VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: gnavs on April 03, 2012, 10:14:49 am
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The fact that it's getting harder and harder to find new injector lines, or at least a decent used set, is starting to bug me.
My background is instrumentation and as such I've bent enough SS tubing to feel comfortable about recreating a set but the issue now becomes the sealing end. I've only ever used Swagelok compression fittings in industrial applications (supplied air lines, methanol injection lines etc) at relatively low pressures, at least compared to what our injection pumps put out. I seem to remember reading somewhere that we'd need to be prepared to see operating pressures in excess of 1500 PSI, can anyone confirm this?
Flared connections will undoubtedly be better at handling higher pressure but I'm not sure if you can create a good sealing flare with SS tubing.
Anyways, I wanted to start gathering information, from you guys as well as some of the tubing suppliers like Swagelok, McMaster Car etc., and seriously look at making a set of lines myself this summer.
So, on to the questions.
- What is the operating pressure between IP and injector?
- Does anyone have experience with flaring SS lines?
- Can I get away with compression fittings?
- Does anybody know the thread size on the IP and injectors?
- What is the size of the standard injection lines? (metric something or other I'm assuming)
Feel free to add your thoughts.
TIA!
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155 bar = 2,248.08493 pounds per square inch
Don't forget to add in a safety factor as well... No telling what value the Bosch engineers used for this.
You may have cracking issues when flaring stainless. How about billet machined ends that are then brazed to the formed lines?
Chris
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If you track down the two original SAE papers on the development of the engine there are some details on the design considerations for the lines. The three I kinda remember are:
- they are made of a special tubing with extra thick walls to handle the actual pressures involved.. per Chris' post
- they are all the exact same length... and IIRC a specific tuned length IIRC. ;)
- they are bent in that specific shape to (a) keep 'em the same length and (b) allow for some physical deformation due to vibration and, once again, the high pressures involved
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I just ordered a set from, ahem, Prothe for $14. I'll let you know if they are any good ( and carry some leaky Boschs in my trunk)
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Stainless wouldn't work. Materials not suited for it. You'll also need a seamless tube, no annealing from welding.
I think there's enough to be found in junkyards....
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IIRC the threads are m12-1.5 but don't quote me. Check the FAQ I am almost positive it was in there. Unless the injectors are more than spec of 155 or they got clogged or something the line will only ever see 155bar as the injector should open there and relieve the pressure.
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I am sure you can make your own stainless steel lines and get them to work. But your effort involved may be huge. That effort may be better spent fixing the leak in your Bosch lines. If they are not cracked, the grooves in the flared ends that is causing them to leak can be sanded out by hand. I have been successful on everyone I did using 400 grit wet dry paper with a twisting motion. I may make a cutter to make the job easier.
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Thought I saw brand new lines on sale on ebay, about $75.00
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I've got three good ones sitting in my Garage, I'd be willing to send to anyone who wants them - for shipping cost. Trying to clean out my garage...
(the forth one (cyl #3) has a small leak)
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I see a lot of 1.6 lines on ebay but none for AAZ's, can they be made to work?
Some points to consider, and I'm just spitballing.
I have enough experience bending tube that I can confidently recreate the factory lines. The lengths and bends would be exact so any sort of "calibration" due to differences in line lengths should be negated. Although, regardless of the line length you'd think that since you're moving a non-compressible fluid through the line and, providing there are no air bubbles, should get injection and pressure when required. This is taking into assumption the SS line itself won't stretch and warp with each stroke.
According to McMaster Carr's website, 316 SS seamless instrumentation tubing is good up to 6300 PSI, depending on the ID and wall thickness. This seems well within the range of expected fuel pressure. There are a few options as far as wall thickness goes, up to 2mm, but even the 1mm thick walls are rated to 5100 PSI.
What's the reason SS isn't suited for diesel fuel? Is there something I'm missing?
