How A CDI Works (Gen 1) - Page 2 - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

 1Likes
Reply
 
LinkBack Thread Tools Display Modes
post #11 of 34 Old 09-17-2014, 10:00 PM
1st Gear
 
Join Date: Jul 2013
Posts: 62
This is an excellent discussion! The Damocles video should be a must watch.

Been pondering the same issues. Was hoping some poor KLR rider's CDI mounting bolts would vibrate off and I'd find a CDI in the street to de-pot.

Interesting thought on how much effort goes into cam timing and carb tuning and zero into advance curves.

The AU article and the stepped core idea is nifty. I was thinking we had a magnet in the coil and a reluctor lump on the rotor (?) so might work better or worse?

If the CDI / pickup coil has an advance curve, could you measure the advance with an old fashioned inductive pickup timing light?

I have a $70 single channel scope. And am building an Aduino datalogger. Still trying to figure out if I can get an advance curve using all of the above.

Re: TPS -- I've heard that the Gen 2 bikes have a potentiometer in the throttle control assembly-pretty cheap on ebay
. If somone can confirm that's true, I'll buy one and include it in my project

Also thought about a slide position sensor. I'm thinking (without trying it) that the slide position could be mapped to a vacuum signal taken from the carb top cover. Vacuum force & spring rate determine position exactly (I think) unless,the slide gets hung up (stiction)

On the manifold vacuum measurement- my old fashioned Bourdon tube gauge is bouncy, but you can still estimate it. I think a digital filter with a long time constant (10-20 revolutions) would be fast enough to do meaningful Arduino control of spark advance. All the arduino would need to do is send a 5v signal to replace the pickup coil signal(? Hypothesis)

So many thoughts, so little time. Any comments or help on my projects would be much appreciated

UncleWray's Motorcycle Painting & Upholstery

Our Motto: "If it looks real bad from a mile away, you know you came to UncleWray"

Our Guar-ron-tee: "If it doesn't look bad from a mile away, we'll drive you closer till it does!"
UncleWray is offline  
Sponsored Links
Advertisement
 
post #12 of 34 Old 09-17-2014, 11:29 PM Thread Starter
5th Gear
 
Join Date: Jan 2011
Posts: 4,330
Quote:
Originally Posted by UncleWray View Post
If the CDI / pickup coil has an advance curve, could you measure the advance with an old fashioned inductive pickup timing light?
Yes!

I think a procedure exists in Clymer, or perhaps in the factory Service Manual, where a timing light is used to verify spark advance vs. rpm.

As I understand the OEM arrangement, the pickup coil and timing mass on the rotor send a trigger pulse to the CDI at the same angular flywheel rotation angular position, regardless of rpm. The spark advance is determined electronically, depending upon the frequency of trigger pulses.

CAVEAT: Postulation, speculation, and wild guess on my part: No authoritative reference available. Only . . . since the geometry is unchanged between the timing mass and pickup coil, and the only trigger input comes from the pickup coil connection, the theory/premise seems plausible, to me; although it may be totally in error.

========================

That said, don't know how the Generation 2 spark advance might be structured; perhaps similarly: Pickup coil pulse rate electronically determines advance of ignition coil electronic switch opening (consequently inducing a spark from decay of electromagnetic field in ignition coil primary winding, "stepping up" voltage via the secondary coil winding).

--------------------------------------------

Interestingly (to me, anyway), the Generation 1 and the Generation 2 ignitions perform in decidedly opposite ways: An electronic switch CLOSES a circuit in a Generation 1 ignition, discharging a capacitor across the ignition coil primary windings, "transforming" a high voltage in the secondary winding to produce a spark; while an electronic switch in a Generation 2 OPENS a circuit (the saturated primary ignition coil winding) to induce a high voltage in the secondary windings producing a spark . . .

======================

Oh, yes; must clarify! The CDI video is not "mine," it was only discovered by me on the Internet! I thought the URL would sufficiently indicate its source, but the URL does not show (unless you "quote" the post where it's contained), since the video clip is embedded. Wish I could claim credit, but . . . I'd have to violate my anti-plagiarism principles to do so!

Last edited by Damocles; 09-17-2014 at 11:48 PM.
Damocles is offline  
post #13 of 34 Old 09-18-2014, 11:07 AM
4th Gear
 
Join Date: Oct 2013
Location: Chilliwack, BC, Canada
Posts: 1,481
CDI (which discharges a capacitor to obtain high magnetic flux increase) is common place in small engines while automotive tend to use magnetic field collapse because of the higher electrical capacity of automotive systems. Magnetic field collapse is the system used with breaker point ignitions powered from the battery. It is generally a bit simpler to avoid the use of the extra stator winding needed to create the charge current for the capacitor by using the DC power from the battery system.

