CDI vs Electronic Ignition

[dtkid]

Question for general knowledge:

What is the difference between a CDI-ignition and an Electronic ignition. I actually thought they were the same.

[focus frenzy]

totally different systems
CDI= capacitor discharge ignition
cdi uses a magneto coil to generate power which is Burt up in the ignition coil/capacitor and is triggered by points or a simple electronic trigger.
it does not require a battery.

cdi is commonly found on dirt bikes and small displacement street bikes, primarily single cylinder bikes.
Honda did use cdi on the cb/cm 400-450 twins
all GStwins from the 250 to the 500 have used battery powered ignitions.

most street bikes larger that 250cc have what is called battery powered ignition, they take power from a battery and it generates high voltage in the secondary windings in the coil, in this case, the electronic ignition controls the ground side of the coil/s
the system used on GS's uses small coils and a trigger wheel to time the ignition as the magnet in the trigger wheel passes the pick up coils a small electrical current is generated in the coils, the ignition control box uses this current (signal) to determine when to trigger the coils.
starting in 82 Suzuki started to use a fully electronic system that also electronically controlled the ignition advance by detecting the engine speed via the signal from the pick up coils.
prior to 82 (and on some 82 models) ignition advance was controlled by the same mechanical advance system the points system used.

on battery powered ignitions, (points and electronic) a battery is required.

[dtkid]

Superb explanation...it actually makes sense to me

[DimitriT]

Focus,

thanks for the explanation. I've always wondered the same.

Follow up question: in priot-to-82 models which have battery powered ignition, do you still need to adjust/replace the points as part of a tune up? From your explanation it sounds like the points are used only for ignition advance. Does this mean they are maintenance free (like the fully electronic post-82 models).

[earlfor]

Points pit and wear down with use. They should be replaced. I replaced mine about every 7-10K miles. Its a good idea to replace condensors at the same time also.

Earl

Focus,

thanks for the explanation. I've always wondered the same.

Follow up question: in priot-to-82 models which have battery powered ignition, do you still need to adjust/replace the points as part of a tune up? From your explanation it sounds like the points are used only for ignition advance. Does this mean they are maintenance free (like the fully electronic post-82 models).

[focus frenzy]

Suzuki used points up to 1979, they switched over to electronic ignition for 1980.

[Tool]

Question for general knowledge:

What is the difference between a CDI-ignition and an Electronic ignition. I actually thought they were the same.

There's a excellent guide at http://www.jetav8r.com/Vision/Ignition/CDI.html

Crude summary:

CDI uses energy stored in a charged capacitor and the coil as a step-up transformer to produce spark.

Points & coil (Kettering) and solid state equivalents use energy stored in the coil when the current flowing in the primary winding is suddenly stopped.

Electronic commonly means any ignition using solid state switching. The first system I put on my car 30 years ago used the points to trigger a transistor switch on the coil primary. Later systems replaced the points with a Hall Effect device or other non-mechanical trigger. Modern electronic ignitions are integrated into the engine management system and do black magic under all engine conditions compared with earlier types.

[Mr. Jiggles]

My old H2 had CDI and put out some impressive voltage. While pulling a plug lead with insulate pliers the current still got to me, so bad that I couldn't let go of the pliers or the throttle. What was it about electronic ignition that made it win out over CDI??

[Tool]

My old H2 had CDI and put out some impressive voltage. While pulling a plug lead with insulate pliers the current still got to me, so bad that I couldn't let go of the pliers or the throttle. What was it about electronic ignition that made it win out over CDI??

:-) indeed. CDI makes a short duration spark and high open circuit voltage. Great for firing wildly variable mixtures found in 2 strokes. They certainly try hard to find other paths to earth when a plug lead is lifted.

With 4 strokes, particularly with the accurate metering of fuel injection, it's better to have a longer duration more controlled spark achievable with other types of electronic ignition.