Discontinued Kubota Injector Lines

[TheOldHokie]

That ah dunno. It's too late tonight to do the math. That's trig, and that makes me have to think!

Anyway, I was going by what NIW posted:




If that number is accurate, AND if the pressure wave speed is the critical factor in the timing, then DIY tubing will be well within the parameters.

No trig - just basic arithmetic. A crankshaft rotating at 2000 RPM sweeps (360) x (2000) / 60 / 1000 = 12 degrees in a millisecond.

 

[TheOldHokie]

The following is excerpted from this scholarly paper on fuel injection system design.

Diesel Fuel Injection

The red highlighting is mine.

So simple arithmetic says in an engine operating at 2000 RPM a millisecond change in signal propagation time will advance/retard SOI by 12 degrees CAD.

Diesel Fuel Injection
Magdi K. Khair, Hannu Jääskeläinen

Start of injection (SOI) or injection timing is the time at which injection of fuel into the combustion chamber begins. It is usually expressed in crank angle degrees (CAD) relative to TDC of the compression stroke. In some cases, it is important to differentiate between the indicated SOI and actual SOI. SOI is often indicated by an easily measured parameter such as the time that an electronic trigger is sent to the injector or a signal from a needle lift sensor that indicates when the injector needle valve starts to open. The point in the cycle where this occurs is the indicated SOI. Due to the mechanical response of the injector, there can be a delay between the indicated SOI and the actual SOI when fuel exits the injector nozzle into the combustion chamber. The difference between the actual SOI and indicated SOI is the injector lag.

Start of delivery. In some fuel systems, fuel injection is coordinated with the generation of high pressure. In such systems, the start of delivery is the time when the high pressure pump starts to deliver fuel to the injector. The difference between start of delivery and SOI is affected by the length of time it takes for a pressure wave to travel between the pump and injector and is influenced by the length of line between the high pressure pump and the injector and by the speed of sound in the fuel. The difference between the start of delivery and SOI can be referred to as injection delay.

 

[Ktrim]

That means it's traveling at 1.32 meters per millisecond.

That means an error of 1.32 meters in the length of the tubing would result in a timing error of 1 millisecond.

That means an error of 13.2 centimeters would result in a timing error of 1/10 of one millisecond.

I would think a careful DIYer could probably manage to keep it under a 1.32 centimeter error margin, which would give a timing error of 1/100 of a millisecond.

That being the case, if the speed of the pressure wave is the critical factor, the timing is not a problem.

The next problem to solve is choosing some tubing. You need to know the pressure of the injection system and then compare that to brake line of the same size. I would imagine that the size would have to be identical. It's sure the safe bet, anyway.

I found here that NiCopp 3/16 can have a working pressure of 4500 PSI and a burst pressure of 17,900 PSI.

Steel or stainless steel should beat that by a bit, I'm guessing, but I was not able to track down any solid numbers.

So if those pressure numbers work out, you have a solution.

Now the problem of flaring. For me, I have never been able to use one of those hand flaring tools successfully. I know many can do great work with them, but I have never gotten the hang of it.

So, when I had a large project to do about 10 years ago, I bought a Mastercool hydraulic flaring tool kit for right around $300, and it saved me that much and more in buying lines. That thing is a BREEZE to use, and gets a perfect flare every time.

I see that that particular model is discontinued now, but I'm sure they have similar. I also see that Eastwood has a similar kit for $360, plus a few Mastercool kits.

They also have line bending tools of various kinds.

If it were me, I'd roll my own without a second thought.

I have the mastercool kit. Absolutely a lifesaver.

 

[Mark_BX25D]

So simple arithmetic says in an engine operating at 2000 RPM a millisecond change in signal propagation time will advance/retard SOI by 12 degrees CAD.

...

The difference between start of delivery and SOI is affected by the length of time it takes for a pressure wave to travel between the pump and injector and is influenced by the length of line between the high pressure pump and the injector and by the speed of sound in the fuel. The difference between the start of delivery and SOI can be referred to as injection delay.

Excellent! The pressure wave IS the critical factor. So there we have it.

Now let's see about that 12 degrees per millisecond.

That means an error of 1.32 meters in the length of the tubing would result in a timing error of 1 millisecond.

