Jet area chart

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by promodracer, Aug 5, 2014.

  1. Mike Canter

    Mike Canter Top Dragster

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    Rpt, welcome to the forum. Emailed you the charts.
     
    #21
  2. rpt

    rpt New Member

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    Thank you very much Mike! My supposition was right.
    Now I have a different problem (don't know if I should open a new thread).

    I'm trying to build a fuel return block with sassy flown nozzles (as far as I know they are already flown with alcohol). Now I'm testing it on a flow bench with a complete setup (barrel valve, check valves, hat and port nozzles) and I can't match the numbers. I take a standard bypass jet and flow the system with it, let's say I take a .090 = 2.05GPMAlky. Now I remove the bypass jet and mount the return block (same position, same check valve) and I set it to the same flow of 2.05GPM (in my case it is .40+.70+.90=2.00GPM). When I test the system in this condition it flows a lot leaner, a lot more than half a gallon! I can't understand why!! I'm sure it's not leaking.

    I'm not using a main return but just an high speed bypass right after the K-barrel valve. The only difference in the two setups is that when I use the bypass pill the check valve is after it. In the other case the check valve comes first and then there is the return block. However that's not the problem because I tried also to remove the CV and I measure the same discrepancy of more than half a gallon.
     
    #22
    Last edited: Jan 16, 2017
  3. Mike Canter

    Mike Canter Top Dragster

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    Let me ask this...what is the spring pressure for the popper in the check valve? Let's say it is set at 50 psi and you have the fuel pressure out of the K valve at 150 psi. That means the bypass jet is seeing flow at 100 psi. Are you taking that pressure drop across the check valve into account?
     
    #23
  4. rpt

    rpt New Member

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    I'm sorry, I forgot to specify. I didn't considered that because it is a really low pressure check (pressure outside of the kvalve varies from 110 to 180 -200 psi depending on the main).
    Actually I'm not sure if it is a 3 or 6 PSI, but I can open it blowing with my mouth. It does the same job of the idle check of the k valve. I was wrong calling it as high speed bypass. Actually it is the same bypass I would have using the one in the k valve.

    Anyway I had your suspect too and I'm fact I tried to test the system without the check valve, to make sure it was not affecting the flow of the main jet. I find the same results (a little bit leaner, as it should be) but always with the same huge difference between jet and block setups.

    I tested the system in the .065 to .125 main jet range (this is what I need) and the gap between the two systems gets larger as far as I increase the main jet...From .05gpm at .065 to 0.8gpm at.125.
    It seems to be a conversion error, that's why I asked you the corrected flow chart to double check my calc.

    At the moment I forget the flow of the nozzle and I use a table with the main jet and the corresponding block tune-up to match the right flow. But I really don't like this approach and I would like to find the problem hidden behind.
     
    #24
  5. Mike Canter

    Mike Canter Top Dragster

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    You are correct in saying the gap gets bigger from .065 to .125 because you have to use area to compute flow and not jet size. One of the problems I discovered years ago was the inaccuracy of flow through Enderle port and bypass jets. You can measure flow through four different jets of the same size and get four different GPMs. I use jets all flow checked and calibrated by Ralph Gorr Fuel Systems

    How repeatable is your setup. Have you tested that. If you run the same test without changing anything five times then do you get the same results all five times?
     
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  6. rpt

    rpt New Member

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    I know the inaccuracy of the Enderle flows and I also buy nozzles from Gorr but till now I was using non flown bypass jets. I have at home some spare jets of Sassy so I've put them in my return block.
    You are telling me I should trust more in my block than in Enderle's jets? Do you think they can be wrong of more than 30%?!

    My setup is not the best one for sure. It's a little bit inaccurate in terms of amount of flow but in the short period tests I can reach a really good ripetibility. In multiple measures of the same thing it stays in between the +-0.05GPM of the mean value (less than 1%).
    The bench needs a lot of improvements, starting from the flowmeter accuracy. The entire fuel system has been tuned by Gorr at the moment I'm using my bench just to compare apples and apples, like in this case.
     
    #26
  7. Mike Canter

    Mike Canter Top Dragster

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    That sounds like pretty good repeatability. Never measured how. far Enderle jets are off but I have seen NOS nitrous jets be 30% off
     
    #27
  8. rpt

    rpt New Member

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    Thank you a lot Mike.
    Let's see what happens on the track. Starting on the safe side
     
    #28

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