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Old 21-12-2018, 21:59   #46
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Re: Injector HP Fuel Line - How to Make?

It's how most of my bets turn out! That's why I can't afford genuine Yanmar parts & I drink. I enjoy finding ways around having to buy Yanmar marine parts now, in fact it has become an obsession not to buy from local Yanmar agent
I only dive holding my breath so 30ft is around my max comfortable-ish depth for scolly gathering but I'll be happy with stuffing my gut all the other goodies if they are deeper. In fact I'm drooling imagining it.
Happy Xmas to you too
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Old 21-12-2018, 22:44   #47
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Re: Injector HP Fuel Line - How to Make?

Someone needs to measure the inside line diameter because it's only .078 of an inch for most injection lines. Breakline have a way larger inside measurement. You have to buy the right size line stock to start with or the line will fail very soon
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Old 22-12-2018, 01:42   #48
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Re: Injector HP Fuel Line - How to Make?

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Originally Posted by ulpilot45 View Post
Someone needs to measure the inside line diameter because it's only .078 of an inch for most injection lines. Breakline have a way larger inside measurement. You have to buy the right size line stock to start with or the line will fail very soon
Yep it's been stated in earlier posts that o.d.& i.d. are to be followed. Ya gotta remember the o.p. is sum kinda helicopter tech. If you make stuffups in that game ya know what happens. I assume all their work is logged & signed off so he has to be careful.
BTW I once yacht ( sailboat in American ) raced for an aero engineer who designed helicopter blades for the US. military, her golden rule was never go in one !!!!
I wish she never told me that. Ignorance is bliss
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Old 22-12-2018, 02:58   #49
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Re: Injector HP Fuel Line - How to Make?

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Originally Posted by ulpilot45 View Post
Someone needs to measure the inside line diameter because it's only .078 of an inch for most injection lines. Breakline have a way larger inside measurement. You have to buy the right size line stock to start with or the line will fail very soon
Well this has certainly piqued my interest .

I thought I should check this out right away so out came the tube cutter!

Yep, the ID is about .078", actually a bit smaller but more than .072". The OD is 6mm (.236").

This puts a different spin on the job. A quick google search suggests getting suitable stock might be difficult; in essence I looking for 6mm OD, ~2mm ID steel tube. I'm sure it can be tracked down but it might take some work.

Bending it might stretch the friendship of my tube bender but we will see!

I also took the opportunity to see how hard it was to remove the end fittings. No joy on the first attempt. The MAPP gas could get the fitting bright red hot but this wasn't enough to release it.

More work required .
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Old 22-12-2018, 05:00   #50
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Re: Injector HP Fuel Line - How to Make?

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Originally Posted by jimbunyard View Post
.............
Thus, I can only come up with two potential reasons for the 'all lines must be the same length' rule (which I always dutifully quote when asked).

The friction in the lines is enough to make a difference due to length (more length=more friction=different pressure), or the different volume in different length lines acts as a kind of accumulator, and allows a slight variation of pressure based on those different volumes, or a combination of both.

Or it could be something I've missed entirely.

It would be interesting if someone familiar with fuel injection theory could actually explain the real reason(s) clearly and conclusively...
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Originally Posted by a64pilot View Post
Line length really shouldn’t matter. Fuel is not compressible.
I’ve not measured, but am pretty sure that they are not equal length.
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All fuel injection lines are the same lengthy and set to a spec by the manufacture it relates to time and volume . Time verses metering how much time it takes to flow thru the line and the amount of time to do it.all calculated by the engine manufacturer. Where it is possible to build your own lines it's better to buy them when possible.
After further reading on the same length issue, I found the following explanation. I don't vouch for it's veracity but it sounds plausible to me.

The injector pump delivers a pulse of fuel into the line. The pulse travels though the line at about the speed of sound or very roughly at 1,000 m/s. If there were a 250mm difference in line length, the time difference will be 250us. At say 3,000 rpm, the crank rotates 18,000 degrees per sec thus there will be a 4.5 degree change in timing for the 250mm difference in line length.

I think the maths is correct and the theory sounds possible!
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Old 22-12-2018, 13:31   #51
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Re: Injector HP Fuel Line - How to Make?

Thats interesting but its hardly likely you'll fabricate a 10" difference in line length, maybe more like 1" max which would equate to a .45 degree difference in timing at stated revs if the calcs apply. You'd be lucky to time it that accurately.
As said earlier you can drill out your fittings & if your replacement pipe doesnt want to fit in you can make a joining sleeve to slip over both of them jam them together & then silver solder. Have used this technique many times in joining pipelines.
I'm BANKING on you to find a work around. You could cut up old tractor injector lines to suit.
Does it say anything in yr calcs about i.d. variation effect?
U r making me nervous Wotname.
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Old 22-12-2018, 14:54   #52
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Re: Injector HP Fuel Line - How to Make?

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Originally Posted by Wotname View Post
I also took the opportunity to see how hard it was to remove the end fittings. No joy on the first attempt. The MAPP gas could get the fitting bright red hot but this wasn't enough to release it.

