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  1. #1
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    Default Injectors again!

    I know, I know! This has been talked about millions of times, and like many I fell for the 703 injector swap.

    I have know mort has been running lean for some time, so once again I have been researching injectors, and from my research I have found a stock 4.0L runs about a 23 lbs/hr injector. And we have all read the articles on swapping to a 703 injector because it has 4 holes in the pintle. But the 703 is only a 16.75 lbs/hr injector. I am running these currently, great gas mileage but has always felt under powered. And since mort is a 4.6L I need to do some research for a proper sized injector.

    I have started by copying all the Bosch injector data into excel, appox 1000 injectors, I know I want an EV6 style injector so I eliminated all but that style, and any that did not have flow data. Now down to 265 injectors, now to research what size a 4.6L really needs...

    Stay tuned!


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    Default Re: Injectors again!

    1000 line spreadsheet, man that is dedication
    230 hp 4.3L Chevy
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  3. #3
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    Default Re: Injectors again!

    Ok so I have a friend who is big into modifying and racing, he has advised me that since I raised my displacement by about 20%, then I should raise my injector size by about 20% and my stock ECU should handle that just fine. So if stock injectors are 23.2 lbs/hr then I should go up to a 27.84 lbs/hr injector. So I am going to add a margin of 3 plus or minus and I get 21 injectors to research.


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  4. #4
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    Default Re: Injectors again!

    Ok I lied I am only going to add to that margin! So 27lbs and up!


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  5. #5
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    Default Re: Injectors again!

    So it looks like a 0280155831 injector is the one I want, it is a 4 hole injector with the proper connector and it's in many volvos, should be some in the local scrap yard. I would like to attach my excel files, but I don't think I can from my phone....


    Perhaps I'll just research a good stock replacement for those of you looking for better than the 703.


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    Default Re: Injectors again!

    Quote Originally Posted by Pookapotamus View Post
    I know, I know! This has been talked about millions of times, and like many I fell for the 703 injector swap.

    I have know mort has been running lean for some time, so once again I have been researching injectors, and from my research I have found a stock 4.0L runs about a 23 lbs/hr injector. And we have all read the articles on swapping to a 703 injector because it has 4 holes in the pintle. But the 703 is only a 16.75 lbs/hr injector. I am running these currently, great gas mileage but has always felt under powered. And since mort is a 4.6L I need to do some research for a proper sized injector.

    I have started by copying all the Bosch injector data into excel, appox 1000 injectors, I know I want an EV6 style injector so I eliminated all but that style, and any that did not have flow data. Now down to 265 injectors, now to research what size a 4.6L really needs...
    I have your answer.

    http://www.jeep4.0performance.4mg.com/tech_specs.html

    The problem is that most of the injectors are flow rated to 43.5psi (3 bar) and you're running a stock 39psi fuel system which drops the injector flow by 5% from the rating.
    The stock injectors flow 21lb/hr at 39psi and you need injectors that flow 15% more to match the displacement increase. Therefore you need injectors that flow ~24lb/hr at 39psi and the closest ones are these:

    http://www.ebay.com/itm/Ford-Fuel-In...9X4t6r&vxp=mtr

    The 0280155831 you're suggesting is way too big.
    Last edited by Cheromaniac; 04-30-2017 at 04:32 AM.

    1992 XJ - 4.6L Stroker - AX15 - Sold 13/12/2016
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  7. #7
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    Default Re: Injectors again!

    Quote Originally Posted by Pookapotamus View Post
    So it looks like a 0280155831 injector is the one I want, it is a 4 hole injector with the proper connector and it's in many volvos, should be some in the local scrap yard. I would like to attach my excel files, but I don't think I can from my phone....

    Going to have to see if I can find out what model Volvos these are in, so I can see if any of the couple Volvos the local JY has, might have some that I can snatch for when I finally manage to do stroker build

    Perhaps I'll just research a good stock replacement for those of you looking for better than the 703.

    This would be awesome to have...even more so if I can actually manage to find some w/ the limited selection my local JY has
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  8. #8
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    Default Re: Injectors again!

    Dino, I did not give you all the info, I am running a 96 wiring harness, and when I did my enduring tank I upgraded my fuel system, I have been to that page before but thanks for bringing it back to my attention.

    I know that the 831's are big, their flow rate @ 43 psi is 28 lbs. but I know I can get them, I do have a second choice that should be readily available, 0280155931 that has a flow rate of 28 as well but people say it's actual flow rate is closer to 24. The stock Ecu should be able to compensate for the extra flow, the same way it is compensating for the reduced flow of the 703.

    So if I use your numbers, my stock 53030778's flow 23.2 + 15% = 26.68, putting both these injectors close, it might depend on which ones I can find in the local wrecking yard cause I can't really afford to drop 300 on newbies.

    At least it sounds like you agree with me that the 703's are totally the wrong choice, too bad I have been running them since I build mort.

    It might have to be trial and error too!


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  9. #9
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    Default Re: Injectors again!



    Once I see if the 831's work for me I will let you know, there really should be a better option than the 703's though, I will look into them and see if I can find a readily available one.


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    Default Re: Injectors again!



    And a trip to the junk yard was fruitful!!!


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  11. #11
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    Default Injectors again!

    Ok 831's in!



    First impressions, massive success! Smoother idle, quieter idle, better throttle response, better air/fuel readings, better sounding on acceleration, better power on acceleration, better fuel mixtures when off throttle, so far no disadvantages showing, fuel economy is probably going to be out the window until I learn to keep my foot off the pedal!

    Over all drive-ability is much better, I will see how it handles hills and passing when I can get out for a good drive. The butt dyno does not seem overly impressed but it's hard to tell, pcm is still relearning, but does feel much much smoother! And sounds so much happier! I think I can actually leave mort running when I order at a drive through!!! No longer sounds like the valves are going to shoot out the top at high rpm!

    Super excited at how this went, and I have a set of 703's that I might have to do some destructive testing on!

    Oh I forgot much better starting too, see how mort starts after sitting at work tonight when it's cold on my way home!


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    Last edited by Pookapotamus; 05-01-2017 at 05:03 PM.

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    Default Re: Injectors again!

    Sounds good so far
    230 hp 4.3L Chevy
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    Default Re: Injectors again!

    Look forward to seeing more on how she does with the new injectors... What model did you get the 831 injectors out of?? and are they only really going to work for the larger displacement of the 4.6, or would they work for the 4.0 (or would they be too much for the for the stock 4.0)??
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  14. #14
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    Default Re: Injectors again!

    I would say they are too much for the stock 4.0L. The pcm would probably compensate but would be best to stay in the 24 lbs zone.


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    Default Re: Injectors again!

    Quote Originally Posted by Pookapotamus View Post
    I would say they are too much for the stock 4.0L. The pcm would probably compensate but would be best to stay in the 24 lbs zone.


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    I'll run what I've got as far as 4-hole injectors for now then.. But will have to figure out where to find the 831 injectors.. and clean them up.. so I'll have them to put together with other parts as I collect them for a stroker build up/install
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