Retro mod fuel system problem

Discussion in 'PSI Superchargers Tech Questions' started by Kendrick Roberts, Apr 23, 2020.

  1. Kendrick Roberts

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    It seemed like such a good idea at the time.
    This is what I have done:
    Slingshot dragster, powerglide, 3:73 gear, 6000rpm(ish) stall FTI converfter
    6.0 LS motor, stock with large hydraulic cam.
    102 MM single butterfly aftermarket intake.
    Smart Spark controls for ignition - 8 stock LS2 (truck) coils
    Belt driven Waterman 700 pump -16T:48T ratio (slightly overdriven)
    Square black Enderle methanol barrel valve off of bird catcher blower hat.
    Secondary bypass @ 2PSI
    Main Jet (as low as 50, as high as 180 --currently 150)
    High speed currently blocked
    Injector nozzles 160 cc electric (approx equal to .046" ish orfice) 100% duty cycle (always on with ignition)
    NOTE: no vacuum break, or air bleed on injector nozzles in conventional LS port position
    F1X procharger 5.4:1 internal overdrive, 46T:32T external overdrive. this blows through butterfly.

    Here is the problem, if you have not already guessed.

    It runs extremely rich at idle, even with barrel valve cut back to 5-10% leakage. Idle speed is unreasonably slow even with butterfly open a bunch -as far as the idle screw will take it
    Throttle response is predictably lean at that point,and gets reasonably good at 50-60% leakage.
    Tried playing with main jet- a bunch - after messing with barrel valve for 3 gallons or so.
    At high idle -- 2500-3000 rpm, it is pulling enough vacuum to hold the surge valve wide open.
    Still way rich until I let some air in.

    Any thoughts, ideas, criticisms?
     
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  2. nitrowannabe

    nitrowannabe Member

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    So you're mixing a very good EFI system with a 1950's MFI system. Dont those injectors need 58psi ? They are always squirting ? What is the Waterman psi ? You have a PC controlled ignition with no ECU ? Hack a stock ECU and have 1200hp like a new Super Stock. But I m probably wrong somewhere. Should be a fun car. FED forever !
     
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  3. Kendrick Roberts

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    I am mixing systems because the car owner and some of the organizations we run with (nostalgia) object to EFI.
    I am attempting to use this type of nozzle because that is what the manifold was built for.
    The EFI systems are usually set up for 45 PSI or so, sometimes corrected for boost.
    The Waterman pump will deliver variable fuel pressure based on engine rpm, nozzle, and return jet sizes. This variable pressure determines the fuel curve.
    Pressure goes up as RPM goes up. My target max fuel pressure is 120+ PSI, but it is less than 5PSI at idle.
    Yes the nozzles are always squirting, just as they would on a conventional MFI system.

    I would dearly love to run EFI, but I am quite comfortable with MFI having run many NA, Turbo, and Supercharged applications, ( this is my first centrifugal) after all, the fastest drag cars on the planet run MFI.
     
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  4. Dave Koehler

    Dave Koehler Member

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    I think you answered your own question. The EFI injectors expect to see that 45 lbs or whatever at ALL rpms do they not?
     
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  5. Bjs344

    Bjs344 Member

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    You mention secondary bypass at 2 psi. It seems like you’d be referring to the main poppet but I’m confused why you called it secondary?

    I’m assuming only 8 injectors total?

    I saw these symptoms once on a k valve. They guy had got confused between the pump saver and the main bypass so basically had no functioning return poppet.

    If it’s so rich at idle, I’m surprised it feels lean on a throttle whack. If its idling super rich there should be enough fuel sitting there for it to come up when you crack it. I mean, that’s basically how MFI works, right?

    You could drill out the throttle blade to raise the idle but that might or might not be a bandaid.

    Could you turn off 1/2 the injectors with a microswitch that’s on in the idle position? Idle egts might be all over the place, but they always are a mess on a roots motor no matter what I’ve ever done.

    How much timing do you have at idle. I would think (hope) you are down around 10-13 on the converter, but maybe it needs a bunch more at idle?
     
