Showing posts with label igniter. Show all posts
Showing posts with label igniter. Show all posts
Tuesday, October 20, 2015
DC-CDI ignition troubleshooting
Many small bikes of today and tomorrow are now using the DC-cdi technology, this is for reliability and mantaining good spark every now and then, but then at somehow and at somepoint, the system fails. How does it fails?
Firstly, we must understand how the system works from start to finish.
We'll now get into the ignition system itself. The outline simple enough. You start inside the left engine side cover, where two
PICKUPS
sit near the rotor and produce a pulse of electric current when the pistons near TDC (Top Dead Center) which is fed to the
sit near the rotor and produce a pulse of electric current when the pistons near TDC (Top Dead Center) which is fed to the
DC-CDI BOX
(Capacitive Discharge Ignition, variously called the "ignitor box", "brain box", etc.). This box has two basic functions. It adjusts the signal from the pickups based on engine speed to change the timing as needed, and a capacitor thats being charged by an internal HV generator in accordance with RPM switches an SCR dumping energy of the CAPACITOR to the primary winding of the
(Capacitive Discharge Ignition, variously called the "ignitor box", "brain box", etc.). This box has two basic functions. It adjusts the signal from the pickups based on engine speed to change the timing as needed, and a capacitor thats being charged by an internal HV generator in accordance with RPM switches an SCR dumping energy of the CAPACITOR to the primary winding of the
IGNITION COILS
so that the secondary winding is "induced" to spit out a high voltage shot to the
so that the secondary winding is "induced" to spit out a high voltage shot to the
SPARK PLUG WIRES and on to the
SPARK PLUG CAPS which in turn sends it to the
SPARK PLUGS
where all this voltage (maybe somewhere between 10kv to 40kv-that's thousands of volts) has enough pressure to make a small current jump the air gap between the electrodes at the bottom of the plug, thereby making a spark. This spark ignites the fuel mixture which, at that point is sitting all around the plug tip in a compressed state, ready to go BANG.
where all this voltage (maybe somewhere between 10kv to 40kv-that's thousands of volts) has enough pressure to make a small current jump the air gap between the electrodes at the bottom of the plug, thereby making a spark. This spark ignites the fuel mixture which, at that point is sitting all around the plug tip in a compressed state, ready to go BANG.
So that is basically what happens But things aren't quite this simple, and so we'll take each element and talk about it in more depth. We'll also note the problems we've run into, the tests that can be made, and the repairs/fixes we know about. Please understand I'm not a trained engineer just an electronics guy. My comments are based on what I've learned from reading, talking with people, and personal experience with the system.
Kawasaki OEM DC-CDI
Ever wonder whats inside an OEM DC-CDI of kawasaki,
I got time to open up one just for all of my readers, with my step by step on how i did it without messing up the circuitry of the igniter. At first before i opened up this little black box. The Unit is covered with rubber epoxy and sometimes hardened epoxy to avoid malfunction from moist and vibration of the motorcycle.
i tried not to mess up with the casing, unfortunately it didnt work for me, the plastic case is too brittle. slowly i chipped the casing with a diagonal cutter starting from the top cover. After hours doing the case thing. ,
The rubber epoxy will be exposed and time to strip it away so that the components of the board will be visible like this.
I used bamboo stick, (do not use hard pointed objects on clearing this epoxy, we do not know where the components are and might get damage by it)..so better yet use stick. ( i did not use any solvent to strip this...i need the entire board intact and the semiconductors un damage...
Read more »
I got time to open up one just for all of my readers, with my step by step on how i did it without messing up the circuitry of the igniter. At first before i opened up this little black box. The Unit is covered with rubber epoxy and sometimes hardened epoxy to avoid malfunction from moist and vibration of the motorcycle.
The rubber epoxy will be exposed and time to strip it away so that the components of the board will be visible like this.
5 pin AC-CDI
Yamaha DT125 CDI
This is the diagram of a china replica CDI (capacitive discharge ignition) of Yamaha DT125 2 stroke machine. The circuit can be used on other existing AC-cdi motorcycle, as long as there is a high voltage generator on the stator.
Read more »
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AC-CDI
Inside an AC-CDI of a GY6 50cc-125cc engine. An AC-CDI is a type of ignition wherein it can be operated without a battery installed on a bike but needing a HIGH VOLTAGE GENERATOR that will charge the capacitor inside the cdi to discharge tthrough your ignition coil producing spark at the spark plug unlike, dc-cd wherein no HV generator is necessary for they have a built in converter inside.
