What I did for NB2 Return Fuel System, DW300, Vacuum referenced regulator, Flyin Miata fuel pump wire kit & NB2 Fuel tank venting retaining roll over valve

Track data logs show I was running at the limit of my return-less NB2 fuel system, not to mention tuning for Florida Sebring heat soak was a PITA.

I decided while going from DW200& 650's to DW300 & ID1050's, I would go full return system with a 3/8" return line instead of the tiny unused vapor line.

Flyin' Miata / Trackspeed fuel pump rewire kit included.

The charcoal vapor system was deleted years ago, but decided to get rid of the big filter and have it exit on the cold side instead of in front of my exhaust that spits the occasional flame.

Will do this in several posts as it was a bunch of steps and lots of photos.

I used #6 AN fittings and line from Improved Racing as you couldn't ask for a better shop to deal with and they are local.
Earls, Aeroquip, XRP or Brown & Miller are all good options, but probably overkill.

The budget method would be push lock lines or plastic QD factory style lines. Of course anyone thinking they are going to build a budget race car is kidding themselves.

The blue fittings you see are Earls or Summit, only because Improved was on back order. I bought everything from Improved racing, Summit Racing and Amazon. Not including the tools and aircraft hardware I had on hand. Adapted my existing Flyin' Miata fuel rail for dual feed.

1. 3/8" return hard fuel line:

Note: My NB2 has ABS, which makes everything harder as it has extra brake lines that take up room right where fuel lines pass up into engine bay.

After talking with a couple regulator companies I settled on a 3/8" return line w pretty Aeromotive regulator. ( I used aluminum which was "easy" but should replace with Copper-nickel (CuNi/NiCopp) or stainless when motor is out next ). ( If I did it again I would also do fuel line in 3/8 which I may do anyway depending on logs.??) Added Lowdoller Motorsports fuel pressure sender to monitor.

Jacked car, removed the underbody braces, a bunch of line supports as well as the rock guard between the engine bay and floor and removed the vapor line. Which is a PITA as it has multiple line clamps and a compound curve.

Using a "polished jaw" line 3/8" line bender, duplicated the vapor line with some modifications for slightly new routing.

37* flaring tool which made short work of setting the tube up to take AN hardware. I prefer flares to ferrules, but that is just me. 37* tooling is much pricier than hardware store angles.

As you can see by completed photos, "I could have made the rear of the line shorter for better packaging."

For the supports. I used a 3/8" ball router and rat tail file to enlarge plastic clamp openings to snugly hold new 3/8" line. While relocating a a clamp on the rear and adding clamps as needed.

 

2. Fuel pump hanger assy. w elimination of NB2 in tank regulator.

I was using a DW200, which I have no complaints about. It was quiet & made over 350HP on pump gas paired with 650 injectors

However I was hitting 100% duty cycle which injectors did not like & can never leave well enough alone. While redoing, I wanted expansion room for any reasonable build or E85.

Enter DW300 along with elimination of stock fuel regulator paired with vacuum referenced regulator.

I used a -6 AN to 11mm OD Aluminum fuel rail adaptor fitting for Toyota/Subaru and some of the leftover 3/8" tube for return drop line replacement for in tank NB2 regulator.

Note; There has been some discussion of the factory pump filter flowing better than the DW filter as well as working better to prevent fuel starvation during long duration LH corners.

Pictured is a new DW sourced filter in the kit vs. a factory NB filter. You can see the difference's. The factory one is better supported internally, (feels more robust) and has a slightly different angle. Not to say the DW wouldn't work fine, however changing is a PITA. Don't forget the tiny washer.

 

3. Flyin' Miata / Trackspeed fuel pump rewire kit & relay.

As a supporting mod to the DW300 I added a Trackspeed / Flyin' Miata rewire kit.

Instructions are a tiny bit off for NB2's, so photos attached showing my install on an NB2.

Eliminated wiring for purge valve while I was at it. TT track car - MS3 does not support, and I don't hug trees.

 

4. Elimination of carbon canister and LH side tank vent, keeping NB2 rollover protection.

While I eliminated my carbon canister years ago by splicing the 5/8" lines together. I wanted a lighter system that exited on LH side of car, instead of above suspension in front of flaming exhaust.

I eliminated all the above by splicing in a 3/8" line and running it over the tank, out the top of the filler tube grommet, to a lightweight marine 3/8" fuel filter as a vent filter, joining the filler drain line which exits behind rear tire using a 3/8" barb tee. Also eliminating the unused hollow purge valve.

My priority is not being able to quickly refill tank during pit stops like an endurance racer. So I did not prioritize max tank capacity and didn't use huge vent lines.

You will notice in photos NB2's use an in tank rollover valve that is connected with a inner tank crossover tube to the top RH side vent tube that runs to the purge valve, charcoal canister, big filter and evaporation chamber.

NOTE: I have not track tested this setup yet.!!! But it "should" work better than disabling fuel cap by drilling or modifying one way vent.

 

 

Need to replace that factory connector with some type of bulkhead wiring. You will melt the connector.

I used this setup from Racetronix

​​​​​​https://www.racetronix.biz/p/univers...4-way/bcws-001

Other people use the studs and wire off each side.