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Do I need larger fuel injectors?

This is a discussion on Do I need larger fuel injectors? within the Internal Engine forums, part of the LSx Technical Help Section category; Hello. I have a 224 cam, polished and ported GM Performance LS2 Heads, Long tubes, with no cats, A K&N ...

  1. #1
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    Do I need larger fuel injectors?

    Hello.

    I have a 224 cam, polished and ported GM Performance LS2 Heads, Long tubes, with no cats, A K&N whisper lid...the normal stuff with a few other mods.

    I expect to make something like 430 rwhp...but am running stock LS1 (it's a 2005 LS1...not the original 2001 motor) fuel injectors with what I assume to be 28.6 lb/hr injectors. How much power can you make with stock injectors? How should I know what size to buy? What can the stock fuel pump support?

    I'm reading and being told that I need larger injectors, from some people. But I'm unsure as to how big. I'm also unsure what the stock fuel pump can support, but have been told for a Normally-aspirated engine that it should be able to support it.

    I'd appreciate any help.

    Thank you,

  2. #2
    TunedbyFrost.com Tuner Frost's Avatar
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    AFAIK there nothing had an ls1 in 05. What size are your injectors now? Is this an Aussie vehicle?

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    no, I have a 2001 z28, but I drove through a deep puddle with the ram air mod....and threw a rod through the block....got a new crate motor in may 2005....ls1 came with a vette oil pan.

    any idea as to what injectors I have/what I need?

  4. #4
    2 SS's are better than 1 Jays00ss's Avatar
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    You will be fine with stock injectors. I will be running a much larger cam and my tuner said I "Might' need new ones. With that cam you are running, you will be fine.
    2000 SS Camaro Heads, Large cam, Fast 90, 9"w/430's and locker, yada yada yada... you get the picture

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    2006 Silverado 2500HD 496 cubic inches of pure muscle

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    Senior Member Danger731's Avatar
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    34 lb injectors minimum

    http://www.fbody.com/calc.htm

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    Senior Member Danger731's Avatar
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    @96 % duty the injectors will handle it according to that calculator

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    I'd go 34lbs'ers minimum.....anything above 70% duty cycle gives me the heebie jeebies....

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    Senior Member Danger731's Avatar
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    Sometimes you can get even larger injectors for cheaper. Less capability on injectors does not mean lower price ! BEWARE.

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    I don't know what to think 2 years ago, before the new much improved heads,I dynoed at 370 rwhp....the new heads should definitely add 50 or so at the wheels, right?

    I know nothing about fuel injectors. What brand/type etc should I buy? My understanding is that you can over buy in size and that the computer will just use less capacity, right?

    oh yeah and merry christmas

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    SOM
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    The rule of thumb is to not go over 80% of duty cycle (but many do). I think you will be close. Fuel pump will be ok. Not to rain on your parade but most people don't go 425 rwhp with a 224/224 but some do and I wish you luck. It is a great torque cam. If you have an 01 with a new longblock I assume they took your stock 26lb. injectors and swapped them onto your new block. 98's I'm sure and can't remember but maybe 99's were the ones that came with stock 28.5lb injectors. Hope this helps.

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    What type of injectors should I buy? I installed GM Performance LS2 Polished and ported heads (same flow and same size as the Z06 ported heads, but much cheaper).

    Should I buy LS1 or LS2 injectors? Is there a difference? Can someone point me in the right direction regarding the specific type or brand of injector that I should be looking for. I'm a stranger in a strange land on this particular issue.

    Thanks, again fellas.

