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Thread: Choosing injectors for batch fire MPI.

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    Fuel Injected! JeepsAndGuns's Avatar
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    Choosing injectors for batch fire MPI.

    Now that I have the 7427 pcm in and running, and getting the hang of tuning it, I am ready for the next step, mod a intake and convert over to batch fire MPFI with this 16197427 pcm.

    So, what are we limited to, as far as injectors that would be compatable? I would think the injectors ohms would have something to do with it?
    If at all possiable I want to run EV6 style injectors with the nice 4 hole spray pattern.
    I have quite a few (12 actually) of the dodge neon 0280155703 injectors laying around. (running these in the 4.0 in my 93 wrangler and love them) They are the EV6 4 hole pattern injectors.
    I measured them and they are 12.5 ohms (plus or minus .1) They flow 238cc/min at 3 bar, witch according to the calculators online I have found, would flow about the right ammount for my engine at around 39-41 psi.

    So what says the experts out there? If not, what other options do I have, that are roughly the same flow rate?
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    Super Moderator Six_Shooter's Avatar
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    Re: Choosing injectors for batch fire MPI.

    Biggest thing is impedance matching, meaning High-Z injectors.

    Then proper amount of flow capacity, or close to it.

    Physical fitment is also a concern.

    If you're modifying the intake anyway, then you can make it and the fuel rail fit what ever injector you can physically fit. If you start with an existing port injection manifold, you will be limited to the size and style that was meant to be used in that intake.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    Fuel Injected! JeepsAndGuns's Avatar
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    Re: Choosing injectors for batch fire MPI.

    Well, this will be on my AMC 401 engine. They stopped making those in 1978, so no factory MPFI intakes, and there is no other brands/type of intakes that can be modded to fit. This will be custom.

    "Biggest thing is impedance matching, meaning High-Z injectors"

    Ok, you just said something in japaniese...lol...I have no idea what that means. Can you enlighten me?
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    RIP EagleMark's Avatar
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    Re: Choosing injectors for batch fire MPI.

    yeah, learn us?

    I know of Peak and Hold injectors, Saturated Injectors...

    So what is High Z?

    Are they just for 280Zs?

    Opps, or is yours a 260Z?

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    Re: Choosing injectors for batch fire MPI.

    Learn ya??? Well, you asked.

    So you're familiar with resistance. In A/C circuits and pulsing DC circuits using coils there's impedance. Impedance is roughly similar to resistance but it also includes things like the canceling effects of currents out of phase and currents dampened by capacitance. Resistance is resistance to electrical flow and is measured in Ohms. It is represented by R in many formulas. Since impedance is also the total resistance to electrical flow it is also measured in Ohms. However, it's represented by Z in many equations to indicate that it's not purely resistance. So what does this mean when selecting an injector??

    Nothing!!

    Resistance is the dominant property of the injector. Resistance also determines the driver type used in the ecm. A high Z injector is a high impedance injector is a high resistance injector is a high Ohms injector. It is more technically correct to say an injector has impedance so you will often see this term and "high Z" or "low Z" used in injector discussions. Saturated injectors have high resistance and peak and hold injectors are low resistance. Saturated injectors and drivers get their name because the circuit is at "full current" the entire time the injector is opened... it's saturated with current. Peak and hold injector drivers get their name because the circuit allows higher current while the injector is opening then lowers current once the injector is open to prevent overheating. An old fashioned GM starter solenoid is the same way, with a "pull in" coil and a "hold" coil. That's a "peak and hold" solenoid.

    Look for injectors with 12 - 16 Ohms and you should be ok.

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    Re: Choosing injectors for batch fire MPI.

    So basicly, we are saying these should work just fine?
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    Re: Choosing injectors for batch fire MPI.

    Yep, that's what Six was saying. Match the Ohms rating and you should be ok.

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    Re: Choosing injectors for batch fire MPI.

    Now the hard part, buying a intake and finding a machine shop that can do the required work, do it good, and at a reasonable price.

