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Fuel injectors

This is a discussion on Fuel injectors within the General Help forums, part of the LSx Technical Help Section category; I'm looking at replacing my 26lb injectors with Ls6 28lb and Ls6 intake. I found a good deal on a ...

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    Senior Member kingls1's Avatar
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    Fuel injectors

    I'm looking at replacing my 26lb injectors with Ls6 28lb and Ls6 intake. I found a good deal on a set of used 28's on Tech also found a set of 30lb design III modified injectors on fuelinjectorconnection.com for $189.95
    With a warranty.
    Would the 30lb injectors be to much with the intake and a refresh tune from Frost with the mods I have listed below? Or would the proper tune allow them to work with my set up!
    I can't buy the used ones(28lb)and have them checked or rebuilt for the price of the 30's already done.
    99 Trans Am, SLP Lid, Blackwing filter, smooth bellow, Ported TB, LS6 intake, Ws6 lower ram air box, OBX LT's, Magna Flow cat back, LS7 clutch, Tick MC, Hurst Shifter, Frost Tune, UMI SFC,LAC, STB, PB, Torq Arm, Super Hawk hood, Torq Thrust II, Kee Audio.
    Strange S60 4:10's, D&S Rotors, S/S Brake Lines.
    Nitto NT05R Track Tire's, 12.7 @ 108 / 1.82 60'
    Wish list.
    Coil overs, Heads & Cam

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    Senior Member kingls1's Avatar
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    30lb Design III modified Fuel Injectors for GM, Ford, Chrysler, Audi, VW

    Flow matched rebuilt with viton o-rings and HD Bosch filter baskets.

    EV1 style plug, EV6 style injector.

    Please specify the vehicle on checkout

    Set of 8

    Product Code: 30LH2

    Your Price: $189.95
    Weight: 2.000 lbs
    Quantity:

  3. #3
    Member Decadence75's Avatar
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    If you can afford to have the car down for a few days, I would just send your current injectors off to FIC to be rebuilt to whatever flow rate you want (up to 48@3bar) and flow matched to within 1% of each other. A larger injector increases the maximum throughput of fuel but it will still only spray as much as the PCM demands of it. The intake will work fine with your stockers resized to whatever you would like. However, you need to make sure that the fuel pump can keep up with the injector demand.

    FUEL INJECTOR CONNECTION - LS1, LS6 INJECTOR RESIZING

    2000 Trans Am T56 Swapped - GMPP "HOT" Cam | LS6 Intake | PnP TB | 25% UD Pulley | Founders adjustable LCA/PHB/TA | Norris Catch Can | TSP 1-7/8 SS LT | TSP True Duals with bullets | SLP Lid | UMI Shock tower brace | Torq Thrust M 17x9 275/40 front 17x10.5 315/35 rear - YouTube Videos - My Car Site

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    Former Mopar Man 2002ssslp's Avatar
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    Better to have them resized over buying new injectors. I'm not sure how much HP gain you will get but for the cost it may be worth it besides having fresh injectors may get you some extra MPG as well.
    My ride is a 2002 Camaro SS SLP #3296 with 30k, LTH, 3" Y, CME, Frost tune, K&N, ported TB, Blackwing lid, Bellows, MSD, Denso Iridium, and 85mm MAF, Bilsteins, Eibach springs, SLP strut brace, Adj. Panhard, TA Girdle, UMI, Pro 5.0, Nitto NT555
    My wife has a 2004 GTO with the rare SAP, 18" wheels, K&N Cold Air System, MSD, Ported TB, Frost tune, Denso Iridium, Flowmaster cat-back, 3200 Yank, 75k

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    Senior Member kingls1's Avatar
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    That is what I was looking to find out if they could be matched with my set up with a tune. my 99 has 26's and the Ls6 had 28's so that is why I wanted the change in injector size to at least match the Ls6 intake. The Bosh III's seem to work well when put to the test on the ad.
    However checking on resizing the stock 26's ($30ea.) still cheaper to go with the already done injectors with a warranty. Plus a mild cam and 243 heads down the road the 30's should handle just fine I'm thinking. Thanks for the reply

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    Senior Member kingls1's Avatar
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    Senior Member Naaman's Avatar
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    Interesting.

    There is a forum for NSXs and a thread there details an experiment conducted by one owner and a local shop who took 2012 injectors from an RDX (with a better spray pattern and considerably more pressure, the stock 1991 NSX injectors put out, IIRC 27 lbs, while the new RDXs put out 42 lbs).

    Anyway, once tuned to utilize the better pattern, the car dynoed a 35 lbft gain and 17 more horsepower (on a 3.0L). Fuel economy was also improved.

    Not sure if it can be done with GM stuff, but I wonder if there is any "room" in the injector design for that kind of improvement (for example, using the injectors from a 2013 Z06 or some such, assuming they are more advanced, better engineered, more efficient, etc), and then tuning the PCM to account for it.

