What kind of high pressure metric fuel fitting is this?

January 25, 2009 3:23 PM

What kind of high pressure metric plumbing fitting is this? [pdf link (85kb) | jpeg link (60kb)]

I am working on a prototype gasoline direct injection (GDI) engine. This fitting connects a high pressure fuel supply line from the fuel pump to the fuel rail that supplies the injectors.

The thread is metric (M14x1.5) and the tube is 8mm OD. It is pretty thick wall stainless steel. I expected it to be metric since the engine is of European origin. I'm pretty sure the other components in this system are Bosch, but I have not had much luck getting technical information from them for other stuff so I am trying AskMe first.

This fitting sort of looks like DIN 3852, maybe some kind of JIS 30° flare fitting variant that I haven't seen before.

I am hoping some tech-savvy mefite can save me some time and tell me the name of this kind of fitting, what SAE or DIN standard to which it conforms that would be great. Since I want to build a fuel system, what I'm really after is a supplier of other fittings. I don't want to build my own or just throw something together because the fuel pressure in the fuel rail is around 120 bar (1740 psi).

The pdf has a bit more technical information, the jpg is one of the pictures in the pdf for mefites who don't like pdfs.

posted by KevCed to technology (14 comments total)

SAE AS5202
posted by Confess, Fletch at 3:45 PM on January 25

I don't think it is SAE AS5202. The thread measures 13.85mm and 1.5mm per thread exactly. The nearest imperial thread to that (from your link) is 9/16-18. I used a thread pitch gauge to compare to 18 tpi and it was way off. It is definitely M14x1.5.

Thanks for the link. I had not considered aerospace fittings. Aerospace has more experience with high pressure fittings than automotive.
posted by KevCed at 4:04 PM on January 25

I didn't think that was it either but it was the only weird high pressure fitting I could think of.

Try looking through the MSC catalog, you might find it there, it's where I found my AS5202 port cutting tool.
posted by Confess, Fletch at 4:14 PM on January 25

Not as much a direct answer, but possibly a different approach (forgive me if this is blindingly obvious):

M14x1.5 are pretty standard European fitting and sensor sizes. When you say you want to build a fuel system, but on a development engine, do you need to use production standard hoses? If not, just convert the fittings to JIC and use swaged aeroquip (aviation) pipes. You can even use the solid aero pneumatic stuff that is easy to find. Aero and racing suppliers are a superb source for this alternative, as we do this kind of thing all the time.

Once you get to a workable solution, then you can find a production source (Bosch have always been fairly reticent with that sort of thing in my occasional dealings with them). Any after market supplier of patter parts in the UK or Europe dealing with the manufacturer you are dealing with (I won't guess, in case I am right) will be able to supply fittings, and manufacturers of swage pipes like that are pretty easy to find. Often you can ask for "Bosch fittings, please" as it is common enough.

Bit of a headache to start with, while things may be changing for configuration and testing, though, so a bespoke fitting that perhaps seals on an o-ring or tapered machined seat (relatively easy to measure) coudl allow you to work much easier until time for production (which may actually, in a big company, make it someone else's department...?).
posted by Brockles at 4:29 PM on January 25

Those are good points Brockles.

Your comment that the M14x1.5 thread is common for fittings and sensors is right on the money. The same bracket+nut+washer combination is used for a pressure sensor elsewhere on the same fuel rail.

I'm not worried about production at all. I am doing research at a university, not at a manufacturer. I don't need to use production standard hoses but I do need to use lines and hoses that are capable of handling the required pressure and compatible with the fuel(s) I will be testing.

This fitting doesn't have a one-off look to it, It looks like a production-type fitting (i.e. mass produced) and I assume from the size of the manufacturers involved (both engine and fuel system) that it's from a well-established standard.

One thing I didn't mention is that I don't want to mangle the fuel line I have already. I'm supposed to return the engine unscathed after my research is complete so I'd like to avoid swagelok and the like. (if I can)
posted by KevCed at 4:45 PM on January 25

One thing I didn't mention is that I don't want to mangle the fuel line I have already.

That's the whole point. If you make an adaptor and use correctly rated hoses for the pressure after that point, then you don't even use the fittings, never mind mangle them. You could make a solid adaptor to mirror the action of the threaded piece of the pipe, still use the washer for sealing, and have a suitable (for your ease of sourcing) thread on the other end - either a BSP pneumatic fitting or a JIC aircraft type fitting. There are plenty of options in the pneumatic and hydraulic world that deal with pressures that high.

The fitting is clearly production type - this doesn't make any difference to you, as you don't want to create a production solution. Use prototype/small volume production stuff, just keep an eye on the ratings. You can produce a perfectly functional and safe plumbing set like this, just not one that is commercially viable for mass production. But that doesn't matter to your research, right?
posted by Brockles at 5:36 PM on January 25

Brockles, I understand your point better now.

In fact I want to do exactly what you describe, that is using an adapter to something more conventional for the rest of the system (i.e. the rest of the supply side). There is still a problem. This fitting is on the engine-side of a fuel line running from the pump to the engine.

The fitting I showed is how I supply high-pressure fuel to the engine. I need to know what kind of fitting it is so I can get an adapter from that to the engine. The point is that the fitting I have is not something I need supply from, it's something I need to get so I can supply the engine through it, that is the only way to connect to the engine.

Moving further upstream, the other end of the line has a fitting that is similar except the flared flange is more spherical than conical. (actually looks like low pressure plastic compression fittings for faucets.) I thought I'd have a better chance of matching this end with something off the shelf.

