CDI worth it?
 

I know there have been many discussions on here about the cdi's.
I understand the AC cdi's are well worth it because it changes it to DC and allows more power.
I have a DC stock CDI. Now that I have upgraded to 58.5 BBk and cylinder head, and A-12 cam,
Is a performance CDI really worth it for me? Is that advanced timing just the thing I need? Can you guys recommend one for me? one with true results that you will stand behind.
Anyways just curious about your opinions.

If I were to purchase one, it would be the adjustable one, that way you have some options for tuning. Some have reported good results, some say they are negligible and went back to stock. Some even say they don't last as long as the stock ones too.

I agree about the adjustable one if I were to purchase performance CDI.
Question is doesn't a cam shaft advance timing? So I guess it makes sense to advance the spark timing too.

No. The advancing you need for proper acceleration and fuel burn is in the ignition system. No different then the old car distributors and their mechanical or vacuum advance. The GY6 does not have an ignition advance in the engine, so it relies on the curve built into the CDI.

The timing referred to by cams and timing chain has to do with keeping the cam lobes in their place so the valve overlap and piston stroke stays in proper correlation. With out it, the valves may/will hit the top of the piston and bend and cause all kinds of havoc. Once the timing is set on the chain and cam(s), that timing does not change. The 'advance' some cam grinders refer to, are the lobes opening the the valves earlier than stock cams. Most manufacturers now refer to this a lift and duration, meaning how far the valve opens, and for how long the valve is held open. Generally speaking, lift and duration increase results in more power, but there is some serious science to getting the grinds correct for different power gains. That area, I am not well versed in.

My ATC engine has a mechanical advance on the cam housing. The weights on the advance rotate out similar to centrifugal clutch weights as the engine spins up, moving the pulse generator in relation to the pick up sensor, which tells the CDI when to fire the coil. This results in better acceleration and cleaner fuel burn. I used a GY6 CDI, which also has a an advance curve built in, but I can adjust the mechanical advance to cooperate with it.

The GY6 has a similar pick up coil on the stator, but it does not advance the timing at all, it is all in the CDI. Advanced timing can make starting easier and better performance, but too much advance results in pre-ignition, and can cause engine damage.

i purchased 2 cdi's on ebay last year the first one was a non adjustable. it had an orange case. it worked roughly 10 minutes and conked out. i then ordered an adjustable cdi with a red case. i have mine tuned right where i want it and with almost a year in my buggy it still functions great. the cdi was considerably longer in length than the stocker. the board and casing was filled with clear silicone. to make it fit correctly in the fuse and relay box i took my band saw and cut the extra length off of the cdi,& just ran some silcone around the edges of the end i trimmed. i hope this helps anyone who may be wondering.

Thanks for the info. Is yours dc?
I am trying to find one without paying an arm and a leg.

yes its dc. i think i maay have payed $20 for it.

http://www.ebay.com/itm/161112787085
What do you think about this one? I am having a tough time finding one.

looks pretty good. the price is a lil higher than i expected but u gota pay to play

You can also get advance keyways to advance or retard the magneto. But as for more power you wont know until you try. My buggy 155cc runs best with the orange advance cdi and my wife's 183cc runs best with stock black cdi.

Thanks guys. Could the advancements in cdi also call for more jetting?