I'm surprised that Kawasaki hadn't done this from the outset but lots of these things hold over. It would be simple enough to convert a Gen1 to use a Gen2 module, assuming trigger coil compatibility, but converting Gen2 to Gen1 module would require a stator change. This is fairly common in dealing with older engines such as the EM600 Honda in the garage at the moment. Belongs to a family member and CDI box is bad and not available. I'm waiting for a small motorcycle module to arrive to get that one going.

I jumpered a GM HEI distributor module with small battery and 12 volt motorcycle coil to check the engine's other condition by running it before ordering. The 'scope showed reasonable trigger and charge coil patterns. One could convert in the manner I jumpered but this would require a battery which would complicate, add expense so converting from "Gen1 to Gen2" seems a poor option. I'm going to try a motorcycle CDI as that will likely charge and trigger.

He has an acquaintence who offered the use of a running EM600 so will check the ignition advance once we determine a means of placing marks on flywheel or fan. I don't know if the EM600 has fixed ignition timing as typical of most older small engines, or whether it has a module based advance. If it runs a fixed advance, and the motorcycle module adds advance, this could be a problem.

Other issues are that there are various trigger strategies used, some engines use a set voltage level to trigger as in the example posted at the beginning of this thread. These will have timing affected by air gap and RPM will tend to advance timing because the speed of cutting of the magnetic lines will be higher at higher RPM which equals higher voltage. Other systems use the reversal of current polarity in the trigger coil circuit to trigger. This is created by the movement of a north-south magnetic source across a coil.

Others use optical (rare today) and other variations of reluctance. One should read that "How it works" as an illustration of one strategy and not to conclude that this is how any specific system functions. Usually trouble shooting will be fine if following the scenario in the post but one may go far down the garden path in trying to adapt or change the system if one concludes that the wrong strategy for triggering is used.

As usual, things are more involved than indicated by magazine articles which are mainly intended for entertainment. Read any camshaft related web discussion and you will see what I mean.
Normk is offline  
 
post #14 of 34 Old 09-18-2014, 11:21 AM
4th Gear
 
Join Date: Oct 2013
Location: Chilliwack, BC, Canada
Posts: 1,481
Simple as pie with a timing light to determine if the system is advancing although not something technicians bother about with modern systems because advance failure is virtually unknown. We did these checks routinely during tune-up with automotive mechanical distributors because the advance would sometimes seize, springs corrode, pins and bushings wear and so on.

Hook a timing light to the plug wire, start the engine and use the light to locate the flywheel "F" mark which should be lined up with the index marks at the center of the viewing port. Then increase engine RPM and the mark should be seen to "move" which indicates advance (moving to earlier) of the spark. Determining the advance curve (advance in degrees graphed to engine RPM requires some means to read the amount of advance. For most checking purposes this can be estimated by comparing the interval between the firing mark and TDC (top dead center mark). Since the initial advance is known, the interval between these two marks will indicate the spacing on the flywheel compared to that number of degrees. Simple enough to estimate.

If the advance places the mark out of sight and/or if more accuracy is required, one can scribe marks onto the flywheel using a degree wheel/protractor, or use an electronic device to retard timing light firing and then read the amount from the timing light. My present light lacks this function because the expense is not warranted for my limited use but most technicians involved with automotive high performance or racing will likely own one. In the old days, every tune up specialist owned an indexible light.

Off to rescue a friend's no start farm tractor.. good news is it's not diesel.



[QUOTE=Damocles;349682]Yes!

I think a procedure exists in Clymer, or perhaps in the factory Service Manual, where a timing light is used to verify spark advance vs. rpm.
Normk is offline  
post #15 of 34 Old 09-18-2014, 05:29 PM Thread Starter
5th Gear
 
Join Date: Jan 2011
Posts: 4,330
Quote:
Originally Posted by Normk View Post
CDI (which discharges a capacitor to obtain high magnetic flux increase) is common place in small engines while automotive tend to use magnetic field collapse because of the higher electrical capacity of automotive systems. Magnetic field collapse is the system used with breaker point ignitions powered from the battery. It is generally a bit simpler to avoid the use of the extra stator winding needed to create the charge current for the capacitor by using the DC power from the battery system.
I think whether a CDI is AC powered (as in the Generation 1 KLR650) or DC powered is a function of design decisions. While the older KLR650 CDIs are powered by AC from the stator exciter coils, some motorcycle CDIs are powered from 12 VDC, or battery power.