The circuit below is from a gy6 based engine. it incorporate a pulse shaping circuit, unlike the cdi of yamaha DT125 posted here Yamaha DT125 cdi.
for more ac cdi circuits and schematic diagram click here
More Ac-cdi schematic for you...
Read more »
The circuit below is from a gy6 based engine. it incorporate a pulse shaping circuit, unlike the cdi of yamaha DT125 posted here Yamaha DT125 cdi.
for more ac cdi circuits and schematic diagram click here
More Ac-cdi schematic for you...
DC-CDI schematic (updated)
DC-CDI counterpart of AC-CDI is an ignition analog or digital that uses low voltage external power supply to work. the difference AC-CDI needs external High Voltage COIL no battery configuration whereas DC-CDI needs a battery without HV COIL.
Looking at the picture on the left, it is a complete schematic diagram of a dc-cdi. Its a 4-pin system, comprising pick-up input, battery +12 volts in, Gnd, and Ignition coil out pins. There is no High Voltage input pin like those of AC-CDI. If it will be differentiated with the AC-CDI here, you will notice theres a transformer diagram on this schematic.The circuit on the RED BOX comprises the internal High Voltage generator of a DC-CDI, where the 12 volts battery in will be converted to 200-400 volts depending on the design of the inverter. This design uses two transistor dc-ac converter with external on/off circuit to charge and discharge the capacitor BLUE BOX via SCR. the HV converter is controlled by the circuit on GRAY box, that as soon as the pulse conditioning circuit sense the pick-up coil will send triggering signal on both SCR and HV oscillator respectively to turn them on and off at the right time.
CDI or Capacitor Discharge Ignition, from the name itself, capacitor is very critical during its operation, must handle charge and discharge time as well as heat being generated by the whole circuit inside the block box, that is why manufacturer uses special capacitors specifically made for ignitions, and not just like those mylar capacitor found on some electronic circuits. They are rated 400 to 630 volts. ranging from .47uf up to 2.2uf. Value is also so critical in every applications and designs. In this circuit, they use 1uf / 400 volts with HV out of 200 volts will equals to 20 mj.
Read more »
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| DC-CDI schematic diagram |
Looking at the picture on the left, it is a complete schematic diagram of a dc-cdi. Its a 4-pin system, comprising pick-up input, battery +12 volts in, Gnd, and Ignition coil out pins. There is no High Voltage input pin like those of AC-CDI. If it will be differentiated with the AC-CDI here, you will notice theres a transformer diagram on this schematic.The circuit on the RED BOX comprises the internal High Voltage generator of a DC-CDI, where the 12 volts battery in will be converted to 200-400 volts depending on the design of the inverter. This design uses two transistor dc-ac converter with external on/off circuit to charge and discharge the capacitor BLUE BOX via SCR. the HV converter is controlled by the circuit on GRAY box, that as soon as the pulse conditioning circuit sense the pick-up coil will send triggering signal on both SCR and HV oscillator respectively to turn them on and off at the right time.
CDI or Capacitor Discharge Ignition, from the name itself, capacitor is very critical during its operation, must handle charge and discharge time as well as heat being generated by the whole circuit inside the block box, that is why manufacturer uses special capacitors specifically made for ignitions, and not just like those mylar capacitor found on some electronic circuits. They are rated 400 to 630 volts. ranging from .47uf up to 2.2uf. Value is also so critical in every applications and designs. In this circuit, they use 1uf / 400 volts with HV out of 200 volts will equals to 20 mj.
CDI Building Blocks
This article will cover how motorcycle capacitive discharge ignition works, its building blocks. How an AC-CDI can be made a DC-CDI, how the internal dc-dc converter of a dc-cdi affects the overall performance. First. we will cover the AC-cdi to which some scooters, moped, and some chinese made 2 wheels utilize. Looking at the picture, it covers the building block of an AC-CDI,
it can easily be distinguished on any bike because they have the so called KILL switch to where it will disable the switching of the SCR or to cut the high voltage generator on supplying the capacitor to off the engine. Kill switch is a must for any ac-cdi circuit, and without it, the exciter or source coil will continue to rotate and supply high voltage to the capacitor.
AC-CDI can be made by enthusiast whether they are analog to digital, from simple to complex form, from fixed to a programmable to where you can adjust the ignition curve to meet your needs on racing or street driveability. Here we will not gather any information about racing CDI, for they are almost the same to what our bike is using, in short, they are only the modified version and sometimes, (this is not a fact but sometimes it is true) that they perform worse than those OEM fitted on our factory bikes, again but not all.
