MyE28.com

My next dilema is deciding which injectors I'm gonna use. I'm afraid if I get the 30#ers I'll run too rich under normal driving conditions. I;m only gonna run 6psi but if I decide to step up how much boost can I run on 24# injectors? I need some expert advice please. Also the 24's are a little more in my price range right now. But if they won't be worth the hassle I'll go higher.

If you're going to run closed loop, does it really matter if the injectors have a larger capacity? The ECU will control the duration based on what it reads from the O2 sensor. Open loop would be a different story.

For only 6psi, 24's are enough, but thats it. You'll need an FMU.

RussC

At a reasonable duty cycle (80-90%), and at a decent BSFC estimation (0.50), 24#ers will only support ~225hp. I'm not sure what you're planning on running, but I'd recommend searching for a set of 32# Ford Motorsport injectors on eBay. Many times you can find killer deals (8 for $120 or so) with low miles on them. For reference, 6 32# injectors under the same conditions will support about 300bhp. The 24# injectors will max out at just under 300, and the 32's will hit their ceiling around 400.

If you need any help, let me know. I'm in your area.

-Kevin-

Thanks kevin, I was hoping to acheive around 300whp. I think this is reasonable since my last turbo project was very inefficent and I was only running my 20# injectors I'm surprised to get the results I did. After better planning and research of this project 300 seems pretty well in my range.
Kevin by the way check your PM

FSAEracer03 wrote:At a reasonable duty cycle (80-90%),
-Kevin-

I have learned/been advised that a 75% duty cycle is much more appropriate for a FI application. You will never "run out" of injector then. It’s all about safety.

Duke M535ti wrote:

FSAEracer03 wrote:At a reasonable duty cycle (80-90%),
-Kevin-

I have learned/been advised that a 75% duty cycle is much more appropriate for a FI application. You will never "run out" of injector then. It’s all about safety.

Well I agree there. The balance of injector choice has to do with having the lowest maximum duty cycle in your application while keeping enough to have a clean idle and throttle tip-in. If the range isn't all that wide between no-load idle and WOT high-rpm use, then the maximum duty cycle can be low.

The lower the duty cycle you use, the cooler the injectors. 90% isn't a wild range, though, but, yes, 75% would be better.

EDIT.... if you're looking for 300hp to the tires, I'd advise using something in the 40# range. That will give you room for estimation error and room for upgrades in the future.

FSAEracer03 wrote: The balance of injector choice has to do with having the lowest maximum duty cycle in your application while keeping enough to have a clean idle and throttle tip-in. If the range isn't all that wide between no-load idle and WOT high-rpm use, then the maximum duty cycle can be low.

I also agree. I have 78 lb injectors and due to the idle issues you stated above, I have had to wire my TEC3 for full sequential injection. This allows the TEC3 to use a much shorter duration signal to the injectors and thus a good idle with big injectors.