Hi!

I've read a lot about 20/20 YS fuel over the last couple of years. I am thinking about buying a .91AC, but don't want to spend the money it will take over the years ahead to use 20% nitro.

Will this engine run well on 5% or 10%, or even FAI? I know it won't make the same amount of power, but what about idle, transition, reliability, etc.?

Thanks,

Dave

We have some who run them on 15% in warmer weather, but less nitro is asking for problems with idle and transition. I don't recommend anything less than 15%.

If you do it, you will also want to drop back in prop size to keep the rpm up. The 91 likes to run at 9000 or a bit more.


Good Flying,
Dave

Thank you for the info. I appreciate the quick response.

Dave

I'm running 2 YS45 2c. with Byron 5%nitro and 20%oil with excellent results. Very low idle and perfect transition ev'ry time.

A buddy of mine is running his YS91 with the same fuel as his other engines (Power Master 10%nitro) and he gets the same results.

So if I were you, I would try the fuel you're using normally cause if you're like me, I hate to have to carry many different kind of fuel and if the engine doesn't run as supposed to (perfectly), then and only then I would switch to 20\20.

But saying a YS can't run good on lower than 15% nitro doesn't convince me. In fact, I would pay more attention to the oil content than to the nitro.

Just my two cents opinion.

I have several YS 4C and I use either of 10% Coolpower or YS 20/20. I have unlimited idle control on both fuels.
A carefully broken in engine will idle much better on most reasonable fuels.

When moving from 10% to 20% I have to richen the needle.

20/20 is great as it makes my non-smoke planes seem like smoke system planes; I always try and run my engines on the rich side but have never compromised on power.

Great Engines these YS.