smoke on ignition startup
Club Member
Joined: Feb 2007
Posts: 16,320
Likes: 306
From: Boynton Beach, FloriDuh
Honestly, I have neither the time nor interest in proving anything to you about a theory that you don't understand and are only repeating from someone else. I know the ignition system system quite well and know exactly how it works, down to the level of designing my own ignition timing maps.
I suspect your all knowledgeable mechanic is confusing your newer Sporty which employs a single fire ignition system, with older (pre 2000) Sporties which used dual fire ignition and fired the plugs on both the compression and exhaust strokes.
I suspect your all knowledgeable mechanic is confusing your newer Sporty which employs a single fire ignition system, with older (pre 2000) Sporties which used dual fire ignition and fired the plugs on both the compression and exhaust strokes.
Club Member
Joined: Feb 2007
Posts: 16,320
Likes: 306
From: Boynton Beach, FloriDuh
Yea, they call that "trying to prove a negative".
Anyone with a decent understanding of motors and ignition timing understands how ridiculous your quote is and that the ECM/ICM can't possibly determine which plug to fire or when to fire it based on your explanation.
Done debating with someone who doesn't understand basic motor and electrical principles. But I guess that's why you take your bike to a dealer for service.
Anyone with a decent understanding of motors and ignition timing understands how ridiculous your quote is and that the ECM/ICM can't possibly determine which plug to fire or when to fire it based on your explanation.
Done debating with someone who doesn't understand basic motor and electrical principles. But I guess that's why you take your bike to a dealer for service.
The CPS has no way of knowing what stroke the engine is on.So the ECM monitors the crank speed and if it detects a drop in speed it assumes that it is the compression stroke however the ECM will quickly determine that it was not the compression stroke due to no increase in RPM. Clutch drag will and does affect the speed at which the starter turns the motor.
Last edited by cHarley; Oct 5, 2010 at 05:23 PM.
Ultimate HDF Member
Joined: Mar 2008
Posts: 7,604
Likes: 38
From: Landrum, SC , elevation 986'
Not a theory it's the way it works. Can get it for you if you can't find it yourself. The CPS has no way of knowing what stroke the engine is on. So the ECM monitors the crank speed and if it detects a drop in speed it assumes that it is the compression stroke however the ECM will quickly determine that it was not the compression stroke due to no increase in RPM. Clutch drag will and does affect the speed at which the starter turns the motor.
If you need more info please contact:
Shannon Babb
Service Technician
started Nov 1998
Master Of Technology / level 5 (highest level achievable)
PHD certified
Smith Brothers H-D (423)283-0620
Call Shannon and argue with him, he'll set you straight.
If you need more info please contact:
Shannon Babb
Service Technician
started Nov 1998
Master Of Technology / level 5 (highest level achievable)
PHD certified
Smith Brothers H-D (423)283-0620
Call Shannon and argue with him, he'll set you straight.
Maybe you and Shannon should Read This article, cause one of yuhs don't have a clue.
CKP - Crank Position Sensor - This sensor provides input signals to the ECM that indicate engine rpm. The ECM also uses these inputs to determine what stroke the engine is in so it can deliver the fuel and spark at the desired time.
Last edited by xFreebirdx; Oct 5, 2010 at 06:53 PM. Reason: speeling =]
Ultimate HDF Member
Joined: Mar 2008
Posts: 7,604
Likes: 38
From: Landrum, SC , elevation 986'
The CPS is timed at top dead center +or-, thats how the ECM knows its starting point and where the crank is on rotation............OH and I think EFI sucks and will never own one.
