School me on advance
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School me on advance

  1. #1
    Senior Member Delemorte's Avatar
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    Default School me on advance

    So i know you can adjust your advance and that will affect your idle but higher in the RPM range what am i looking for in advance? Will a higher advance mean higher end RPM or is that not a concern?

    I got it runnin ok I just dont know the ins and outs of advance and thought i would ask the pro's.

    BTW, i think right now im set at 4 degrees before TDC at idle and once warm is around 1k. If i start getting below 1K it start idling rough. max RPM is currently right at 5K. Im not sure what advance it is at speed since my co-pilot is carrying my unborn child and is banned from the boat. Im hoping this weekend my buddy is gonna come out with me so i can check the advance. By getting info now i will be better prepaired for this weekend.
    Quote Originally Posted by jetboatperformance View Post
    the ensueing fire would likely be extinguished by the sinking however

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    Living in a cage of fear thatguy's Avatar
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    Well, I'm no pro, but I have screwed around a lot with advance settings.
    In a jet boat, your "initial" advance is merely a by product of your total advance settings.
    No one drives a jet boat at idle once you are off the trailer.
    Many "lock" the advance mechanisms' completely out, so initial is set at the total advance wanted. (generally 35* in a BBC)
    I PERSONALLY feel that it is easier starting, and less strain on starters, to use the mechanical advance in my distributor on my Miller.
    However, I have "set" my distributor using the MSD spring and bushing kit to "dial in" only 14 degrees of mechanical advance, with the light springs having all of the advance in by 2200 RPM+-. (21* at idle)
    What this means is that, basically, as soon as I start accelerating off idle (1000 RPM) it starts dialing it in and is almost immediately at full advance (2200-2400 RPM) It is in effect "nearly" locked out, but with a little mercy dialed in for starting.
    I played with it extensively trying many different spring, weight, and bushing configurations, but always ending up at 35* total. Different ways of getting to 35* is what we are trying to maximize.
    By using the adjustable, inductive timing light, we can record advance rates, total advance by mech., and vacuum means, and RPM that each stage happens at.

    I would think that in a heavier boat, with less power, you may need a little more gradual, and longer, curve. (more like a car needs)
    But the total will GENERALLY be the same.

    I don't know if any of this makes sense, I just got back from having a couple of REAL GOOD margaritas!
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
    Where I fought in many guises,
    Many names, but always me."

    Gen. George S Patton

  4. #3
    Jet boat service
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    I like to set my motors up with 10-12 degrees initial advance for better idle and low end response. You need to know how much your distributor is advancing mechanically. I usually set up mech advance at 24 degrees, all in by 3000 RPM for a total of 34-36 degrees. ( 10-12 plus the 24) It does make a difference what motor you are trying to tune. Big chevys (454) 36 max depending on compression and type of induction. 502's don't like much over 32 degrees total. Supercharged motors 30 degrees max. If you are running 10:1 compression on pump gas you may want to limit the timing to 32-34 degrees total. If your motor is running lower compression numbers you have a bit more room to play with. Good luck. Jim

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    According to various laws of physics, it takes a finite ammount of time, in milisecconds, for the mixture charge in an engine cylinder to burn after spark ignition.

    Within a very small range, this "burn rate" does not change. Turbulence in the combustion chamber does affect it, but not much.
    The exact blend of fuel affects it, again, not very much, unless you completely change the base fuel (alcohol or parafin (diesel fuel) vs. gasoline).

    In order to get power from expanding heated gasses (which is how and internal combustion engine generates power), you need to ignite the mixture before the piston reaches TDC, or the piston will be moving away before burn is completed, reducing the pressure pushing on the piston. This is why firing AT TDC is a theorhetical used to teach how the engine works, but, is incorrect in practice.

    The ammount of "lead time" (or "advance) you need to ignite the mixture is not the same at all engine speeds. Since the piston speed changes, and the mixture burn rate does not, you must ignite the mixture earlier the faster the piston is moving, to stay the best ammount "ahead" of it to produce the correct ammount of pressure, to produce power.

