Hi,
Im just wondering what is a good range for fuel injector size for say 300-400whp. I know this is apretty broad range but I have no idea what kind of power im going to make and I want to go with an injector that isn't too small and max out duty cycle but I dont want one too big so it flows too much even after de-tuning . I would prefer 450cc because they are sooo cheap but it may not be big enough for a T3/t4 @ 15psi. Let me know what your running and what your duty cycle is at?

 

A 450cc injector will be way too small for that kind of power. If you are worried about the cost of the properly sized injector, you seriously need to rethink this build because with 300 whp, there is a whole lot to go wrong if you continue buying cheap parts.

Anyways, I would go with somewhere in the range of 750cc or higher. Use this link to figure out which size you should be looking at: http://www.rceng.com/technical.htm#WORKSHEET

 

oops double post

 

that sure is a really nice calculator! thanks man . I guess im going with 660cc injectors at least thats what it says I should go with if I want 400 crank horsepower and duty cycle @ 50%. With 450's the injectors would be at 75% which I would rather stay away from.

SHmoo, what is your injector duty cycle at right now? What size are they?

What is my fuel pressure at the rail? I thought it was 42psi from Honda? In the calculator it says 175psi?

 

OK, good choice.

I am running 310cc right now, but for the most part, they are maxed out at the stock fuel pressure and 9 psi, so if I plan on 10 psi, I need to upgrade. I am only running 8.5 psi right now, so they are pretty close to being maxxed out, which puts a lot of strain on them. 450's would be good since they are so cheap and they will allow plenty of breathing room for 10 psi.

The fuel pressure at the rail that they are measuring is at WOT. 42 psi is just at idle. If you had a fuel pressure gauge mounted in the cockpit, you would easily be able to know what your fuel pressure is at WOT.

 

You might consider a staged-injector setup if your ECM can handle it. I ran RC440 injectors at 80% duty cycle on my Teg when it was turbo'd at 15psi. They did fine, except at idle, where the duty cycle and pressure made a very bad spray pattern, which caused the car to stumble and bog. A staged-injector setup uses the small injectors at idle up until the turbo kicks in, then adds your secondary injectors for the extra fuel needed.