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Thread: N20/Fuel jet sizes

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    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    N20/Fuel jet sizes

    Those who know, please post jet sizes for various nitrous shots.

    Thanks!

    I'll stick it for reference.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
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    Re: N20/Fuel jet sizes

    Directly from Zin's PM to me a while ago.

    standard jetting/HP will be: 40HP, 34N/18F; 50HP 37N/22F; 60HP 39/24; 70HP 41/26; 80HP 43/28; 100HP 46/30; 125HP 52/33; 150HP 61/38.

    These are for N/A engines and you should be aware of the fuel jetting as every car is different and fuel pressures vary alot. I found I needed alot larger fuel jetting.

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    Supporting Member Turbo Mopar Contributor
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    Re: N20/Fuel jet sizes

    The jetting is based off fuel pressure so with the reference reg it will change. Dynotunenitrous.com has a nice jet calc if you know the fuel pressure you will be running. Problem with running nitrous on a turbo car, if you start spraying it early before you are at your max boost it will be lean. If you spray it the whole run you might be better off setting up another regulator for just the nitrous.

  4. #4
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    Re: N20/Fuel jet sizes

    You should jet according to your base fuel pressure setting

    Start out a bit fat and use a wideband

    Here's a handy calculator

    http://www.robietherobot.com/NitrousJetCalculator.htm

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    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: N20/Fuel jet sizes

    Quote Originally Posted by OnLooker View Post
    The jetting is based off fuel pressure so with the reference reg it will change. Dynotunenitrous.com has a nice jet calc if you know the fuel pressure you will be running. Problem with running nitrous on a turbo car, if you start spraying it early before you are at your max boost it will be lean. If you spray it the whole run you might be better off setting up another regulator for just the nitrous.
    This is incorrect. As boost rises, so does fuel pressure. So is your base fuel pressure is 55psi, the fuel pressure will remain 55 + boost pressure, so your fuel volume thru the jet should remain constant troughout the boost curve.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
    Project Log:
    http://www.turbo-mopar.com/forums/showthread.php?69708-The-Contraption-2013-14&highlight=

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    Re: N20/Fuel jet sizes

    OK, scratch that. I had my setup on a log intake and was spraying before the turbo. That calc still worked good for picking jets though.

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    turbo addict Turbo Mopar Contributor
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    Re: N20/Fuel jet sizes

    wow I just realized from this that nitrous and rising rate regulators are not friends.

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    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: N20/Fuel jet sizes

    Quote Originally Posted by Ondonti View Post
    wow I just realized from this that nitrous and rising rate regulators are not friends.
    Yup, because if your fuel pressure rises exponentially in relation to your boost pressure, your a/f is going to get richer and richer.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
    Project Log:
    http://www.turbo-mopar.com/forums/showthread.php?69708-The-Contraption-2013-14&highlight=

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    Re: N20/Fuel jet sizes

    Quote Originally Posted by OnLooker View Post
    The jetting is based off fuel pressure so with the reference reg it will change. Dynotunenitrous.com has a nice jet calc if you know the fuel pressure you will be running. Problem with running nitrous on a turbo car, if you start spraying it early before you are at your max boost it will be lean. If you spray it the whole run you might be better off setting up another regulator for just the nitrous.
    Is there a chart out there that has jet size = x amount of HP?

    Are the numbers on NOS jets the hole size? Example NOS jet 035 = 0.035" ?

    James Reeves - Reeves Racing
    World's Fastest 8 Valve - 146.88 mph
    86 GLH-T 9.99 at 143.78 mph
    86 GLHS #169 Mom's - complete Super 60 car
    87 Shelby Z 14.16 Dad's - mostly stock, no sh*t!
    88 Shelby Z 13.5 - been in storage for 15 years
    03 SRT-4 12.24 Mom's
    07 Charger 5.7L 12.48 Dad's

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    Re: N20/Fuel jet sizes

    Quote Originally Posted by Reeves View Post
    Is there a chart out there that has jet size = x amount of HP?

    Are the numbers on NOS jets the hole size? Example NOS jet 035 = 0.035" ?
    Someone posted this link http://www.robietherobot.com/NitrousJetCalculator.htm before and it seems pretty acqurate.

