N/A Fuel System Question
 

After i get done doing everything to my engine that i want to do. Im going to add bigger injectors.

550 Primary
720 Secondary
Walbro 255lph Fuel Pump

For the primarys Im not sure if I should go with 720s instead since I might be going with a B-port on the secondary ports. im leaving the primary ports alone.

Should I get a good pressure regulator to complete the upgrade aswell?

I have most of the other stuff in mind, S-AFC, wide band, etc.
The link below will basically tell you what im going to be doing to the engine
http://www.geocities.com/racingrotary/fmods.htm

Justin

And why would you do that in an NA engine where the stock 460CC injectors are already big enough for anything up to 250 HP?

I dont want to run lean at all and I also dont want to try maxing out my injectors. they say they can run at 250 hp or 260 or 270 but have they really been tested in a n/a rex pushing 250 or so and staying at a nice a;f mixture? there is going to be alot more air going into my engine.

You don't need to upgrade the fuel system. In fact, you'll probably find that you're running too rich with the 460cc injectors.

You're throwing a bunch of good money away for zero gain. As Aaron said, the stock injectors can safely (i.e. not maxed) flow enough fuel for ~250hp, which you'll never reach without a bridgeport. If you bridgeported the engine then the most you would need is a pair of 550cc/min secondaries and stock primaries.

Ok, back in my day.....(About 2 months ago. :D )I had a 90 n/a Rx-7 with a bunch of mods. With the stock fuel system, I had to lean my car out as much as 29% from what the stock ecu wanted to run my car at. And that was making 167rwhp on a mustang dyno. Something that not many people have done.

Listen to NZ and Aaron they know what they're talking about. :) CJ

Re: N/A Fuel System Question
 

You want to use the smallest fuel injectors possible. This is not only for control purposes, but also because fuel injectors usually atomize best around 60-70% DC. Also, large injectors are expensive. ;)

4x460cc injectors are good for about 250bhp @ 80% DC
4x550cc injectors are good for about 300bhp @ 80% DC
2x550 + 2x720cc injectors are good for about 350bhp @ 80% DC.

Knock yourself out with the below link. Plan on .55 BSFC to be safe, but your engine will probably have a little bit better BSFC than this if tuned well.
http://www.rceng.com/technical.htm

Note that you can always add a couple psi to the fuel pressure if needed, assuming your fuel pump can handle it. Most injectors will flow well up to 58psi (4bar).

Yes.

The SX regulator is good.
http://www.essexind.com/sx_main.htm

BTW, Walbro makes cheapo fuel pumps. They work, but they are not made very well. If you just look at one you will see what I mean.