Fuel system upgrade
 

Hey guys, i am in the process of upgrading my fuel system to accommodate my single turbo build. Im wanting to know if its possible to keep the factory primary rail + injectors and incorporate the new secondary rail shown in the picture, or should i just switch to an aftermarket primary aswell?
https://cimg9.ibsrv.net/gimg/www.rx7...e316222ade.jpg
https://cimg8.ibsrv.net/gimg/www.rx7...17d6d5315c.jpg

Hey man

While you can utilize the oem primary rail and injectors with an aftermarket secondary setup I would not recommend it on a single turbo setup. With a single setup comes more power (typically) which means you have much less margin for error when it comes to fueling. I'm sure they're functional but I have a hard time putting much stock in the reliability of 25+ year old injectors.

Thing is aftermarket primaries and rail are cheap compared to the larger secondaries, so its probably worth it to just cover all your bases.

Skeese

I kept the stock primary rail and injectors and modified to allow AN fittings and lines to match my aftermarket secondary rail.

Now I am looking to make more power and the easy way to get the fueling is an $120 primary rail and 2 injectors for a couple hundred more.

You might as well spend the money now and not have to worry about fueling, new lines, re tuning, etc... down the road.

If you want to upgrade just the secondary rail and injectors, the Full Function Engineering FD stepup kit has everything you need. I do prefer to do both rails and all the injectors but on a budget this works for a moderatate hp application.

Hey thanks for the replies, im learning towards doing the primary rails aswell although im only really after no more than 400whp.
My next question is am i able to reuse my factory FPR, and do i need to get an aftermarket FPD?

as a side note, my secondarys are EV14 2200cc, is it worth upgrading my primarys to EV14 725cc, or get the EV14 550cc as its same cc as stock?

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/first-impressions-rotary-performance-secondary-fuel-rail-1119103/

^RotaryPerformance.com fuel rail upgrade; very practical for your application & HP goals.

Most modern injectors are flow rated at 43.5psi base pressure, so you need an adjustable regulator.

I have always wondered how those selling the "fuel step up kits" that retained the oem pressure regulator on the stock primaries but upgraded the secondary rails to large aftermarket injectors expected it to function correctly. I can see it being possible but I can only imagine you'd be cutting yourself short given the 38 psi base pressure if it permanently set to run at. Not to mention that you have no data on aftermarket injectors at 38 psi so you'd be shooting in the dark there, which kinda invalidates the point of running a modern ecu and injectors.

Skeese

Stock primary rail has a pulsation damper. It is intended to smooth out any fluctuations in fuel flow before it enters the rails. Pressure is regulated by the regulator on the end of the secondary rail. I've found no detriments running the stock injectors at higher pressures but aftermarket injectors may not flow their full ratings at less then recommended pressure.

Except the fact that they aren't consistent injector deadtimes across a pressure and voltage variance. It's a poor choice.

What is the issue? A pressure regulator at the end of the secondary rail sets the pressure for the system.

ahhh I stand corrected. Admittedly it has been a long time since I have had any interaction with factory FD rails outside of removing and tossing them.

Skeese

We clean and flowtest the injectors on just about every build. I very often find that they are 10-20cc apart in flow. In a stock or near stock car, the rear rotor tends to run leaner so I put the higher flowing injectors in the rear position.

Since you're going beyond the factory spec with them, you should have a deadtime table with the following axis filled out for your customers then, to input into their ECUs.

8v, 10v, 12v, 13v, 14v, 15v, 16v

x

38psi, 43.5psi, 45psi, 50psi, 55psi, 60psi, 65psi, 70psi, 75psi, 80psi, etc

I had my nearly new(3k miles) ID1000cc injectors cleaned and one of them was dripping and the other spray pattern was just fair as well. I expected my older injectors to be like that but not these new ones. In fact my old stock injectors (old build) seemed to have a better spray pattern before cleaning than the ID's according to the spec sheet on their last cleaning.

Inadequate Filtration? What did you use? The more advanced the injector, the more advanced your filter should be...

I don't think it matters much. If you can't afford to upgrade stock primaries, you can't afford to tune the car so far to the edge that they are the reason you could experience an engine failure as a result of a marginal voltage variance.

If tuning to the ragged edge, you better have premium parts in all critical areas.

We factor it in during our tunes, but often you are dealing with limitations of an ecu platform as cars running stock injectors will often have a relatively simple ecu like a pfc.

I dont believe you need that expensive F750 fuel filter for ID injectors. Ive been running them in front of a big weldon with a 10 micron stainless steel element with clogs for years. Actually got another one in yesterday...

https://cimg8.ibsrv.net/gimg/www.rx7...20993e53bd.jpg
Skeese

Just an FYI I believe both Autronic and Motec have profiled the stock side feeds. I don't remember if the Autronic injector profiles are transparent so I'll have to double check that.

The step-up kit is a pain in the ass if you're still running stock twins. Possible to use, but not ready-to-install the way I had anticipated

Did ID do the cleaning of the injectors? I had a ID725 that was leaking after shutdown. When ID tested they said it was a faulty injector and replaced it free of charge even though the injector was a few years old and had maybe 6,000 miles on them.