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Injector sizing

This is a discussion on Injector sizing within the External Engine forums, part of the LSx Technical Help Section category; I have my intake off and was wondering if it would be any benefit to swapping out the injectors. I ...

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    Member beach cruiser's Avatar
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    Injector sizing

    I have my intake off and was wondering if it would be any benefit to swapping out the injectors. I running a LS6 Intake, Ported TB, and longtubes with Texas Speed y pipe and hooker aerochamber muffler. It's on a 2000 WS6, so it has the bigger cam. Any thoughts?

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    Veteran Hi-Po's Avatar
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    No, if you have the stock cam, the stock injectors are fine. Swapping to a larger injector will net you zero extra power and would require a tune.

    Stock injectors.
    370 CI - Twin 6766 Turbo - Jakes stage 5 4L80E - MWC 9" - Holley Dominator

    Build in progress...

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    cutting and welding mark21742's Avatar
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    Quote Originally Posted by Hi-Po View Post
    No, if you have the stock cam, the stock injectors are fine. Swapping to a larger injector will net you zero extra power and would require a tune.

    Stock injectors.
    he has the 26lb injectors doesnt he? one of my friends was maxing the 26lbs out in his F-body with just bolt ons, but i can't remember what year came with the smaller injectors.

    but HiPo is right, if the ones you have now aren't maxing out you will get no gains

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    Veteran Hi-Po's Avatar
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    I love this website, and post it often. I swear I had it in my HP thread, Ill get it added.
    http://www.rceng.com/technical.aspx#...tor_Worksheet_


    Put your est horsepower at the flywheel into the calculator. That will get you really close. Your injector is 26.4# and your fuel rail pressure should be 58PSI. Play around with this website and its calculators. If you have anymore questions on the matter, post up.

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    Member beach cruiser's Avatar
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    Ok, according to the worksheet, I need 24.6 lb/hour injectors so I'm ok with the stockers. My estimates were, 360hp at the crank, does that sound about right for my mods? I havn't had it on the dyno yet to know what it has at the wheels. Was scheduled for last Sat but I developed a nasty oil leak that ended up being the Oil sending unit that I broke installing the intake the first time!

    Any tips on how not to break it this time?

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    Veteran Hi-Po's Avatar
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    Like said, your stock injectors should be fine. When I messed around with the calculator for your mods, I was getting good numbers.

    You just gotta be really careful. That's all I can say. I think my OPSU is built from solid steel because I have hit it so many times with it still standing strong You know where its at now, just have to keep a close eye on it this go around.

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    last time i checked, i thought the 98 ls1s had the larger injectors? 28's?

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    Member beach cruiser's Avatar
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    Ok, I left the stock 26lb injectors in. On the Dyno, I'm running lean with the mods I have. I swapped on an SLP lid and bellows and went WAY lean, like 15.3 lean. I havn't had it tuned yet, but would swapping over to 28lb injectors help at all? Would I have to have a tune to run those for a while? Or will they just fatten up the fuel amount based on the computer thinking they should be 26lbs? BTW, it put down 332HP with the intake/header combo.

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    cutting and welding mark21742's Avatar
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    What was your highest injector duty cycle percentage?
    You should beable to fix your lean problem with a little fue tuning.
    No you can't just swap to bigger injectors without tuning for them.

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    Member beach cruiser's Avatar
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    Not sure on the duty cycle percentage, but using the calculator about, it looks like 93%

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    cutting and welding mark21742's Avatar
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    Quote Originally Posted by beach cruiser View Post
    Not sure on the duty cycle percentage, but using the calculator about, it looks like 93%
    If it hits over 85% your due for bigger injectors....if your hitting 93% then you need them, but don't put them in and run the car till your at the tuner.
    If you not going to go absolutely wild with the car I'd look for a deal on some 36 pounders.

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    Quote Originally Posted by beach cruiser View Post
    Ok, I left the stock 26lb injectors in. On the Dyno, I'm running lean with the mods I have. I swapped on an SLP lid and bellows and went WAY lean, like 15.3 lean. I havn't had it tuned yet, but would swapping over to 28lb injectors help at all? Would I have to have a tune to run those for a while? Or will they just fatten up the fuel amount based on the computer thinking they should be 26lbs? BTW, it put down 332HP with the intake/header combo.
    Even though the injector change would be relatively small, Never, ever change injectors and run the engine. Even for a mile down the road to your tuner. That's enough time to wash down the cylinders/rings.

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    i'm almost 100% sure you don't need larger injectors... your mods aren't enough to need larger injectors... if you put in a larger cam than the stocker than maybe you'd need larger... i'm guessing you dynoed 305-310 rwhp with your mods... are you auto???

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    i just seen you we're tuned yet... when you get your tune it will straighten up your air/fuel ratio...

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    Member beach cruiser's Avatar
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    No I actually Dynoed at 332 with the stock lid and 319 with the SLP, Check out the dyno sheet link. My car is an M6, My buddy had his car on the dyno right behind me, he has a 98 Z28, Shorty headers, SLP lid and a catback, he came in about 305 with an A4. That tells me the Dyno was pretty acurate.

    http://www.ls1.com/forums/showthread...46#post2265246

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    Quote Originally Posted by beach cruiser View Post
    No I actually Dynoed at 332 with the stock lid and 319 with the SLP, Check out the dyno sheet link. My car is an M6, My buddy had his car on the dyno right behind me, he has a 98 Z28, Shorty headers, SLP lid and a catback, he came in about 305 with an A4. That tells me the Dyno was pretty acurate.

    http://www.ls1.com/forums/showthread...46#post2265246


    332 x 15% (dt loss for m6) puts you right around 381 at the crank... the SLP lid will give you a far greater gain with the tune than the stock lid will (sure you already knew that)... the place where you had the dyno run done, do they do dyno tunes??? if not you might be close enough to frost to have him do one!!!

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    Member beach cruiser's Avatar
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    I talked to Frost, He's about 2 hours away. He wants to do it on the Dyno based on the Dyno sheet (that shop only does Mustangs and Imports). I'm only about 3 miles from VA Speed, and Ed and Shawn do great work, but they are not cheap. It's a wash between the VAS and Frost as far as costs, but VAS is much more covienent. Using 381 in the injector calculator puts me right on the edge for the injectors.

    I just want to have all the bases covered when I get it tuned, I'd hate to drop all that money only to be told I need bigger injectors and that's going to be xx more money...

    Thanks for the help

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    Quote Originally Posted by beach cruiser View Post
    I talked to Frost, He's about 2 hours away. He wants to do it on the Dyno based on the Dyno sheet (that shop only does Mustangs and Imports). I'm only about 3 miles from VA Speed, and Ed and Shawn do great work, but they are not cheap. It's a wash between the VAS and Frost as far as costs, but VAS is much more covienent. Using 381 in the injector calculator puts me right on the edge for the injectors.

    I just want to have all the bases covered when I get it tuned, I'd hate to drop all that money only to be told I need bigger injectors and that's going to be xx more money...

    Thanks for the help
    frost will take great care of you... i wish he was in my area!!! he knows what he is doing and does it at a very reasonable cost...

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