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Thread: Dynamic ignition timing

  1. #1
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    Dynamic ignition timing

    How many degrees should the ignition timing be set @ 4000 RPM? 07-3 Dyno cam and a 96-3 Dyno cam - both cards say 29*-30* static timing but between the 2 engines I have one retards 4* and the other retards 6*. NOt sure what to shoot for @4000?

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    Set it at 30 at 4000. If that's what advance you want. Use the coil that retards the least.

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    This came up on another thread without answer.
    If static is 30 , the coil retards 4* .
    You would set the static at ,34* to achieve the 30*.
    Seems so simple , but is it correct?

  4. #4
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    On the flatheads stockers ,we were hung up for years on the 28-29* timing.As springs ,ports and fuel delieverly was improved along with the camshafts, the RPM's went up.So, just saying, I increased the ignition timing on stockers and modifieds too.

  5. #5
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    I understand the math even tho' I'm no Alvin Nunley I called Dyno and they say to set the initial timing at 29*-30* and also said that no one had asked them before what the timing should be at 4000 RPM and didn't have a recommendation, only to set it at 29*-30* on the bench and that it is based on the average retard. Is 29*-30* at 4000 RPM what works best? I don't have a dyno and I don't want to pull it apart at the track to try different settings. I can just bump it up 2* each week until it seems to fall off I suppose...

    @flattop1 - I searched the other threads too but didn't find a definitive answer either

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    No, Tony, this is not correct. (at least not in my opinion)
    Set the timing at 30* at 0 rpm. (on the bench - That is what I call "static" timing.)
    At 4000 it will have retarded. They all do. If you set it at 30* @ 4000, it will have too much advance throughout the powerband (and especially around peak torque, which is where the damage will start,) and cause all sorts of issues, too much heat, even knock or detonation.

    The coil that retards 6* @4000 is a lot. 2 or 3 degrees is pretty common. What is the idle rpm that you are comparing to? 2000?
    Check and record the timing drop again at 5000, 6000, & at 7000/7200 (or whatever peak rpm for that engine is.)

    For the 04-3 cam, I've had timing all over the place (very conservative and wildly advanced) to make it work. One thing for sure, is that it takes a REALLY good flowing carb to make that cam work on top end.
    The 96-3 is a very forgiving cam on set-up (again, in my opinion.) 07-3, for the most part, is the same. They won't make the top end power that the 04-3 does, but will make up for it from 4000-6000.

    Hopefully that helps.


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    Thanks and God bless,
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    Carlson Racing Engines
    Vector Cutz
    www.CarlsonMotorsports.com
    29 years of service to the karting industry
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    bcarlson@CarlsonMotorsports.com

  7. #7
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    Brian:

    If your cam card calls for 34 to 36. set it at static at 35

    At 4,000 it is 33
    At 7,000 it is 30
    What would you do?

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    "I can just bump it up 2* each week until it seems to fall off I suppose..."

    Yes IMHO that's all you can do without a dyno.

    The main change which everything else revolves around is as rpm's increase the speed of your piston increases. The simple of it is at every rpm you need to put the right amount of fuel and air into the cylinder and light it at the right time so you get the most power from your fuel.

    If at 4000 rpm with 29*-30*'s of advance timing ignites the amount of fuel and air you put into the cylinder at the right time, you'll in theory get the most power possible for what you have at 4000 rpm. If you make the intake, exhaust and/or fuel delivery system better, the simple of it is at 4000 rpm you'll be able to put more air and fuel into the cylinder. Do that and in theory you'll have to ignite sooner.

    Everything boils down to as far as timing goes to having the right amount of time to burn what ever fuel is in the cylinder. And as rpm's increase so does piston speed which reduces the time you have per stroke to burn fuel.

    You won't read or hear of the relationship between rpm, piston speed and how increasing piston speed gives you less time to burn fuel requiring a change in timing or a reduction in fuel if you do not have variable timing anywhere but on here. At least you won't find it written prior to the concept being introduced on here.

    If you don't have a way to advance or control timing as rpm's increase, your only option is to reduce the amount of fuel per burn you put into the cylinder because of increasing piston speed. You will still use more fuel as rpm's increase simply because you burn less fuel more often. But the amount of fuel per burn will have to be reduced as rpm's increase because piston speed increases.

    yep with out a dyno all you can do is put the thing on the track and change timing up or down until it starts to fall on it's face. The question then becomes are you going to make it "better" because being better it is the whole point of racing, by changing the timing or changing the amount of fuel put in the cylinder at that rpm?

    answer: You ain't going to make it better by changing timing because before you changed the timing the last time it was as good as it was going to get. The only way to make it better where it fell on it's face is to change the amount of fuel being burnt and the timing. You can't move ahead on performance getting more rpm out of your engine without changing both timing and the amount of fuel being burnt. One hand washes the other. ...

