Injector HP Fuel Line - How to Make?

[Compass790]

I'll easy come up with a work around for that problem cobber but I'll wait to see if you get stock first.

[Compass790]

Originally Posted by jimbunyard

Believe I've got it figured out, or at least figured out enough for me to use the explanation if questioned.

Would like to say that it was a reasoned calculation based solely on the ideas given above and powers of reflection, but, sadly, this is not the case.

While trying to determine where best to put anti-hammer stacks (or whatever they're called) in copper lines while moving a friends water heater, and realizing I didn't know why they were even needed (some systems hammer, some don't), I decided to look it up (though a minutes consideration would have answered the question---thanks [for nothing] Google). Well, turns out it's the inertia of the water in the pipe, or rather the sudden opening and closing of valves interrupting the inertia built up by the moving water, which cause transient pressure spikes, which, depending on the volume moving through the pipe, can be huge.

Neither the pressure nor the volume-induced transient pressure spikes seem relevant in the tiny volumes contained in the injection lines, nor does the leakage around the P&Bs (because the 'leakage' should be the same for each; thus they cancel out of the equation).

The 'expansion' of the pipes also seems an unlikely candidate; if the volume changed significantly enough to swell the pipe, given the (roughly) million cycles in 10 hours of running mild steel would undergo, permanent distortion should result. I've yet to see this in any engines I've worked on.

Additionally to the 'pressure question', common rail engines run at about 4-6 times the injection pressure of mechanically injected engines, yet their injection line walls are only around 2 mm thick (for 10 mm OD lines), and they're (depending on the manufacturer) subject to 3-5 times more of these pressure spikes, due to the multiple injections-per-power-stroke of common-rail engines.

So my story, and I'm sticking to it (until a better one comes along), is that the reason for having the lines the same length is precision of injection, which is kept as accurate as possible by having the same, smallest amount of fuel necessary in each line, thus avoiding the 'inertial inaccuracies' entailed in trying to move differing volumes though the line.

Ah Jim,
The brain worm is still there in me too. Just to come back to the point about the importance of length of injection line. In a multi-cylinder diesel mechanical injection engine the cylinder furthest from the inj pump has a much longer line than the cylinder closest to it yet they must fire at the same degrees BTDC ( apart frm being maybe 180o apart) as I assume the pump cam is not ground different for each cylinder.
I could see how you could individually alter the timing to suit injector line length with an ECU engine but I doubt it's done with a mechanical therefore my conclusion is that the length cannot be that critical. I'll stretch that conclusion a bit further & say that the i.d. also is not that critical assuming wall thickness is adequate.
Feel free to shoot the theory down in flames but I'm sticking to it until I get a better argument

[Compass790]

Actually I was hoping to get a response from someone who could tell me if the pump cams are individually ground to suit the length of injector lines in a mechanically injected diesel rather than to just suit firing order.
That would be a good answer to the question AFAIK. Calling all injection pump designers out there???
Need to know wether I'll get to eat wild salmon, halibut & prawns as a change from crays ( lobster ) snapper & green lipped mussels :-)
Not lookn gud @ present but it's a fluid situation.

[ulpilot45]

Originally Posted by Compass790

Actually I was hoping to get a response from someone who could tell me if the pump cams are individually ground to suit the length of injector lines in a mechanically injected diesel rather than to just suit firing order.
That would be a good answer to the question AFAIK. Calling all injection pump designers out there???
Need to know wether I'll get to eat wild salmon, halibut & prawns as a change from crays ( lobster ) snapper & green lipped mussels :-)
Not lookn gud @ present but it's a fluid situation.

The pump cams are ground to the firing order .Then the individual cylinders are set to the proper lift to port closure as set by the manufacturer. All line length is designed to allow for the engine to active the right timing by time verses metering as an engineered spec

[Compass790]

Okaaaay. I need to know how the timing is altered to suit inj. line length, if it isn't in the pump cam lobes where is it? Are you saying it's in plunger relief cuts? If so, are the plungers individually numbered to match cylinder number?
Excuse my ignorance, I've only worked on a single cylinder injection pump but I've learnt enough to ask some questions. Hope you can educate me a bit more but I need an explanation of how it works.
thanks C790

[ulpilot45]

Originally Posted by Compass790

Okaaaay. I need to know how the timing is altered to suit inj. line length, if it isn't in the pump cam lobes where is it? Are you saying it's in plunger relief cuts? If so, are the plungers individually numbered to match cylinder number?
Excuse my ignorance, I've only worked on a single cylinder injection pump but I've learnt enough to ask some questions. Hope you can educate me a bit more but I need an explanation of how it works.
thanks C790

I will try to make this simple there is drag induced in the line by the fuel moving thru it there is an amount of time it takes for the line to empty and a retraction value from the delivery valve that stops secondary injections some of the other posts referred to it as water hammer all this is and engineering value

[NYSail]

Did you call your local Yanmar dealer to see if they are still available??

[Compass790]

Originally Posted by ulpilot45

I will try to make this simple there is drag induced in the line by the fuel moving thru it there is an amount of time it takes for the line to empty and a retraction value from the delivery valve that stops secondary injections some of the other posts referred to it as water hammer all this is and engineering value

Okaaay that still doesn't explain where in the engineering is the individually tailored response to the different injector line lengths? Please explain how the pump/cams/plunger or delivery v/v are different for each line
Sorry I can't make my question any simpler

[Compass790]

Originally Posted by NYSail

Did you call your local Yanmar dealer to see if they are still available??

Maybe Wotname will be. haha

[NYSail]

Originally Posted by Compass790

Maybe Wotname will be. haha

Yea I replaced mine on my old Yanmar (3HM35f) engine. They came ready to install with all the exact bends. Installed them with a beer and went sailing a few hours later.

[Compass790]

Originally Posted by NYSail

Yea I replaced mine on my old Yanmar (3HM35f) engine. They came ready to install with all the exact bends. Installed them with a beer and went sailing a few hours later.

That's nice but this thread is not called "how to buy injector lines?"
Tho that may happen!

[NYSail]

Some people have a thread name not knowing what is readily available.......
just trying to help.

Good luck!

[Compass790]

Wotname ( the O.P. ) would be grateful that you are trying to help but you need to read the whole thread to get the picture if you have time.
cheers

[Wotname]

Originally Posted by NYSail

Did you call your local Yanmar dealer to see if they are still available??

Yes, they are available ex Yanmar; about $100 each but I'd rather make them (DIY) if at all possible. Not just for the bucks but also the challange,

I should know next week if the correct tube stock and nipples can be sourced locally and at what cost, so standby

[Compass790]

Originally Posted by Wotname

Yes, they are available ex Yanmar; about $100 each but I'd rather make them (DIY) if at all possible. Not just for the bucks but also the challange,

I should know next week if the correct tube stock and nipples can be sourced locally and at what cost, so standby

Yea ya need a good challenge Wottie, those injectors were too easy!