gracer7-rx7

iTrader: (16)

I spent a good amount of time searching the forum yesterday but there are a few things that I need help understanding...

I'm working on swapping a fuel injected 13b rotary from an "S5" FC RX7 (1989-1991) into a 1983ish FB that was originally equipped with a 12a. This is a race car so no interior or creature comforts are present which simplifies things a bit since I don't care about lights, hvac whatever.

I have the engine, manifolds, wiring harness, ECU, coils etc. I think I have a grasp of what to do with these - i.e. mount the engine and route the wiring. Easier said than done

Right now, I'm struggling with understanding fuel delivery. I know I need a different, more powerful fuel pump but does it need to be installed in-tank? I also understand that I need a larger diameter fuel deliver line which I can manage.
Any insights and advice is appreciated.

Thanks.

mazdaverx713b

iTrader: (91)

An external pump should work just fine. I installed a 13B from a GSL-SE in my 85 GS 11 years ago and used the original external pump. You shouldn't have an issue using a high volume external pump. You may have to fabricate a bracket as my friend who did the exact swap you're considering did. He did an S5 swap into an 85. When I did my swap, I bought aluminum fuel line and ran new feed and return lines with it. It bent and flared perfectly. I got the fuel line in enroll from Summitt.

j9fd3s

iTrader: (3)

you have a couple easy choices for the fuel pump:

the cool kids take an FC/FD pump assembly and top of the tank, and weld it into the 1st gen tank.
#2, you can use a GSL-SE pump, its external, bolts in, needs some pipes fabbed (if you're lucky you can find someone parting one, the FC ones would actually be close to fitting too)
#3 you can use a Walbro pump, they make an external EFI pump.
#4 pretty sure i've seen Australian cars with the stock carb lines and the fuel pump under the hood

you probably want to run the stock FC fuel pump relay setup. the 79-83 cars just run from the key, the 84-85 is like the FC

LongDuck

Some thoughts from a long-time SE EFI driver, and trying to cover this in sequential order of fuel flow;

1) Fuel delivery specific to EFI engines requires a large feed hose (1/4"ID+) from the tank to the pump in order to provide a high volume flow to the high pressure pump. Keeping the pump close to the tank (or in-tank, as suggested above) is the best option to get good pressure. Any further from the tank, and the pump will suck the feed hose closed and hurt pressure consistency.

2) A separate, plastic cone Fuel Filter is located in this large hose feeding the pump. This 2" long cone filter is often overlooked as a source of problems, but is a secondary filter apart from the fuel pickup filter and sock to prevent gunk from getting into the pump. It's cheap insurance, and does catch and hold stuff that you don't want in your pump.

3) Fuel Pump and Pulsation Dampner - the stock pump is about $377 from Mazdatrix and is bulletproof. Case in point, my original pump lasted to 240k miles and I replaced it only because I didn't want to get stranded somewhere - it still worked 100% compared to the new OEM pump I put in. You could do a lot worse with an aftermarket pump, is my point ***if you're sticking with an RE-EGI intake with only 2 injectors***. The engine swap you mention has 4 staged injectors, and you may run into problems running them all at once (SE is 2x 680cc low-impedence injectors with FC 2x550cc and 2x760cc, high-impedence, IIRC - I could be wrong, I don't own an FC). There is a Pulsation Dampner (PD) mounted to the output of the OEM pump which is matched to the PD on the fuel rail at the intake. These are included to prevent hydraulic hammer effect on the injectors and for consistent fuel pressure through the lines.

4) Fuel Filter is a high-pressure, all steel - or aluminum - with a large internal volume and metal lines. This is placed AFTER the high pressure pump in an SE to filter the high pressure fuel before it goes up the metal feed line to the engine. The metal fuel lines, both feed and return, are larger than those on carb'd cars.

5) Fuel Rail for the SE as mentioned above is only 2 injectors and a vacuum controlled Fuel Pressure Regulator (FPR) and Pulsation Dampner (PD). The FPR senses intake vacuum from the plenum and under high load sucks down a diaphragm against the return line, bumping effective fuel pressure from about 31psi to roughly 44psi at WOT. This helps with fuel flow under load without exceeding injector duty cycle. The PD on FC engines are known to leak which has led to some engine fires. The SE-specific PD on the fuel rail isn't known for this and are very reliable (I have 245k miles on my original and still going...).

6) Fuel Cut (aka Circuit Opening) Relay is a SAFETY item and should not be bypassed, especially on a race car. It's purpose is to turn off (open the circuit) to the Fuel Pump in the event that the engine stalls so you don't continue to spray high pressure fuel into a car fire. Bypass it at your own risk. Also, bypassing this relay commonly results in engine flooding on startup...

... you knew there'd be 7 items, right?

7) High pressure Fuel Hoses need to be used throughout. If you try to use standard fuel hose, it is not reinforced internally and will expand and contract in use eventually which crazes the rubber and results in pinhole leaks along it's entire length. Think of this as a fuel atomizer which is a dangerous thing around electrical and hot exhaust components. Replace every bit of your fuel hoses with "HIGH PRESSURE FUEL HOSE" which will be plainly marked as such.

Reply back with your Fuel Injector staging setup and what intake system you plan to use and I'd imagine you'll get some interest from the FC guys who know more about what may be needed to get that working properly on first startup. Good luck,

gracer7-rx7

iTrader: (16)

Thanks for the education fellas. That helped tremendously.