Hello friends! I recently did a fuel cell setup in my hatch. I only have a stock 4age (small port I believe), anyway, we found out my injectors are not functioning properly. We removed them, and one was worn out. So I got some 450cc hi-impedance rx7 fc injectors, and bypassed the resistor box. I know I dont "need" the 450cc's, but I wanted to ask you knowledgable ae86 enthusiasts if I'll be alright without a tune, running on the stock ecu. Or is this a major thing and needs a tune pronto? Thanks for your time and advice, in advance!

On a stock ECU you will be lucky if the car runs at all with those injectors.
Also note that a bigger injector is only an upgrade once you max out the potential of the existing injector.

I don't have personal experience with the SP but in my personal experience with the GZE ECU and watching others tune turbo builds on the LP ECU I would say the stock ECU can handle about a 15% increase in injector size. Along with a wideband and tuning that should be able to be made to work. With no increase in airflow there will be no gain from it.

The increase you are talking about is going to be far outside your stock ECUs ability to compensate. The 4AGZE that starts with 365 injectors cannot properly run 440s. The one person I ever saw pull it off halfway acceptably was running a grunt box and about 19 PSI boost. It would still run too rich off boost but his AFRs would come in line once he was cramming that massive volume of air through the intake.

More importantly to even have a chance of making this work you will need to buy a wideband ($150-$300) and probably at least an FPR ($80). If you cut the fuel pressure enough to make it work you would probably sacrifice spray pattern and atomization. In the end you will have spent much more time and money than you would have finding stock injectors and if anything lost a little performance and efficiency.

Thumbs up! That's the answer I wanted to hear! It doesn't run right at all. I have a few 4age mr2 injectors I could replace the old broken injectors, I guess lol. Thank you very much for that answer!

I have a set of small port injectors, PM me if interested

i think some accord injectors will work but iv tried the civic injectors from an obd1 civic and my car didnt run well. it ran but it was too rich for sure