What is the full function of CDI?

[Lunytune]

Please, don't just give me the simple answer, "controls the electrical and igniton". I want more detail.

My JDM DIO seems to "coast" when it hits 60 kmh (37mph), motor quietens as though a governor is kicking in. As soon as speed drops, you can hear the engine begin to roar again. Is that the CDI? Speed is not an issue, as I don't really care to redline the engine anyway. A governor would be the best protection from my WOT son in law.

[CaptDan]

Lunytune requests:

Please, don't just give me the simple answer, "controls the electrical and igniton". I want more detail.

I'm not an electronic ignition expert, but I play one in my mind.

(C)apacitor (D)ischarge (I)gnition -solid state version of the venerable point-based mechanical ignitions of yore - is essentially a microprocessor-driven circuit programmed to 'fire' at precise time intervals. Because there are no moving parts, these units are virtually bomb proof and don't wear out. Well - put another way - they can CRAP out. But that's another issue.

My JDM DIO seems to "coast" when it hits 60 kmh (37mph), motor quietens as though a governor is kicking in.

I reckon that's a function of the CVT - or (C)onstantly (V)ariable (T)ransmission. Consisting of a pair of pulleys, a drive belt and a series of rollers, this mechanism is in a constant state of shift. Depending upon the wheel speed, the 'variator' (fancy name for a pulley that expands and contracts athwartships) alters the ratio between it and the aft drive pulley. At higher speeds, the CVT 'relaxes', allowing the engine to chill out. When throttle demand is engaged, the opposite occurs, providing more torque to bear on the drive belt.

Simply put, when you reach a certain speed on flat ground, your Dio motor is taking a break, enjoying a Lucky, and reading the Sunday funnies.

Hope at least 21% of the forgoing is helpful.

CaptDan>

[eliteguy50]

CaptDan- great explanation of the cvt.
but if it is coasting (speed drops) and then roaring...sound more like it is hitting a limiter rather than the gradual change (assuming constant throttle position, not an operator snapping the throttle) experienced in the cvt

[devenex]

I've heard that JDM CDI's are restricted. Not sure why Honda went restricting mufflers, intakes or variable pulleys here in the US, but I would guess is a difference in laws/regulations.

This is why you see those "performance" CDIs on ebay all the time because for ppl w/ some models it actually is a performance gain as with one mod all restrictions can be shed.

[bradthreee]

Your stock tranny gears only let you go so fast. Sounds like its time for some aftermarket replacements.

[Lunytune]

So far so good. Don't stop.
You gurus are going to have to get together, whether it's the CDI or Variator. I tend to agree with Eliteguy more than Dan on this. It would seem the variator would take all the powerplant would dish out. In other words, when it red-lines. I do not sense the powerplant redlining on the DIO, just coasting, sipping RC, and eating a moon pie. But on the other hand, I sense redlining with my SA50/Polini. Since speed is not my goal, I kinda wish the SA50 acted like the DIO. However, the DIO will outperform the SA50, in coming off the line and top speed too. Yeah, I already raced my SIL, me on the SA, him on the Dio, so I know which one is stronger. The JDM Dio.

Tazland sent me a couple of extra jets today, one for the Elite Dio I'm building, and an extra I ask for to put in the Polini. Both are 100's. So we'll see how that effects the Polini.

Don't stop. I want to learn more about the CDI. BTW, I just this morning realized where it is. It's the silly little thing that gets in the way of battery replacement.

[devenex]

veedubh even brought this up when you were asking about how much a dio was worth:

jdm scooter have speed restricted cdi , there are many aftermarket cdi, posh, daytona, kiss, kitaco and many mores.

from here: http://www.hondaspree.net/phpBB3/viewto ... CDI#p82676

[Lunytune]

veedubh even brought this up when you were asking about how much a dio was worth:

jdm scooter have speed restricted cdi , there are many aftermarket cdi, posh, daytona, kiss, kitaco and many mores.