The complete CDI circuit in this latter case involves an inverter, converting DC to AC, a transformer, stepping up the consequent AC voltage, and rectification of this higher AC voltage to charge a capacitor. Further "downstream," the systems are similar (capacitor discharged across ignition coil primary winding to produce high voltage in secondary winding and resulting spark).

This information corroborated by the author of, "Understanding Stators" on ADV.

Basically, Generation 1 ignitions are capacitive discharge ignitions, and Generation 2 ignitions are inductive discharge ignitions, like our old points-condenser-coil ignitions. Each approach has its strengths and weaknesses.

I favor the Generation 1 ignition; as a minimum, the bike will run with a dead battery or without a battery at all. Generation 2 must have 12 VDC to run, either from an adequate battery, or sufficient output from the alternator/rectifier circuit.

As to implanting a Generation 2 ignition on a Generation 1 KLR650; better have a compatible ignion coil, along with the latter-day igniter. The resistance specifications of the two coils are considerably different, the Generation 1 coil functioning essentially as a transformer, and the Generation 2 coil primarily as an inductive device . . .

Last edited by Damocles; 09-19-2014 at 06:19 AM.
Damocles is offline  
post #16 of 34 Old 09-19-2014, 12:21 AM
4th Gear
 
Join Date: Oct 2013
Location: Chilliwack, BC, Canada
Posts: 1,481
Yes, I know. I do these things frequently. ;-)

Last edited by Normk; 09-19-2014 at 12:32 AM.
Normk is offline  
post #17 of 34 Old 09-19-2014, 07:14 PM
1st Gear
 
Join Date: Jul 2013
Posts: 62
My earlier excitement about advance curves was misplaced....

My thought was--I don't see how they would get spark advance with the circuit in the video. If Kawi left it out, think of the performance gains!

Doh! They didn't leave it out, as shown on page 210 of the holy book of Clymers. The fact that it's there & is probably about 30 degrees makes wringing another 50 hp ;-) out of the KLR beast unlikely.

Was trying to think how the CDI might generate that advance curve--needs another internal circuit/logic to provide a delay. I like the pickup coil voltage idea cause it would change nicely with engine speed. Must ponder.

Back in the '70s (1970's not 1870's) I had a timing light with the dial on the end. Those were the days. Wish I'd kept it and the '67 Olds 442 that I used it on.

Also in the 60's and 70's, there was quite a buzz in the DIY market for Transistorized Ignition. Actually CDI. They sub-optimized the system so you could use your old magnetic collapse coil. Would have worked better if they'd used a transformer coil like the KLR Gen 1

Another musing....I think the big difference in ignition design philosophy Gen 1-2 was the kick start possibility of the Gen 1. Maybe they sold it that way in some markets. No kick start and you might as well delete the exciter coil and run the ignition off the battery. Can probably get a few more watts out of the stator if you don't have to fool with the exciter coil.

UncleWray's Motorcycle Painting & Upholstery

Our Motto: "If it looks real bad from a mile away, you know you came to UncleWray"

Our Guar-ron-tee: "If it doesn't look bad from a mile away, we'll drive you closer till it does!"

Last edited by UncleWray; 09-19-2014 at 07:21 PM.
UncleWray is offline  
post #18 of 34 Old 09-19-2014, 07:40 PM
4th Gear
 
Join Date: Oct 2013
Location: Chilliwack, BC, Canada
Posts: 1,481
I didn't recognize that you thought the KLR ignition lacked speed related ignition advance or would have clarified. It does have advance although I don't know whether the advance is air gap related, processor related or a combination. Some have claimed a modest improvement in the KLR from a programmable ignition module although not certain whether the claims were from someone who had actually done the work and measured or the more probable that it was from someone who read a magazine article and began to make claims based on this exalted expertise. ;-)

Most bike ignition advance is simply engine speed related, as I tried to describe earlier and this must assume maximum operating temperature conditions and wide open throttle since there is no way for the system to detect otherwise. My younger son has promised to lay out a processor for me which would allow ECT input, perhaps ACT, and allow an input engine load. Sorry, ECT = Engine Coolant Temperature; ACT = Air Charge (intake) Temperature. Not certain that this is worth the effort but part of that is that I'm becoming amazingly lazy.

There should be a modest gain available through optimizing the advance curve for WOT (Wide Open Throttle) even if one ignored the ECT, ACT, and engine load factors. One must assume some consideration regarding emissions, as evidenced by the legal requirements at time of sale and of the exhaust cam retard & lean air fuel jetting.

A simple advance of the exhaust cam, re-jetting and remapping of the ignition advance should improve things. You will be well aware of those factors from your 442 experience.

