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Thread: Replacement Fuel Injectors = Better MPG?

  1. #1
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    Default Replacement Fuel Injectors = Better MPG?

    My 4.7HO has plenty of miles on it (over 100,000 miles).

    Here is an example of perfectly clean and refurbished stock injectors vs. different Bosch injectors:
    http://www.youtube.com/watch?v=bHf-6ohkgbA

    The condition of the stock injectors in that video would give you their best possible performance. Even with that, you can see how poorly the injectors atomize the fuel. It is more like a squirt gun shooting fuel into the cylinder head.

    It seems that if you could atomize the fuel better, you should get better fuel mileage as well as maybe even better performance. The question is if $300 for a set of 8 is worth it. Maybe if you were looking at replacing the injectors anyway.
    2004 WJ Charcoal Limited 4.7L H.O., QuadraDrive, Goodyear Wrangler w/Silent Armor Tires
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    Registered oldgeezer's Avatar
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    Quote Originally Posted by MrBaz View Post

    ..................

    Here is an example of perfectly clean and refurbished stock injectors vs. different Bosch injectors:
    http://www.youtube.com/watch?v=bHf-6ohkgbA

    The condition of the stock injectors in that video would give you their best possible performance. Even with that, you can see how poorly the injectors atomize the fuel. It is more like a squirt gun shooting fuel into the cylinder head.

    ..............
    Hate to say this, but your comments about the condition of the stock injectors suggests that you might be somehow be connected with the company, precisionautoinjectors. How do you know that the stock injectors were actually "perfectly clean and refurbished" and that the so called stock injectors hadn't been modified for the advertising purposes of the video?
    2001 WJ Limited, 4.7L, Quadra-Drive -- Kenne Bell Supercharger, Stillen Rotors with MM pads (F/R), Addcos (F/R), Kolak 3 inch exhaust with large case MagnaFlow, Rogue Chrome wheels, DRL activated, and Blaupunkt 3.5" dash speakers.

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    Quote Originally Posted by oldgeezer View Post
    Hate to say this, but your comments about the condition of the stock injectors suggests that you might be somehow be connected with the company, precisionautoinjectors. How do you know that the stock injectors were actually "perfectly clean and refurbished" and that the so called stock injectors hadn't been modified for the advertising purposes of the video?
    Use common sense. I have over 800 posts of this forum. Registered plenty enough long ago, and you think that one single post about this issue means I'm associated with the company?

    Their website doesn't even have the injectors, and I found a better website to purchase the exact same injectors.

    I have seen many other videos about the same Seimens injectors from other people to believe it. Bosch does some things well; injectors happen to be one of the one things Bosch does very well.
    Last edited by MrBaz; 09-05-2010 at 07:21 PM.
    2004 WJ Charcoal Limited 4.7L H.O., QuadraDrive, Goodyear Wrangler w/Silent Armor Tires
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    I don't know Baz.. seems like a waste of money unless you know that you've got a problem. My HO now has 115k on the clock, but on a trip to Louisville and back last week, VIC was reporting 17.9. I usually drive city around 15.5 MPG.. so it's nice to see it doing what it's supposed to on the long trips.

    Historically around here on the forum, there's not a lot to be done to improve on the factory mileage numbers.
    ~Mark

    2004 H.O. QTII Freedom Edition

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    Quote Originally Posted by WWWJD View Post
    I don't know Baz.. seems like a waste of money unless you know that you've got a problem. My HO now has 115k on the clock, but on a trip to Louisville and back last week, VIC was reporting 17.9. I usually drive city around 15.5 MPG.. so it's nice to see it doing what it's supposed to on the long trips.

    Historically around here on the forum, there's not a lot to be done to improve on the factory mileage numbers.
    I'm thinking of rebuilding my 4.7HO with 10.5:1 pistons (coated skirt and top), bored 20 or 30 over, ported heads, headers (yes, they CAN fit), tuning, etc. and just trying to get some ideas. I would have the injectors either replaced or serviced anyway before putting them into a newly built engine. It just seems like a better mist pattern would be better.