The issue at the moment seems to be the sealing end itself. Compression fittings should handle the pressure but I'm not sure if prolonged vibration could have a negative effect. The other option is flaring the SS tubing, which may have its own challenges. I've stumbled upon a few threads in muscle car and speedboat forums where this topic has come up. The key points to flaring SS tubing are
- cut the tubing with a hacksaw, not a tubing cutter as this will harden the end you're trying to flare
- chamfer the hell out of the inside
- scuff up the outside with a wire brush
- use a drop of oil on the flaring tool
Even then I'm sure this would take a few tries before getting it right, hell it took me 3 or 4 tries to get my brake line flares perfect.
I'm still optimistic on this, I don't see why it can't be done but maybe I need to fail miserably before I learn any better. Seems like that's the best way.
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I would be very interested in you doing this semi-commercially as one of my lines has sprouted a pin hole leak and a machine shop wanted $100+ PER LINE...
I just had a browse of the lines on ebay as gnavs mentioned and am surprised at the prices for being new un-used OEM lines flared with nuts and everything ($50-$70 + ~$10 shipping). I have a 1.6 pump on an AAZ and I have been using 1.6 lines. They never really sealed perfectly and they required some lets call it "tooling" to get them to line up correctly. The seller seems pretty focused on making sure you have the exact lines for the application. Cars being made in different countries apparently makes a difference?
I don't mean to hijack the thread here so anyone who can answer me please pm me; can I just buy the 1.6 NA lines for $20 less or will i need to man handle the lines to fit regardless? I seem to recall i had to bend them a tiny bit to make them fit perfectly and if its just a slight alteration that's not exactly detrimental to the lines is it? My line has started to leak at a place where it has never been bent (very odd).
Lastly, OP, do you think you could make lines for less than $50? I'm sure you would have several folks on here interested if you could supply new lines using your set as a template.
I'd also rather give a fellow vwdiesel.net user my $50 over someone on Ebay.
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Although, regardless of the line length you'd think that since you're moving a non-compressible fluid through the line and, providing there are no air bubbles, should get injection and pressure when required.
That pressure "wave" takes time to travel through the line. Even though the fluid is not compressible, it takes a few milliseconds for the pressure to reach the injectors once the pressure is delivered on the injection pump side. Milliseconds can translate to significant differences in degrees of timing when the engine is actually running.
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I've got three good ones sitting in my Garage, I'd be willing to send to anyone who wants them - for shipping cost. Trying to clean out my garage...
(the forth one (cyl #3) has a small leak)
Dang thats the same one that leaks on my set. :(
If the lines are not originally stainless steel then what are they made of?
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That pressure "wave" takes time to travel through the line. Even though the fluid is not compressible, it takes a few milliseconds for the pressure to reach the injectors once the pressure is delivered on the injection pump side. Milliseconds can translate to significant differences in degrees of timing when the engine is actually running.
That's exactly what I figured. The longer the line the longer that wave will take to reach the destination but I would imagine as long as I kept the new lines relatively close to the original length that "reaction time" would be negligible. Either way, like I said, I'm comfortable enough with bending tubing to make them the same +- a couple mm. Should even be able to use the OEM injector line clamp holder thingies.
Regarding price, at this point I'm not sure. The original set will likely be a bit more than any future ones simply because of the R &D (or more accurately trial and error) that will go into it. Parts can be ordered via McMaster Carr, and if I can get away with compression fittings rather than flared connections it'll make things even easier. If I do go ahead and start making them for fellow vwdiesel.net folks I can order the right stuff in bulk and hopefully keep costs down. Extra bonus if I can source the stuff from my instrumentation buddies (lots of scrap tubing and fittings "go missing" in that industry) but that all seems to be Imperial stuff.
So far, according again to McMaster Carr, a 2m length of 316SS tubing is around $100 for use with instrumentation (compression) fittings and a bit cheaper to go with tubing that would end up being flared. What's cheaper, messing around trying to flare SS tubing or spending the extra dough for compression fittings?
