Port Nozzel pressure

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Brad671, Jul 28, 2008.

  1. Mike Canter

    Mike Canter Top Dragster

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    Dave, sorry I confused you. Yes, leak testing a BV is so you know how much fuel is going through the BV at idle. The percentage amount is a reference so if the car is rich or lean you can adjust the percentage up or down. The point I was trying to make is that a lot of tuners will tell people what percentage to set their BV at. You will see this a lot on this forum and other forums or at the track. Some will say set it at 83% some will say 78% some will say 85% and racers will go and set their percentage leak down to what they were told. The problem is that unless everyone uses the same reference and sets their BV the same way as to what lines are hooked up or not then they don't have the same reference. Being 2% or 3% off because the fuel lines were or were not hooked up can make a difference. If you are doing your own thing with your own tuneup then that percentage number is your reference and you can set it up anyway you want. I have always been told and use the standard of having the lines disonnected and the return capped off. If somebody tells you a percentage to set your BV at then ask if the fuel lines are on or off.

    The other thing that can confuse the leakdown numbers is the idle speed. The percentage leakdown with the BV and hat set at 2000 RPM is different to the percentage leank down with all set at 2700 rpm isle. If one is going to listen to other racers to get oneself started then talk apples and apples and not apples and oranges.
     
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  2. secondwindracing

    secondwindracing top alcohol

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    we set our barrel valve by using manifold temp.
     
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  3. SoDak

    SoDak Active Member

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    Interesting!

    How have different blowers or engine combinations compared?
     
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  4. Alkydrag

    Alkydrag Sr. Dragster

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    I was taught to check the leak with the lines disconnected. But, that's not the way the motor runs. So I check it with them connected. I believe it's a truer reading.
     
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  5. Brad671

    Brad671 New Member

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    Port nozzle pressure

    What is the purpose of running a poppet in the port nozzle side of the system?
     
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  6. Mike Canter

    Mike Canter Top Dragster

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    The port poppet keeps the port nozzles shutoff during idle so that all the fuel goes to hat to lubricate and cool the blower. If not you would wear the stripes right out of it. The blower would also get super hot at idle.
     
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  7. Brad671

    Brad671 New Member

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    Port nozzle pressure

    Thanks Mike, I thought it may have had something to do with that.
     
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  8. lucky2wd

    lucky2wd Member

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    if the blower is getting hot at idle (I haven't checked it with a temp gun but it is very hot quickly) , does that mean that poppet is set too low?
     
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  9. Alkydrag

    Alkydrag Sr. Dragster

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    I think your confused. Port fuel is below the blower, so it has nothing to do with how hot the blower gets. If your blower is getting hot at idle, then you need to add some area to the hat nozzles or increase the BV leak.
     
    #29
  10. SoDak

    SoDak Active Member

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    hmmmmm,
    I think Lucky is right on. With the port nozzles on at idle and definitely the hats are on, compare this to only having the hats on. The blower will be cooled more by having the ports off at idle.
    My $.02
    Lucky, maybe you should put your system on my flowbench?
    Maybe in the dead of this next South Dakota winter you could bring it up from cozy Arkansas:D:eek:
     
    #30
    Last edited: Aug 1, 2008
  11. Mike Canter

    Mike Canter Top Dragster

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    Lucky, is your port nozzle set at? Have you checked it lately? Rootes blower should run pretty cool at idle. If you feel under the rear of the blower it should be real cool to the touch.
     
    #31
  12. Mike Canter

    Mike Canter Top Dragster

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    I mean the port poppet not the nozzle....sorry.
     
    #32
  13. TD4141

    TD4141 New Member

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    I'm glad I found this since I am just getting into blown alcohol. I'll be searching other threads about fuel systems and following this as well.

    1 question though. I havent even bought my setup yet, but I will have it all very soon. So I dont know anything about this stuff yet and am learning.

    How do you actually do this leak test? If you are checking to see what it is at idle and the lines are all unhooked " or still conected " how do you turn the pump? Is this something that has to be done off the motor?
     
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  14. mbaker3

    mbaker3 New Member

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    Here is a link to the one that I have and use. I got it from Good Vibrations:
    http://goodvibesracing.com/barrel_valve_leakdown.htm
     
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  15. TD4141

    TD4141 New Member

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    aahhhh. so your testing with air and not alcohol. We test our gas all the time since we run nitrous, but we use the feul itself and get flowing pressure. Thats why I was confused. Looks like I will need to get a gauge set. :)

    Thanks
     
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  16. Mike Canter

    Mike Canter Top Dragster

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    I have compared fuel to air in testing and setting poppets and it does not make enough difference to worry about so I don't make it complicated. As far as leak down in a barrel valve it doesn't make a difference because the leak down percentage is merly a reference so you know where you are and what change you made and it allows you to return back to a specific leak down percentage if you have taken anything apart and are putting it back together.

    Flowing fuel for nitrous is a totally different thing.
     
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  17. mbaker3

    mbaker3 New Member

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    Putting Mike's response in your and my "easy to understand" terms ;)
    Using air to do a leak down test will not show a result much different than if you figured out how to do it with whatever fuel you use. (gas or alcohol). Mike is just saying the test is just telling you an approximate "percentage" of leak-by when the barrel valve is in the closed position (idle). In other words, how much gas / alcohol is getting to the hat when you are sitting at idle with the throttle closed. It is a reference percentage for you to use to get your system set up initially whenever you have made a change. I know , I know, now I am making this sound complicated. Use the percentage as a starting point, adjust from there.
    Example:
    You remove the hat and disconnect the linkage, the butterflys have to come out so you can reach the bolts behind them. You need to get it bolted back up and you have no clue where your barrel valve linkage was set. ....... set it back to that original leak-by percetage and you have a great starting point!
    Sorry, I truly made this too long and drawn out but .........:D
     
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  18. TD4141

    TD4141 New Member

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    :D it's all good info.
     
    #38
  19. mbaker3

    mbaker3 New Member

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    I know, ......... that's why I love this place!:D
     
    #39
  20. Mike Canter

    Mike Canter Top Dragster

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    Dave you are right on.

    Also if I set a poppet using air to 60 psi then I see it pop right at 60 with fuel on the data logger. No real difference between leaking down with air on the poppets and what I see during a run with fuel on the poppets.
     
    #40

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