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Old 05-02-2013, 06:42 AM   #31
foxtrapper
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But, for a bike in factory tune, run what the manufacturer recommends. Period.
And run only the manufacturers recommended tire size, at the manufacturers recommended pressure. Period.

Oil too. Manufacturers recommendations only. Period.



Do not ever evaluate for yourself alternatives to the manufacturers recommendations.
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Old 05-02-2013, 03:09 PM   #32
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Originally Posted by DesmoDog View Post
Dual plugs cause the mixture to burn faster..
the fuel charge once lit will only burn so fast. it doesnt matter how many spark plugs u used to lit it. of course dual plugs help guard against misfire but that is beside the point. dual plugs help disipate internal cylinder heat which in turn reduces internal cylinder pressure .
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Old 05-02-2013, 04:36 PM   #33
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Originally Posted by BikeMan View Post
the fuel charge once lit will only burn so fast. it doesnt matter how many spark plugs u used to lit it. of course dual plugs help guard against misfire but that is beside the point. dual plugs help disipate internal cylinder heat which in turn reduces internal cylinder pressure .
If you look at the timing specs , a dual plug head uses less ignition advance.
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Old 05-02-2013, 05:54 PM   #34
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Originally Posted by joexr View Post
If you look at the timing specs , a dual plug head uses less ignition advance.
maybe but i doubt it. ya just be losing HP. not sayn u wrong. dont matter to me . i'm running stock timing 4*BTDC. and its fixed. i cant change with out buying mod..
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BikeMan screwed with this post 05-03-2013 at 07:06 AM
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Old 05-02-2013, 06:21 PM   #35
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maybe but i doubt it. ya just be losing HP. not sayn u wrong. dont matter to me . i'm running stock timing 4*BDC. and its fixed. i cant change with out buying mod..
You have two ignition points in the combustion chamber leading to quicker burn , so less advance is needed. I didn't make this up , it's fact.
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Old 05-02-2013, 06:42 PM   #36
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Originally Posted by BikeMan View Post
the fuel charge once lit will only burn so fast. it doesnt matter how many spark plugs u used to lit it. of course dual plugs help guard against misfire but that is beside the point. dual plugs help disipate internal cylinder heat which in turn reduces internal cylinder pressure .


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Originally Posted by joexr View Post
You have two ignition points in the combustion chamber leading to quicker burn , so less advance is needed. I didn't make this up , it's fact.
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Old 05-02-2013, 07:08 PM   #37
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Originally Posted by BikeMan View Post
the fuel charge once lit will only burn so fast. it doesnt matter how many spark plugs u used to lit it. of course dual plugs help guard against misfire but that is beside the point. dual plugs help disipate internal cylinder heat which in turn reduces internal cylinder pressure .
One spark plug, right in the center of a 10" cylinder head. The flame front moves at 1" a second. This scenario would take 5 seconds to cover the cylinder, radiating out from the center spark plug.

Two spark plugs, equidistant in that same 10" cylinder head. The flame fronts again moves at 1" a second. This scenario would take just over 3 seconds to cover the cylinder, with two flame fronts radiating out from the two separated spark plugs.

Follow?
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Old 05-02-2013, 08:03 PM   #38
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Originally Posted by foxtrapper View Post
One spark plug, right in the center of a 10" cylinder head. The flame front moves at 1" a second. This scenario would take 5 seconds to cover the cylinder, radiating out from the center spark plug.

Two spark plugs, equidistant in that same 10" cylinder head. The flame fronts again moves at 1" a second. This scenario would take just over 3 seconds to cover the cylinder, with two flame fronts radiating out from the two separated spark plugs.

Follow?
You are kidding right. At just 5000 RPM, thats revolutions per minute and only 60 seconds in a minute, how many seconds do you think each power stroke last.
there seems to be considerable disagreement about combustion flame speed.............both about assumptions and the speed itself. The most cited speed is 32.8 ft/sec to 82.0 ft/sec. But running at 3000 rpm, there is only a window of 10 milliseconds for the combustion event to take place.

There was a Honda tech paper a few years ago which covered their work re determining just how high a 4 stroke could rev before the combustion process could no longer keep up. I don't know the bore diameter, but they ran it as high as 33,000 RPM.

http://www.highperformancepontiac.co...stion_chamber/
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Old 05-02-2013, 10:31 PM   #39
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You are kidding right. At just 5000 RPM, thats revolutions per minute and only 60 seconds in a minute, how many seconds do you think each power stroke last.
I'm guessing he was trying to explain a concept using simple terms, not describe the event using accurate numbers. Concept being two plugs make the mixture burn faster.
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Old 05-02-2013, 11:24 PM   #40
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You are kidding right. At just 5000 RPM, thats revolutions per minute and only 60 seconds in a minute, how many seconds do you think each power stroke last.

I doubt highly that he was suggesting that the flamefront moves at an inch pre second.
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Old 05-03-2013, 12:39 AM   #41
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Originally Posted by BikeMan View Post
the fuel charge once lit will only burn so fast. it doesnt matter how many spark plugs u used to lit it. of course dual plugs help guard against misfire but that is beside the point. dual plugs help disipate internal cylinder heat which in turn reduces internal cylinder pressure .
[citation needed]

Dual spark plugs are for redundancy (primarily in aviation) and burn efficiency (flame fronts, fuel burn, etc.). You're the first person I've ever heard try to argue against this.
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Old 05-03-2013, 12:55 AM   #42
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Originally Posted by opmike View Post
[citation needed]

Dual spark plugs are for redundancy (primarily in aviation) and burn efficiency (flame fronts, fuel burn, etc.). You're the first person I've ever heard try to argue against this.
http://rennsportsystems.com/letstalk...twin-ignition/

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Porsche has used twin-ignition in their air-cooled racing engines since the 4-cam Carrera engines. The high-domed pistons necessary for high compression ratios requires another spark plug to start another flame front on the other side of the piston dome. The best place for the spark plug is the middle of the combustion chamber. From the center, the flame front will have the least distance to travel for complete ignition. This reduces the need for as much ignition advance to start and finish the combustion process ...
Either way he is right. I remember flashing chips for camaros and such in high school, you started 15* before TDC with the ignition and bumped it up by degree, the couple dual plug bikes I've plutzed with (a Ducati and a Harley) were both running like 3* degrees before TDC on timing at full tilt.
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Old 05-03-2013, 02:26 AM   #43
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Good stuff on that Rennsport page. Thanks for the link.
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Old 05-03-2013, 04:26 AM   #44
foxtrapper
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Originally Posted by DesmoDog View Post
I'm guessing he was trying to explain a concept using simple terms...
I would have thought it was glaringly obvious.

foxtrapper screwed with this post 05-03-2013 at 06:00 AM
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Old 05-03-2013, 08:27 AM   #45
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Originally Posted by joexr View Post
quicker burn , so less advance is needed. I didn't make this up , it's fact.
its a more complete burn is the truth of the matter. hence the reduced timing required. but its not a quicker burn. even with dual plugs and domed pistons the burn is still not as complete or quicker as u call it, as a single plug located in the middle of the cylinder using flat top pistons. per rennsport link. IMHO, the big advantage of dual plugs is internal cylinder heat dissipation.
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