    ... maybe I'm just winging it not knowing squat and ain't no engine builder with experience because this is all just IMHO and ain't necessarily right anyway. ...

    edit: Do you need more top end or better bottom end is not about getting the most out of your engine. It's about setting up your engine to best fit racing needs. If a better bottom end gets you a racing advantage on the track then that's what you do. If you need more rpm's or top end to have an advantage then that's what you do.

  9. #9
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    Brian I have a 410 sprint engine timing question for you and I don't think it's hijacking this thread because I think if the question is ok and you can answer it because the question was ok, it will help with understanding of timing.

    You explained to statically set the kart engine timing to 30* and go from there because the coil because of it's nature will drop off at racing rpm. What comes to mind if I'm remembering correctly is when setting timing on a 410 the norm is put it at 32*'s in the hole. Figuring both the kart engine and the sprint 410 engine are both burning the same alcohol fuel the 32*'s I probably wrongly remember shouldn't really be different then the kart 30*'s. It makes me think there's an inherent difference between the two because one used points to trigger and the other used the coil and some mechanical lag or maybe just because the parts are bigger and you can't do things as fast, must cause the difference. I don't know and that's all just probably wrong bull and miss understanding leading to the real question I wanted to ask you.

    We ain't got the cash to have a module Mallory distributor or crank magnets and still use old style ignition stuff. This discussion got me wondering if your using a newer legal 410 distributor setup, would you also then reduce a little how much in the hole you set the timing? It doesn't matter if you say yes or no or I don't know, I just got to wondering about it???

    thanks and Marcis71 I hope I'm not screwing up your thread and question with my input. If I am please say so and I'll delete my inappropriate input. You won't hurt my feelings Marcis.



    paul

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    Quote Originally Posted by CarlsonMotorsports View Post
    No, Tony, this is not correct. (at least not in my opinion)
    Set the timing at 30* at 0 rpm. (on the bench - That is what I call "static" timing.)
    At 4000 it will have retarded. They all do. If you set it at 30* @ 4000, it will have too much advance throughout the powerband (and especially around peak torque, which is where the damage will start,) and cause all sorts of issues, too much heat, even knock or detonation.

    The coil that retards 6* @4000 is a lot. 2 or 3 degrees is pretty common. What is the idle rpm that you are comparing to? 2000?
    Check and record the timing drop again at 5000, 6000, & at 7000/7200 (or whatever peak rpm for that engine is.)

    For the 04-3 cam, I've had timing all over the place (very conservative and wildly advanced) to make it work. One thing for sure, is that it takes a REALLY good flowing carb to make that cam work on top end.
    The 96-3 is a very forgiving cam on set-up (again, in my opinion.) 07-3, for the most part, is the same. They won't make the top end power that the 04-3 does, but will make up for it from 4000-6000.

    Hopefully that helps.


    -----
    Thanks and God bless,
    Brian Carlson
    Carlson Racing Engines
    Vector Cutz
    www.CarlsonMotorsports.com
    29 years of service to the karting industry
    Linden, IN
    765-339-4407
    bcarlson@CarlsonMotorsports.com
    Brian - I am comparing static timing (30*) to dynamic timing at 4000 RPM (24*or 26* depending on coil). I am spinning the engine with an electric motor coupled by pulleys and a belt and using a timing light against marks I've made on the flywheel and a pointer and I am using a spark tester between the plug wire and grounded to the head to complete the ignition circuit. I've checked and rechecked my timing marks to verify the dynamic timing and am very confident my numbers are accurate, but it may be the numbers aren't correct because of no load? but that doesn't seem to me that it would make a difference, would it? If I read into your reply I would think that you suggest 27*-28*@4000 RPM? 30* static with a 2*-3* retard?

    @Paul - no problems, I'm all for learning all aspects

  11. #11
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    Quote Originally Posted by Marcis71 View Post
    Brian - I am comparing static timing (30*) to dynamic timing at 4000 RPM (24*or 26* depending on coil). I am spinning the engine with an electric motor coupled by pulleys and a belt and using a timing light against marks I've made on the flywheel and a pointer and I am using a spark tester between the plug wire and grounded to the head to complete the ignition circuit. I've checked and rechecked my timing marks to verify the dynamic timing and am very confident my numbers are accurate, but it may be the numbers aren't correct because of no load? but that doesn't seem to me that it would make a difference, would it? If I read into your reply I would think that you suggest 27*-28*@4000 RPM? 30* static with a 2*-3* retard?

