I'm switching from 20 to 10% oil content in my fuel on the CDi engine using the low-oil conversion parts. Any advice as to how I should expect the engine to behave? More/less on the fuel mix?

You will end up leaning the needle a little bit. That will be the biggest change.

Arch

Hi jon
I don't like the low oil fuel. [>:]
Because, a motor becomes hotter, and the power becomes smaller a little bit.
The low oil fuel in the midsummer, this are the worst for me.
I like about 20% oil on the cdi motor.
But, is it cool in Oslo?[X(]
kobago

not a fan of low oil..


gary

having a good amount of oil never hurt any YS.

I agree. I ran the low oil and wasn't impressed. Didn't see enough difference to justify running it. The smoke trail is so faint with the Cool Power 30% LS that it hasn't made a real difference and the engine will run cooler with the 20% oil content.

Arch

I am a fan of the low oil parts that YS offers and I use them. I generally burn 15 plus cases of fuel between each rebuild most of the time + or - a case or two.


gary

I've heard about issues with the pumps and the low oil fuels.

Guys,

I wanted to share my experiences with different fuel viscosities. I undertook some fuel testing a couple of years ago to compare a leading 30% nitro heli fuel (denoted Fuel A in the graphs) with a prototype fuel of similar constituency (Fuel B). There were several aims with one aim being to test the engine performance as a function of variation of fuel viscosity and another to reduce the smoke production during F3A flights. All tests were done on the same day so weather conditions could be comparable. Needle settings were optimised during each test. A single schedule of PO9 was flown and the model landed. Each time crankcase, cylinder head and exhaust gas temperatures were recorded.

The results were surprising in many ways but the relevant bit here was that more oil lead to higher temperatures and lower engine speeds. At the worst case 23 % KL200 oil (standard Klotz super techniplate: denoted normal viscosity oil in graphs) reduced engine speeds by up to 200 rpm compared with the 20% KL198 (denoted low viscosity oil in graphs) mixture with engine temperatures rising by 22 degrees C at the cylinder head.

I guess any thermodynamic system will have an optimum lubrication vs fuel mixture but the evidence here clearly suggests that anything more than 20% oil in a DZ170 leads to poorer performance and higher temperatures, with the incumbant effect on engine longevity.

Best wishes

Keith

Very nice work Keith!
Bryan

Keith, was there any reason for running 23% KL-200? as opposed to the 20% KL 198?

Hi Bryan / Rendegade,

Yes the YS instructions state oil content as 20 - 23%. Most pilots like their engines to last and would try to provide best conditions for longevity and hence might lean to 23% oil. In fact some manufacturers produce fuel to cater for YS engines using 23% oil. This I believe is partly to allow pilots to stick within warranty conditions and / or for the afore mentioned feel good factor. I think however if depends strongly on what oil you use; maybe there is an oil out there where 23% content is good, but clearly this is not the case with the oils I used, and which are present in most heli fuels that YS use.

I hope to do more work like this on the CDi blends; currently I'm using 25% nitro / 10% KL198 oil with great success and my CDi turns an APC 18.1 x 11 at 7950 - 8000 rpm with idle down to 1500 rpm.

Keith

Keith, thanks for that.

I have to admit, while I don't run YS engines, however the information is good. I was a little concerned that a reduction in viscosity between the KL-200 and the KL-198 would create a correspodning reduction in lubricity.

I think I may be wrong :S

Somebody mentioned in a thread a while back that some manufacturers mix their fuel by weight and others by volume so x% oil in one may not be the same as x% oil in another.

I mix by volume but have converted them to weights and use electronic scales to mix now so I don't need a separate mixing container, I just keep topping up the same old bottle adding new ingredients to old fuel and hitting the TARE button on the scales, it also keeps the molar proportions the same irrespective of fluid density changes due to temperature.

Anyway cut a long story short, it just so happens that in my brew of 20% oil (by volume), the percentage of oil by WEIGHT is 22.4%. Could be where YS got their 20%-23% range from?

Just for kicks same brew:
by volume = 15% nitro 20% oil 65% methanol
By weight = 19.4% nitro 22.3% oil and 58.3% methanol........

Ran it with 30/10 now, aerosynth competition oil. Just a quarter turn clockwise on the pump to smooth out some roughness in midrange and it ran nicely, no real change noticed apart from the fact that my tach battery was dead :-)

measuring by weight is the most accurate, not sure what different companies use... volume can change with temperature a little.