You got me dude. I missed that somehow, but I do have a good excuse... called old timers disease . Refreshing my memory on that helps a lot in my understanding of my Dio performance. I have no intention of upgrading it though. I like it the way it is. Wish I had a restricter like that on the SA50/Polini.

[devenex]

No sweat Luny, I was mostly frustrated because I've heard it a million times but couldn't find a really good source. Then I searched this forum and that made me laugh a little as the 3rd result.

[808BMW]

I'd rather have a CDI restriction.

You can buy an aftermarket cdi pretty cheap, and if you ever want it off, it just unplugs and you can plug in your stock cdi.

[Arnadanoob]

Unless you were planning on making and designing your own CDI (pointless for a SA50), the inner workings of a CDI is pointless as it's one of those fine tuning devices that don't exactly increase power by itself, but it may help to squeeze out a little more on a very modded engine.

The main purpose of it is very similar to a car's ECU however not nearly as complex and detailed. It has a capacitor like the name implies that feeds the proper amount of power to the coil and determines when the coil fires. So it does control your ignition timing and its timing curve in that respect however some OEM CDI's do have restrictions limiting your rpm range. The reason why most would replace is because of a defect in the unit or to remove a restriction like in the Japan units.

Some have the cheaper race CDI's which we've found to do almost nothing, don't improve power (but at least doesn't hurt it), don't affect much of the spark timing and doesn't provide a hotter spark. The ones we used to have custom made for us (from the Philippines) were a unit so large it's about the size of a brick, had multiple large ultra fast charge/discharging capacitors, a circuit to fine tune the ignition curve (this was necessary for bores having unique port timings in relation to the pipe being used) and a spark so hot most plugs would only last about 100 hours before requiring a replacement due to severe electrode wear.

- The key things about a CDI unit is don't replace it unless its defective or restricted.
- Install the unit in an area where it can receive some ventilation (because it does get warm) but not out in the open where moisture can get to it.
- Ensure the area were the wires come out of the unit is fully sealed (usually is by the factory with epoxy).

[Arnadanoob]

However if you really must know, this is just a small introduction of a CDI unit.

http://www.gill.co.uk/products/digital_ ... nition.asp

[Lunytune]

However if you really must know, this is just a small introduction of a CDI unit.
http://www.gill.co.uk/products/digital_ ... nition.asp

I LUV IT!!!
Having grown up with points and condensors, etc, this CDI stuff is absolutely fanstastic. Now I know why I don't work on my own car anymore.

[Accolay]

I've heard that JDM CDI's are restricted. Not sure why Honda went restricting mufflers, intakes or variable pulleys here in the US, but I would guess is a difference in laws/regulations.

This is why you see those "performance" CDIs on ebay all the time because for ppl w/ some models it actually is a performance gain as with one mod all restrictions can be shed.

I think that's it. Like the 1987 SE50P I have vs. the 1987 SE50S. The "P" model is moped legal (at least in Minnesota), a restricted 49cc and top speed of around 25mph, while the SE50S model has a top speed of (I'm told) 40-43mph. I believe the only difference is in the CDI...

[Lunytune]

I've heard that JDM CDI's are restricted. Not sure why Honda went restricting mufflers, intakes or variable pulleys here in the US, but I would guess is a difference in laws/regulations.

I think that's it. Like the 1987 SE50P I have vs. the 1987 SE50S. The "P" model is moped legal (at least in Minnesota), a restricted 49cc and top speed of around 25mph, while the SE50S model has a top speed of (I'm told) 40-43mph. I believe the only difference is in the CDI...

Government regulations are killing us and Honda is just trying to adjust.

Now that I'm learning more about scooter CDI's I realize that is the same device in our cars and trucks that control ignition and fuel injection. Aftermarket Performance companies make CDI's which change the timing curve and fuel injection to produce more power, fuel efficiency, etc, than the OEM vehicle. People have been improving on Detroit's product for years, and I doubt that will change.