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    Senior Member kingls1's Avatar
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    Well I talked with Frost about changing the injectors and he told me to Never Ever use modified injectors and sent me this link about drilled injectors The truth about drilled injectors
    He also said if I had 28lb injectors put them in and he would tune for them, however the 26's would be just fine. He said injectors don't make or take power either they are big enough or not and my 26lbs are. So just he just save me some money. thanks Steve.

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    Member Decadence75's Avatar
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    Interesting...

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    TunedbyFrost.com Tuner Frost's Avatar
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    Found this thread digging around...

    Please spread the word about modified injectors. They are not ok.

    Thanks guys.

  11. #11
    Moderator 35th-ANV-SS's Avatar
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    Good to see Steve back posting on the site!

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    Moderator Firebirdjones's Avatar
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    Yes, good to see Steve, been MIA for a while.


    Here's some food for thought. Maybe Steve could add to this or maybe correct it.

    Using the formula with 26 lbs. injectors

    Lbs. per hour X duty cycle / .50 bsfc. Should equal HP per cyl. Multiply by 8 and that gives you a flywheel HP estimate they will support.

    So I get... 26 x 85% / .50 which equals 44.2 HP per cylinder

    Multiply by 8 and those 26 pounders supports 353 HP at the flywheel.

    Sounds weak kneed to me but I believe that formula is based on a fuel pressure reading of 43.5psi (is that correct in thinking so Steve??)

    In which case that HP number should bump up a bit when running 58 psi at the fuel rail.

    Still sounds weak to me though since these cars can easily make that much HP at the rear wheels with mild mods, let alone at the flywheel.

    So what gives? Care to add something I'm obviously missing Steve?

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    Moderator 35th-ANV-SS's Avatar
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    I found an online calculator which compensates for fuel rail pressure and I used 58psi instead at 85% duty cycle. It calculated 408HP at the crank.

  14. #14
    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by 35th-ANV-SS View Post
    I found an online calculator which compensates for fuel rail pressure and I used 58psi instead at 85% duty cycle. It calculated 408HP at the crank.
    I used 85% duty cycle in the calculations above as well, as that's generally considered the most that you want to see.

    I think the difference is the 58psi you used. I think that formula above is based off 43.5 psi from the old TPI days.

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    Moderator 35th-ANV-SS's Avatar
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    Correct. I was just showing the power increase difference from 43.5PSI to 58PSI.

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    Moderator Firebirdjones's Avatar
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    Sitting here thinking about it, even 400HP at the crank isn't all that much. Considering you can make that at the wheels fairly easy with a cam swap and supporting mods. Starts to make those 26 pounders questionable if you want to keep the duty cycle at 85%.

    Must be alot of fudge room here. Considering they aren't telling you how they arrive at that 400 crank HP since there are varying ways on a dyno to do that. Different correction factors, whether it's gross or net (with or without accessories). So I'm not putting a ton of faith in the formula without knowing all the variables.

    Seeing as how I lose about 80HP from the time my engines hit the dyno cell, to the point where the car is on a chassis dyno. Alot of that is because the engine by itself is dyno'd with no accessories, electric water pump in some cases, dyno headers, etc... When the engine is in the car everything is hooked up, (A/C, PS, mechanical water pump, chassis header etc...) then all your driveline losses, for a real HP rating at the tire. So I never see the simple 15% difference that people claim on a chassis dyno when trying to convert that to flywheel HP.

    With that said, 400 crank HP isn't hard to achieve in this manor, and would likely only yield about 320-330 RWHP in my case.
    Last edited by Firebirdjones; 01-24-2014 at 05:07 AM.

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    Moderator 35th-ANV-SS's Avatar
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    Maybe people are almost maxing out their injector's duty cycle? At 95% duty cycle, 26lb/hr injectors will support 456HP lol.

  18. #18
    Moderator Firebirdjones's Avatar
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    Yeah seems to be some "grey" area with this formula. I guess it would get you in the ballpark with a new build, then watch duty cycle while on the dyno.

    Has me curious now, I can't remember what the duty cycle was on my wifes car but I seem to remember it was up there. I may just have to go out and log for giggles and refresh my memory.

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    Moderator 35th-ANV-SS's Avatar
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    I was always told you want to keep them at or around 80%. I suppose if you go up to 85%, it wouldn't be a big deal. I wouldn't want to go any higher than that though. Just asking for trouble.

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    Senior Member kingls1's Avatar
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    Thanks for the info, this fuel injection stuff is all new to me and I'm learning alot, and I have not ruled out the 28lb injectors as of yet. Just seems to me if they were paired with the LS6 intake from the factory wouldn't hurt to stay with them!

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