high speed question

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by rb0804, Nov 16, 2010.

  1. rb0804

    rb0804 Member

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    If I change the jet in the high speed assembly will it affect the opening pressure of the popet? When I check the cracking pressure should I check it with the orfice in place? Thanks.
     
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  2. Mike Canter

    Mike Canter Top Dragster

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    No, the size of the high speed jet does NOT affect the opening pressure of the poppet. You can set it with or without the jet in place. A closed poppet will feel the same pressure pushing against it regardless of the size of the jet. Normally they are set without the jet and jet holder attached because it is easier.
     
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  3. rb0804

    rb0804 Member

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    I was thinking that there might be some sort of pressure drop across the orifice which would slightly delay the opening of the high speed and that it may be more acurate to install the jet after the popet. Thanks for clearing that up for me Mike!
     
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  4. Mike Canter

    Mike Canter Top Dragster

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    If it is not yet flowing then there can be no pressure drop. To carry the subject a little further. If you have a 150 psi of fuel pressure on the line before the jet or orifice and then a 50 psi crack pressure poppet then the pressure of the fuel measured between the orifice and the poppet is the difference between the two which is 100 psi. So this means if you had a 60 HS jet with a 50 psi crack pressure on the poppet then that 60 jet would see the flow based on 100 psi fuel pressure and not 150 psi fuel pressure. Where this makes a real big difference is if you are using an electric solenoid without a poppet versus a High Speed that just has a poppet. The fuel bypassed by the solenoid without a poppet is greater.

    If you have Jetsize software you can actually see this change in GPM. Where you put the High Speed bypass on the main page put in a 60 jet with a 50 psi poppet and see what it gives the GPM flow. Now take out the 50 psi poppet and put in zero for no poppet and see the GPM through the 60 jet change.
     
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  5. rb0804

    rb0804 Member

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    I am talking about the fuel has to flow through the orfice (a restriction) before it can start to apply pressure to the popet assembly. I am talking about a pressure difference from the pump side across to when the popet starts to open. I would think the electric solenoid would flow better because it is either full open or full closed. It doesn't have the ability to 'crack' like the spring popet. My thinking is if the jet is installed post popet, would the popet flow more like the electric solenoid? Let me ask you this then: Which way do you install the electric solenoid? Jet first, then solenoid or solenoid then jet? Or does it matter?
     
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  6. Mike Canter

    Mike Canter Top Dragster

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    The answer still to your original question is that the orifice changes the flow and not the pressure in a poppet. You can have an increase in pressure without actual flow. If the poppet has not reached its crack pressure then it sees the pump pressure against it until it exceeds the set crack point. The spring inside the check valve or poppet is pushing against the incoming pressure and that is why it subtracts from the total pressure.

    It doesn't make any difference to the poppet if the jet is before it or after it. There is a reason why we don't put the jet after the poppet but I can't remember. Maybe it will come back to me later (CRS creeping in).

    Yes you are correct in that a solenoid is either open or closed and a poppet is slower in opening and that does make a little difference when fine tuning on when you want the bypass to be there. For a High Speed the the pump pressure is usually rising pretty fast at the normal point you want it to open so it is not very slow in opening.

    The norm on an electric solenoid is to put the jet before the solenoid. Again can't remember why. It problem results in a smoother more accurate flow through the jet.
     
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  7. Tony Bolt

    Tony Bolt New Member

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    Mike try hard to remember the reason to put the jet before and not after. All NOS jet are after the solenoid. (That I have seen) Just would like to know.
     
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  8. Mike Canter

    Mike Canter Top Dragster

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    Tony if you put a nitrous jet before the solenoid you would need eight solenoids (which has been done). That is not the same thing.
     
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  9. rb0804

    rb0804 Member

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    Maybe another fuel injection guru will chime in with an explanation. Have you ever checked the pressure in the high speed return line? By taking the example above, if you have 150 psi @ the pump and a crack pressure of 50 psi your saying that the pressure @ the jet should be 100 psi correct? So would pressure in the high speed retun hose be 100 psi or would it be less? Could it be that we do it that way because its always been done that way and we just consider that 'the standard' or is there a good solid reason of why we should install the jet first. I still think that the restriction that the causes would decrease the pressure acting on the popet. I am thinking like this; if your using a straight thru style barrel valve and your pressure at the pump is 150 psi. Lets say for the sake of argument we have 100 psi post barrel valve because we have created a leak with the main jet. Would pressure still be 150 psi on the other side of the main jet or would it be less? Anyone ever done pressure testing on return lines? Does it matter if your using a -6 or a -8 for thr high speed popet? Would one open softer or sooner then the other?
     
