Is there a huge difference by running a splitter off your send line and run the fuel rails in parallel... like this picture? The stock setup runs through the primary rail then to the secondary... it just seems like having them in parallel would mean more lines/fittings to buy.

 

My general theory is less fittings - because I suck at plumbing and the lower # of possible leaks the better for me.

I have them setup in parallel this time. Since I have had my fuel system setup 7 or 8 different ways I have done just about every combo.

Bottom line is the fuel system just needs do deliver and adequate fuel consistently. I have seen people with 400 rwhp running a single 6AN line in series and they were fine. I dont think you have to worry about it unless you are shooting for 400+ rwhp.

 

Sorry but in your pic there is no return line that I can find . With a splitter you will need two splitters so you can pipe the rails back to a single return line .In my way of thinking that is to many connections that are not needed to do the job .I run a 3/8 inch line from the pumps connection out of the tank to the filter then to the front .Then ss braded to the sec rail first then a ss hard line to the pri rail then ss braided to the FPR . From there back to the stock return line . It works and not to many connections to leak and the set up did not cost an arm and leg .

 

The return line is coming out of the bottom of the FPR. Most FPR have dual inlets so you can plumb the rail lines into that.

 

The pic is so large on my screen ,but I see it now thanks .I do not remember my fpr having two ports but that would save some money .But still to many places to leak and to much money for me .

 

I believe the theory is with parallel, is there is more of a surge capacity, and less chance for pressure variation through the system as more elbows and volume is drained off the
System.


Clearly the stock system is ran in a series format so it can’t be that bad (though part of there motivation is cost) but a parallel setup would probably be a slightly better setup, and there is usually 2 ports for bleed off on higher quality units such as aeromotive.

Personal opinion, (if in plain view) one of the ports is blocked off looks a little odd IMO, and it really isn’t that much more for the few fittings it takes to run it in parallel.

And it leave options for fuel temp sensors

 

Back from the dead. Does anybody know if the tap sizes in the first picture of this post would work for an FD (since it's marked FC3S)? Has anyone replaced the hose that goes between the primary and secondary rails?

 

I am no fuel expert, but I would think that you would the single line going to the splitter to be a -8 line. Reason being that a -8 line would carry volume, while the reducing to a -6 would help with pressure. It's just doesn't look like you would have enough volume from the -6 single line to keep a good amount of pressure on both -6 lines (after the splitter) if you were to really put those injectors to use.

Now, I have my lines in parallel from the pump back. One pump feeds each rail. I did mine this way, although costing more in the end(more line, fittings etc..) because of peace of mind. Like I said, I'm no expert but the parallel setup was what I saw too many times on high hp rotaries. A proper series setup should work if you have proper hose sizing and what not. I think the issue is that they are different size injectors on one line, and it's hard to compensate fuel flow when the secondary injectors come online, which are normally bigger ones.

Just my $.2 ..

(Flame suit on)

 

Thanks for the input, but would anyone like to actually answer my questions? j/k

 

My question boils down to this. What tap size can you use on both sides of the stock primary and secondary rails (preferably without having to drill first)? The Banzai write-up on the FPD elimination says you can tap the primary rail input with a 1/4" - 18 tap, so I'm assuming that you can use that same tap on the primary rail output. What I can't find is an appropriate tap size for the secondary rail.

 

besides doing it for show, this fuel system mod is utterly pointless for your setup (unless you are just doing a PD elimination). 550/1300 and stock rails and lines with FPR are fine for non sequential twins.

but I'm guessing a 1/4 NPT tap would also work for the secondary rail. Most people just ditch it on the FD though. What is the point? You can't use top feed injectors with a side feed rail.

 

Okay we've got a guess for 1/4 NPT. Anybody know for sure? I'd hate to get down there only to have to wait on a fitting while my car is down.

 

One final question. I've read that 90 degree fittings on the ends of the primary rail are necessary to clear the OMP injectors, while I've seen straight fittings used by Banzai on the primary rail. Does anybody know if 90 or 45 degree fittings should (or should not) be used on the primary or secondary rails due to clearance issues?

 

I tapped my primary rail with 1/4NPT and used 45 degree barb fitting and cleared the oil injectors. Regarding the OEM secondary rail, I'm not sure about tapping but Sard makes an adapter that simply bolts to the end. http://www.rhdjapan.com/jdm/SARD-Fue...ru-Mazda-10689

 

Cool. Alright, 45 degree adapters from 1/4NPT to 6AN on the primary rail to clear the OMP injectors. Thanks for the pic and good lord is your engine clean. I was aware of the Sard part but at $35 + shipping a pop I'd prefer a $7 adapter if possible (plus a connection which doesn't reuse the screws that seem to strip so easily would be a bonus). Anybody out there tapped the secondary rail?