ANALOG AC-CDI
The simplest form of cdi which compose of discrete components, like resistor, capacitor, transistor, an scr and diodes.
Here shown in the picture is an analog simple easy to build cdi. It has no advance function, the trigger of the scr is straight forward.
When pulses from the pick-up coil is sensed, it will produce voltage near but not more than 5volts. It will then be configure by D3 for positive pulse, and condition by the R2 and C2 for noise removal of the pick-up coil for SCR Q1 gate triggering.
Exciter or source coil will produce 60-120 volts, this depends on the power of the coil, is then converted by D1 to DC for C1 charging..
When the pulse arrived at SCR gate, it will be triggered and shunting the capacitor charge to ground and dumped it on the ignition coil, and because ignition coil is just a straight forward step up transformer, primary will then produce magnetic field transferring power to secondary winding and because of the ratio between the two windings about 1:100, secondary will produce a brief 20,000kv - 30,000kv then onto the ignition wire, then finally at the tip of the spark plug gap to produce an ARC.
DIGITAL AC-CDI
On the other hand, a digital AC-CDI form the name itself, compose of perhaps some digital ic like, microprocessors to where configuration of advance thru PC is probable. some uses micros like PIC, AVR, freescale, and the likes. example of this can be found from site like
http://sportdevices.com/ignition/ignition.htm
Comparing to the simple analog AC-CDI posted above, the triggering circuit before the gate of the SCR went from the microcontroller pic16f84A to which must be programmed according to the specification of your motorbike, I'll not tell you exactly how this circuit works, for all of the data are within their site.
This circuit can operate with or without battery but nonetheless, since microcontroller IC needs constant supply, it may be best to use a battery to avoid failure.
Again, there is the STOP engine button connected to the gate of the scr via ground to of course stop the engine.
The microcontroller do all the stuff for pulse conditioning, as well as retarding or advancing the ignition to make room for a configurable driveability of your motorbike.
AC-CDI , can be configured to work as a DC-CDI with the help of a high voltage dc-dc converter in replacement for the high voltage generator coil that supply the necessary voltage to charge the capacitor, and the more complex yet very effective dc-cdi comes to play.
DC-CDI
Here a block diagram of this kind of ignition controller found nowadays on motorbike, the exciter coil, or source coil, or high voltage generator coil is omitted. but then a battery is in placed to power up the cdi. KILL switch is also omitted for once the power supply coming in from the battery is cut, there is no more power for the internal high voltage converter to use hence cutting of any means of charging the capacitor turning off the engine.
Only difference of the DC to AC type, here there will be a more complex circuit composed of the high voltage dc-dc converter that will act as the exciter coil or source coil. I will take this dc-cdi schematic for example.
The circuit on the red block is the source of the high voltage and act as the source coil of an AC-CDI system. Its a free running oscillator, but unlike the exciter coil produces continuous voltage, HV converter must be turned off in relation to the triggering of the SCR switch. This is not to cause a shorted path when the SCR dumps the charge of the capacitor. They are timely tied together.
Depending on the frequency of the oscillator, this has a big effect on how fast it can charge the capacitor at higher revolution of the engine. This circuit sometimes limit the overall performance of any Capacitor Discharge ignition built. If they can be made to be more powerful then we may be able to have a higher performance cdi as what those so called racing cdi does. but we all know that having a powerful ignition output means more voltage is needed thus more current consumption on the battery. Other's often states that changing the charging capacitor to a higher value compensate for this trade off,
"As the size of the capacitor is increased, the output of the ignition also increases, however the oscillator must be made more powerful. Certain trade offs must be made in design for a particular application."
still without improving the High voltage converter circuit, ignition limitations is in place.
There are many variations of the HIGH VOLTAGE CONVERTER used on a dc-cdi, other uses the typical low cost forward converter type some uses the switching mode type with onboard IC like SG3525, UC3845, other use microcontroller to switch it on and off. There are too many variation of producing high voltage for this kind of ignition. The trade-off is actually the design, the size and the frequency of the oscillator to charge the capacitor at a faster time.
I am into currently modifying this OEM dc-cdi of my motorbike by replacing its onboard converter to a more powerful one posted here
suzuki-shogun-oem-dc-cdi
and will try to use this kind of high voltage converter schematic
I am into modifying for a smaller pcb for this so that i can put it right on top of the original dc-cdi board. This high voltage can be configured by modifying the feedback control resistors R2 and R3.
