I'm new to the gas engine arena.......I just bought a CHI ignition system for my 31cc Ryobi, will a 6 volt battery give a hotter spark than a 4.8v battery?

Marc

Can the CHI ignition tolerate a 5 cell pack? If it can, I would believe it would provide a more robust spark..

With a 31cc Ryobi you don't need to worry about a hotter spark.... The CH on 4.8v will run over 10,000RPM

Thanks Terry........My unit has the syncro spark built in. How can I be sure that it is actually retarding the timing at idle. I'm still trying to get the engine to idle slower that 2300 rpm. (ideally about 1900-2000) Any suggestions would be greatly appreciated.

Marc

A. Put a CH ignition without the SS on the engine and check RPM
b. Use a timing light and some marks on the prop hub.

At what voltage will I see a performance issue? Would 4.5v be enough to run the ignition? Just curious as to how critical I need to watch the voltage.

Thanks,
Marc

As the battery gets low the ignition will start to miss at WOT. If you ignore the miss it will get worse and then the engine will get real quite.
Charge before 4.4v

Great info........sorry for so many questions. I bought the unit from one of the engine manufactures and didn't get any documentation. I had to go to the CH website to download instructions. I'm sure that I'll have more questions as time goes on.

thanks for your timely response,
Marc

In response to the timing light, we did that but couldn't get the timing light to work...after we put everything up we realized that the high tension lead has quite a bit of shielding which probably fouled up our testing.

Marc

Curious, I spoke w/ Adam at BCMA. He suggested a 4 cell vs a 5 cell. Said the 5 cell would "just draw more current".

Dave

The post below by TKG answers this much better than I did so I divert to his post for the reasoning for using a 4.8 volt pack instead of a 6v pack.

When we test the CH ignitions we use a 4.8v regulated power source, we also use a spark plug with the side electrode cut off. That is about a .125" gap. The ignition is run at 12,000 rpm and is expected to fire across that gap.
The spark voltage at the plug only goes as high as need to fire the gap. Once the arc starts there is no futher increase in voltage. It takes about 12kv to fire a plug in a running engine. The CH voltage can go to over 25kv, so there is enough reserve to fire a fouled plug.
Make you life simple use a 4cell pack, for our engines and the rpm turned, 6v gains nothing

Great info guys.......I'm new to this forum and it's got a ton of info. I'm sure that I'll be posting more questions. I'll be using a 1200 mah Nimh pack for my ignition system.

Thanks again,
Marc

Originally Posted by TKG

When we test the CH ignitions we use a 4.8v regulated power source, we also use a spark plug with the side electrode cut off. That is about a .125" gap. The ignition is run at 12,000 rpm and is expected to fire across that gap.
The spark voltage at the plug only goes as high as need to fire the gap. Once the arc starts there is no futher increase in voltage. It takes about 12kv to fire a plug in a running engine. The CH voltage can go to over 25kv, so there is enough reserve to fire a fouled plug.
Make you life simple use a 4cell pack, for our engines and the rpm turned, 6v gains nothing

Yes - BUT (there is always a but) some new ignitions on the market are designed around higher voltage inputs - -I guess the designs have other issues than that in a straightforward spark setup - the new MVVS needs at least 6volts to start and a 7-8 volt setup is required -some others were setup to use the little LiIon setups -up to 9 volts

Is the spark any hotter ? I bet not as hotter (more current) sparks simply erode the plug. Firing under very high pressures like a four stroke turbo fed race engine sees - is not part of our two stroke -even piped engines -see.
some racing two stroke open exhaust engines turn up very fast - but the cylinder pressures are LOWER than torque tuned two strokes, using tuned systems .
As Terry notes- for all the rest - 4.8 does the job nicely - I do opt for modern NIMh extremely low impedance cells -a 4 cell 1400 ma Intellect pack weighs under 4 ounces and the output will supply all the ignition "spike" can grab--way faster current output than any older packs having double the ampere hr ratings.