    If I end up purchasing them, I'll throw them in the motor as it is now to see if my mileage increases any.
    I used to get 22mpg highway, but now I'm down to 19/20mpg highway. I've got some other things to replace as well (fuel filter, some vacuum lines)
    2004 WJ Charcoal Limited 4.7L H.O., QuadraDrive, Goodyear Wrangler w/Silent Armor Tires
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    Opinion here..
    On a fresh rebuild, or slight mod, I would absolutely go with the better technology.If something newer and truly better exists that is within reason and isn't something like the "tornado" why the heck not.. I use newer style molded silicone gaskets where I used to use cork?? FI has replace Carb's, not that a carb'd engine can't be super efficient, heck Direct Injection is replacing all other forms of FI as we know it right now, and the basis for DI is fuel atomization and placement at the perfect point in the intake track ??? wouldn't work with an older style injector either...

    It's not like Jeep looked for the most expensive injectors to put in in the first place, nor where the Bosch even out at the time, IIRC. But as for just dropping them in for the sake of replacing perfectly good ones, or slightly aging ones. I wouldn't spend the big bucks.. Undoubtedly though spray pattern and atomization inside the cylinder is key to the burn..and better is just that..


    Yeah BAZ...... I knew it, knew all along you worked for the company, I just knew it, you're a plant, trying to sell us all the "stuff" when you joined almost three years ago, I knew you where plotting, waiting for this day, just setting us up...now we got you.. kidding obviously.. Keep me posted if you try them out..
    2000 5.2 4x4 WJ

  7. #7

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    Quote Originally Posted by MrBaz View Post
    I'm thinking of rebuilding my 4.7HO with 10.5:1 pistons (coated skirt and top), bored 20 or 30 over, ported heads, headers (yes, they CAN fit), tuning, etc. and just trying to get some ideas.
    For the piston coatings, I would do the friction reducer on the skirts but wouldn't do the coating on the piston crown.

    I have both coatings on my pistons for my 403, after getting it done I was talking with a dyno shop and they said the coating on the piston crown was a waste of money. He said he dynoed engines with and without it and didn't notice a difference in power output between the 2.

    Maybe on a race engine where every bit counts it would be worth it. But on a street engine I don't think it is cost effective. Save the money and use it elsewhere.

    About the injectors, since you are doing a rebuild you might as well get new injectors. There might be a little to be had in power on the injectors spray pattern. I don't know if it will make that much of a difference in fuel economy. With the stock injectors with that heavy stream of fuel, if it was running rich because of poor atomization the computer would see that it was running rich and pull fuel. Also that spray is hitting either the floor of the port or the back of the intake valve, have you ever take a garden hose with a nozzle and sprayed it at the ground, the water sprays off in all directions in a bunch of finer streams, same happens inside the intake port with the injector.
    Last edited by ram3412; 09-05-2010 at 11:27 PM.
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    I don't know if buying the more pricey injectors is worth the extra money. I'm running the stock and original on my 4.0 (now just passed 240K) with an average hwy mpg of about less than 18, still good for me.

    The second testing done shows although the stock injectors made for a more of a stir agitation in the tubes, at the end of the test, it was at near level of the liquid used.

    Not being an engineer, I don't see the advantage of these performance injectors so I was thinking had the fluid level been much less then yes, maybe those newer injectors makes financial sense. Otherwise, I'd just stick to OEM injectors and call it a day.
    ** 1999 GCL, 4.0, automatic transmission, RWD, purchased at 42,000, now at original 281,100 miles (08-2014), overall runs good. Original tranny rebuilt at 231K, still on original alternator and starter and engine (fingers crossed).

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    Quote Originally Posted by ram3412 View Post
    For the piston coatings, I would do the friction reducer on the skirts but wouldn't do the coating on the piston crown.

    I have both coatings on my pistons for my 403, after getting it done I was talking with a dyno shop and they said the coating on the piston crown was a waste of money. He said he dynoed engines with and without it and didn't notice a difference in power output between the 2.

    Maybe on a race engine where every bit counts it would be worth it. But on a street engine I don't think it is cost effective. Save the money and use it elsewhere.

