what size injectors should i get 24,26,30,32? i know thats probably about what i need.
I just read his signature, that's all. Based what he has in his sig bolted onto a 302 he isn't going to be making the necessary power to require 30lb'ers Now if that combo was bolted to a 331 or 347 it WOULD be making more hp thus requiring bigger injectors.Since when did C.I.D. determine injector size?
Damn nice explinationI will say it again with his current combo (depending on cam specs). He could possibly see 330rwhp now add in 15% drivetrain loss and your at 379hp which is pushing 24s a little much. Now that aint leaving to much room for growth. Hence my suggestion for 30#s.
Injector HP ratings: divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines.
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.
304 HP x .85 = 258 HP
385 HP x .85 = 326 HP
480 HP x .85 = 408 HP
Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.
See http://users.erols.com/srweiss/ to get the calculators used in these examples.
Here's the duty cycle explanation. Duty cycle is how much of the time the intake is open the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.
If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.