Road Master
Joined: Jul 2010
Posts: 1,045
Likes: 102
From: Waukesha, WI
CPS and CKP sensors are either hall-effect or magnetic AC generator type, either way they have an odd "tooth" (wider than the rest) that is read by the ECM as #1 cylinder TDC. These sensor rings typically have keyways so that they will only go on the camshaft or crankshaft one way, to ensure TDC is read. There is no way to establish which stroke the engine is on based solely off of crank/cam speed, it's impossible - take a straight 6 engine- there is a power stroke every 120* of crank revolution, 90* for an 8 cylinder and 180* for a 4 cylinder. The mass of a flywheel or flexplate/torque converter keeps the engine speed consistent between power strokes and there will be no RPM drop on an engine that isnt misfiring. Waste-spark systems DO fire on the exhaust stroke because the coil packs generally work for companion cylinders, so piston location is the same regardless which cycle is taking place.
Regardless, OP- did the "smoke" come out of the A/C or the pipes? Odds are what you saw was atomized fuel and air being expelled through either an open intake valve (engine "spinning back" from letting go of the starter) or out the pipes as a wasted charge as the ignition was syncing.
Regardless, OP- did the "smoke" come out of the A/C or the pipes? Odds are what you saw was atomized fuel and air being expelled through either an open intake valve (engine "spinning back" from letting go of the starter) or out the pipes as a wasted charge as the ignition was syncing.
Last edited by 95th 1200; Oct 5, 2010 at 07:23 PM.
Outstanding HDF Member
Joined: Apr 2010
Posts: 2,765
Likes: 199
From: Johnson City, TN
Look it's not that hard to understand the CPS can only tell the ECM what speed and where the crank is in the 360 degree rotation. There is no way that the CPS can determine what stroke the engine is on since the complete cycle of a four stroke engine is 720 degrees. The ECM sees a slow down in rotational speed as the piston comes up on compression and fires the ignition. It's not rocket science and surely you guys can understand it if you try. Think about it and read the above linked article carefully. Do the research and you will understand how it works. Then you will be able to disseminate accurate information. Anyone can say that they have certain knowledge and abilities when it comes to how the ignition of a modern motor works but without taking the time to completely research this subject you are simply blowing smoke in hopes everyone will believe that you are knowledgeable on the subject. I am not trying to discredit anyone, only asking that you do your research before you pontificate. Or you could simply go to you local H-D dealer and ask someone who has been trained. It's really that easy.
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Outstanding HDF Member
Joined: Apr 2010
Posts: 2,765
Likes: 199
From: Johnson City, TN
CPS and CKP sensors are either hall-effect or magnetic AC generator type, either way they have an odd "tooth" (wider than the rest) that is read by the ECM as #1 cylinder TDC. These sensor rings typically have keyways so that they will only go on the camshaft or crankshaft one way, to ensure TDC is read. There is no way to establish which stroke the engine is on based solely off of crank/cam speed, it's impossible - take a straight 6 engine- there is a power stroke every 120* of crank revolution, 90* for an 8 cylinder and 180* for a 4 cylinder. The mass of a flywheel or flexplate/torque converter keeps the engine speed consistent between power strokes and there will be no RPM drop on an engine that isnt misfiring. Waste-spark systems DO fire on the exhaust stroke because the coil packs generally work for companion cylinders, so piston location is the same regardless which cycle is taking place.
Regardless, OP- did the "smoke" come out of the A/C or the pipes? Odds are what you saw was atomized fuel and air being expelled through either an open intake valve (engine "spinning back" from letting go of the starter) or out the pipes as a wasted charge as the ignition was syncing.
Regardless, OP- did the "smoke" come out of the A/C or the pipes? Odds are what you saw was atomized fuel and air being expelled through either an open intake valve (engine "spinning back" from letting go of the starter) or out the pipes as a wasted charge as the ignition was syncing.
Road Master
Joined: Jul 2010
Posts: 1,045
Likes: 102
From: Waukesha, WI
Cranking is no different than running, the engine is just spinning slower. When there is an acceleration or deceleration detected by the CMP its read as a misfire. ECM "knows" which stroke the engine is on whenever its rotating because the odd "tooth" is #1 cylinder TDC compression. Always.