Been flying glow 2 strokes for about a year. I just put an OS FS70S with a 13x5 Zinger wooden prop, using Wildcat 15%fuel on my H9 Twist. This my first 4 stroke. My question is that 1/2 throttle and full throttle feels and sounds the same is this normal? Also I seemed to have quite a bit of oil under the fuse. RPM's were about 10200, do I need to maybe lean it out a little more for better verticle and full speed throttle response?

Thanks,
Joel

I use my OS .70 with a 13/6 Zinger wood prop and it turns about 9700 rpm on the ground, you are about right for a 13/5, the throttle difference between half and full is not all that much, she's running the way it is supposed to, these are really sweet engines, and so trouble free, I love them.

A lot of engines, 2 & 4 stroke, aren't necessarily at half throttle when you are at half stick. You can program throttle expo to make your half stick position become half throttle on the engine.

I'm not sure about leaning your engine just for more vertical power. You should set it like OS outlines in the manual, which is probably a few hundred RPMs on the rich side of peak. You could find more vertical by lowering the pitch of your prop.

You can not lean out in a 4 stroke engine as in 2 stroke engine cause the 4 stroke engine need enough oil in crankcase to lubricate moving parts inside.

Jens Eirik

[b]Joel:

I have been using reversed expo on my throttle for a long time, setting it so that the carb is about 80% open when the stick is at the 1/2 position. Makes a much smoother feeling throttle. The last half travel is, as you noted, a lot less power increase than the first half.

Bill.

If your not experiencing any rpm increase between 1/2 and full throttle....

....the engine is over-propped.

FBD.

A 13-5 is hardly too much prop for the OS 70.

13-8? Perhaps. 13-5? No way.

If anything...a 13-5 is slightly underpropped. Depends on the model, and how boogered up the throttle linkage is.

'Race

jlank,

For props, it really depends on what you're looking to do.

I'm running a H9 Twist as well, but with a Magnum 91 4-stroke. I originally ran Zinger props because they were readily available and relatively inexpensive...

But I found that on the Twist, where I wanted that thrust for 3D/funfly stuff, the Zingers didn't work all that well. Not bad, but I felt it could be better. After some experimenting, I ended up with an APC 15x4W and really liked it. Lots of "umph"...

With a 70, I'd try the APC 13x4W. A friend runs this on a Magnum 70 (similar performance to your OS 70) and it works well, spinning around 10k RPM static. You will notice the spool-up is a bit slower, since it's a wide-blade heavy prop, but these props seem to really beat the air and generate a lot of thrust.

As far as your throttle is concerned, I don't seem to notice this on my engines.... I can hover at less than 1/2 throttle, then go up to 3/4 for a graceful pull-out or jam it all the way to full for rocketing out of it. Have you checked your linkage as RaceCity mentions? Are you able to go to full throttle without the throttle servo buzzing and/or bending the wire? Are you using end-point adjustments (EPA) to keep this from happening? If so, you should readjust your linkage so you have full throw from 0 to full with no EPA adjustment.

Hope this helps...

Thanks guys!


Joel