Cdi vs TCI

[Lkhangee]

Hi,

What's the difference and advantages of one over the other.
Some folks told me earlier Chinese tuk Tuk Tuk Rickshaws used tci bit since the mechanics that would take care of tuk Tuk in this part of the world are uneducated and Ill trained an only knows how to assemble and disassemble so the only word from them is that that was complex system and would fail frequently. Which is now replaced by dc cdi ignition system.

Can someone shed some light on it? If it's any better? At working diagrams and manual.
Regards

[Megadan]

This is a very difficult thing to explain in a quick manner.

The simplest way to explain it is that in a CDI, the coil itself stores no voltage, and when given the signal to fire, the Capacitors in the system send a high voltage pulse through the primary coil to ground, that induces the secondary coils with then fire the plug.

TCI ignitions, in a sense, work the exact opposite of a CDI. Unlike a CDI, the coil on a Transistor ignition has constant power to the coil. When the ignition event is triggered, it cuts primary voltage to the coil, causing it to collapse which induces the secondary coil to fire.

CDI systems have the advantage of very low resistance across the whole system, which means that they tend to fire very hot and very quickly which makes them much better in high power, high rpm situations, but they can sometimes be a bit less stable at low RPM - often why it sometimes sounds like our Chinese bikes will miss from time to time at idle. That is also why our bikes tend to run a Resistor plug or resistor cap - it adds a little resistance after the coil, which helps slow the spark discharge rate down a little to try and stabilize it at lower engine speeds.

TCI systems are essentially a modern day version of points. Many aftermarket electronic ignition conversions for old points style bikes are Thyristor or Mosfet fired TCI systems. These types of ignitions tend to be much more stable at low RPM, and tend to have a longer life span. The downside is that they also tend to have a much higher internal resistance in the system. That high resistance makes them less reliable at high RPM, and can start to fall off in spark strength, eventually causing the spark to get so weak that the compression in the cylinder can actually suppress it.

The reason you see CDI systems used a lot on our style of bikes is because they tend to require operating in higher RPM ranges (over 4000-5000), at which CDI is far more consistent and reliable. You will also see many race applications convert to CDI systems for this same reason.

Hope that helps.

[Lkhangee]

Originally Posted by Megadan

This is a very difficult thing to explain in a quick manner.

The simplest way to explain it is that in a CDI, the coil itself stores no voltage, and when given the signal to fire, the Capacitors in the system send a high voltage pulse through the primary coil to ground, that induces the secondary coils with then fire the plug.

TCI ignitions, in a sense, work the exact opposite of a CDI. Unlike a CDI, the coil on a Transistor ignition has constant power to the coil. When the ignition event is triggered, it cuts primary voltage to the coil, causing it to collapse which induces the secondary coil to fire.

CDI systems have the advantage of very low resistance across the whole system, which means that they tend to fire very hot and very quickly which makes them much better in high power, high rpm situations, but they can sometimes be a bit less stable at low RPM - often why it sometimes sounds like our Chinese bikes will miss from time to time at idle. That is also why our bikes tend to run a Resistor plug or resistor cap - it adds a little resistance after the coil, which helps slow the spark discharge rate down a little to try and stabilize it at lower engine speeds.

TCI systems are essentially a modern day version of points. Many aftermarket electronic ignition conversions for old points style bikes are Thyristor or Mosfet fired TCI systems. These types of ignitions tend to be much more stable at low RPM, and tend to have a longer life span. The downside is that they also tend to have a much higher internal resistance in the system. That high resistance makes them less reliable at high RPM, and can start to fall off in spark strength, eventually causing the spark to get so weak that the compression in the cylinder can actually suppress it.

The reason you see CDI systems used a lot on our style of bikes is because they tend to require operating in higher RPM ranges (over 4000-5000), at which CDI is far more consistent and reliable. You will also see many race applications convert to CDI systems for this same reason.

Hope that helps.

Immense thanks for the detailed reply.
Currently my engine 163ML liquid cooled is using ac cdi system from a 125cc cg replica bike.

Is it advisable to convert to DC cdi system.

Also what is the current draw by the dc cdi from the battery?

[humanbeing]

Originally Posted by Lkhangee

Also what is the current draw by the dc cdi from the battery?

Typical: http://www.cqxbmp.com/company/doc-2-34319.html
Some better one: <30mA | <500mA | as low as 5V