Minimum nitro contents
 

Hi Dave,

Here in The Netherlands a litre (quarter of a gallon) nitro costs about 20 to 25 $.
At what minimum nitro contents a YS91 still runs acceptable?

Thanks,
Hans

Minimum nitro contents
 

Greetings from USA!
In warm weather, you might be able to use 15% nitro, but YS engines are designed to use and like higher nitro fuels. Too bad nitro is so expensive over there. It also helps to lower the prop size if you want to runs less nitro and use glow plug heat.
See You,
Dave

Minimum nitro contents
 

It is a problem for us in Europa that these excellent engines are designed to be run on a lot of nitro. My own experience is that the oldest YS 120 SF with small valves runs good on 5 % nitro. A later version of YS 120 SF had bigger valves and was stronger but it needed at least 10 %. Otherwise they will rattle in a way that sometimes is called detonations.