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    member since may 2000 nhraformula's Avatar
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    i dont see a need for anything above stock injectors
    2000 nhra edition formula
    a few bolt ons, 379 rwhp
    11.96 @113.25

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    Senior Member Danger731's Avatar
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    Quote Originally Posted by SOMbitch View Post
    The rule of thumb is to not go over 80% of duty cycle (but many do). I think you will be close. Fuel pump will be ok. Not to rain on your parade but most people don't go 425 rwhp with a 224/224 but some do and I wish you luck. It is a great torque cam. If you have an 01 with a new longblock I assume they took your stock 26lb. injectors and swapped them onto your new block. 98's I'm sure and can't remember but maybe 99's were the ones that came with stock 28.5lb injectors. Hope this helps.
    98, 01, 02 = 28.5lb
    99, 00 = 26 lb

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    Senior Member Danger731's Avatar
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    Quote Originally Posted by nhraformula View Post
    i dont see a need for anything above stock injectors

    explain

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    member since may 2000 nhraformula's Avatar
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    Quote Originally Posted by Danger731 View Post
    explain
    two of my friends here have f-bodies with the lgx whatever cam, the biggest one.
    one has stock injectors and the other doesnt.
    both cars are making about the same power and likewise times.

  16. #16
    Visualize°Design°Create SSwt00SS's Avatar
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    Quote Originally Posted by SOMbitch View Post
    The rule of thumb is to not go over 80% of duty cycle (but many do). I think you will be close. Fuel pump will be ok. Not to rain on your parade but most people don't go 425 rwhp with a 224/224 but some do and I wish you luck. It is a great torque cam. If you have an 01 with a new longblock I assume they took your stock 26lb. injectors and swapped them onto your new block. 98's I'm sure and can't remember but maybe 99's were the ones that came with stock 28.5lb injectors. Hope this helps.
    im sitting at 437/404 with a 224...

    or if you dont like those numbers, i can show you where i was at 444/395 with the same 224...

    oh, this is with stock injectors as well...

    Last edited by SSwt00SS; 12-26-2007 at 12:00 PM.
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    TunedbyFrost.com Tuner Frost's Avatar
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    stock 2000 injectors (26s !) usually peter out before 400rwhp. I have seen dozens do it, so you are an absolute exception here, not a rule or guideline. Most 28s are static just before the power you've made as well.

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    Visualize°Design°Create SSwt00SS's Avatar
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    Quote Originally Posted by Frost View Post
    stock 2000 injectors (26s !) usually peter out before 400rwhp. I have seen dozens do it, so you are an absolute exception here, not a rule or guideline. Most 28s are static just before the power you've made as well.
    once i decide on a custom cam to step-up to, i will be bumping up to larger injectors. im currently cycling around 90%. i understand there are exceptions and variances as each car is different and each car has the capacity and capability to respond to the exact same mods completely different to one another, respectively...

    that's why i love this hobby but makes one so frustrated as well. there is no carbon copy for "roll out" performance. people find what works for them and their goals. imagine my surprise when i dyno'd higher than a guy with similar mods (he had 5.3 heads and an MS4 to my Patriots Stage II Ls6 'style' heads and Comp224), and i put down more power than him...

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    Quote Originally Posted by SSwt00SS View Post
    im sitting at 437/404 with a 224...

    or if you dont like those numbers, i can show you where i was at 444/395 with the same 224...

    oh, this is with stock injectors as well...

    Click for full size

    If you reread my post you will see I said MOST DO NOT but SOME DO. So what's your point? There are a lot of variables to dyno #'s and that is a horse that has been beat to death so we don't need to go over that again. Very nice #'s and I especially like your torque curve. I will be happy if I can do as well after my H/C swap, especially if I end up with the 5.3's.

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    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by SSwt00SS View Post
    once i decide on a custom cam to step-up to, i will be bumping up to larger injectors. im currently cycling around 90%. i understand there are exceptions and variances as each car is different and each car has the capacity and capability to respond to the exact same mods completely different to one another, respectively...

    that's why i love this hobby but makes one so frustrated as well. there is no carbon copy for "roll out" performance. people find what works for them and their goals. imagine my surprise when i dyno'd higher than a guy with similar mods (he had 5.3 heads and an MS4 to my Patriots Stage II Ls6 'style' heads and Comp224), and i put down more power than him...

    You have some magic on 2 fronts then... those are very high numbers for Patriot heads. The last set I tuned happened to have a TR 224 in it as well with Hooker headers, PTB, ls6 intake and that setup made 415rwhp, but needed things to be at 13.0:1 to get those numbers.

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