Im putting together a budget 302 and i have a edelbrock performer intake, and a 75mm throtle body and a set of tfs 170 heads and tfs stage 1 cam and long tube headers and 4:10 gears with a 5spd. will the stock 19 lb injectors be ok with this set up? Or do i need to go bigger?
I would upgrade to 24lb or 30lb injectors to stay on the safe side, depending on future mods maybe even 42lb if your looking into forced induction or nitrous. you could run a kenne bell boost-a-pump with the mods you have, but I think with your set up the 19lb'rs would be right on the edge. remeber you gotta get a different mass air to match your set up to.
Not sure what these guys are seeing in your setup.
But 24's are the right injector for you.
You don't size injectors for the future, you size them for what you have right now.
And the dyno tune with a chip instead of just using the right meter is an incredible waste of money in this case.
Fivemustangs, you do understand he has a pushrod setup with a return style fuel system right? A KB boost a pump????
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.
Example:
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.
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.
Diagram courtesy of Tmoss & Stang&2birds
Other fuel system components you'll need with bigger injectors
Remember that if your increase injector size, you need to increase fuel pump size too. If you don't the larger injectors will run out of fuel pressure. The minimum recommended fuel pump size would be a 155 LPH unit which is good for 440 naturally aspirated HP. You can go larger if you want to, the excess is returned to the tank.
If you choose larger injectors, you will need a matching calibrated MAF or a custom tune. I recommend PMAS MAFs. See HOME - they are rebuilding their website as of 30-Sep-2010, so you may not find all the information you would like to have.
I would also recommend that you plan on installing a adjustable fuel pressure regulator with the new pump. It will help you tune the system. I recommend Kirban fuel pressure regulators. See Kirban Performance
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.
Yeah, 24# is perfect for that set-up and will give you room to grow as well. Many guys over inject the car, I know I have learned a lot over the last few years and use a smaller injector then I would have in the past.....so much easier on tuning and drivabilty.
Like I said 24 or 30lb injectors, I just mentioned the 42's becuase I went with the 30's on my 95 and then decided the upgrade to a turbo the next year and wished I put the 42's on to begin with. But the 24lb will work very good. I thought boost-a-pumps work with both return and non-return fuel systems? but bigger fuel pump is always a good idea to.