Timing Curve
Posting Guru
Joined: Mar 2006
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sure - for the sake of conversation, I suppose we could say that in any given vehicle, the amount of spark energy available to contribute to spark duration is constant.
but i'm not sure I follow where you're trying to go with trying to find ways to add timing.
you don't need to burn the spark interminably...you just need to burn it long enough for the fastest possible consumption of the fuel charge.
these older head designs are less efficient, so they benefit from more timing than newer models. however, continuing to add timing isn't the answer.
think of the increased timing as a band-aid to help remedy the slow combustion that results from an less-efficient head design.
your goal isn't to increase timing - it is to optimize the combustion.
but i'm not sure I follow where you're trying to go with trying to find ways to add timing.
you don't need to burn the spark interminably...you just need to burn it long enough for the fastest possible consumption of the fuel charge.
these older head designs are less efficient, so they benefit from more timing than newer models. however, continuing to add timing isn't the answer.
think of the increased timing as a band-aid to help remedy the slow combustion that results from an less-efficient head design.
your goal isn't to increase timing - it is to optimize the combustion.
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Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
sure - for the sake of conversation, I suppose we could say that in any given vehicle, the amount of spark energy available to contribute to spark duration is constant.
but i'm not sure I follow where you're trying to go with trying to find ways to add timing.
you don't need to burn the spark interminably...you just need to burn it long enough for the fastest possible consumption of the fuel charge.
these older head designs are less efficient, so they benefit from more timing than newer models. however, continuing to add timing isn't the answer.
think of the increased timing as a band-aid to help remedy the slow combustion that results from an less-efficient head design.
your goal isn't to increase timing - it is to optimize the combustion.
but i'm not sure I follow where you're trying to go with trying to find ways to add timing.
you don't need to burn the spark interminably...you just need to burn it long enough for the fastest possible consumption of the fuel charge.
these older head designs are less efficient, so they benefit from more timing than newer models. however, continuing to add timing isn't the answer.
think of the increased timing as a band-aid to help remedy the slow combustion that results from an less-efficient head design.
your goal isn't to increase timing - it is to optimize the combustion.
Thread Starter
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Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
I wonder if heat is a factor as well? Engine maintains a higher temperature at higher rpms, maybe fuel and air pick up a little more waste heat on the way in? Just a thought. I'm stuck using my phone for the next week. Hate thumb typing. Will research what I can, but most of it will have to wait until I get home.
Posting Guru
Joined: Mar 2006
Posts: 1,182
Likes: 1
oh, gotcha.
there aren't any physical limitations, once you get rid of the distributor. top fuel cars run far more timing, as FF mentioned, for alcohol-based fuel.
https://www.onallcylinders.com/2015/...-race-engines/
You also asked why engines don’t need more timing above 2,800 rpm. This is an arbitrary rpm point, but based on experience, a fixed timing number of 32 to perhaps 40 degrees seems to work for most normally aspirated, pump gas engines. It is possible that if we doubled the engine speed from 6,000 to 12,000 rpm that timing changes might be necessary, but the doubling of speed from 3,000 to 6,000 is not sufficient to demand major changes in timing.
It is highly entertaining that we're discussing 6000 rpm timing curves on a vintage inline 6 forum.
there aren't any physical limitations, once you get rid of the distributor. top fuel cars run far more timing, as FF mentioned, for alcohol-based fuel.
https://www.onallcylinders.com/2015/...-race-engines/
You also asked why engines don’t need more timing above 2,800 rpm. This is an arbitrary rpm point, but based on experience, a fixed timing number of 32 to perhaps 40 degrees seems to work for most normally aspirated, pump gas engines. It is possible that if we doubled the engine speed from 6,000 to 12,000 rpm that timing changes might be necessary, but the doubling of speed from 3,000 to 6,000 is not sufficient to demand major changes in timing.
It is highly entertaining that we're discussing 6000 rpm timing curves on a vintage inline 6 forum.
Thread Starter
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Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
oh, gotcha.
there aren't any physical limitations, once you get rid of the distributor. top fuel cars run far more timing, as FF mentioned, for alcohol-based fuel.
https://www.onallcylinders.com/2015/...-race-engines/
You also asked why engines don’t need more timing above 2,800 rpm. This is an arbitrary rpm point, but based on experience, a fixed timing number of 32 to perhaps 40 degrees seems to work for most normally aspirated, pump gas engines. It is possible that if we doubled the engine speed from 6,000 to 12,000 rpm that timing changes might be necessary, but the doubling of speed from 3,000 to 6,000 is not sufficient to demand major changes in timing.
It is highly entertaining that we're discussing 6000 rpm timing curves on a vintage inline 6 forum.
there aren't any physical limitations, once you get rid of the distributor. top fuel cars run far more timing, as FF mentioned, for alcohol-based fuel.
https://www.onallcylinders.com/2015/...-race-engines/
You also asked why engines don’t need more timing above 2,800 rpm. This is an arbitrary rpm point, but based on experience, a fixed timing number of 32 to perhaps 40 degrees seems to work for most normally aspirated, pump gas engines. It is possible that if we doubled the engine speed from 6,000 to 12,000 rpm that timing changes might be necessary, but the doubling of speed from 3,000 to 6,000 is not sufficient to demand major changes in timing.