Here is what I can tell you about CDI's. I've tried many and have so many just laying around. Weather AC or DC 99% of the performance CDI's are designed for the scooter which due to it's weight will use a different advance curve. Since you have a DC volt CDI I will concentrate on it. I have yet to find a DC volt performance CDI that benefits our buggies. The stock CDI is your best bet since the timing curve is set up for the heavier buggy. As far as the adjustable CDI's are concerned, they all use a dash pot for adjustment which has been proven to be inferior. I had always figured this to be due to cheap manufacture but a few years back at the dealer expo I was talking to the MSD rep and considered having them make them up for the buggy but the price of $400.00 kept me from doing so. What I learned from him made me realize that the design using the dash pot adjustment was the problem and not the manufacturing process. MSD had tried the performance CDI's using the dash pot only to discover they will not hold the timing for long due to the excessive bounce and vibrations and this is why they currently use a usb with computer to program them for the entire circuitry is sealed in the epoxy therefore nothing can vibrate loose. Now I will point out the link you provided for the eBay CDI. This is a prime example of someone who sells a product they know nothing of. First if you scroll down to the diagram it shows 2 wires to the 2 pin plug. I have yet to run across a DC system that has 2 wires going to the 2 pin plug. Only the AC systems use this other pin. Second he states if your headlights come on with just the ign. turned on this indicates a DC system. It all depends on how the system was wired as to weather the lights run off the Stater or battery. Weather an AC or DC volt system they will only produce current while running. All stators put out AV volts then as the AC current passed through the regulator rectifier it is converted to DC volts. AC voltage is more stabilized then DC voltage which is why the old DC generators used on cars years ago your headlights would dim at idle. AC current is a more consistant current and does not fluctuate with RPM. The early ignitions were run off of AC volts and for that reason 2 wires were used on the 2 pin plug of the CDI. Next he states that a DC system will not run without a battery. All the battery is for is to start and that is it. If your Kimco DC volt scooter battery is dead all you have to do is use the kick start and away you go. The last thing he states is you will not be bogged down due to a rev limit for his has none. Most if not all CDI's use a 7800 rpm rev limit. This is not to limit speed or power but to save the engine from premature ware. Unless you have some very serious mods to your engine it will peaked its power output at 7800 rpm and pushing it over the 7800 rpm limit will not give you any more power for it's been used up. Again realize that what I'm saying here refers to buggies only,for scooters are much lighter and is much easier to bring the power curve to a higher threshold. The threshold will be determined by weight over displacement as well as cam and head for which there is nothing currently available performance wise to bring our buggies above that threshold.

Wow make that quote a sticky Tom.
Thanks. I will save my money rather than using something it for something I don't even need. That is pretty much the explanation I was looking for rather than a simple yes or no. ( very thorough) I think the only thing you forgot in your answer was the obvious NO. :lmao:

Tom,

Just wondering, have you ever advanced the timing by rotating the stator plate? It would seem like you would get a bit more power by doing this, but of course, you can go too far.

There is no adjustment there, I use a 5 deg. offset keyway

I have been through sever AC CDI's (2pins). I think I notice slight performance increase (I haven't compared the two statistically with results of my buggy). In my experience from a few different vendors, it isn't worth the money. My latest experience with one aftermarket CDI was somehow it prevented the engine from starting. I was getting significantly lower readings with a multi meter compared to the stock CDI. So if you ever come across your buggy not wanting to start, you're getting fuel and a weak/no spark (exactly my situation) it may be worth your time to check your CDI/coil. If you do decide to buy an aftermarket CDI, keep the old one handy. Mine died in BFE, long walk.

I got this one from the hammerhead performance site. My buggy is ripping around like mad now, but I fixed my jetting/fuel delivery problems so it's hard to tell what the CDI alone did.
http://hammerheadperformance.com/per...cdi-coil-combo

Those are good CDI's but as I said in earlier posts the draw back is that they use a dash pot as adjustment. The adjustment does not hold up after time. My personal experience with that identical CDI both AC volt and DC volt is adjustment will loosen after 6-12 months depending on how much riding you do. The constant jolting will after time cause the adjustment to loosen. This is a common flaw which is why Mallory has gone to the programmable CDI in their off road series CDI's. I would also suggest using a solid copper core spark plug with tungsten tip. Iridium tipped plugs will burn out the electrode in no time. The coil produces 50,000 kv and the CDI allows for a long duration spark which is overkill in a stock or lightly modified engine. The big advantage is in the adjustable timing since it can be custom tuned to the engine until the adjustment loosens and won't hold the timing which will certainly happen in time. I still use this exact type CDI on my single seat blade ACV and my Challenger DCV, but only when drag racing it. Trail riding I switch back to my other performance CDI.