CDI options

[Zman]

I was playing with some different CDI units on our 2004 DE300 and my 2000 XC327 big bore. Both bikes had the original CDI units with black heat shrink. The one on the 2000 was the older box shaped style.

I tried a 2011 250 Six Day dual map on the 2004 and while the dual map button made a minor difference between settings, both settings were considerably more pipey than the original CDI and it put a noticeable hit at about 2/3 up the power band. It also added a little more high rpm over rev. It gave it more of a MX power band that would be fun for open fast tiding but would be a bit too much in tight woods.

My 2000 327 has always had a super linear power band that I could lug like a 4 stroke enduro bike. While it had great power down low and through the mid range and a modest top end, it signed off about 1000 rpm sooner than the 2004 DE300.

I had two CDI options to try on the 327, a blue heat shrink CU7490 and a yellow CU7460 off a 125. I tried the yellow first. I was really surprised how big of an impact it had on the overall power band. The power came on a lot harder just above idle, pulled very strong through the mid range and it added a MX like hit in about 2/3 up the power band. It gained about a 1000 rpm on the top end and revs similar to the 300 with the dual map Six day CDI.

On the down side the yellow version had a negative impact on the low rpm luggability. It seemed to stall easier where it was very difficult to stall previously and it was hard to modulate the power as it came on hard and fast so it spun to easily in technical wet hills.

Later I tried the blue version and it seemed to be a nice mix of my old CDI bottom end power and still has the gained a bit of a hit in the upper rpm and it gained the extra high rpm over rev it never had before.

I think this is going to be a bonus for the Michelin tire company.

One more thought, those old stock black heat shrink CDI units could help out the guys looking to tame their 300s.

[motopsycho87]

Never seen those part numbers before? Got any links or care to elaborate? Check my posts for success with RM125 CDI

I also have a KTM 250SX CDI to try when I'm bothered

[Jakobi]

My 2010 engine and 2013 engines are setup very similarly in terms of cylinder height and head modification but run very differently with the same jetting and gearing.

I haven't mapped the cylinder ports, or compared pipe shape/volume to any extent, however one has a Kokusan CDI and the other a JDRacing Italian model (from memory). I wouldn't be surprised if they have different maps.

Also, TSP has been using programmable CDIs on the Ktm 2T ranges and finding significant gains in power across the rev range simply by tuning the ignition map. Something that's often overlooked I think.

[Zman]

Those part numbers came off the KOKUSAN CDI unit.

[motopsycho87]

Originally Posted by Jakobi

My 2010 engine and 2013 engines are setup very similarly in terms of cylinder height and head modification but run very differently with the same jetting and gearing.

I haven't mapped the cylinder ports, or compared pipe shape/volume to any extent, however one has a Kokusan CDI and the other a JDRacing Italian model (from memory). I wouldn't be surprised if they have different maps.

Also, TSP has been using programmable CDIs on the Ktm 2T ranges and finding significant gains in power across the rev range simply by tuning the ignition map. Something that's often overlooked I think.

How would you compare them?

[Jakobi]

No idea how you'd actually find out what maps are being used in particular CDI units.

Seat of the pants may indicate some variances if testing both units on the same bike with no other changes, and some dyno time would confirm it.

[motopsycho87]

You need an oscilloscope and signal generator, feed a signal that emulates the revs of the bike, supply the input with the required voltage, and measure the output on an oscilloscope... In other words, too much hassle!

There's a lot of info on how different advances and retards generate different power, but not a lot of info on whole curves and power at specific revs.

Was thinking about getting my bike up to a dyno and testing out the ec300, rm120 and sxs250 cdis.... Should I set up a PayPal fund? Lol