In the worst possible case I'll just mangle the line I have or maybe take a trip to a Bosch plant and wander off the tour until I can find the parts and adapters I need. :P
posted by KevCed at 8:08 PM on January 25

Ok. It's really not as hard as you are making it out to be. You're thinking far too techically about this, with DIN's and standard numbers. It's much more simple, and there us no magic to adaptors at all. If you use an adaptor to change the method of attaching to the engine, you can use any hose you want for the supply. Just screw the adaptor into the fuel rail, and attach whatever you chose the other end of the adaptor to be - there will be a selection of M14 x 1.4 to 'x' adaptors available off the shelf. In the same way, the (sounds like standard pipe round taper to me) other end of pipe may need an adaptor to whatever hose you choose to use between the two points. I'd convert the both ends to a standard aeroquip size, if it were me, and then I'd have freedom with the hose length and routing.

You know the thread. You know (or can measure) the taper. That is all you need. That is all an adaptor needs to define it. There is no 'standard number' you need, you just look for a male to male adaptor from a standard pipe supplier and match it up. If you can't find the exact taper, just buy the nearest one and machine the angle to suit - surely you have the facilities?

It is possible that you just pick the size with what you know - a M14x1.5 (100degree taper seat) adaptor to (say) -6 JIC is a perfectly good way to order an adaptor from a suitable supplier. If they don't sell it off the shelf, you'll have to try a bit harder - like machining the taper seat, as I say. It'll be a male taper so it's dead easy on a lathe.

The vast majority of hose fittings are of one of two or three standard styles - female taper, male taper or ball end. If you're still struggling, take the fittings (and the pipe and the rail, if you want, and a print out of the drawing) to the nearest decent sized industrial pneumatic supplier and just ask the guy at the counter. Tell him what you want to do, and ask his advice about pressure ratings (ie don't get a crappy seal on the bolt surface for those pressures. USe a copper washer or the taper seat itself). This is all standard stuff, and he may well even have something in stock that will fit.
posted by Brockles at 8:55 PM on January 25

It is as hard as I am making it out to be. What I think I failed to explain is that the male end I'm trying to identify is the "from". The "to" is the slightly chamfered hole in the fuel rail. I need to know what the "from" format is so I can get one like it.

I am not using the stock fuel pump (for various reasons) so I either have to connect to the spherical end that it used to, or connect directly to the fuel rail through the fitting that is the subject of this post.

Is that clearer?

What it boils down to, your excellent suggestions notwithstanding, is that I need to know what kind of fitting this is, or where to buy them. I do appreciate you taking the time to type repeated replies.
posted by KevCed at 9:11 PM on January 25

One thought— you're at a university. Many (most, I'd think) universities still have a machine shop or two, specifically for making instruments, teaching apparatus, experiments, models, and so on. They may well be able to duplicate the business end of the fitting you're looking at even if they can't identify it. (Basically, I'm saying what Brockles is saying, but with an in-house machine shop.)
posted by hattifattener at 11:27 PM on January 25

It is as hard as I am making it out to be.

I understand your frustration, and maybe I am not explaining myself well enough but (having done countless similar projects) I'm sorry but it really, really isn't. There is no magic to adaptors, and you seem to be under the impression that it must be some magic, specific one. It isn't, it's just a threaded hole with a taper at the end. That is ALL there is to it. It just looks harder because the thread is in the collet.

I need to know what kind of fitting this is

You do. It's an M14 x 1.5 thread with a 100deg male tapered seat. You already have as much of a specification as you need. The only potential complexity is making sure the tread is long enough to mean it tightens up on that collet properly - again, this should be relatively easy with a standard part. As long as it goes tight without the underside of the head hitting the collet, you're good to go.

or where to buy them

Goodridge, Aeroquip, Earls, Aviation Spruce, Bob's Pnemumatic parts store - anywhere selling aviation or a large selection of pneumatic fittings. M14 x 1.5 is not an unusual fitting size at all. Then just pick whatever you fancy for the other end of the adaptor - to suit whatever pump you wish to use.
posted by Brockles at 5:00 AM on January 26

Thank youBrockles and hattifattener.

One problem is that I'm an engineer. See the first joke here.

I know that I can design and machine a fitting that will be compatible. I have done that a few times at an internship I did at a heat exchanger OEM. I want to avoid that if I can because I'd rather not deal with gasoline/ethanol fuels at these pressures.

Brockles, there is some "magic" to high pressure fittings. These kind of fittings need smooth sealing-faces and a commercial fitting is probably hydrostatically tested. Sometimes the angle of the seat and the angle of the male fitting are not identical, and a crush-washer is "wedged" in a certain way. I don't have info and I'd rather not guess. I'm being extremely conservative here in the hopes that this is a standardized fitting. If I'm going to buy something from any of those stores I need to know what kind of fitting I'm looking for, hence this question.

That's all a long-winded way of saying that I would rather buy a commercial fitting, if one exists, but I will make one if I have to.
posted by KevCed at 6:47 AM on January 26

It's a Japanese 30 Degree flare fitting also called a Komatsu fitting.

More info here.
posted by Confess, Fletch at 9:54 AM on January 26

I took the fitting to a dealership for the manufacturer in question. One of the techs said he had seen something similar in a Diesel common rail application but nothing similar here in the US.

Walking home from the dealer I found an auto shop who gave me contact info for a hydraulics company whose specialty is oddball metric fittings.

After all that I finally got confirmation that I can go ahead and modify this line to suit my application.

I'm still pretty sure it's a standardized fitting for the OEM or one of its suppliers but it's a moot point right now.

Thanks for the replies and advice!
posted by KevCed at 7:08 AM on January 29