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Do I need more Injector/Fuel pump

Discussion in 'Modified 1995-2001 Explorers' started by Notpretty, May 16, 2012.

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  1. Notpretty

    Notpretty New Member

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    1971 Bronco W/98 EXP 5.0
    New to the forum...Hi all...

    I have:

    1998 Explorer 5.0
    AFR Heads with Intake port matched to it
    Cam swap Comp Cams
    Basic Operating RPM Range 1,200-5,200
    Intake Duration at 050 inch Lift 210
    Exhaust Duration at 050 inch Lift 215
    Duration at 050 inch Lift 210 int./215 exh.
    Advertised Intake Duration 266
    Advertised Exhaust Duration 270
    Advertised Duration 266 int./270 exh.
    Intake Valve Lift with Factory Rocker Arm Ratio 0.533 in.
    Exhaust Valve Lift with Factory Rocker Arm Ratio 0.533 in.
    Valve Lift with Factory Rocker Arm Ratio 0.533 int./0.533 exh.
    Lobe Separation (degrees) 114
    Computer-Controlled Compatible Yes


    Headers...just 1 5/8" primaries but free flowing no cat
    Using a Moates Quarterhorse to tune it
    Roller Rockers...pedestal mount.
    I have 30# injectors, but don't know if I need them
    Thinking of Turbo in future, but not yet. Don't ask why...snow wheeling thing.

    Everything else is basically stock...bottom end is bone stock so compression is supposed to be 9:1ish with these heads
    The air intake will be larger with a larger MAF sensor, but still have the stock explorer throttle body.

    The main question: Do you think I'll get over the 300 HP mark where I need to start thinking about larger injectors? If so, will my 30# injectors be fine and will the stock fuel pump cause a potential lean condition...or is it going to be fine?

    I'm a rock crawler and this motor is in a 1971 Early Bronco with more drivetrain toys than one could imagine...40K+. I am learning this EFI performance thing on the fly so don't assume I know what I'm doing. The cam is a compromise between torqure and increased lift/duration.

    Thanks for any feedback
     
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  3. Notpretty

    Notpretty New Member

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  4. techieman33

    techieman33 Explorer Addict

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    30lb injectors are plenty, stock explorer pump will be fine as well.
     
  5. ExDude

    ExDude B

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  6. FIND

    FIND Well-Known Member

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    I don't see you needing anything more than stock fuel and induction on what you've got. You should consider optimizing your throttle body, and I would hope you change to a different intake than the stock airbox. Save changing the fuel system for forced induction. What headers are you using?
     
  7. ExDude

    ExDude B

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  8. techieman33

    techieman33 Explorer Addict

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    If boost is a possibility for the future I say just throw the 30's in now so you don't have to mess with them later. If your keeping the factory computer I would recommend henson performance to do the tuning. He can write you a tune that will have you really close without you having to mess with everything or visit a dyno. And it will probably cost about the same as the moats.
     
  9. ExDude

    ExDude B

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  10. RangerSVT

    RangerSVT Active Member

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    The size injectors you need will depend on how much boost you run. You will also need a wide band air/fuel ratio gauge so you will know if your injectors are doing the job. Getting a fuel rail pressure gauge will tell you if your fuel supply (fuel pump) is sufficient. If you start running lower fuel pressure under boost, you will need to upgrade. I'm boosting using an M90, and the stock fuel pump is good up to about 7psi, after that its starts falling off. The 30 lb squirters are good through 8 psi, which is where I'm at now. Anything over 9psi and i would up the injectors. I also rock crawl, and you might want to think about supercharging rather than turbo. Don't get me wrong, I'm a turbo guy, but in the rocks, you want power right off idle...

    SVT
     
  11. ExDude

    ExDude B

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  12. Notpretty

    Notpretty New Member

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    Okay guys. I'm not running any boost... Not yet. Turbo may be in my future but for now don't assume it.

    I do plan on having it tuned on a dyno. I have purchased the moats device that connects to the stock computer and gives me access to modify just about everything and even data log. My hope is the guys running the dyno can squeeze out all they can with that set up.

    So, most are saying at 5200 RPM or less the 19# injectors should be fine. And I agree with that for the most part. But I do have brand new 30's and since I can alter the program via the moats, My question really is should I run them? Will it be an issue?

    I will run this motor at 5200 or a bit more during occasions when deep snow wheeling conditions require it. I'm running 40" tires on a rock-crawling, snow wheeling 71 Bronco. That is also when a future turbo would come in handy. The higher HP can get you up on top of the snow floating more and thus progressing farther.

    This question started with my concern that when I put the foot to the floor with 19# injectors I might go lean and fear a big boom...deep in the mountains, at night, in 8 feet on snow.
     
  13. FIND

    FIND Well-Known Member

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    I don't really see you needing more than those 19# injectors can deliver. With the 30# injectors, you are definitely not going to be pushing them ever, but whenever the computer limps or does anything similar, you are going to wash out your cylinders and ruin your engine just the same. Stuff happens...
     
