Hello

The advantage of cdi is the possibility of using fuel with little oil, the plane remains very clean. I use 9% oil (25% nitro).
The 175 uses a little more fuel. With 680 cc, 170 cdi flight last about 20 minutes, 175 cdi 15 minutes.
When I go to field with friends spend the day, I take my 5 liter and can do many flights.

Engine cooling is very important.
I made a change on my underbelly as shown on pics (before and after) and gain is about 20 degrees