    @Paul - no problems, I'm all for learning all aspects


    Thanks and the setup you have is cool. To compare load and no load have you tried it with and without the spark plug in to see if there's a difference? Sounds like you have the spark plug out probably to make it easier to spin with the electric motor. If you have the plug out I just had and idea. I figure it would be hard to install the plug while it was spinning to see if the timing changed and I also figure with the pulley system the belt might slip and you can't get it up to speed if you check with the plug in. How about if you screwed some sort of valve setup into the plug hole? That way you could start it spinning with the valve open and close the valve simulating the plug being in after it was already up and spinning? Thinking about that more, would that also show how timing changes out on the track under load and no load or less load? Thinking more on it might it help find by playing around with it what might be done to get the best of of the engine when you get back on the gas after lifting. Clutch engagement is one thing but wouldn't clutch engagement go hand in hand with engine response?


    ... hummmm... thinking about fuel injection on a 410 and what your doing and the bull I asked about. One of the most critical things on a 410 engine to get throttle response is how well and evenly you set your butter flies to seal. The more the same and well set all cylinders the better the engine responds to getting back on the throttle. This conversation is making me think response in both a V8 and a single cylinder kart engine is about how the application of renewed load is applied. I'm going to say now it might be very important to get an engine loaded as quickly as possible to get the best response out of it? Thinking even more off the wall, might throwing some slop in the ball game at the right place to control how things come together loading for power output be important? ... nawwww, forget it just proly dumb. ...


    but this stuff sure is fun to think about

  12. #12
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    Quote Originally Posted by paulkish View Post
    Thanks and the setup you have is cool. To compare load and no load have you tried it with and without the spark plug in to see if there's a difference? Sounds like you have the spark plug out probably to make it easier to spin with the electric motor. If you have the plug out I just had and idea. I figure it would be hard to install the plug while it was spinning to see if the timing changed and I also figure with the pulley system the belt might slip and you can't get it up to speed if you check with the plug in. How about if you screwed some sort of valve setup into the plug hole? That way you could start it spinning with the valve open and close the valve simulating the plug being in after it was already up and spinning? Thinking about that more, would that also show how timing changes out on the track under load and no load or less load? Thinking more on it might it help find by playing around with it what might be done to get the best of of the engine when you get back on the gas after lifting. Clutch engagement is one thing but wouldn't clutch engagement go hand in hand with engine response?


    ... hummmm... thinking about fuel injection on a 410 and what your doing and the bull I asked about. One of the most critical things on a 410 engine to get throttle response is how well and evenly you set your butter flies to seal. The more the same and well set all cylinders the better the engine responds to getting back on the throttle. This conversation is making me think response in both a V8 and a single cylinder kart engine is about how the application of renewed load is applied. I'm going to say now it might be very important to get an engine loaded as quickly as possible to get the best response out of it? Thinking even more off the wall, might throwing some slop in the ball game at the right place to control how things come together loading for power output be important? ... nawwww, forget it just proly dumb. ...


    but this stuff sure is fun to think about
    I have only tested it with the spark plug hole open I'm not sure how the electric motor will respond to the extra load. It would be pretty easy to throw the compression gauge in the plug hole but that wouldn't necessarily simulate load on the engine it would only make the piston come up harder on the compression stroke putting load on the electric motor not on the engine??? I think the only way to put load on it would be running on the kart or on a dyno. I hadn't really thought about whether or not load would make a difference in coil retard until I was replying to Brian's comment, I had only assumed that it didn't make a difference. It will be interesting to know if it does make a difference...

  13. #13
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    Ten Four . Static it is.
    Some of the difference in the two types of engines flathead and ohv is combustion chamber shape. And the ability to get a complete burn and the flame front movement.
    (Disclaimer if I understood everything I know id be a genius)
    Last edited by flattop1; 02-13-2018 at 11:50 AM. Reason: Spell

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    I think your idea to use compression gauge is good. Your interest in timing which is lighting the fuel mixture is totally about the compression stroke. Load on the track occurs during the power stroke. Doesn't momentum to assist in compression help you during the power stroke and isn't that the opposite of load? I'd sure be curious to watch and see if timing changes when you close the valve on the gauge. If it doesn't then it doesn't. But unless you try it to see, what ever your or my speculation is is just speculation. ...


    sure is a fun discussion

  15. #15
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    You have to check ignition timing while the engine is under load. (on the dyno)
    For that matter, you really need to set the fuel system (kart or sprint car) while the engine is under load.


    Biggest difference between the two engines (other than the 1950's design of the flathead) is the compression ratio. You have to put a whole lot of advance in a stock flathead to get it to hit a knock meter....a couple of degrees of advance on a 410 motor and it'll shake the whole dyno cell and knock bearings right out of the thing (if not break the short skirt piston first.)

