Fuel rail

DaveEFI · Post by **DaveEFI** » Fri May 01, 2015 3:05 pm

I'm intending changing to later high impedance injectors on my SD1 with MegaSquirt. The later injectors have a different connection to the fuel rail, so that will have to be changed too.

The SD1 has the fuel tank pipe runs on the nearside - all the Hotwire and Gems fuel rails I've seen have the connections to the offside. I have both a hotwire and Gems fuel rail here.

I'd rather not have fuel pipes looping all over the place, so I'd like to modify one to nearside feeds. On the gems one, the regulator can simply be turned round through 180 degrees, so that's one sorted, but the other one is a bend in the steel. What it needs is cutting and rotating though 180 degrees.

I'm not confident of my welding ability. I was hoping a domestic end feed solder coupler might be used - but the OD of the pipe is 15.8mm while even the old 1/2" imperial copper size is 15.3mm Even if I could find one.

Spongo · Post by **Spongo** » Fri May 01, 2015 3:42 pm

Maybe a hydraulic supplier like Hyphose etc could come up with a fitting that will do the job?

JSF55 · Post by **JSF55** » Fri May 01, 2015 4:27 pm

Dave I used a hydraulic fitting on mine, you just need to order a 90o one ?

idle air control by jsf55 pics, on Flickr

DaveEFI · Post by **DaveEFI** » Fri May 01, 2015 11:13 pm

On the rail I'm intending using, that's where the regulator goes. I'm happy with than end, as turning the reg through 180 degrees makes that fine. It's the other pipe which is the problem.

The snag (as I see it) is the pipe bends almost as soon as it is past the injector boss, making it difficult to use a compression fitting.

Any chance of a pic of the other end?

JSF55 · Post by **JSF55** » Fri May 01, 2015 11:42 pm

Best I could find, looks like I've turned through 180o to fit the other way?

injectors and rail by jsf55 pics, on Flickr

JSF55 · Post by **JSF55** » Fri May 01, 2015 11:43 pm

Here's it painted up

fuel rail and pressure regulator by jsf55 pics, on Flickr

DaveEFI · Post by **DaveEFI** » Sat May 02, 2015 11:01 am

Thinks for the pics. That's a hotwire one. Looks like you've broken the weld for the regulator bracket, rotated it 180 degrees and rewelded. On the original, the bracket is also welded to the other the pipe - I assume its proved strong enough in practice with only the one fixing? Or perhaps the bracket is to also support the pipe, rather than just the reg?

I'm still temped to use the GEMS one. One end of that is OK without any mods, simply by rotating the reg.

Why is nothing ever simple?

JSF55 · Post by **JSF55** » Sat May 02, 2015 8:03 pm

I was looking at it and remembered how clumsy the compression fitting looked, I found a suitable barb and took it to a local fab shop who tigged it for me, no charge

I never had any issues with fuel leaks !

stevieturbo · Post by **stevieturbo** » Sat May 02, 2015 8:59 pm

I'm pretty sure I soldered a brass fitting onto a fuel rail I used years ago as I needed to cut the feed side short.

As long as you clean back to bare steel and both materials are happy with solder then it should be a good strong joint ( assuming a good overlap much like a plumbing type joint )

For the return I just made up an adaptor to remote mount a reg. That was on hotwire rails

unstable load · Post by **unstable load** » Sun May 03, 2015 6:23 am

Does the fuel HAVE TO go in at that end?
What if you blanked it off there and went in at the boss on the front of the engine?
If you are going to go cutting and welding, then you could T it in wherever you want, as long as the rails aren't for some reason location sensitive.

stevieturbo · Post by **stevieturbo** » Sun May 03, 2015 7:54 am

it is usually preferred for full flow rails. ie, flow in one end and out the other.

But no, it would be quite fine to have a feed enter in the middle and one half be a dead end, the other half with a regulator mounted on it.

A little odd, but perfectly fine.

Or you could just dead end the rails completely and mount a regulator just prior to the rails which can really simplify things ( although you'd need an aftermarket regulator, the OEM just wouldnt lend itself to this route )

DaveEFI · Post by **DaveEFI** » Sun May 03, 2015 8:51 am

Interesting. The SD1 rail is a ring with an in and out. The Thor one is two dead ends with just an input - a sort of Y. I assumed that used a pressure controlled pump rather than reg? It's also much smaller in diameter - higher pressure?

I'd have thought a dead end type would be prone to vapour lock on a hot start?

No problem using domestic type end feed solder fittings. The safe working pressure of that is way higher than the fuel rail.

stevieturbo · Post by **stevieturbo** » Sun May 03, 2015 9:11 am

DaveEFI wrote:Interesting. The SD1 rail is a ring with an in and out. The Thor one is two dead ends with just an input - a sort of Y. I assumed that used a pressure controlled pump rather than reg? It's also much smaller in diameter - higher pressure?

I'd have thought a dead end type would be prone to vapour lock on a hot start?

No problem using domestic type end feed solder fittings. The safe working pressure of that is way higher than the fuel rail.

most efi's operate with similar pressures.

The regulator can go anywhere on the high pressure line, whether after the injectors, or right at the pump.
I'm not going to say it doesnt matter, because to a degree it does, but largely if the rest of the setup is designed correctly to work with that layout, then it doesnt matter.

Many modern cars have a dead end line with the regulator in-tank near the pump and run a fixed rail pressure.

I've had 2 of my rails dead ended for several years, with the other pair being a full flow type.

Just saved on lots of hoses everywhere when there really was no need.

But it is always best to have the FPR local to the injectors/rails, preferably after the injectors, but by no means essential.
And if a boosted application, definitely preferable to have a FPR referenced to manifold pressure.
For n/a, really no big deal if it is or isnt.