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YS 91AC CDI - Lubrication

Old 06-18-2012, 08:51 AM
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Default YS 91AC CDI - Lubrication

I have a couple of YS 91AC engines that I am planning to switch from glow to CDI while still using glow fuel. It is my understanding that the fuel consumption of CDI is reduced by ~30%, so my concern is with lubrication. Whatever the A/F mixture ratio is, it will always contain the original proportion of oil in the fuel (using PowerMaster Heli 15% nitro 23% LV oil) , so will there be a lubrication problem when leaning the fuel mixture by 30% to work properly on electronic ignition? As an aside, Mark Fuess of Greater Southwest Aero Modelers has changed a 91AC and a 110 to CDI and never reported a problem. I have read the change to CDI on these engines leads to cooler running engines, perhaps the high oil requirement is to cool the engine and deal with the higher temperature on the non-CDI version.

On a related topic, I find interesting that the Saito FG-20 gasoline engine requires only 5% oil while the glow version requires 20%. Both have the same exact connecting rod part (no bushed ends or needle bearings), yet the gasoline version runs much hotter and has an A/F mixture about half of the glow version. I realize that gasoline has some lubricity, but it can't that much to drop the oil content by 15%. I know the YS utilizes a 2 stroke lubrication scheme. Thanks...
Old 06-18-2012, 09:14 AM
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Default RE: YS 91AC CDI - Lubrication

Interesting conversion, but this is a direct support forum and the 91AC was not offered as a CDI so you might be better served posting this to the general engine forum. I will say that I loved my 1.70 CDI for it's reliable low idle.
Old 06-19-2012, 04:14 AM
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Default RE: YS 91AC CDI - Lubrication

The Oil content on the YS depends on the engine design not the ignition, the latest 170's and the 170CDI and on ar low oil engine design.

I use 23% oil in my engines, even on the low oil ones, it works equally well and there is no problems at all with the CDI.

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