    About the injectors, since you are doing a rebuild you might as well get new injectors. There might be a little to be had in power on the injectors spray pattern. I don't know if it will make that much of a difference in fuel economy. With the stock injectors with that heavy stream of fuel, if it was running rich because of poor atomization the computer would see that it was running rich and pull fuel. Also that spray is hitting either the floor of the port or the back of the intake valve, have you ever take a garden hose with a nozzle and sprayed it at the ground, the water sprays off in all directions in a bunch of finer streams, same happens inside the intake port with the injector.
    Noted. I'll just stick with the skirt coating then.
    2004 WJ Charcoal Limited 4.7L H.O., QuadraDrive, Goodyear Wrangler w/Silent Armor Tires
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    I have Bosch injectors in my 04 Dodge Ram cummins diesel. The Bosch electronics were plagued with problems in the early years on Chrysler Co. made vehicles when Daimler started pushing the german parts on them. I'd find a better after market injector - there's a reason the Bosch's only cost $35 a piece vs. $100 for real performance injectors.
    2004 WJ Laredo 4.7L - 2.75 KOR lift, QTII, BFG KM2's 245/75R16's on OEM Silverblade1 wheels, 4.10 gears, Front Detroit True-trac, Rear Vari-Lok, Addco Sway Bars, spidertrax wheel spacers, IRO Budget Rocksliders ||
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    Quote Originally Posted by Planetcat View Post
    I have Bosch injectors in my 04 Dodge Ram cummins diesel. The Bosch electronics were plagued with problems in the early years on Chrysler Co. made vehicles when Daimler started pushing the german parts on them. I'd find a better after market injector - there's a reason the Bosch's only cost $35 a piece vs. $100 for real performance injectors.
    The Bosch 4-hole injectors are $308 for a set of 8 from one website I found.

    I could get 'Stinger' performance fuel injectors from airram.com for $448 for a set of 8. But honestly, who makes those stinger injectors? For all we know, they could be Bosch(or Accel). Granted, I can order them in any flow rate I need (and what I probably will do if I end up going forced induction).

    Anything has got to be better than the Siemens Deka stock injectors.
    Last edited by MrBaz; 09-07-2010 at 07:02 PM.
    2004 WJ Charcoal Limited 4.7L H.O., QuadraDrive, Goodyear Wrangler w/Silent Armor Tires
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  12. #12
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    Thumbs up better injectors



    Well, I am one who DID an injector change years ago (2003). With the original stock beer-keg intake, the 5.9 stock engine (ZJ at 39k miles) would ping like rattling rocks in a tin can, and had poor or rough idle. I found a deal on a used set of Ford Motor Sports 24 lb Bosch type injectors with the 4-hole spray pattern, out of a mustang GT the owner was modifying. $100 shipped to my door. They were a direct fit match for the factory Dodge parts, but flowed a little more fuel. Took the chance and wow, what a difference! idle smoothed out nicely; pinging totally disappeared, throttle response really improved - off-idle stumble gone, seat of the pants dyno said "YES!"

    As far as fuel economy, can't say because I couldn't keep my foot out of it! Fun-ville! Bottom line: the injector change improved driveability. Of course I can't leave well enough alone and made a bunch more changes since then as my sig shows. I recently ordered a matched set of remanufactured 4-hole spray injectors for my specific Mopar application and mods. The Ford injectors work, but don't match my engine's ECM electronically - the FoMoCo's are running too rich (now at 74k miles), in spite of the ECM trying to maintain ratio. Health issues have kept me out of my tool box so I've not been able to install those yet, but my goal here is better fuel economy.

    So for me, changing from single shot to 4-hole pattern DID improve performance cheaply. YMMV ...
    '99 XJ Sport 4x4 "Amethyst Pearl" aka: "The Grape..."
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    I know this is a GC forum, but for the subject matter, I can state that replacing my stock injectors from stock to Bosch from FiveMotorSports.com made a huge difference as described by Wesley. I did keep my foot out and did see an improvement.

    I didn't have choice in replacement as they were leaking, which is a common problem for a 1990 XJ (ever hear of engine fires on XJ's?).
    2000 WJ Limited - 4.7 QD Stock
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    Quote Originally Posted by sjx426 View Post
    I know this is a GC forum, but for the subject matter, I can state that replacing my stock injectors from stock to Bosch from FiveMotorSports.com made a huge difference as described by Wesley. I did keep my foot out and did see an improvement.

    I didn't have choice in replacement as they were leaking, which is a common problem for a 1990 XJ (ever hear of engine fires on XJ's?).
    That actually the website I found them on.
    If I do buy them I'll let everyone here know how they deliver on the 4.7HO.
    2004 WJ Charcoal Limited 4.7L H.O., QuadraDrive, Goodyear Wrangler w/Silent Armor Tires
    Raybestos Advanced technology rotors w/ ThermoQuiet pads
    v3 headlights w/HIDs

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