Hallo: I read sometime ago that the os 1.60 fx has 145 deg. of exaust port timing . Considering the use with tuned pipe ( in pattern flight) can be a good idea to increase these timing to about 155 deg.?

I don't think you need to change the exhaust port timing for pattern use. You will need to change the size of the intake ports which is vert risky proposal. Check this web site for recommended set up and you will be fine. I use this engine for two or three years in pattern with no problem. Very reliable engine.

http://www.rcpattern.com/2cycle.htm

Karl Mueller has done some work on porting the 1.60. THis is the same guy who makes custom headers for the engine. You might try contacting him.

Jon

I increased the exhaust duration about 12 degrees with no ill effects on idle or midrange. Top end power increased 200-300 rpm with the same pipe if I remember right. I don't have my records with me now. I use a mixture control carb but I think it would work fine with the stock carb.

If the plane has enough power now it may not be worth the trouble.

I got around 200 more RPM by going to an old OS .61 RF ABC-P carb; larger bore. An OS 1.40 carb gives similar results. It helped, but what the engine really needs is more low to mid range torque with an accompanying instantaneous throttle response. That is where the YS really excels over the OS 1.60. I've heard that the mini-pipes for the 1.60 may help this situation, but I converted to YS without trying it. There is another thread on this topic.

I also found on two different airplanes that a 17x12W works much better than an 18.1x10 on the 1.60. Better uplines, in spite of the larger pitch. I suspect that the smaller diameter helped it spin up faster also.

The attraction of the 1.60 to me was the price and availability, bang for the buck. As you get further and further away from the stock configuration, the advantage goes down. The YS gives you that out of the box. Higher initial cost and more expensive fuel, but you don't have to mess with it.

I have done alot of experimenting with the OS 160 over the past four years. I am currently using one in a Focus II. The set up is..... OS 160, Perry Pump, Mueller Header, Hyde Mount, Macs 1092 Pipe, Cool Power 15%.
After trying all of the two blades with about the same results eveyone else has had, I decided to try a three blade. Went with a 15 x 13W APC and results are astonishing! It idles all day long at 1600 RPM
and has a top end of 8400 RPM, the throttle response is in a complete different league that any of the two blade props, and unbelievable braking on downlines! The engine has tork at any RPM with this prop.
Yanks the Focus II off the ground at less than 1/2 throttle. I would suggest to anyone using the OS 160 to try this prop. I wouldn't change anything on the engine until I tried that Prop.

Greg

I agree with Greg. I used the three blade prop re-pitched and results were impressive. This was around 3-4 years ago. I never went back to two blade using the OS 160. In that time I was flying the Focus I and the Hydeout. Downline breaking was excellent also.

Vicente "Vince" Bortone

I flew a three blade for a couple of years, 15.75x11 (Lockhart repitch). Then I got an airplane that just wouldn't track well in and out of radii. Went to a two blade, and it transformed the airplane. Some planes just need the additional diameter of propwash. Went to a two blade on my backup, and it worked better on that also. Every airplane is different, and responds differently to different props. An 18.1x10 works as well in braking as the three blade. Two blades are heavier and take longer to spin up, another consideration. But a two blade is also more efficient than a three blade.

Your mileage may vary!

I agree. I flew the Abbra with both props and the 2 blade 18.1x10 was better in the Abbra compared with the 3 blade.

VB