NB Fuel lines simplified?

Divo · Postby **Divo** » Mon Jul 04, 2011 8:37 pm

Hi,

Building a Clubman using a 2002 NB engine. Need to run 2 hard fuel lines from tank/fuel pump (MX5) to engine and a breather line from tank to charcoal canister in engine bay. Can somebody give me an idea of what the intake fuel line connects to at the engine end and where the return line connects to at engine end please and any other connections I need to make between fuel line components.

cheers

Mark

93_Clubman · Postby **93_Clubman** » Tue Jul 05, 2011 2:11 pm

Just had a look at my NA8 fuel rail & an NB8A fuel rail: fuel supply (via fuel filter) hard line & fuel return hard line both attach to the fuel rail, one via a vacuum activiated solenoid attached to the end of the fuel rail. As you say, the third line (also a hard line on the NA8) goes to the charcoal canister. AFAIK there are no other connections between fuel line components, as from memory there are just the three lines exiting the top of the tank/ fuel pump/ fuel gauge sensor assembly. Can't confirm this is exactly the same on the 2002 NB8B motor - there may be slight differences as there are slight differences in this area between NA8 & NB8A.

Postby **NitroDann** » Tue Jul 05, 2011 5:20 pm

Its a returnless system, does that help.

Dann

Hellmun · Postby **Hellmun** » Tue Jul 05, 2011 9:35 pm

I've asked this before and was told the NB8A fuel rail returns but the NB8B one doesn't. So the NB8A fuel rail is a better setup but you can drill and put in a fitting to make it return on the NB8B. As I understand it the 4th cylinder runs very slightly leaner compared to a returning system due to slight starvation from the delay of re-filling the end of the rail. Personally I was going to just run an M-tuned larger bore fuel rail from 949racing when I go turbo and hook up a returning line from that.

Postby **NitroDann** » Tue Jul 05, 2011 10:22 pm

Woah! Dont forget to add a fpr if you make the returnless rail a return setup. Haha. Dont foget lol.

Dann

Hellmun · Postby **Hellmun** » Tue Jul 05, 2011 11:30 pm

Looks like the NB just has a dampener and the NA had an FPR. So yeah looks like a new regulator would be required. I always thought NB's had them too though I've never tinkered with the current fuel setup.

http://www.flyinmiata.com/support/instructions/misc/Fuel_Rail.pdf

Divo · Postby **Divo** » Thu Jul 07, 2011 9:36 pm

Thanks guys.

It seems the fuel pump sender unit I have is from an earlier model than the 2002 NB. Mine requires an intank fuel pressure regulator to set up the returnless system. I think I have to use an external FPR after the fuel filter with a tee junction. This allows the fuel to go to the fuel damper and into the fuel rail and the rest to return to the fuel tank - at least I think that's how it should work.

Feel free to clarify or correct me if I'm wrong.

cheers