    With a mag, you're points gap makes a big difference in timing. Setting them at the standard .010" vs .018" gap will show up on a timing light. Also consider if your mag has advance built in or if it's locked out, etc. With an MSD, the timing is very forgiving (ie long duration spark.) It's my belief that you can make as much power with a good magneto (ie rare earth, external coil, etc) set up correctly as you can with a plug & play MSD. The MSD gives you a pretty wide cushion of error before bad things happen.
    Of course, the MSD has many other advantages over a magneto; but if you're simply tuning for power, either can be tuned to peak performance. I distinctly recall when Earl Gaerte suggested that we invest in an MSD over our hopped up mags at the time, and I asked him to show the performance difference and he just smiled and said something to the effect of "You kids are sharp enough to continue using what you've got." Of course, Sarah did most of the fueling and ignition on my cars at the track, so I may be speaking above my paygrade here. We still have several good mags (using one in AJ's 305 car currently), but some of the WoO stuff we had was purchased used from other teams, so we kept the MSDs and crank triggered deals on them. I like the MSD from a practicality standpoint (pretty much foolproof.) I have no problem working with a well built mag though either.

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    thank you

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    One thing about testing timing on these kart engines that really complicates it is having to remove and reset the flywheel. You can't use a timing tape or pre marked flywheel because tdc changes each time.
    That is where the adjustable coil bracket or flywheel come into play for testing.
    Question now is ; with the flatty being well developed is there enough gain to make out of the normal timing needed?
    my feeling is there is not.

  18. #18
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    Didn't see it mentioned here. Spark timing is affected by anything that changes the resistance across the gap of the plug.
    Fuel and type, humidity, compression, coil output.plug gap, even plug heat range.

    The timing light only reads when the spark overcomes the resistance across the gap.
    Something to think about.

  19. #19
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    Quote Originally Posted by flattop1 View Post
    One thing about testing timing on these kart engines that really complicates it is having to remove and reset the flywheel. You can't use a timing tape or pre marked flywheel because tdc changes each time.
    That is where the adjustable coil bracket or flywheel come into play for testing.
    Question now is ; with the flatty being well developed is there enough gain to make out of the normal timing needed?
    my feeling is there is not.

    Absolutely!

    Before I got ahold of one of Mike Clements' adjustable timing coil brackets, the time spent changing timing took forever. Now, you could use an ARC adjustable center flywheel, but then you're talking about a different magnet, location, keyway position, etc when it gets changed back to the stock flywheel.. hint: It WILL change when you go back to the stock flywheel. The adjustable coil bracket is definitely the way to go. No, I don't have an extra available.

    We used to spend the better part of 2 months in the winter doing testing; cams, lash, valve springs, pipes, jetting, timing, etc etc.
    With all of the indoor races that we have now, there really isn't time to spend testing all those things anymore. All this aside from the fact that the flathead has evolved to the point that it is...there are few new leaves to turn over in the R&D department. This constant testing is a big reason the clone stuff is so expensive right now as well --- as new parts are imported in, it takes a lot of time to test all this stuff and it comes at a cost.

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    Hortsman had a pair also .not quite as trick as the Clements model still functional.
    ,,3 hp and 5 hp flywheel. Took me a while to figure how it fit . Locates the coil at 11 o:clock.

  21. #21
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    fro a direct answer to the OP's question we always went for 27 degrees around 4000 when setting or checking for dynamic timing for a stocker... like a few things on a methanol engine small changes didn't do much one way or the other but we found 27 degrees to be pretty close on any engine turning close to 7000.. to change it is fairly easy.. just have a chart with static in the hole depth for each degree of timing( still is plastered to my work bench) and vary the depth depending upon what you needed once you tested from a given in the hole setup.. I have a couple of fixed bars set to different depths then simply added feeler gauges to give me what I needed.

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  22. #22
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    Quote Originally Posted by jglenn View Post
    fro a direct answer to the OP's question we always went for 27 degrees around 4000 when setting or checking for dynamic timing for a stocker... like a few things on a methanol engine small changes didn't do much one way or the other but we found 27 degrees to be pretty close on any engine turning close to 7000.. to change it is fairly easy.. just have a chart with static in the hole depth for each degree of timing( still is plastered to my work bench) and vary the depth depending upon what you needed once you tested from a given in the hole setup.. I have a couple of fixed bars set to different depths then simply added feeler gauges to give me what I needed.



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    YMMV
    Thank you, that's what I was looking for. I do have the chart on my bench and a tool that looks exactly like the one in your pic. I'll get set up to put a load on the engine and check my timing under load. Thanks Again!

  23. #23
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    Way back when Tecumseh had the coil behind the flywheel we used a continuity tester and a in the hole type shim to set the points ignition.I've used degree tape ,timing light and etc.I'd set the timing at roughly 28*-30* in the hole, and wear it out.There's no magical formula.I've built 100's of flatheads and the're very inconsistent.Somewhere between .180-.195 in the hole is what most people aim for.I'd bump it up if I were planning on turning over 6800 rpm.

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