissions from boat engines mean nothing. There is no environmental reason to pay the additional expenses of purchasing and repairing high technology computer controlled engines. The main greenhouse gas is water vapor which is about 70 times more abundant than CO2. The main driver of climate variation is variable solar activity, not anthropogenic CO2. Throughout history, ice ages have come and gone with not a drop of oil not a lump of coal having been burned.

[japarker11]

Originally Posted by Jim Cate

Indeed it is, but a factor of six lower that the figure posted by Shaneespirit in#104 (180,000 psi). Such a pressure would be an engineering nightmare to safely handle and I thought it worth a fact check.

Jim

What is the liquid is in the "common Rail" ? Answer - motor oil at continuous operating pressures less than 3000 psi. Hence, hoses and fittings are constructed to 3000 psi hydraulic standards.

The liquid subject to 30,000 to 180,000 psi? #2 diesel fuel. Where does this occur? Inside the injector nozzle tip during the solenoid on cycle measured in milliseconds. And, the 180,000 psi is pretty much a theoretical number based on the ratio of the piston the oil is acting on to the plunger area pressurizing the tip orifice.

It was developed by Caterpillar in response to Al Gore's "smokeless diesel" mandate of the mid 90's. It requires a fancy 100 VAC signal/activating current to a solenoid on each injector, ala the $1000 ECU. The Fed's we're so impressed with fuel efficiency and opacity performance, they forced Cat to licence it to their competitors at which time they exited the over the road truck engine market.

In the diesel fleet we have had one of these in a 25 yo pick up......yes, the ECU did crap out and the only way to move it was a tow. Besides the standby ECU, the 12 or 24 volt systems must be maintained in good operational charge states to have the ECU generate the correct injector solenoid signal.

Hope this lowers some blood pressures. As for government interference, for marine applications, already there are after market ECU s circumventing OEM units. So the only guy you need to worry about is Musk and Starlink[emoji846]

[RaymondR]

Originally Posted by japarker11

What is the liquid is in the "common Rail" ? Answer - motor oil at continuous operating pressures less than 3000 psi. Hence, hoses and fittings are constructed to 3000 psi hydraulic standards.

The liquid subject to 30,000 to 180,000 psi? #2 diesel fuel. Where does this occur? Inside the injector nozzle tip during the solenoid on cycle measured in milliseconds. And, the 180,000 psi is pretty much a theoretical number based on the ratio of the piston the oil is acting on to the plunger area pressurizing the tip orifice.

It was developed by Caterpillar in response to Al Gore's "smokeless diesel" mandate of the mid 90's. It requires a fancy 100 VAC signal/activating current to a solenoid on each injector, ala the $1000 ECU. The Fed's we're so impressed with fuel efficiency and opacity performance, they forced Cat to licence it to their competitors at which time they exited the over the road truck engine market.

In the diesel fleet we have had one of these in a 25 yo pick up......yes, the ECU did crap out and the only way to move it was a tow. Besides the standby ECU, the 12 or 24 volt systems must be maintained in good operational charge states to have the ECU generate the correct injector solenoid signal.

Hope this lowers some blood pressures. As for government interference, for marine applications, already there are after market ECU s circumventing OEM units. So the only guy you need to worry about is Musk and Starlink[emoji846]

What you appear to be describing is a system whereby a hydraulic pump is generating 3,000 psi hydraulic fluid which then drives a 60:1 hydraulic intensifier situated in the injector nozzle to pump diesel at 180,000 psi in the injector nozzle to spray the diesel into the combustion chamber.

If you want to atomize diesel that should do it but a bit more complicated than the more usual systems.

[Jim Cate]

^^^^

So, is this the method used in the small diesels used in yachts? Does not seem to be what they describe in literature, but I may have missed the memo.

Wikipedia and several other sources differed in their descriptions... I have no personal experience or expertise to offer in the conversation.

Jim