The thing I need to confirm now is the nut size on both pump and injector ends. I'll be up working on my car again this weekend (hopefully wrapping up exhaust and taking it for a brisk drive) so I'll try and get some measurements on the stock stuff and go from there.
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Tools for this project also need to be taken into consideration.
Muthaflippin tube benders are several hundred $$, and a good flare tool runs the same. Time to hit up kijiji...
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I don't think compression fittings are recommended on anything that is pressurized. One of those air over hydraulic flaring tools would probably work perfect, but $$$
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How do you intend on interfacing either a compression or flared fitting to both the delivery valves and the injectors?
Chris
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I just sold out and bought from prothe. I'll post in detail about quality and other useful info...
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How do you intend on interfacing either a compression or flared fitting to both the delivery valves and the injectors?
Chris
Same here. Just can't see how it can be done.
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SS is ALOT more brittle than regular steel, FWIW..
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I just sold out and bought from prothe. I'll post in detail about quality and other useful info...
...like what brand of beer cans they were made of?.. you should have waited for mine to come in....
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meh with shipping its $25. I'm not too worried about it. Worse comes to worst i'll make a pop tester out of one of the lines.
What are the original (oem) lines made out of?
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Stainless Steel has several nasty quirks which might mess things up.
Comparatively brittle, I think it work hardens which will make doing the bubble flares a right bugger. Stainless galls with itself, not sure it won't do the same with the injectors, this will bugger up the sealing surfaces. It gets weird pinhole corrosion problems with salt. Lastly it will look just a little bit effete. ;D
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We use both silver brazed fittings and Parflanged tubing for brake and hydraulic tubing. Our pressures go up to about 3500 psi.
Check out the Parflange machine at http://www.parker.com/literature/Tube%20Fittings%20Division%20Europe/euro_tfd/EMDC/4390%20UK.pdf (http://www.parker.com/literature/Tube%20Fittings%20Division%20Europe/euro_tfd/EMDC/4390%20UK.pdf) as it can handle stainless. That would take care of the ends. As far as durability, the process is used on aircraft brake systems so I think that speaks for itself.
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During my research I came across this, from pipe fitting site.
Types of compression fittings:
There are two basic types of compression fitting:
Type-A or non-manipulative fitting: These fittings are easy to install and do not require any modifications to the tubing. Type-A compression fittings are also known as olive and can be installed using an ordinary wrench for tightening the surrounding nut. These fittings are usually used for water connections.
Type-B or manipulative fittings: Installation of Type-B fittings require flaring or belling the tubing. In order to remove this type of fitting, a specialized pulling tool is often used for siding the nut and olive away from the pipe or tube. The type-B fitting is mostly used for gas lines.
(http://www.lytron.com/Tools-and-Technical-Reference/Application-Notes/~/media/Images/Lytron/Tools%20and%20Technical%20Reference/Application%20Notes/mechanical%20grip%20type%20fittin.ashx?w=243&h=180&as=1)
Using this picture a reference, you can see that if the angle of the sealing face of the fitting body is known then mating it to an appropriate flare or ferrule shouldn't be a problem (providing it isn't some VW proprietary thing). Typical bubble flares seem to be 37 degrees which leaves the threaded nut as the next piece of the puzzle.
Perhaps SS isn't the way to go because of it's brittle nature, especially if flaring is the only option, but that doesn't mean the lines can't still be fabbed by hand. I scored a set of AAZ lines and IP yesterday at Pick n Pull so at least I have something to study.
I still have hope for this.
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FYI: I can get these lines from my wholesaler for $12.00-12.50 each,
pre-bent, with two sealing nuts, and even the rubber sleeve. Anyone who has access to the basic import wholesalers, Worldpac or IMC, should be able to get them for you. They are made by a company I have never heard of, Cohline GmbH.
**List is $79 each, but they cost 12-13 ea.
Part nos:
068 130 301 Cyl. 1
068 130 302 Cyl 2, etc...
Lots of places on the internet selling them at $15-20 ea.
-Brad