I am looking to use a 224/230 XER comp cam. I am going to be doing the obvious valve springs and timing set. We will be tuning using HO tunes. My question is at what point after this will I need to upgrade the injectors?

 

At the point where your injectors go above 90% duty cycle at WOT. Mind you most everyone just jump on the gun and change injectors, while they should check and measure fuel psi at rail to see if they are getting the most of their injectors. 58psi is the target pressure. If much less at WOT, then a better fuel pump and harness should be looked at first.

 

Look at ot this way, the smaller the injector is, the longer it stays opened to get the ssme amount of fuel out as a huge injector that opens for less time....the longer you can hold the injector open the better quality air/ fuel mix you will get. Can you take a stock engine that had 28 lb injectors and drop 60 lb injectors in with a tune, yes, but the bigger injectors will open and close so quick to dump the same amount of fuel in that the port and chamber will have a harder time mixing the fuel with air properly.

Personally I like to stay under 85% and if I see 85% I will set the injector size up.

 

When you log in HP Tuners, you should be able to check the injector duty cycle. If it's above 80% at WOT, then you will probably need to upgrade the injectors.

 

Cool ok