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    Last edited: Apr 25, 2020
  6. Bjs344

    Bjs344 Member

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    Plenty of cars running mechanical pumps and efi without problem. I don’t see any way they are making 45 psi at idle
     
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  7. Kendrick Roberts

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    Yes , 8 injectors directly over the port
    15 degrees of timing at an idle
    I am also puzzled by the throttle response following the barrel valve but not the idle, I cannot affect idle speed with the barrel valve on this (I too am tempted to drill a hole in the butterfly, but it shouldn't be necessary)
    The bypass is the one Enderle calls the secondary, I always called it the idle bypass, but on those square black barrel valves it does both main jet and idle so...
    I actually have it set up more like an NA motor with a separate main jet bypass. The secondary on those is usually set to 20-30PSI, but I now have this one all the way down to unmeasurable check valve status

    My guess on this system is that since I am running only ventless port nozzles, I am getting too much pressure differential at the nozzle tip, so even at 2PSI at idle, with 14" of vacuum, I basically have a 9PSI pressure drop at the nozzle tip at idle.
    With the barrel valve cut back to nothing(ish) it goes to no fuel flow as soon as I open the throttle and lose my pressure drop. Hence the poor throttle response.
    That is until I open up my barrel valve.
    On turbo MIF systems, we used a vented nozzle that had the vent ported upstream of the butterfly so it did not see vacuum, and id id not blow all the fuel out of the vent under boost because upstream of the butterfly was still downstream from the turbo (Am I saying this right? I hope this makes sense). They worked fine.

    I thought about using a 555 chip to create a duty cycle for these injectors just at/near idle with a microswitch like you suggest, but now we are back in EFI land. :(

    So, if I am right, how do I fix this? If I am wrong...WTF?
     
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  8. TOL

    TOL Active Member

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    Why don't you just build a proper MFI system for a turbo-like application, forget the EFI nozzles, and make adapters to hold the MFI nozzle bodies using the stock holes that you already have? Hilborn or others for example. I got really confused following this thread to be honest. Decide EFI or MFI and then use the hardware to suit the one you chose? That would be my suggestion.
     
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  9. Bjs344

    Bjs344 Member

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    The chip at idle makes sense. There are guys running gas primers that way in alky bracket cars. I might unplug 4 injectors first as a quick look to see if that is any better. The fuel will still get sloshed around in the intake.

    The high delta p at the injectors might explain the problem. I put unvented nozzles in the hat of my blower motor (long story why) and it made it pretty frustrating to tune the idle.

    It seems like you have it plumbed like a hilborn setup ( I have one of those too) with a jet in a poppet teed off of the main feed to the BV? If that’s the case, the BV outlet would be capped off I think? Not sure I understand.

    I would try three things besides/before manipulating injectors:

    1. I can’t quite understand how you have the return(s) plumbed, is this a method you’ve used before and are you sure it’s correct?

    2. I would try between 20 and 25 degrees at idle assuming you can immediately knock it back to 15 with your controller. SBE 6.0 I would potentially ramp down a little lower until it’s off the converter to keep the rods in it. I’m an LS virgin myself, thats just what I’ve heard

    3. Everything else checks out could you put a leanout solenoid between the pump and the BV with the idle microswitch? You could put a ~.250 pill in there, and could try just putting a .250 in the main first to see if it would idle with a decent bv setting. You could then increase the “idle check” pressure so that when you close the idle leanout at throttle crack you’d get more of a “pump shot”. I’ve thought about trying blown gas at some point in the future and this was the first thing I was going to try
     
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  10. Kendrick Roberts

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    I agree, that was what I initially planned.

    Then I got clever.

    I thought I had a good solution to putting injectors in this manifold since MFI nozzles for it do not exist. I (or someone) would have to make them. Thought this would give me a nice clean shutoff as well with no fuel drooling into the cylinders after shutdown.
    Yes. I am probably not describing it properly. The plumbing is very conventional.
    Main jet teed into pump output after filter
    High speed teed parallel to main
    Seccondary on barrel valve dump port that aligns with hole in barrel spool at or near idle
    When you do these Endele systems this way, you put a blank main jet in the BV, but you still need to dump fuel at high RPM with throttle closed, so secondary bypass is still needed.

    Timing is a good idea

    I like your leanout idea too

    Right now, since I am probably going to have to make my own nozzle bodies. I am going to first try to make a vent system for these nozzles.
    But I am also going to try the timing trick. It would probably run cleaner no matter what else I do.

    Keep em coming.
     