Read more »
AC-CDI can be made by enthusiast whether they are analog to digital, from simple to complex form, from fixed to a programmable to where you can adjust the ignition curve to meet your needs on racing or street driveability. Here we will not gather any information about racing CDI, for they are almost the same to what our bike is using, in short, they are only the modified version and sometimes, (this is not a fact but sometimes it is true) that they perform worse than those OEM fitted on our factory bikes, again but not all.
ANALOG AC-CDI
The simplest form of cdi which compose of discrete components, like resistor, capacitor, transistor, an scr and diodes.
When pulses from the pick-up coil is sensed, it will produce voltage near but not more than 5volts. It will then be configure by D3 for positive pulse, and condition by the R2 and C2 for noise removal of the pick-up coil for SCR Q1 gate triggering.
Exciter or source coil will produce 60-120 volts, this depends on the power of the coil, is then converted by D1 to DC for C1 charging..
When the pulse arrived at SCR gate, it will be triggered and shunting the capacitor charge to ground and dumped it on the ignition coil, and because ignition coil is just a straight forward step up transformer, primary will then produce magnetic field transferring power to secondary winding and because of the ratio between the two windings about 1:100, secondary will produce a brief 20,000kv - 30,000kv then onto the ignition wire, then finally at the tip of the spark plug gap to produce an ARC.
DIGITAL AC-CDI
On the other hand, a digital AC-CDI form the name itself, compose of perhaps some digital ic like, microprocessors to where configuration of advance thru PC is probable. some uses micros like PIC, AVR, freescale, and the likes. example of this can be found from site like
http://sportdevices.com/ignition/ignition.htm
 |
| PICTURE property of SPORTDEVICES.COM |
This circuit can operate with or without battery but nonetheless, since microcontroller IC needs constant supply, it may be best to use a battery to avoid failure.
Again, there is the STOP engine button connected to the gate of the scr via ground to of course stop the engine.
The microcontroller do all the stuff for pulse conditioning, as well as retarding or advancing the ignition to make room for a configurable driveability of your motorbike.
AC-CDI , can be configured to work as a DC-CDI with the help of a high voltage dc-dc converter in replacement for the high voltage generator coil that supply the necessary voltage to charge the capacitor, and the more complex yet very effective dc-cdi comes to play.
DC-CDI
Only difference of the DC to AC type, here there will be a more complex circuit composed of the high voltage dc-dc converter that will act as the exciter coil or source coil. I will take this dc-cdi schematic for example.
The circuit on the red block is the source of the high voltage and act as the source coil of an AC-CDI system. Its a free running oscillator, but unlike the exciter coil produces continuous voltage, HV converter must be turned off in relation to the triggering of the SCR switch. This is not to cause a shorted path when the SCR dumps the charge of the capacitor. They are timely tied together.
Depending on the frequency of the oscillator, this has a big effect on how fast it can charge the capacitor at higher revolution of the engine. This circuit sometimes limit the overall performance of any Capacitor Discharge ignition built. If they can be made to be more powerful then we may be able to have a higher performance cdi as what those so called racing cdi does. but we all know that having a powerful ignition output means more voltage is needed thus more current consumption on the battery. Other's often states that changing the charging capacitor to a higher value compensate for this trade off,
"As the size of the capacitor is increased, the output of the ignition also increases, however the oscillator must be made more powerful. Certain trade offs must be made in design for a particular application."
still without improving the High voltage converter circuit, ignition limitations is in place.
There are many variations of the HIGH VOLTAGE CONVERTER used on a dc-cdi, other uses the typical low cost forward converter type some uses the switching mode type with onboard IC like SG3525, UC3845, other use microcontroller to switch it on and off. There are too many variation of producing high voltage for this kind of ignition. The trade-off is actually the design, the size and the frequency of the oscillator to charge the capacitor at a faster time.
I am into currently modifying this OEM dc-cdi of my motorbike by replacing its onboard converter to a more powerful one posted here
suzuki-shogun-oem-dc-cdi
and will try to use this kind of high voltage converter schematic
I am into modifying for a smaller pcb for this so that i can put it right on top of the original dc-cdi board. This high voltage can be configured by modifying the feedback control resistors R2 and R3.
Shogun DC-CDI schematic
Digital DC-CDI by the way uses microprocessor on the pulse shaping circuit to maintain integrity and reliability of giving out right timing all the time when the spark plug will fire the combustible material inside the combustion, it is also to where the ignition map of the engine is stored for accurate timing. Many OEM uses MCU specific for their design and no available datasheet for us to understand it fully. This OEM upon analyzing the entire board has an Rx, Tx, and ground port, and if only i have the datasheet of the IC, perhaps we can be able to extract the data and dump it to a computer for further enhancement.
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