While the improvement is unlikely be 50 hp ;-), some gain might be seen.

Mapping on top of that to improve partial throttle/partial throttle ignition curve might provide a nice increase in ride-ability and mileage.

I'm battling with some tubeless tire issues at present but might get to some advance work of son comes up with a platform which isn't too onerous to program.

I keep hoping that someone has done the work and will simply offer the simple and inexpensive solution.

Still, it might be out there. How many years before EM did the dyno work and posted the exhaust cam advance? Some must have known of that simply from having made a timing mistake.




Quote:
Originally Posted by UncleWray View Post
My earlier excitement about advance curves was misplaced....

My thought was--I don't see how they would get spark advance with the circuit in the video. If Kawi left it out, think of the performance gains!

Doh! They didn't leave it out, as shown on page 210 of the holy book of Clymers. The fact that it's there & is probably about 30 degrees makes wringing another 50 hp ;-) out of the KLR beast unlikely.

Was trying to think how the CDI might generate that advance curve--needs another internal circuit/logic to provide a delay. I like the pickup coil voltage idea cause it would change nicely with engine speed. Must ponder.

Back in the '70s (1970's not 1870's) I had a timing light with the dial on the end. Those were the days. Wish I'd kept it and the '67 Olds 442 that I used it on.

Also in the 60's and 70's, there was quite a buzz in the DIY market for Transistorized Ignition. Actually CDI. They sub-optimized the system so you could use your old magnetic collapse coil. Would have worked better if they'd used a transformer coil like the KLR Gen 1

Another musing....I think the big difference in ignition design philosophy Gen 1-2 was the kick start possibility of the Gen 1. Maybe they sold it that way in some markets. No kick start and you might as well delete the exciter coil and run the ignition off the battery. Can probably get a few more watts out of the stator if you don't have to fool with the exciter coil.
Normk is offline  
post #19 of 34 Old 09-21-2014, 07:26 PM
1st Gear
 
Join Date: Jul 2013
Posts: 62
The old 442. As a late teenage tuner I read the magazines and did stuff. I made it run much worse than stock so Dad made me put it back the way it was...

I've been looking at microprocessors and Arduino seems like the one for me. EZ software, lots of cookbook hardware and plenty fast processing ( I think) for the KLR. Could be wrong but thought the Megasquirt guys were using some variant these days.

UncleWray's Motorcycle Painting & Upholstery

Our Motto: "If it looks real bad from a mile away, you know you came to UncleWray"

Our Guar-ron-tee: "If it doesn't look bad from a mile away, we'll drive you closer till it does!"
UncleWray is offline  
post #20 of 34 Old 09-21-2014, 07:45 PM Thread Starter
5th Gear
 
Join Date: Jan 2011
Posts: 4,330
Quote:
Originally Posted by Normk View Post

A simple advance of the exhaust cam, re-jetting and remapping of the ignition advance should improve things.
Simply advancing the exhaust cam one cam sprocket tooth subtracts 15 crankshaft degrees of valve overlap.

I don't understand how jettisoning valve overlap produces the claimed 10 % horsepower increase across the rpm spectrum. Don't deny it's there, just wonder how it's produced. Most (if not all) "performance" cams have increased valve overlap, not reduced (compared to stock).

Automobiles with "variable valve timing" advance BOTH intake and exhaust valve timing with rpm, not just the exhaust valve timing alone. Kawasaki advanced both intake and exhaust valve timing on its V-twin ATV engines, transitioning from utility to sport models, moving the horsepower peak upward, rpm-wise.

I'm sure men of good will conscientiously performed the "MC Mod" experiments, but if only a slight gain was measured, I'd wonder at the accuracy/precision/repeatability error budget of the dynamometer involved.

---------------------------

I imagine spark advance is determined by the pulse rate of the pickup coil output. I don't cognate the "air gap" considerations mentioned; don't know where the air gap might be located, its significance, or its adjustability; but . . . that's just ME!

Last edited by Damocles; 09-21-2014 at 07:48 PM.
Damocles is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Kawasaki KLR 650 Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Cdi Jim Sizemore 1987 to 2007 Wrenching & Mods 9 08-05-2013 05:26 PM
CDI temp Jeepflambe 1987 to 2007 Wrenching & Mods 5 03-21-2013 09:28 PM
CDI Ignition box? txroller How To's & Tech Guides 1 07-14-2011 10:55 PM
CDI Ignition box? txroller Other KLR's - 250, 600, Tengai, C Models, KLX... 2 07-14-2011 01:44 PM
CDI extra wire Raven7777 1987 to 2007 Wrenching & Mods 1 12-19-2010 10:31 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome