As I continuously modify my car, I am wondering at what point to upgrade my injectors. I understand that being NA the stock ones are fairly sufficient, but what power levels am I needing to hit before upgrading. I have seen a few NA setups floating around here with larger injectors, and most often they are those with ITB's. I dont have ITB's but I do have an intake manifold and cams coming in the near future. Essentially my main questions are:

1. When will i max out the stock injectors
2. What should i upgrade to?


Any comments are welcomed and appreciated, thanks.

 

Unless you plan on making over 360whp NA you won't have to. That's when they give it up on a SC'd car with an EMS.

 

My experience was titled with 360 rwhp max in the title of the thread a few years back. I would like to point out the title is misleading.

During the discussion it was noted that the fuel curve rapidly went lean above 320 rwhp indicating the injectors were no longer putting out enough fuel to maintain the correct state of tune. The factory injectors were 100% duty cycle and were unacceptably leaned out. It did make 360 rwhp but it was going out of tune at that point. The correct conclusion from the thread should be 320 rwhp max with factory injectors.

 

Thanks for the correction. I don't think the NA setup is going to touch 320whp

 

So, the correct answer is "never" for NA engines?

 

Yup.

 

I run 750cc injectors on my NA setup. But that is for a couple reason. I like having room to flow more fuel if I want to. Also if you have plans on running nitrous you will be able to increase duty cycle if you wana run a dry system. It really comes down to if you are going to be running EMS. If that is the case I would look into some 550cc injectors and you will be just fine for almost any NA setup.

 

Stock injectors are 360cc/min. More than enough. There is such a thing as too much.

 

The ITB's I just ordered are comming with 440cc/min Bosch injectors, but I doubt I'm going to run them. I'm going to keep the stock injectors until I do cams and a stroker kit...only after that time will I put the 440cc injectors in. Unless you're running a dry kit and have it set up through the EMS like mentioned before, it's gonna take a crapload of N/A mods to necessitate putting in larger injectors.

The following information is derived from AEM's EFI basics 1.3 pdf that ships with an AEM EMS:
"Naturally aspirated engines have a BSFC of .48 to .50.
Injector sizing: ((estimated horsepower)x(BSFC)x(1+safety margin (typically 15-30%, your decision))/# of injectors = pounds/hour".

You can then convert pounds/hour into cubic centimeters per minute, and know exactly what size injectors you should be using.

 

Good GOD that's an impressive mod list!!