Hey do you know what size the supply fitting is on the fuel rail of a GS400, it looks like I am going to make some changes to the fuel system. I need to know if the rails are NPT or metric and what size?


Anyone?

 

Hey Morris,
What are you planning to do? Are you running a bigger line? It's a fine thread, I will check on the size tomorrow.
JP Importz

 

Well I am still working out the details, I may add a second pump. But at a minimum I am going to use the -6 for the supply and then use the stock liine for the return.

Right now I am using the stock line to supply the rail.

So if I am going to run the -6 supply I need to be able to plumb the -6 into the rails. I really dont want to have to drill and tap the rail unless I absolutely have to.

The end caps were metric, and I am guessing that the supply fitting on the rail is metric also. If so I am out of luck and will have to drill and tap it for a NPT fitting so that I can use a AN to NPT on the rail to hook up the supply from the y block.


This is all becasue I seem to be getting inconsistent fuel pressure, as I start moving from vacume towards boost my fuel pressure on the rail starts to drop off when it should be increasing.

I am guessing that the problem is that the walbro isnt able to supply enough pressure. If it was a volume issue my guess is that the psi would fall close to zero.

OR something in the tank is hosed up.

Either way I am going to have to open things up and I dont want to have to do that again so I may just try to address everything at one time.

I am at 45psi at idle, as I accelerate it sometimes drops as low as 35psi when it should be increasing.

Another option would be to install a booster pump and see if that solves the problem. But I am leaning away from this option right now.

 

not saying it would be the easiest option, but you could always just weld a fitting on the ends of the rails instead of doing a fitting. i had to have that done since my rail ended up right at the firewall and a straight fitting wouldnt have fit.

 

yea thats a thought I read about someone doing that over on dot net. They even had the bungs at summitracing. My only concern is that I dont have anyone that could weld aluminum. Isnt that a special welding machine that is needed for aluminum?

 

Are you running the returnless fuel system? If you are, I would get the BEGI rising rating regulator. It will raise 7 pounds of fuel pressure for 1 pound of boost. Also here is a quick chart for injectors calculation:
Flow Rate= (HP x BSFC) / (#Injectors x Maxcycle)
Let me know if I can help
JP Importz

 

nope I have a return line in but I am using the aeromotive fpr, which is 1:1. If you come across what size the fittings are on the rail that would be tons of help.

Thanks

 

The size is M12x 1.12
JP Importz

 

Well it looks like good news Summit has -6AN to Metric 12mm adapters, both in 1.5 pitch and 1.25 pitch. My guess is that one of those is gonna be the right thread.

 

Or you can weld it. Send us the rail and we will weld it for ya .
JPI

 

you just gotta find someone who can tig weld to do the aluminum.

 

Anyone have any suggestions as to whether I shoud go with a booster pump or a second walbro?

 

guess that depends on total horsepower you plan to make. two walbros will definetly support a ton of power, but they are kinda a pain to get set up.