    After a certain ammount of advance, even this does no more good, and only ignites it too early.

    That's the basic primer version.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
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    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

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    Senior Member jetboatperformance's Avatar
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    Sean I havent thoroughly read this thread , but put the initial at 8 to 10 run 36 to maybe 38 ttl (all in at 2500) take it out and "stand on it" and BTW I'm increadibly Honored by your siggy line Thanks Tom

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    First you didn't say what type of ignition system your running so some systems are easier to set up than others.If you do not have a MSD I would strongly advise you to save your money and invest in one as soon as possible.Most any good system will fire your engine but the MSD was built with ease of tuning and max performance in mind,they are simple to adjust and nearly bullet proof.When it comes to jet boats and timing you need only worry about setting total advance and make sure your full advance by 3000 rpm. Full advance should be 34 to 36 degrees so set it there and don't worry what the idle timing is. If your idle RPM goes up to much then adjust it down at the carb.You can calculate your idle timing by taking your total timing and minus your mechanical advance. Example: total timing =36 degrees. Mechanical advance =16 degrees. 36-16=20 so 20 degrees will be your inital timing. I run a MSD on my 509 with the timing locked(no advance) at 36 degrees(another benifit to the MSD). this works very well on a jet boat and makes timing easy since your always at the same timing wether at idle or wide open. I'm sure some one will tell you that if you lock the timing your starter will drag when cranking the engine,if you have a good starter and battery it will not drag when cranking. should you still be concerned MSD makes a starter retard box just to drop timing when cranking the engine. Good luck.

  9. #7
    Senior Member H20MOFO's Avatar
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    Have you set it/checked for total advance/timing yet?? To most, that is the most important. Assuming your pointer is correct. If you're at 4*(initial) you may benefit from more timing. Like thatguy said 35 ish for total is a good starting point.
    Another Hot Boat refugee

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    Senior Member STRETCH's Avatar
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    Default Ghetto!


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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Quote Originally Posted by thatguy View Post
    I PERSONALLY feel that it is easier starting, and less strain on starters, to use the mechanical advance in my distributor on my Miller.
    However, I have "set" my distributor using the MSD spring and bushing kit to "dial in" only 14 degrees of mechanical advance, with the light springs having all of the advance in by 2200 RPM+-. (21* at idle)
    What this means is that, basically, as soon as I start accelerating off idle (1000 RPM) it starts dialing it in and is almost immediately at full advance (2200-2400 RPM) It is in effect "nearly" locked out, but with a little mercy dialed in for starting.
    I played with it extensively trying many different spring, weight, and bushing configurations, but always ending up at 35* total. Different ways of getting to 35* is what we are trying to maximize.
    By using the adjustable, inductive timing light, we can record advance rates, total advance by mech., and vacuum means, and RPM that each stage happens at.
    I run 35* total, but, did not want more than 8 to 12* or so at idle and so I run the 25* bushing in my MSD Ready 2 Run, with the lightest and seccond to lightest springs in it (1 ea), so as to not get any advance right at idle.
    My idle is under 900RPM, and that setup starts my advance coming in just over 1,000RPM, and is all in something in the 2500RPM area.
    Works absolutely great in my old cruiser sled, not interested in wasting half a summer trying every possible permutation of parts to try to find 1/2 a HP that I'll never be able to tell is there anyhow.
    Starts easy, runs crisp, clean, perfect throttle response from idle to just shy of 6-grand, could not ask for more.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
    H.L. Mencken

    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

  12. #10
    Senior Member shimp's Avatar
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    Quote Originally Posted by STRETCH View Post

    Nice, I assume this locks in your mechanical advance at full advance?

    If one was to want to buy an MSD Ignition for a jetboat which would be the choice? For a non-high horsepower jet, just a regular, stock type motor, no blower, 16:1 compression or nothing like that, just 9.5:1 with oval port type heads?

