I have a '94 FD3S w/street port (Mazdatrix Templates), Apex Intakes, Downpipe, and BOV on stock twins.

What psi can the stock ECU and injectors handle? Can I boost 12 psi safely?

I plan on getting a boost controller and PowerFC in the future but not anytime soon. My next mods will probably be hard intakes pipes, catback, and then the boost controller.

And when should I upgrade fuel system? I've read 13 psi or higher I need fuel upgrade and intercooler and a ECU to manage the new injectors?

But for now I just want to know if I can up to 12 psi on my stock ECU and injectors with intake, dp, cb, street port.

 

I know alot of people say 12 psi is fuel cut...but I frequently saw 14-15 psi on stock twins and ecu with the same mods as you + catback. Seemed like it took it just fine, my A/F gauge (even though they aren't too accurate) never leaned out.

I think you'll be okay, but fyi....my turbos went bye-bye after about 5,000 miles of the 14-15 psi.

 

I thought the stock injectors were pretty maxed out at 14psi. ?

 

Isn't the stock ECU max duty cycle for the stock injectors somewhere between 60-65%?

According to the fuel calculator it says the max horsepower at the flywheel is like 260ish.

I don't know what to do...I want to run 12 psi but only if absolutely safe with the stock ECU and fuel system.

 

No, you should not run over 10 psi with the stock ecu. Especially with a streetport, which requires retarding the ignition timing a bit.

Brad, I believe you have to overboost for 2 straight seconds for the stock ecu to enact fuel-cut. I'm surprised that never happened to you. How long did you run like that?

mor: You will need a programmable ecu, like the PFC, to run larger injectors. You will need larger injectors to SAFELY run 13+ psi for daily use. Also, IMO, running over 10 psi with the stock intercooler is asking for trouble. I can't believe how much I had to turn down my boost controller to maintain 10 psi when I upgraded to the PFS SMIC (small by IC upgrade standards). I easily gained 1-2 psi just from the IC, which means your turbos will be running easier and cooler when keeping the same boost level.

 

Nope, never hit fuel cut. I thought it was surprising too...I even removed and re-installed my boost gauge just to be sure it wasn't reading wrong. First and second gear would just spike to 14 psi, but in third and fourth it would hold fairly solid at 14 psi. I only started seeing this when it got cold out too (like 40 F).

I ran it like that until my turbos went, which was maybe 5,000 miles. I would have turned it down, but 14 psi is so much more fun than 10 psi!! Plus blowing the turbos gave me an excuse to go single

 

I got all the bolt on's..99 twins..etc etc... I'm perfectly happy toddling around at 10-11 psi... why is there such a need to run 14psi and above...

I guess just call me gramps..

 

I don't think you can safely run more then 11lbs on the stock ECU and 1bar on a moded ECU (Pettit, M2). I ran 14.5lbs with a Pettit ECU and even with injectors hitting 100% ( I beleive @ 1bar) I had no fuel problems but I did melt the 2nd turbo (sequential) after about 20k mi.