RE: YS 1.70DZ?
I guess there are some out there. Here is a quote from Troy Newman off the YS support forum.
"170 has a little more low end torque. As with all of Yamada's changes. A little more power here, a little smoother there.
They are always playing with things to make the best engines, with the best power, lightest weight and so on.
The reality is the 170 will likely replace the 160 but they are 99% the same engine. They bored it out to give more displacement. As a result some parts like the piston-ring-sleeve, case, head had to be changed all to fit the larger bore. Its not a case that the 160DZ is obsolete its just that the newer better power setup for the future is the 170. I know I will still use them interchangebly. The difference is just not that much. I have several 160's and don't see changing them out just to go to 170's. They really work the same. I run the same props, same fuel and they pull the same in how I'm flying the models.
The principles and ideas are the same since the 140DZ.
Larger displacement means you can get more power lower in the throttle band. This is where the 160 and 170 shine. They are brutes at pulling the models down in the low power curve of 25% to 66% throttle."
Troy