I have a 2001 5.3 silverado I recently put a cam in. I am planning on upgrading the injectors soon due to high mileage on them and was planning on putting the 8.1L injectors in because of the cam swap. Under normal driving conditions will they be putting the same amount of fuel in the engine. Or do the increase fuel flow across the board? Where is the best place to buy the injectors at? I've seen them on eBay but the prices on them are all over the place so I didn't know if there were any major differences other than the regular ones and marine. I only want the regular ones.

 

When you put injectors in, you will need a tune. The larger injector would add too much fuel without a tune. The classifieds on here are a good place or ebay.

 

The computer is programmed for the flowrate of the injectors you currently have. By using the flowrate it calculates how long to leave the injector open based on how much air its measuring as entering the engine. Larger injectors have a larger flowrate, meaning they flow more fuel for a given amount of time. If you put in larger injectors and the computer still thinks the small ones are in there it will keep it open too long so you will run rich. Under normal driving the trims might correct this, but at WOT you will be very very rich. To say it another way, when you put in larger injectors and have the computer reprogrammed it knows to not keep them open as long so you end up injecting the same amount of fuel as before so everything works correctly.

You need a retune whenever you change injectors, no question.

 

the standard 8.1L truck injector is 31 lb/hr at 43 psi and the marine are 44 lb/hr at 43 psi. so that is why you see truck injectors much cheaper

 

Ok good info. That answered my questions.

 

You can copy all the injector data for the 8.1 injectors off the hp tuners respitory. That is what i did .Once programmed the bigger injectors willl not effect your gas mileage until you go full throttle.

 

That's what I was looking for. Only really need them at full throttle. I got a mail order tune from Nelson for the cam and long tubes. Think they can set it up like you are talking about