Replace missing injector tubes

[jstapler]

Could someone please give me the injector tubing size for tube that runs from injector to pump, tubing Size and flare fittings size if special fitting. Thanks Moe

 

[Russell King]

I have no idea what size they are.

I recently replaced those on my similar L185 and they were available from the dealer. I don’t remember the exact cost but it was not very much money for both.

 

[Jsjac]

I think the length of the injector lines changes the timing.
Not sure how much it will affect how the engine runs.

 

[BAP]

Could someone please give me the injector tubing size for tube that runs from injector to pump, tubing Size and flare fittings size if special fitting. Thanks Moe

For What? Hard to answer without knowing what you are working on

 

[GreensvilleJay]

I'm with BAP....
for WHAT !??
I will NO 'assume' it's for the tractors under your name......

it could be as easy as looking at kubota online parts page......

 

[Daferris]

Your best off getting them from a dealer. All of the tubes must be exactly the same length. By the time you get the steel tubing, bend it and get the fittings (or reuse yours) along with the flare tool ( unless you have the correct one for the ends needed) your going to have more into making them than it would cost just to buy them.

 

[Henro]

Your best off getting them from a dealer. All of the tubes must be exactly the same length. By the time you get the steel tubing, bend it and get the fittings (or reuse yours) along with the flare tool ( unless you have the correct one for the ends needed) your going to have more into making them than it would cost just to buy them.

This question related to the OP's question I think.

WHY do the tubes all have to be EXACTLY the same length? Seems like if they are full of fuel, and since fuel is essentially an non-compressible liquid, that length would not matter in practical terms.

Please explain...

 

[Daferris]

This question related to the OP's question I think.

WHY do the tubes all have to be EXACTLY the same length? Seems like if they are full of fuel, and since fuel is essentially an non-compressible liquid, that length would not matter in practical terms.

Please explain...

The best way I can explain this it to take 1 tube that is 10" long and another tube the same diameter 10' long (the dramatic difference in the length is to exacerbate/ make more visual the difference. Well both tubes are full the start of the fuel coming out would be delayed slightly on the longer tube. Reason is mainly the surface friction of the fluid on the sides of the tube as well as the rate of acceleration of the fluid movement because of the "fluid stack" or inertia of the weight of the fluid in the line. There will be other factors and I am not a engineer in fluid dynamics. But the differences will effect the timing of the injection event.

 

[Henro]

The best way I can explain this it to take 1 tube that is 10" long and another tube the same diameter 10' long (the dramatic difference in the length is to exacerbate/ make more visual the difference. Well both tubes are full the start of the fuel coming out would be delayed slightly on the longer tube. Reason is mainly the surface friction of the fluid on the sides of the tube as well as the rate of acceleration of the fluid movement because of the "fluid stack" or inertia of the weight of the fluid in the line. There will be other factors and I am not a engineer in fluid dynamics. But the differences will effect the timing of the injection event.

I can see that, and also think tube expansion during the pressure increase at the injection time could affect things too.

But I keep wondering if these conceptional issues are actually a realistic concern. Just wondering if tube length differences have actually been proved to make a difference in practical terms.

No doubt if one tube was a mile long and another was 5 inches, there would be a significant difference in timing. But what if one was 5” and the other 8"?

 

[woodman55]

Another factor is the very small amount of time involved. 2000rpm = 1000 injection cycles/minute. Plus if it is doing multiply injections/ cycle ( pre, main, and post injections), then we are talking even smaller amounts of time and fuel quantities.

 

[TheOldHokie]

I can see that, and also think tube expansion during the pressure increase at the injection time could affect things too.

But I keep wondering if these conceptional issues are actually a realistic concern. Just wondering if tube length differences have actually been proved to make a difference in practical terms.

No doubt if one tube was a mile0 long and another was 5 inches, there would be a significant difference in timing. But what if one was 5” and the other 8"?

Good work Henro you got me all geeked up.

The internet can be a wonderful thing and I think this answers the question:

The fuel injection pressure waves moves in the injection tubes at speed of sound in diesel fuel. This is a finite number so all tubes must be of tuned(same) length to ensure no effect on fuel injection timing.

It is the arrival of the pressure wave not the fuel itself that controls the timing. Using the graph below we can see that the speed of sound in diesel varies with pressure but let's call it 1500m/sec.

Using that value the arithmetic is pretty simple if you have a calculator - a one inch change in length alters timing by .000017 seconds = .017ms.

Dan

 

[cthomas]

I know on the diesels I have worked on(GM, VW and Mercedes) the fuel injector lines do loops on the lines close to the pump and straighter shots to the furthest ones, never measured them, but I bet they are the same length of tube regardless of injector location.

 

[North Idaho Wolfman]

It's 1000% NOT a DYI task.
You don't make fuel injector lines, you buy them.
They are not off the shelf fittings or material.

 

[Henro]

Good work Henro you got me all geeked up.

The internet can be a wonderful thing and I think this answers the question:

The fuel injection pressure waves moves in the injection tubes at speed of sound in diesel fuel. This is a finite number so all tubes must be of tuned(same) length to ensure no effect on fuel injection timing.

It is the arrival of the pressure wave not the fuel itself that controls the timing. Using the graph below we can see that the speed of sound in diesel varies with pressure but let's call it 1500m/sec.

View attachment 108069

Using that value the arithmetic is pretty simple if you have a calculator - a one inch change in length alters timing by .000017 seconds = .017ms.

Dan

Interesting! Thanks Dan.

So I guess my follow up question would be: Is 17 millionths of a second for a 1 inch difference significant?

No pony in this race, just curious.

 

[TheOldHokie]

Interesting! Thanks Dan.

So I guess my follow up question would be: Is 17 millionths of a second for a 1 inch difference significant?

No pony in this race, just curious.

Above my pay grade. I would think that's noise given the other variables inherent oin old style pumps.

Dan

 

[TheOldHokie]

Interesting! Thanks Dan.

So I guess my follow up question would be: Is 17 millionths of a second for a 1 inch difference significant?

No pony in this race, just curious.

Once I get geeked its hard to stop.
Just doing a little more arithmetc:

A diesel crankshaft running 2000 RPM sweeps 2000/60 x 360 = 12000 degrees per second.

A .000017 second delta in start of ignition = ..000017 x 12000 = .204 crankshaft degrees.

Ponder that.

Dan