  13. #11
    Senior Member Delemorte's Avatar
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    Quote Originally Posted by jetboatperformance View Post
    BTW I'm increadibly Honored by your siggy line Thanks Tom

    Dude.. I laughed so hard when you put that in that thread.. I called no less than 3 people to share i was laughing so hard...

    Quote Originally Posted by 509Daytona View Post
    First you didn't say what type of ignition system your running so some systems are easier to set up than others.If you do not have a MSD I would strongly advise you to save your money and invest in one
    MSd distributor control box and rev limiter. I swapped out the mixed and matched precious set up with all MSD...

    Quote Originally Posted by H20MOFO View Post
    Have you set it/checked for total advance/timing yet?? To most, that is the most important. Assuming your pointer is correct. If you're at 4*(initial) you may benefit from more timing. Like thatguy said 35 ish for total is a good starting point.
    No i have not.. I lost my co-pilot... i got a replacement this weekend to help sort it out.. Standing on the gas and sitting in the engine compartment is hazardous to my health.


    Quote Originally Posted by SmokinLowriderSS View Post
    Iwith the lightest and seccond to lightest springs in it (1 ea), so as to not get any advance right at idle.
    I swear to god i am a moron.. I tossed those extra springs.. need to buy new replacements...



    Any way thanks guys for all the good info. this gives me a great place to start
    Quote Originally Posted by jetboatperformance View Post
    the ensueing fire would likely be extinguished by the sinking however

  14. #12
    Living in a cage of fear thatguy's Avatar
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    Quote Originally Posted by SmokinLowriderSS View Post
    I run 35* total, but, did not want more than 8 to 12* or so at idle and so I run the 25* bushing in my MSD Ready 2 Run, with the lightest and seccond to lightest springs in it (1 ea), so as to not get any advance right at idle.
    My idle is under 900RPM, and that setup starts my advance coming in just over 1,000RPM, and is all in something in the 2500RPM area.
    Works absolutely great in my old cruiser sled, not interested in wasting half a summer trying every possible permutation of parts to try to find 1/2 a HP that I'll never be able to tell is there anyhow.
    Starts easy, runs crisp, clean, perfect throttle response from idle to just shy of 6-grand, could not ask for more.
    I have the exact same distributor. Sounds like we are real close in our set ups.
    I did it all in one day, last summer, mostly to see how the different set ups responded.
    I get a little better idle while cold with the higher initial, but I am also over carbed with the 2 660's, I think.
    But it works pretty good the way it is.
    I only ever have 1-2 people in it, don't pull any tubes, and it is either at idle, or over 4 grand, so it works for me!
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
    Where I fought in many guises,
    Many names, but always me."

    Gen. George S Patton

  15. #13
    Senior Member Delemorte's Avatar
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    Quote Originally Posted by thatguy View Post
    it is either at idle, or over 4 grand, so it works for me!
    Wait a minute.. you mean a jet boat does not have to run either at idle and WOT? I thought it was just one or the other
    Quote Originally Posted by jetboatperformance View Post
    the ensueing fire would likely be extinguished by the sinking however

  16. #14
    Living in a cage of fear thatguy's Avatar
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    Quote Originally Posted by Delemorte View Post
    Wait a minute.. you mean a jet boat does not have to run either at idle and WOT? I thought it was just one or the other
    Only when Debbie is driving!!
    She idles until my ass is 1/2" from being on the passenger seat, then it goes WOT and stays there until I scream at Her.
    Sometimes I wish I didn't know what all those little gauges mean either!
    Tommy
    Quote Originally Posted by Rexone View Post
    Tommy please remove all Jimsplace quotes from your sig and don't put more back. He doesn't like it and it is against the rules. Thank you.
    "So as through a glass, and darkly
    The age long strife I see
    Where I fought in many guises,
    Many names, but always me."

    Gen. George S Patton

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