    To be on the safe side, I always jet rich on the fuel side at first and work my way down.


    Oh and have fun you crazy kid.

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    Re: N20/Fuel jet sizes

    Just for fun, and what my jetting will be next trip to the track.

    The Fuel jet size should be 0.687" or 17.445mm

    A Nitrous jet size of 1.25" or 31.75mm should produce:
    70564.38 HP with 1 port(s)



    Actual HP to the wheels: 59979.72 HP

  12. #12
    Supporting Member Turbo Mopar Contributor zin's Avatar
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    Re: N20/Fuel jet sizes

    Quote Originally Posted by Reeves View Post
    Is there a chart out there that has jet size = x amount of HP?

    Are the numbers on NOS jets the hole size? Example NOS jet 035 = 0.035" ?
    Yes, the number on a NOS jet is the size in thousands of an inch. Somewhere I've got a chart that lists HP for a given size jet. For now I'll post the charts I have handy.

    As for larger sizes, as are likely to be used in a single nozzle set-up, "stock" jetting is as follows:


    HP - Nitrous - Fuel (@ 35-40PSI)
    50 / 37 / 22
    75 / 41 / 26
    100 / 46 / 30
    125 / 52 / 33
    150 / 61 / 38

    Since we typically run higher pressures, expect that you'll need to come down on the fuel jet to get it dialed in better, but start with these numbers to see how your engine will react, sometimes they really like the extra fuel, sometimes not, but it's better to have it and not need it, than need it and not have it!

    The attached charts are mostly for direct port applications, one showing the HP the other shows how the fuel jet will change depending on the fuel pressure. Finally, the Word doc is what we send out with our flow tools. Hope you all enjoy!

    Mike
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    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government - lest it come to dominate our lives and interests." - Patrick Henry

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    Re: N20/Fuel jet sizes

    Quote Originally Posted by Gaboon View Post
    Someone posted this link http://www.robietherobot.com/NitrousJetCalculator.htm before and it seems pretty acqurate.

    To be on the safe side, I always jet rich on the fuel side at first and work my way down.


    Oh and have fun you crazy kid.
    I saw the link, which will be very handy, but I wanted to see if there was a chart out there that showed which jet to use for what HP level, and then I can see which fuel jet I'll need to match.

    Quote Originally Posted by zin View Post
    Yes, the number on a NOS jet is the size in thousands of an inch. Somewhere I've got a chart that lists HP for a given size jet. For now I'll post the charts I have handy.

    As for larger sizes, as are likely to be used in a single nozzle set-up, "stock" jetting is as follows:


    HP - Nitrous - Fuel (@ 35-40PSI)
    50 / 37 / 22
    75 / 41 / 26
    100 / 46 / 30
    125 / 52 / 33
    150 / 61 / 38

    Since we typically run higher pressures, expect that you'll need to come down on the fuel jet to get it dialed in better, but start with these numbers to see how your engine will react, sometimes they really like the extra fuel, sometimes not, but it's better to have it and not need it, than need it and not have it!

    The attached charts are mostly for direct port applications, one showing the HP the other shows how the fuel jet will change depending on the fuel pressure. Finally, the Word doc is what we send out with our flow tools. Hope you all enjoy!

    Mike
    I had read somewhere that NOS jets were not in thousandths of an inch, so I just wanted to make sure.


    Thanks for the info!

    I'm going to make a spread sheet with HP per jet size and then fuel jet size based off fuel pressures.

    James Reeves - Reeves Racing
    World's Fastest 8 Valve - 146.88 mph
    86 GLH-T 9.99 at 143.78 mph
    86 GLHS #169 Mom's - complete Super 60 car
    87 Shelby Z 14.16 Dad's - mostly stock, no sh*t!
    88 Shelby Z 13.5 - been in storage for 15 years
    03 SRT-4 12.24 Mom's
    07 Charger 5.7L 12.48 Dad's

  14. #14
    Supporting Member Turbo Mopar Contributor zin's Avatar
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    Re: N20/Fuel jet sizes

    Quote Originally Posted by Reeves View Post
    I had read somewhere that NOS jets were not in thousandths of an inch, so I just wanted to make sure.
    Glad I could help, if you want/need any other specific info, just let me know and I'll see if I can get it for you.