It is highly entertaining that we're discussing 6000 rpm timing curves on a vintage inline 6 forum.
Posting Guru
Joined: Mar 2006
Posts: 1,182
Likes: 1
in theory, yes.
but I don't think I've ever heard anyone say they installed a MSD box and subsequently backed off on the timing.
we've gotten into the area where you'd have to do dyno pulls or quarter-mile runs to *really* get at the answer.
You'd need to dyno-tune it as best you can on stock ignition, then install a hotter ignition, and take it for another run to see if anything changes.
It'd be very, very interesting.
but I don't think I've ever heard anyone say they installed a MSD box and subsequently backed off on the timing.
we've gotten into the area where you'd have to do dyno pulls or quarter-mile runs to *really* get at the answer.
You'd need to dyno-tune it as best you can on stock ignition, then install a hotter ignition, and take it for another run to see if anything changes.
It'd be very, very interesting.
Thread Starter
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Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
in theory, yes.
but I don't think I've ever heard anyone say they installed a MSD box and subsequently backed off on the timing.
we've gotten into the area where you'd have to do dyno pulls or quarter-mile runs to *really* get at the answer.
You'd need to dyno-tune it as best you can on stock ignition, then install a hotter ignition, and take it for another run to see if anything changes.
It'd be very, very interesting.
but I don't think I've ever heard anyone say they installed a MSD box and subsequently backed off on the timing.
we've gotten into the area where you'd have to do dyno pulls or quarter-mile runs to *really* get at the answer.
You'd need to dyno-tune it as best you can on stock ignition, then install a hotter ignition, and take it for another run to see if anything changes.
It'd be very, very interesting.
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Posting Guru
Joined: Mar 2006
Posts: 1,182
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amen.
there's a dyno or two near me. I took my Galaxie last year. 3 pulls for $80.
it was an eye-opening experience, and absolutely worth it.
although the car runs like a Timex watch, it was way lean at WOT.
and even though i'd run the numbers on the size of air cleaner element...taking it off improved HP noticeably.
there's a dyno or two near me. I took my Galaxie last year. 3 pulls for $80.
it was an eye-opening experience, and absolutely worth it.
although the car runs like a Timex watch, it was way lean at WOT.
and even though i'd run the numbers on the size of air cleaner element...taking it off improved HP noticeably.
Thread Starter
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Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
Now that I'm back home with computer access again I'll see what I can't figure out. Maybe me and Google can stack enough up for you guys to fill in the blanks.
Would be nice to get some good solid theory worked out so maybe the next guy hitting the Dyno can take some data points for us to compare.
Would be nice to get some good solid theory worked out so maybe the next guy hitting the Dyno can take some data points for us to compare.
4wd Low
Joined: Apr 2022
Posts: 14
Likes: 0
All the examples of timing curves I have seen are stepped... Not round. I have been reading up on recurving duraspark distributors for weeks. Took two weeks to find anything worth reading.
So now I have it in my head that the advance should be linear. Just a straight diagonal line. Can someone with a deep personal understanding of this stuff explain why that's wrong so we can go on to talk about nice smooth(not stepped) CURVES that would exist in a perfect world?
I went a little crazy in the third week of reading up on this. Pretty sure I redesigned the advance mechanism in the distributor, both mechanical and vacuum about a dozen times in my head. Even put a couple on paper. But I really don't have enough of an understand about it. Although it does excite me. I really am looking forward to tuning my truck when I eventually get it put back together. Really want to try some of those ideas I had, I'd love to squeeze as much HP and economy out of this truck.
So, can I talk anyone into kicking around theory with me?
Also, shout out to @AbandonedBronco It was your post on the fordsix site that got me started on this. I couldn't find anything on timing until I found your post. Gave me a pretty good understanding and more search terms.
So now I have it in my head that the advance should be linear. Just a straight diagonal line. Can someone with a deep personal understanding of this stuff explain why that's wrong so we can go on to talk about nice smooth(not stepped) CURVES that would exist in a perfect world?
I went a little crazy in the third week of reading up on this. Pretty sure I redesigned the advance mechanism in the distributor, both mechanical and vacuum about a dozen times in my head. Even put a couple on paper. But I really don't have enough of an understand about it. Although it does excite me. I really am looking forward to tuning my truck when I eventually get it put back together. Really want to try some of those ideas I had, I'd love to squeeze as much HP and economy out of this truck.
So, can I talk anyone into kicking around theory with me?
Also, shout out to @AbandonedBronco It was your post on the fordsix site that got me started on this. I couldn't find anything on timing until I found your post. Gave me a pretty good understanding and more search terms.
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