Hi, would it be able or better is it planned to make some sort of dual spark outputs for dual spark arrangement. I have i 3cyl. even fire engine. It would be great to select different advance for the second set of spark plugs or only a table to define a difference from the first plugs depending on engine load/speed?
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Twinspark spark timing table
Re: Twinspark spark timing table
Perhaps this could be partially done by claiming it's a 6 cyl, then tuning accordingly. Would I be guessing correctly if I thought this might be an aviation application. I know planes commonly have 2 spark plugs per cyl. It's the entire redundancy thing.
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nighthunter
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Re: Twinspark spark timing table
Hi,
its not an aviation application. I know that in flight engines it is for redundancy. Mine is an smart/mercedes 700ccm 3cyl petrol boosted engine. It has twin arrangement, but the sparks are not symmetricaly placed in head. But as the piston travels one is lower than other. I looked at the timing by scope and there is a little delay between the sparks. It is for better burn of the mixture at high RPMs and high boost levels. If i disconnect the "slave" plug set the engine has in the middle/top RPM range about 1/3 less power.
its not an aviation application. I know that in flight engines it is for redundancy. Mine is an smart/mercedes 700ccm 3cyl petrol boosted engine. It has twin arrangement, but the sparks are not symmetricaly placed in head. But as the piston travels one is lower than other. I looked at the timing by scope and there is a little delay between the sparks. It is for better burn of the mixture at high RPMs and high boost levels. If i disconnect the "slave" plug set the engine has in the middle/top RPM range about 1/3 less power.
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AndreyB
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Re: Twinspark spark timing table
So if one is lower than the other do you think the control logic could be that it simply delays the second one by specified angle? (say 10 degrees of camshaft, time delay would be calculated based on RPM?)
So what I am asking is it's easier for me to start by having the simplest implementation. I can add a complete second timing map but I'd rather do something much easier at this point.
So what I am asking is it's easier for me to start by having the simplest implementation. I can add a complete second timing map but I'd rather do something much easier at this point.
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nighthunter
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Re: Twinspark spark timing table
Hi, last drives i had hooked up scope as i drove. It seems that the second timing is following the primary spark in order of 0-15 degs . But it is only dependent on RPMs not on load. I thought that is was dependent on boost, but seems that it is not. Only change in RPMs affect the second spark timing. All other things on rusefi runs great and smooth and I will be verry happy if someday that feature would be implemented.
Btw. just a little off topic: on my "dev board i had to remove PA5 because it not worked It was still low. Is some sort of problem on discovery kits with PA5?
Btw. just a little off topic: on my "dev board i had to remove PA5 because it not worked It was still low. Is some sort of problem on discovery kits with PA5?
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AndreyB
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Re: Twinspark spark timing table
https://sourceforge.net/p/rusefi/tickets/320/
this one is not so little, let's move this question somewhere elsenighthunter wrote:just a little off topic
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Re: Twinspark spark timing table
I also added this to the ticket discussion.
1. I understand that the OEM ECU varies secondary spark delay between 0º and 15º, just based on RPM. If the secondary spark feature should be implemented, I would just add a full secondary spark table, based on RPM and Engine Load- not an offset table purely based on RPM.
2. How the hell does a secondary, later spark generate more power? The flamefront is already underway. The only thing I could see happen is knock. But more power? Maybe if the primary spark is too retarded for optimum power and the secondary flamefront speeds things up. Sounds more like a way to optimize emissions and not power to me. Meh.
1. I understand that the OEM ECU varies secondary spark delay between 0º and 15º, just based on RPM. If the secondary spark feature should be implemented, I would just add a full secondary spark table, based on RPM and Engine Load- not an offset table purely based on RPM.
2. How the hell does a secondary, later spark generate more power? The flamefront is already underway. The only thing I could see happen is knock. But more power? Maybe if the primary spark is too retarded for optimum power and the secondary flamefront speeds things up. Sounds more like a way to optimize emissions and not power to me. Meh.
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nighthunter
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Re: Twinspark spark timing table
I dont know how, but is really does a big effect on the engine power. I wondered how it is possible too. Thanks for adding the ticket.
Re: Twinspark spark timing table
I should have been more explicit- sorry.
Based on no evidence whatsoever, I think that advancing the primary spark angle more would cause the same gains in torque as adding the second spark.
I seem to remember that highly advanced timing does create more of one the nasty combustion end-products. I don't remember which one. So one way to get around that is to not advance the spark so much. But that robs power. So what do we do? Have a relatively late primary spark, but then hit it with a second spark at a later time and in a different location, so full combustion pressure exists at the same crank-angle as it would with more advanced primary spark. No power loss and better emissions.
Until the feature of secondary spark exists in rusefi, try if advancing primary spark without any secondary will make the same power. I believe it should.
Power can be estimated using VirtualDyno: http://www.virtualdyno.net/
Based on no evidence whatsoever, I think that advancing the primary spark angle more would cause the same gains in torque as adding the second spark.
I seem to remember that highly advanced timing does create more of one the nasty combustion end-products. I don't remember which one. So one way to get around that is to not advance the spark so much. But that robs power. So what do we do? Have a relatively late primary spark, but then hit it with a second spark at a later time and in a different location, so full combustion pressure exists at the same crank-angle as it would with more advanced primary spark. No power loss and better emissions.
Until the feature of secondary spark exists in rusefi, try if advancing primary spark without any secondary will make the same power. I believe it should.
Power can be estimated using VirtualDyno: http://www.virtualdyno.net/
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nighthunter
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Re: Twinspark spark timing table
Thanks for explanation. I will test it tomorrow.
Re: Twinspark spark timing table
When you have 2 spark plugs, you generally force the plug to be very much off center, some times pretty much in the cyl wall. When you spark in this area it's easy to get knock, so you are limited in how much advance you can use. They eventually generally standardized on a single plug closer to the center of the head, which prevent the knock issues, and allows you to advance the timing to get the power.
I agree this head design is likely an earlier attempt at emissions, in the end making your head with only one plug works basically just as well. However that's the head he has. I doubt it had any better HP/weight ratio. I'd bet it was about the same, or less HP/weight.
I agree this head design is likely an earlier attempt at emissions, in the end making your head with only one plug works basically just as well. However that's the head he has. I doubt it had any better HP/weight ratio. I'd bet it was about the same, or less HP/weight.
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Re: Twinspark spark timing table
Agreed- of center sparks are... less than optimal.
Found an image of a Smart head online:
So I'd suggest advancing timing a few degrees and fire the plugs at the same time. That should help considerably with getting the lost power back.
OP: Did you scope the stock timing advance to come up with your spark map or did you come up with it some other way?
Found an image of a Smart head online:
So I'd suggest advancing timing a few degrees and fire the plugs at the same time. That should help considerably with getting the lost power back.
OP: Did you scope the stock timing advance to come up with your spark map or did you come up with it some other way?