    As a side-note on the NOS jets, the newest Stainless Steel jets are made a bit differently these days, back before NOS was sold ('99), they were brass and just drilled with whatever size drill (thousands), but after Holley "lost the rabbit" and couldn't build a good jet to save their lives, they out sourced them to a medical orifice manufacture that builds jets to a flow standard rather than a hole size, the net effect is a jet that is within 3% of it's target, regardless of the hole size. In practice, a 28 jet will still almost always be .028", but it could be slightly bigger or smaller, but it will still hit it's flow target, which is what is really important anyway. I have to say that the stainless NOS jets are the nicest jets that have ever been produced, by any manufacture! Heck, if they didn't mind the astronomical rejection rate, they could offer jets within .5% of a given target flow rate! Of course, none of us want to pay $50 a jet!

    With all this said and done, most jets produced today are of fine quality, and would likely be in a +/- 5% range or better, but NOS is the only one that 100% flows their jets (it's part of the manufacturing process) and so can guarantee their accuracy.

    Now, is it really that big a deal? On a direct port system? Yes. the more jets you have to deal with the greater the chance of tolerance stack-up and the problems that can bring, especially when trying to maximize a particular tune/hp level. Is it important in a single nozzle application? Not really. Stock tune-ups will have anywhere from 10-15% extra fuel already in the tune, so even if the nitrous was 5%+ and the fuel 5%-, it wouldn't be dangerous.

    Clear as mud right?

    Mike
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government - lest it come to dominate our lives and interests." - Patrick Henry

    Bad laws are the worst sort of tyranny.
    - Edmund Burke

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    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: N20/Fuel jet sizes

    Another plus with the SS NOS jets... the numbers are laser etched into the jets instead of stamped into it. I have a hard time reading alot of the old brass jets.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
    Project Log:
    http://www.turbo-mopar.com/forums/showthread.php?69708-The-Contraption-2013-14&highlight=

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    Re: N20/Fuel jet sizes

    Quote Originally Posted by zin View Post
    Glad I could help, if you want/need any other specific info, just let me know and I'll see if I can get it for you.

    As a side-note on the NOS jets, the newest Stainless Steel jets are made a bit differently these days, back before NOS was sold ('99), they were brass and just drilled with whatever size drill (thousands), but after Holley "lost the rabbit" and couldn't build a good jet to save their lives, they out sourced them to a medical orifice manufacture that builds jets to a flow standard rather than a hole size, the net effect is a jet that is within 3% of it's target, regardless of the hole size. In practice, a 28 jet will still almost always be .028", but it could be slightly bigger or smaller, but it will still hit it's flow target, which is what is really important anyway. I have to say that the stainless NOS jets are the nicest jets that have ever been produced, by any manufacture! Heck, if they didn't mind the astronomical rejection rate, they could offer jets within .5% of a given target flow rate! Of course, none of us want to pay $50 a jet!

    With all this said and done, most jets produced today are of fine quality, and would likely be in a +/- 5% range or better, but NOS is the only one that 100% flows their jets (it's part of the manufacturing process) and so can guarantee their accuracy.

    Now, is it really that big a deal? On a direct port system? Yes. the more jets you have to deal with the greater the chance of tolerance stack-up and the problems that can bring, especially when trying to maximize a particular tune/hp level. Is it important in a single nozzle application? Not really. Stock tune-ups will have anywhere from 10-15% extra fuel already in the tune, so even if the nitrous was 5%+ and the fuel 5%-, it wouldn't be dangerous.

    Clear as mud right?

    Mike
    AWESOME info! Thanks so much!

    Quote Originally Posted by contraption22 View Post
    Another plus with the SS NOS jets... the numbers are laser etched into the jets instead of stamped into it. I have a hard time reading alot of the old brass jets.
    I have both kinds of jets. I had many old brass ones from when I used a fuel cheater solenoid and fogger nozzle as a 5th injector. I purchased two more nozzles back then and they came in as the nickel plated (?) with laser etched or screen printed numbers. I never got around to using them before I went to alchol.

    This nitrous kit I have that a friend is letting me borrow also has both kinds of jets.

    Some of the numbers that are stamped on the brass ones are either not legible, or stamped off the edge of the jet so bad they are not legible.



