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Discussion Starter · #1 ·
I was researching this on here...most of the questions came from 5.0s so I'm sure its different. I have every bolt on except UDP. Should I upgrade from 19# injectors to 24# or even 30# (excessive?)?? If so when I do and get it tuned, with a new MAF, would I notice a difference in performance or hp? Any info is helpful thanks. The car is an 03 GT.
 

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Discussion Starter · #3 ·
Thats good to know!
-How much were your cams installed?
-Also would upgrading to 24# later on even do anything performance wise or only capability wise?
-Do you recommend a bigger MAF?

:bounce2:Thanks.
 

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You don't need a larger MAF until you can peg the electronics in the one you have, which won't happen naturally aspirated.

I would say the upgrade to 24# injectors should happen with heads and aggressive cams, and over 300rwhp. That would be a safe place to change them over. Not too early, to where you get idle problems, but you're sure to have enough fuel for heads and cams.
 

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The 2010 FRPP Catalog has a real nice write up on sizing injectors and MAF. I don't recall the exact details but stock injectors will support you a long way.
 

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There was an article I read a short while ago and basically it said you should never have your injectors in a place where they are working at over 80% of their total rating. If an injector gets close to continuous on duty, then they will overheat and fail. So if the injectors are rated at 19# then you should not actually have them trying to go over 80% of 19# or about 15#. There is a formula for how much horsepower you will make with certain pound injectors. The fuel pressure also will affect the output of the injector, and if your fuel pump can not keep the pressure up the injector will try to compensate and open longer. The rpm's of the engine also will limit the amount of time the injector has for a cycle, meaning to open and then close again. It is possible that the injector size would seem right but that the engine is leaning as there is not enough time for the injector to supply the required fuel. This is where a dyno and the special oxygen sensors can give an indication if your injectors are of the correct size or undersize. You would more than likely need a retune from Bama or some other tuner if you go to the larger 24# injectors so that the computer can properly cycle them. Sometimes it is a wise move to find the expert performance tuning shop in your area and with a series of tests they can tell if the fuel pump is right, the injectors are correct, if the pulse width is right etc. I personally would not want to risk losing a motor that had all the bolt ons you say you have just to save a few bucks of testing and to keep the pride of the backyard mechanic. Those are my thoughts...... the FRRP Catalog and some searches on google or yahoo would be a good place to start your research. Never assume everything is fine, that is what usually will bite you and cost you $ in the long run.

Just some thoughts from my years of playing with muscle cars. Hope it helps you move in the right direction... good luck
 

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With my mods (see sig) 19# were are 90% so I upgraded to 24's with the stock MAF. My A/F was perfert and flat so the meter was not pegged. Just remember that you MUST have a tune after changing injectors otherwise you will run extremely rich at anything off idle IF the car will run at all. I would send your money else where until you have every bolt on, and some larger cams, a stroker or just notched pistons, ported heads, or THS heads.
 
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