So we'd need a length error of 1.32 meters to get that 12 degrees. I have to think that 12 degrees would be very undesirable, but then, I also have to believe that the average DIYer can do a lot better than that.

That means an error of 13.2 centimeters would result in a timing error of 1/10 of one millisecond.

That means that a 13.2 cm (5.2 inches) error gets you a 1.2 degree timing error. I have no idea if that's critical, but I am pretty sure most of us can do better than 5 inches. (Okay, let's keep it clean, guys! )

So a 1.32 cm (0.52 inch) length error would get you a 0.12 degree timing error. I'd bet most of us can manage that.

But let's be sloppy (and keep the math simple) and say we can keep it within 2.64 centimeters (1 inch). That's a timing error of 0.24 degrees.

Two inches gets you half a degree.

I'm no expert on this, but I'm betting that's not a problem.

What say you, Good Sir?

 

[TheOldHokie]

I have the mastercool kit. Absolutely a lifesaver.

You can do a lot with a drawer full of tube nuts and compression sleeves.

Dan

Excellent! The pressure wave IS the critical factor. So there we have it.

Now let's see about that 12 degrees per millisecond.





So we'd need a length error of 1.32 meters to get that 12 degrees. I have to think that 12 degrees would be very undesirable, but then, I also have to believe that the average DIYer can do a lot better than that.




That means that a 13.2 cm (5.2 inches) error gets you a 1.2 degree timing error. I have no idea if that's critical, but I am pretty sure most of us can do better than 5 inches. (Okay, let's keep it clean, guys! )

So a 1.32 cm (0.52 inch) length error would get you a 0.12 degree timing error. I'd bet most of us can manage that.

But let's be sloppy (and keep the math simple) and say we can keep it within 2.64 centimeters (1 inch). That's a timing error of 0.24 degrees.

Two inches gets you half a degree.

I'm no expert on this, but I'm betting that's not a problem.

What say you, Good Sir?

I say I learned a lot with this question. For example :

1. I learned a lot of the old Roosa Master pumps are statically timed at 1° BTDC because they use the end not start of injection as the reference
2. I learned Roosa Master also made pumps that had advance mechanisms that adjusted timing dynamically based on RPM and load
3. I learned they made diesel timing lights that used a transducer attached to the #1 fuel pipe to sense the expansion at SOI and used that as the trigger to fire the strobe
4. I learned that the timing lighrs in (4) were useless on the pumps in (2)

And last but not least I learned that curiosity about arcane technical questions that are of no interest to most people will still keep me online into the wee hours of the morning.

Sign me

Seepless In Maryland

 

[Mark_BX25D]

Sign me

Seepless In Maryland

Well, I'm glad you aren't leaking, anyway!

This has been a good discussion. I'm still waiting for NIW or someone equally knowledgeable to chime on on the tolerances for timing. Just seat of the pants I think we're good, but I'd hate to bet an engine on that.

 

[Henro]

My gut was telling me what Mark has calculated. Interesting discussion. I assume the calculation, that an inch difference to tubing length would add a 0.24 positive difference to timing, is accurate.

My guess is a fabricator could cut that length difference to less than a half inch without much effort.

So what difference would 0.12 degrees make in the real world?

Probably not much in reality...but no clue here. I would take my chances though, and see what the results were.

Using my carpenter talents, I bet I could make the lengths match within a quarter inch...without blinking an eye.

 

[Mark_BX25D]

I'm still wondering about the tolerances for timing on a diesel engine. I haven't been able to find anything yet that states a tolerance in terms of time, but I did find this article on timing the Cummins 4BT. It says:

Pump-to-engine timing is extremely critical. Pump timing that is off by only a few crankshaft degrees will cause:
1. Poor performance – starting and power.
2. Excessive smoke and emissions.
3. Poor fuel economy.

(I added the emphasis.)


So we are told that "a few crankshaft degrees" is no bueno. What is "a few", and what is that in terms of our time calculations?


Recall some of the calculations:

But let's be sloppy (and keep the math simple) and say we can keep it within 2.64 centimeters (1 inch). That's a timing error of 0.24 degrees.

Two inches gets you half a degree.