    For a intake, so far this one is looking like its gonna be the best bet.
    http://www.summitracing.com/parts/EDL-7531/

    Right now I am running the regular edl. preformer intake, and looking at it, it doesnt look like it would lend itself to be easy to mod for injectors because of the way the runners are cast. The air gap looks like a modded preformer and it looks like it wouldnt be too hard to set up for injectors, as the runners are shaped a little diffrently and are more even where the injectors would be.
    They also make a open plenimum intake, but its a high rpm intake, and I dont want that. This is a lower rpm engine, I rarely take it past 3k, sometimes as high as 4k if I am really standing on it, but thats rarely.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    RIP EagleMark's Avatar
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    Re: Choosing injectors for batch fire MPI.

    Looks like it has a spot for injectors. I know Marlo might take on the job, he's the one that does the GM/IH Hybrid distributors.

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    Re: Choosing injectors for batch fire MPI.

    Dual plane carby intakes are often tough to convert to efi. Large, open plenums are usually better for high rpm use in carburetors but in EFI an open plenum doesn't hurt low end like it does with the carb. If you can get a Torker for decent $$ it could be tuned to work.

    What would be really nice to get is a long runner intake to compliment a low rpm cam. I'm not sure how much you want to pay to buy a carbie intake thane have it adapted, but maybe building a manifold from scratch is cheaper or at least more rewarding for the price? Plenty of guys selling "sheet metal intakes" could build something.

    Indy cylinder heads sells a manifold that might be a nice choice, if it fits the stock heads. Price book showed the manifold at less than $400. Maybe injector holes could be added before shipping?


    More info: http://www.moparmusclemagazine.com/tech ... to_19.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;"

    MSD sells a "special" stepped mill / drill bit which has proper dimensions for many injectors. This can be used to put injector openings into a manifold flange provided there's enough aluminum there. And you can by injector "sleeves" designed to be welded into a manifold. I might be able to dig up the box of sleeves I have here to get MFG and part number if needed.

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    Re: Choosing injectors for batch fire MPI.

    Quote Originally Posted by 1project2many
    Dual plane carby intakes are often tough to convert to efi. Large, open plenums are usually better for high rpm use in carburetors but in EFI an open plenum doesn't hurt low end like it does with the carb. If you can get a Torker for decent $$ it could be tuned to work.

    Interesting. I had looked at the torker intakes and the runner design looked like it would be about right, and easy to mod for injectors, but I have been writing it off because I thought it would kill my low end. So from what your saying, the longer runner open plenum intakes like that are actually better for mpfi and wont kill my low end? This engine rarely sees over 3K rpm, and about the highest I ever rev it is 4K when I am really hammering on it. But thats not very often.
    The indy intake seems nice, but I dont see provisions for a PCV and other normal vaccume ports. Even though its got the bosses in it for injectors, I think its geared more twards race engines. I'm gonna do a little more looking around and see what I can dig up.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    RIP EagleMark's Avatar
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    Re: Choosing injectors for batch fire MPI.

    Long runners and open plenums don't effect engine preformance on port injected motors. It does on carbed motors because the fuel and air is mixed in the intake. Hence a wet intake manifold. Port injected is dry intake manifold. It just supplies air.

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    Re: Choosing injectors for batch fire MPI.

    Quote Originally Posted by EagleMark
    Long runners and open plenums don't effect engine preformance on port injected motors.

    I would agree for the most part, to a point. The exception to that is the TPI setup. i.e. long small cross section runners that did make a difference below(for the better) and above(actually hurt) 4500 rpm.


    I have been thinking about building my own intake for MPFI on the Camaro. I just haven't quite settled on a runner design I like. I want the injectors pinted directly at the back of the valve not the bottom of the port where the intake meets the head. Still in the planning stages though.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
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    RIP EagleMark's Avatar
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    Re: Choosing injectors for batch fire MPI.

    That is a better pointing position. But to build and intake for a Chevy when so many are available?

    I think the pointing at valve is not done originally because of injector clearance to intake and fuel rail issues. Batch fire would make no difference, seqencail... maybe...

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    Re: Choosing injectors for batch fire MPI.

    Quote Originally Posted by EagleMark
    That is a better pointing position. But to build and intake for a Chevy when so many are available?

    I think the pointing at valve is not done originally because of injector clearance to intake and fuel rail issues. Batch fire would make no difference, seqencail... maybe...
    I was thinking that batch fire would be more important to have it pointed at the valve because if the injector fires at a closed valve the hot valve would help to keep the fuel vaporized until it opens, maybe better than the side of the runner can. If the injector fires at or ahead of an open valve it wouldn't make much difference....no?
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

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