    I think where I was getting confused about NOS jets was that HOLLEY jets are not in thousandths of an inch. ??

    James Reeves - Reeves Racing
    World's Fastest 8 Valve - 146.88 mph
    86 GLH-T 9.99 at 143.78 mph
    86 GLHS #169 Mom's - complete Super 60 car
    87 Shelby Z 14.16 Dad's - mostly stock, no sh*t!
    88 Shelby Z 13.5 - been in storage for 15 years
    03 SRT-4 12.24 Mom's
    07 Charger 5.7L 12.48 Dad's

  17. #17
    Supporting Member Turbo Mopar Contributor zin's Avatar
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    Re: N20/Fuel jet sizes

    Quote Originally Posted by Reeves View Post
    Some of the numbers that are stamped on the brass ones are either not legible, or stamped off the edge of the jet so bad they are not legible.


    I think where I was getting confused about NOS jets was that HOLLEY jets are not in thousandths of an inch. ??
    If you have brass jets that don't look so hot and/or have illegible numbers, can them, those are the ones that Holley was loosing their mind while trying to reproduce the jets NOS had made for years, but Holley just couldn't quite get it, hence the new stainless jets. I wouldn't trust those as far as I could throw them!

    In regards to the Holley jets, you are correct, you might notice there is a small table in the HP jetting chart that gives a rough cross reference from thousands and Holley jet sizes. A bit of trivia on the Holley jets, they are numbered by flow rates (what scale I don't know for sure), you also might notice there are a few different Holley numbers that have the same size hole. That is because in a carb, they could chamfer the inlet side and pick up flow without the need for a differently drilled jet. This is also why I'll never (by my choice anyway) use a Holley carb jet for flow testing or pressure setting as some old timers in Pro Mod will do. It's not that it can't work, it just isn't accurate to what you'd see going down the strip. I won't bore you with the details as to why, but I'll hazard a guess you all can figure that one out!

    Mike
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government - lest it come to dominate our lives and interests." - Patrick Henry

    Bad laws are the worst sort of tyranny.
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    Re: N20/Fuel jet sizes

    Here's a few pics of the preliminary install. I ordered a shorter hose from bottle to solenoid, and shorter hoses from solenoids to fogger nozzle.

    Also ordered a telephone cord type momentary pushbutton (for steering wheel) and a blow down tube and racer safety valve

    Anyone see any problems with the pics? Not a trick question, just want to know from nitrous junkies of any problems I might run into.
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    James Reeves - Reeves Racing
    World's Fastest 8 Valve - 146.88 mph
    86 GLH-T 9.99 at 143.78 mph
    86 GLHS #169 Mom's - complete Super 60 car
    87 Shelby Z 14.16 Dad's - mostly stock, no sh*t!
    88 Shelby Z 13.5 - been in storage for 15 years
    03 SRT-4 12.24 Mom's
    07 Charger 5.7L 12.48 Dad's

  19. #19
    turbo addict Pat's Avatar
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    Re: N20/Fuel jet sizes

    Quote Originally Posted by Reeves View Post
    just want to know from nitrous junkies of any problems I might run into.

    Nice install, very clean. I especially like the solenoid bracket you made. The only thing I'd be careful of is if your nozzle is pointed up, it makes it a bit trickier to change jets (can drop them). If you have the nozzle pointed slightly down, you have gravity working to your advantage changing jets. Not a big deal at all, but something I picked up doing mine.

    The only real problem I'd watch out for is cramping in your cheeks from the big freaking smile you're going to have on your face when you start using it.

  20. #20
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: N20/Fuel jet sizes

    The only problem i see is that you really should have two bottles. Big ones.

    But I think it looks great!

    You already mentioned the safety blow-down tube, you may want to consider an RPM window switch as a safety in case of bogging or traction issues. I would definitely get a WOT switch if you don't already have one.

    Also make sure that the floor boards are reinforced with diamond plate, and also think about adding a MIS (manifold integrity sensor), that you can monitor with your laptop.
    Last edited by contraption22; 08-26-2009 at 09:32 AM.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
    Project Log:
    http://www.turbo-mopar.com/forums/showthread.php?69708-The-Contraption-2013-14&highlight=

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