fuel pressure

Discussion in 'PSI Superchargers Tech Questions' started by lucky devil, Aug 17, 2008.

  1. lucky devil

    lucky devil Member

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    Hi Guys , I am relativeley new to blown methanol , so might be asking a few questions.
    Where is the best place to read fuel pressure from ?
     
    #1
    lucky devil, Aug 17, 2008
  2. jody stroud

    jody stroud ZOMBIE Top Dragster

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    I don't know the best place to check pressure but I read my pressure before the barrel valve right after my filter. Seems to work for my car.
     
    #2
    jody stroud, Aug 17, 2008
  3. thjts

    thjts New Member

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    Fuel System Info

    There are A LOT of good threads on here with all sorts of fuel system info that will be very useful to you, but you'll have to search for them. Some of them start off under a heading that is loosely related, and various answers and comments will cover what you're looking for.

    Mike Canter, Will Hanna, Jim Phillips, Bob Szabo, are just some of the guys (amongst others) who are a wealth of information, so look for threads they've contributed to. Have a good read of everything that is written, and read it several times to make sure you've got it right. 'Cut and paste' copies of the text and save it somewhere on your computer or print it if you want to.

    Bob's got a couple of good methanol books, and another one is by Ken Lowe of Australia. Buy them, do some study, and use them in conjunction with what you read on here. It's great!

    Happy Motoring,
    Paul.
     
    #3
    thjts, Aug 18, 2008
  4. eli

    eli Banned

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    According to Ken Lowe's book, the nozzles set the pressure, so I'm going with anywhere right before the nozzles and after the barrel valve. ;)
     
    #4
    eli, Aug 18, 2008
  5. superpro453

    superpro453 Member

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    Wayne

    If the nozzles set the pressure, the pump makes it. So anywhere between the pump and the nozzles - it should be the same.

    Martyn
     
    #5
    superpro453, Aug 18, 2008
  6. Mike Canter

    Mike Canter Top Dragster
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    Selecting the fuel pressure tap point depends on what information you want. If you use software such as Davenport's Jetsize then it should be before the barrel valve because the software computes a generic loss across the barrel valve already in the software. So if you use the after the BV pressure then your Jetsize Tuning Modifier has to compensate for the double pressure drop across the BV. ( I know that this maybe a big surprise to some but if you have already locked in your Tuning Modifier and Jetsize is working for you then don't change it. I understand that Davenport is working on making it selectable as to where you pick off the pressure). So, if you are using some kind of software for tuning then you should find out what pressure point is needed. If you are just monitoring the pump pressure for pump wear then before the BV is probably best. The problem of doing it before the BV is that you see a lot of pressure pulses on the trace from the pump. Idealy you want to monitor it at two points, one right before the BV and one at the distribution block. If you are just using the pressure to find out what you want to set the high speed bypass point at then I would recommend after the BV. I have found that because the pressure trace is smoother after the BV that it is easier to see the pressure change as each bypass opens or closes.
     
    #6
    Mike Canter, Aug 18, 2008
  7. lucky devil

    lucky devil Member

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    Thanks for the response. I have another question!
    What pressure would you expect to see , I know there wont be a deffinative answer. At the moment Iam reading fuel pressure after the barrel valve , right where I figured it should be , and only see 82pounds of pressure. I was expecting to see a bit more than that.
    I have both of Bobs books and can only say good things about them. Iam asking the questions to get a number of opinions. As one guy said already the threads on here are of great wealth and experience.

    Thanks....Wayne

    P.S visit www.luckyydevil777dragracing.com
     
    #7
    lucky devil, Aug 18, 2008
  8. SoDak

    SoDak Active Member

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    Fyi

    Here's a common mistake when using a tattle tale psi gage.

    If the gage is before the BV then the psi your seeing on the tattle tale is bogus because it depends on how fast you close the throttle at the end of your run.

    Like Mike asked, what are you trying to do?
     
    #8
    SoDak, Aug 18, 2008
  9. Mike Canter

    Mike Canter Top Dragster
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    Wayne for ease of comparison I look at fuel pressure either at 8000 RPM or 9000 RPM. That is so one can copare apples to apples. I like a pressure to be somewhere in the 140 to 180 range but that depends on what mainjet size the density altitude is dictating. I think that keeping pressures up helps in atomization but that being said there a a lot of motors out there running pressures in the 80 to 120 range. To raise the pressure requires you to downsize either the hat nozzles, or the port nozzles or both. This takes a little computing to keep the GPM the same with the smaller jets and the higher pressure. I like Davenports Jetsize software to do it for me but Bob Szabo's book has a good explanation on how to do it with a calculator.
    The pressure drop across a BV varies from around 12 to 20 lbs depending on the setup and how many GPMs are being flowed.
     
    #9
    Mike Canter, Aug 18, 2008
  10. lucky devil

    lucky devil Member

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    Thanks so far. Iam trying to learn more about tuning / going quicker. The fuel pressure , as Mike says , leads me to think could be atomising better if I had more pressure. As I said Iam still new to it all really and like to learn rather than "buy" a tune.
     
    #10
    lucky devil, Aug 18, 2008
  11. Mike Canter

    Mike Canter Top Dragster
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    Lukydevil, check your PMs
     
    #11
    Mike Canter, Aug 18, 2008
  12. CannoyRacing

    CannoyRacing New Member

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    Software

    Where would i get the Davenport Jet Size Software?
     
    #12
    CannoyRacing, Aug 19, 2008
  13. Mike Canter

    Mike Canter Top Dragster
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    Acceleration Enterprises in Canada phone 403.938.6200. You will also need a good weather station.
     
    #13
    Mike Canter, Aug 19, 2008

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