  14. Notpretty

    Notpretty New Member

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    I'm no expert. I've gotten conflicting feedback about using over sized injectors. Some say it's no issue others say its bad but never explain in clear terms why it's bad...terms I understand anyway. Washout? Hurt engine?

    Obviously they have sizes for a reason but is 30 close enough or way too much..?
     
  15. FIND

    FIND Well-Known Member

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    I mean with the amount of fuel going into the engine in limp mode, it will wash the oil off the cylinder walls and such. Limp mode is a default program that runs much richer than you would normally want and doesn't use much sensor input for engine controls. Pretty much just throttle position and RPMs. That is a lot more fuel... That is a rate more than 150% of normal... In limp mode, you will be putting at least twice as much fuel in as you would on your tune at cruising speeds.

    Plus, with higher rate injectors, your fuel won't get good atomization without air mixing in at the same rate, which means you won't have as much efficiency with combustion. Why do you think OEMs don't just buy one size of injector for everything? A 14lb injector is no cheaper to produce than a 48lb. I just don't see you really pushing stock injectors too far on your setup even if you sit at 5200 rpms... But, you will be tuning it anyway, so you can just decide if you want to go up to larger injectors once you see what kind of duty cycle you are running those 19s at. You want to stay under an 80% duty cycle as a general rule of thumb. Even still, 24# injectors would still be a better choice than 30s. If you go by the old rule, take flywheel horsepower times .07 on an OHV SB V8 and that will get you in the neighborhood of the injector size you need. If you figure 300 hp on your build, that comes out to 21#, so 19s shouldn't be far off, but you might need to upsize. I don't know how well 30# injectors would run at the low duty cycles you will need for idle and low RPMs too.

    Lastly, it takes a certain amount of time to open and close an injector, and the PCM only has so much resolution, so if you are talking about something under 2ms, then you are going to have trouble. Granted, I don't think you will go under that just going up to 30# injectors, but yeah... A .1 ms adjustment on a 5 ms open time is a much finer adjustment than a .1 ms adjustment on a 3ms open time. Of course, if you go with 30# injectors, you could tune for e-85 if you add an adjustable FPR so you can regulate fuel pressure a bit better. Of course, tuning for e-85 on a vehicle without the proper sensors means ONLY running e-85, so yeah... Probably not something you are interested in, but it was a passing thought.
     
    Last edited: May 18, 2012
  16. ExDude

    ExDude B

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    Last edited: July 6, 2012
  17. RangerSVT

    RangerSVT Active Member

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    The motor doesn't see above 5k rpm...as far as over size injectors, anything over stock size needs (should) be retuned for it, otherwise the chance of dumping too much fuel (washing out) can occur. Bigger is better than too small, better to be too rich than too lean. This is why you here its better. You here its not better cause it could cause washing, but the people that say this dont know or understand that it needs to be tuned for the bigger injectors. There are 03 cobras and lightnings out there running 100+ lb injectors (with other supporting mods as well). According to those latter people, the owners will wash there engine out if it idled for just 5 minutes with those injectors...

    SVT
     
  18. FIND

    FIND Well-Known Member

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    No one said not to tune. I was talking about washing out if the engine enters limp mode. Damage to sensors or wiring is easier to do offroad than on, so yeah.... That is why one should give a little thought to what might happen in that situation. Either way, there are still some other issues too.
     
  19. ExDude

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    Last edited: July 6, 2012
  20. RangerSVT

    RangerSVT Active Member

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    My particular setup doesn't see north of 5k, but that doesn't mean all crawlers won't see that. It comes back to the driver's style of driving. He might crawl, but might also see the occasional mudpit. He might also have to give her hell for a hill climb. Typically the crawling world don't see high rpm, and if they do, its not on a regular basis. As stated above, limp home mode is always a possibility, but personally is not a high enough chance for me to take running my motor close to the stoich or lean mark. But then again, that's my preference, doesn't mean its wrong, or for everyone. I'm just trying to bring the facts and reasons for the opinions given :salute:


    SVT
     
    Last edited: May 18, 2012
  21. RangerSVT

    RangerSVT Active Member

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    Here are the specs for a few Ford injectors...
    Injector Lb/Hr /Max V8 HP/ HP supported by 1 injector/Ford injectors color
    14 Lb/Hr 228/ 28.56 Gray
    19 Lb/Hr 310/ 38.76 Orange
    24 Lb/Hr 391/ 48.96 Lt Blue
    30 Lb/Hr 490/ 61.19 Red
    36 Lb/Hr 587/ 73.44 Dk Blue
    42 Lb/Hr 685/ 85.68 Lt Green

    Keep in mind these numbers are for naturally aspirated engines where vacuum is pulling the fuel into the combustion chamber. On boosted engines, you have pressurized air applying force against the fuel exiting the injector, reducing its rated output...

    SVT
     

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