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  11. Bjs344

    Bjs344 Member

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    Ok, I’m with you on the plumbing except I think that the poppet on the BV in this configuration is now a pump saver and needs a poppet at ~100+ psi?
     
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  12. Dave Koehler

    Dave Koehler Member

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    It is because he does not have enough pump to get 45 psi at idle. Bigger pumps than needed used by EFI guys means more volume per revolution, especially at idle and just dump off the rest.

    Plus he is trying to make the barrel valve control the idle. i don't see a good way to have it both ways with this configuration.. Either the barrel valve and mfi or a controller and efi. Basically the mfi is fighting the efi for off idle control.
     
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  13. TOL

    TOL Active Member

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    Kinsler Fuel Injection nozzle adapters. EFI/MFI. Done for years already. Or, easy enough to make your own, or have a shop make up a few. I think the decision tree is pretty simple: 1) You have an ECU, use EFI injectors, 2) You don't have an ECU, use MFI nozzles........
     
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  14. Bjs344

    Bjs344 Member

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    The EFI nozzle with power applied should be the same as having a non-aerated MFI nozzle installed. There is no “fighting” because here is no Efi controller, they’re just jammed open.

    So, if you’re saying a non-aerated nozzle will never work, ok, but I think you’re getting stuck on the nozzle having wires connected to it.

    If he put a nozzle jet holder in line before the injector would that somehow make you less skeptical about his setup?

    Oh, and I don’t believe anybody is making 45 psi at idle with a mechanical pumped efi. At least not the ones I’ve seen.
     
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  15. Kendrick Roberts

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    I am a huge Kinsler fan, have been for a long time.
    I did not know they made anything like that.
    I have seen adapters to go the other way (from MFI to EFI)
    I was working with Kinsler when EFI first came out back in the day...
    Back then we could not justify the extra expense.

    Boy have things changed.

    I was just on their site and don't see those adapters. Do you have a part number?

    I am currently making my own adapters with a vent, hope it works.
    Gonna jack a bit of timing in there too, and back it off near stall. ;)

    Right now it looks like I will have to modify the manifold to put MFI nozzles in there, I am just trying to avoid that.

    A bit lazy I suppose--on top of being stubborn.

    It seemed like such a good idea at the time....
     
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  16. Dave Koehler

    Dave Koehler Member

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    OK, I didn't catch that this is really an MFI using disabled EFI injectors.
    Wonder what the final nozzle size becomes?

    To get pressure at low rpm you go way big on pump. It's the volume per pump revolution that makes it work. Let's say a 10 gpm pump would give you all you need to make the target HP. To get the pressure up enough to start you use a 20+ gpm pump and dump off the rest. Some use this so they don't have use an electric pump to get it started.
    Now that this has become an MFI mess I will drop any reference to pumps. :)
     
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  17. Kendrick Roberts

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    Update.
    Nozzle vent system helped a bunch. I am running the vents for all 8 nozzles from a single 1/4" plastic line--around 3/16" ID-- of the quick connect shark bite variety
    The nozzles are rated at 160cc/min@45PSI which is roughly equal to a .046"-.050" orfice.
    My target is 1000 to 1200 HP , and I have run that much HP in the past with 8 x.050" hat nozzles on a 6-71 and the same size pump.

    Idle is still a bit slow, and it occurred to me that in the past all of my systems had multiple butterflies with a .002" to .006" gap + whatever air got in through the nozzle vents. (at idle)
    I did some math, then pulled my single butterfly throttle body off and got a big surprise. (you EFI types probably already knew this...)

    The throttle body is actually machined so that--as you rotate the throttle shaft, there is only air gap changing on the top of the butterfly until 15 degrees of throttle opening or so. The bottom edge of the butterfly only has enough clearance so that it does not touch --between .001" and .002" constant for first bit (10 to 15 degrees) of throttle blade rotation.

    This means I have much less air than I am used to getting as i opened the throttle--that is until I get serious about opening the throttle--and less air coming by at an idle, even a quite (positional-ly speaking) high idle. This would mean my barrel valve (fuel delivery) will always be ahead of my air supply at low throttle angles.

    Does this make sense to anyone but me? I could be wrong.
     
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  18. Bjs344

    Bjs344 Member

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    Glad it’s working better. I’d still be tempted to drill a hole in the blade, especially if it’s thick enough to put a 1/16 npt plug back in it if you needed to
     
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