More work required .
Here we go again!!!!!!!!!!!!!
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Old 22-12-2018, 15:10   #53
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Re: Injector HP Fuel Line - How to Make?

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Here we go again!!!!!!!!!!!!!


Yep, that it what I was thinking also - here I go again!!!

Mind you, I got extra pressure this time - the wager between Compass790 and EngNate. I gotta put in some extra effort for our Commonwealth cousins (both of them).

Hopefully it will keep some CF readers amused

Back to issue, I am presuming the heavy wall thickness (2mm in a 6mm OD) is necessary to cope with the millions of high pressure pulses over the life of the lines. So I will have to start looking around - clearly not a popular DIY material available everywhere.

My first port of call will be the local injector shop - they previously advised they will make them up if necessary but they try to avoid it if possible (buy new) but perhaps they can supply or suggest sources for the tube.
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Old 22-12-2018, 15:25   #54
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Re: Injector HP Fuel Line - How to Make?

FYI ...https://www.alibaba.com/product-deta...46e94a41da00Jc
They produce the size you need but wether they'll send you any by China post well thats another story. I have my fingers crossed tho.
EngNate mite post a link to extremely cheap 2qm20 fuel lines
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Old 22-12-2018, 15:30   #55
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Re: Injector HP Fuel Line - How to Make?

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Originally Posted by Compass790 View Post
FYI ...https://www.alibaba.com/product-deta...46e94a41da00Jc
They produce the size you need but wether they'll send you any by China post well thats another story. I have my fingers crossed tho.
EngNate mite post a link to extremely cheap 2qm20 fuel lines
Small Qty Process Charge. $250

Look harder if ya wanna win

Right now I'm counting on EngNate...
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Old 22-12-2018, 15:59   #56
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Re: Injector HP Fuel Line - How to Make?

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Small Qty Process Charge. $250

Look harder if ya wanna win

Right now I'm counting on EngNate...
Ya have to talk hard to get them to send you a sample. How's yr Mandarin? lol
I must confess I didn't scroll dwn to the min charge bit.
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Old 23-12-2018, 03:42   #57
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Re: Injector HP Fuel Line - How to Make?

I was a bit surprised to be informed that the wall thickness was so high and the ID so small, if it's not required for strength purposes then I think it safe to assume it's for fluid mechanics reasons and that the combination of tube expansion with fluid compressibility dictate design.

Assuming say 4 litres an hour fuel consumption that's 4,000,000 cubic millimetres of fuel divided by sixty = 66,666/minute divided by say 2750 revs = 24.24 divided by 3 cylinders (3GM30 assumed) = 8.08 multiplied by 2 = 16.16 cubic millimetres of fuel pumped each stroke of the fuel pump.

Not an insignificant volume and probability easily handled by the pump pumping more to compensate for the tube expansion/compressibility problem but perhaps a problem when the engine idles and consumption drops to about 1/5th of that volume and combined with the leakage around the pump plunger and injector plunger it would become a significant problem.
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Old 23-12-2018, 06:26   #58
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Re: Injector HP Fuel Line - How to Make?

If your local shop can't help, I'd bet a call to these folks might get you everything you need, maybe even under your 50.00 cutoff...


Fuel Lines :: Scheid Diesel
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Old 25-12-2018, 03:26   #59
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Re: Injector HP Fuel Line - How to Make?

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I was a bit surprised to be informed that the wall thickness was so high and the ID so small, if it's not required for strength purposes then I think it safe to assume it's for fluid mechanics reasons and that the combination of tube expansion with fluid compressibility dictate design.

Assuming say 4 litres an hour fuel consumption that's 4,000,000 cubic millimetres of fuel divided by sixty = 66,666/minute divided by say 2750 revs = 24.24 divided by 3 cylinders (3GM30 assumed) = 8.08 multiplied by 2 = 16.16 cubic millimetres of fuel pumped each stroke of the fuel pump.

Not an insignificant volume and probability easily handled by the pump pumping more to compensate for the tube expansion/compressibility problem but perhaps a problem when the engine idles and consumption drops to about 1/5th of that volume and combined with the leakage around the pump plunger and injector plunger it would become a significant problem.
I don't know but suspect they are so heavy-walled because the pump pulse delivers a hammer blow to them which causes vibration. Always you have more trouble with pipelines that have pulse loads and it's also what causes hydraulic hoses to fail. But you would need a hydraulics engineer to chime in for a definitive answer.
I'm curious as well as to why i.d. is critical as assume the diesel is incompressible as mentioned by A64 earlier
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Old 25-12-2018, 05:44   #60
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Re: Injector HP Fuel Line - How to Make?

I'm guessing here. There may be trace amounts of dissolved oxygen in diesel fuel that is compressible. I do know there is dissolved oxygen in water because that's what fish need. What we do know is that injection lines aren't as simple as plumbing lines and might be better off using OEM. Some things are just too complex to fully understand all the nuts and bolts that make it. We don't need to engineer a jet to fly in one.
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