I can't say for sure what "a few degrees" means, but most of these adjustments are being made by manually rotating the pump. That's not going to get you tenth of a degree accuracy.

I'm pretty sure that 0.24 degrees is going to be just fine.

If it were me, I'd grab a roll of NiCopp, my Mastercool flaring tool, a few fittings, and get to work.

And I'd almost certainly have to scrap and start over with at least one line because I'd get the thing flared and then see the fitting that was intended for it sitting on the workbench!

 

[PoTreeBoy]

I'm going to throw in that the diameter, at least the inside diameter, is probably critical also, since it affects the fuel velocity and, therefore the injector performance. How much, I haven't a clue.

 

[5030su]

Wow! I can't believe I'm the first to run into this issue with injector lines on a Kubota diesel being discontinued. I prefer not to attempt fabrication myself due to the extremely low tolerances required and the lack of proper tools.

I’m was reaching out in hopes of finding either a replacement set or a fabrication shop that may already have experience with these injector lines. However, I have sent my old set to Scheid Diesel, and I am hopeful they will be able to create a new set that meets the necessary specifications.

Any guidance or recommendations you could provide would be greatly appreciated. Thank you for your assistance!

 

[TheOldHokie]

Wow! I can't believe I'm the first to run into this issue with injector lines on a Kubota diesel being discontinued. I prefer not to attempt fabrication myself due to the extremely low tolerances required and the lack of proper tools.

I’m was reaching out in hopes of finding either a replacement set or a fabrication shop that may already have experience with these injector lines. However, I have sent my old set to Scheid Diesel, and I am hopeful they will be able to create a new set that meets the necessary specifications.

Any guidance or recommendations you could provide would be greatly appreciated. Thank you for your assistance!

Ummm - lots of guidance in the previous discussion. I believe your diesel shop will be more than capable of meeting the extremely undemanding tolerances.

I will be interested in knowing how well they got the tubes bent so the ends match up to the connection points on the tractor. That strikes me as the biggest challenge when working remote.

Dan

 

[TheOldHokie]

I'm still wondering about the tolerances for timing on a diesel engine. I haven't been able to find anything yet that states a tolerance in terms of time, but I did find this article on timing the Cummins 4BT. It says:



(I added the emphasis.)


So we are told that "a few crankshaft degrees" is no bueno. What is "a few", and what is that in terms of our time calculations?


Recall some of the calculations:



I can't say for sure what "a few degrees" means, but most of these adjustments are being made by manually rotating the pump. That's not going to get you tenth of a degree accuracy.

I'm pretty sure that 0.24 degrees is going to be just fine.

If it were me, I'd grab a roll of NiCopp, my Mastercool flaring tool, a few fittings, and get to work.

And I'd almost certainly have to scrap and start over with at least one line because I'd get the thing flared and then see the fitting that was intended for it sitting on the workbench!

Just from the looks of the OEM pipes I had my doubts about brake lines and flare fittings. This is from a shop that fabricates diesel injector pipes:

Fuel injection tubing undergoes special processing to insure there is no metal flaking in the ID due to the pressure pulses. For injector pop pressures up to 350 bar the standard size (on Bosch systems) is 6 mm OD and 2 mm ID. The minimum bend radius is covered by both SAE and DIN specifications. Generally the tube end seats (sometimes referred to as ball ends) are roll formed.

We fabricate our own injection lines with a port for piezoelectric pressure sensors used in dynamic injection timing and for the observation of pressure pulse irregularities. In the past we obtained our injection tubing from Metric and Multistandard Components Corp, union nuts from Bosch and the the ferrules/ball ends from a Michigan company whose name escapes me at present. The ball ends (seats) are attached to the tubing with silver solder. We've had excellent results even when observing some pressure pulses in excess of 400 bar.

Dan

 

[007kubotaguy]

If you have not found injection lines yet I should have a set. Let me know if you're still in need of them.

 

[5030su]

If you have not found injection lines yet I should have a set. Let me know if you're still in need of them.

Yes, New or used and price. Will the fit a M5030sumdt ?

 

[Yooper]

From my water jet experience, the tubing was either 17-4 or 15-5 stainless that would handle 55,000 psi.