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  10. Mike Canter

    Mike Canter Top Dragster

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    Well I am backing out of this discussion because you ask me a question and I give you an answer and you tell me I am wrong. I don't believe you understand the basics in tuning an alcohol motor and controlling the fuel that actually goes into the motor. I don't know what you are trying to do or prove. The standard is fluid dynamics.
     
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  11. aj481x

    aj481x Member

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    Here's an extra little goody, blown engines rarely, if ever, benefit from high speeds.
     
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  12. rb0804

    rb0804 Member

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    Thanks to all for the replies. Mr. Canter if I offended you I am sorry. I enjoy your input as well as others. I did not mean to pick a fight with you or insult your intelligence. I am just thinking out loud, theoretically speaking. Truth is I don't run a high speed, I was just curious of some of the whys and why not's. Things were just not making sense on that one (I've been known to have a thick head sometimes). You have probably forgotten more about blown alcohol then I know. It is nice to have a resident expert here like yourself to help us newbies. Thanks again.

    RB
     
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  13. Mike Canter

    Mike Canter Top Dragster

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    RB, your apology is accepted and thank you.
     
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  14. rb0804

    rb0804 Member

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    Just for the record it was the words 'simple hydralic system' that broke it wide open for me. Sometimes I get so wrapped up with other things I forget we are talking hydralics. the pressure pushing on the popet will be the same as the rest of the system for this reason and we won't see the pressure drop across the orfice until that popet opens and begins to flow.
     
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  15. SoDak

    SoDak Active Member

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    I might have time to play with this tonight on the flowbench but chances are it will be next week.

    As far as the BV you're talking about, on the system I have on the flowbench right now: there is 180 psi at the inlet of the cube BV and 160 psi inbetween the nozzle jets and the BV. This is with a .115 MP. Not sure if this helps you:confused:

    In 2004 we had a situation where the HS would cycle between opening and closing several times in a 4-5 second dyno sweep, according to the HS flowmeter. I don't remember the details, but in this situation it helped to put the MP on the downstream side of the poppet at least as far as the opening/closing, keep in mind we changed other things also so its hard to know?? I do remember that you couldn't tell any difference in the HP curve from cycling to smooth, we just assumed it had to be better.
     
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  16. SoDak

    SoDak Active Member

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    From what I can remember...
    There was a port check in the system, but it probably opened around 10-15 psi vs the approx 60 psi HS.

    The HS was plumbed into the hat distribution block and we moved it down by the pump so there were certainly no apples to apples (before the poppet vs behind it) tests. I'm assuming we changed the crack psi when we did this but don't recall.

    It was a -6 poppet.

    I'm surprised you bring up spring rate as I beleive it to only move 5-15 thousands anyway? Maybe it moves more than that...
     
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  17. rb0804

    rb0804 Member

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    I have another question along the same line. I have seen some fuel systems in the past that have the idle popet located down near the pump on the return block. Does it make a difference if the popet is on the barrel valve or on the return block? Since system pressure is uniform though out it shouldnt matter where in the system it is located correct? The only things that I can come up with is that you now have a high pressure line running forward instead of a low pressure line (in case of a rupture or leak). The other thing would be if the line backed up? I am sure that a certian sized hose only has so much flow capacity for a given length, which in this situation might not even be close to that, but the thought did cross my mind.
     
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  18. Mike Canter

    Mike Canter Top Dragster

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    Doesn't make any difference where the idle poppet is located. Some move it down on the return line for safety. You come off the BV on the idle return with a smooth wide radius 180* fitting and run the hose further back down to the poppet this makes for less chance that a broken belt will hit a fuel line.
     
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  19. Critical Mass

    Critical Mass Member

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    Staying on the High Speed subject:

    I am thinking of removing my high speed, 70 jet/65 psi, on my blown alky jet boat to improve my run consistency. The logger shows that the port line pressure is all over the place during the run; like its bouncing off the poppet. Is this normal? The inlet fuel pressure to the BV runs around 110 psi. Thanks in advance for the input.

    Joe
     
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  20. Mike Canter

    Mike Canter Top Dragster

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    No that is not normal to bounce all over the place. If you put the pressure sensor on the pump side of the BV then you will see what appears to be a sawtooth pattern of spiking due to the pulses coming from the pump gears. This is normal. If you are at 110 psi on a 65 psi poppet then that poppet is wide open. Something else to confirm is the poppet crack pressure of the pump saver.
     
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