After flying my DA-50 for a few flights I want to change the throttle response using a throttle curve. My 9Z has a 13 point curve with 11 setable positions on the curve, I am assuming most leave the endpoints at 0 and a 100... After doing a little reading here on RCU it appears that most gassers get most of their power when the carb is open about 65% to 75% and that there is little RPM increase above that. Instead of go through a trial and error process at the field (I did that yesterday and was not happy with the results) I thought I'd try to figure out a likely curve using this information.

To get a linear response you want to carb to be open about 35% (half the average between 65 and 75%) when the throttle is at straight up (50% travel). So I set that point on the curve and adjusted the lower values back to 0% to make a smoothly increasing curve. Then I set the 12th point to 75% and set the points between it and the middle (35% value) to get a smoothly increasing curve. I left the last point at 100%...

Does this sound reasonable? I was unable to get to the field today to try it out...[:@]

Sounds reasonable but have only used a 9C. Additionally I'm curious as to how you set your endpoints and linkage. Do you have them set to maximize the full throw range of the servo (140 on each side of center); What are the distances on the servo and carb respectively of the linkage attachment points to the center of rotation? How many degrees of angle do you have on the carb from idle to the butterfly being fully open?

My setup is kind of interesting. Since I am using a Hitec digital servo on the throttle I programmed the servo so that its endpoints are at the points the servo starts to bind. This means that my AFR is 140 and ATV are 100. The ATV at the low end is only 90% since you need the throttle open a little for idle and idle trim adjustment... The idle kill pulls the throttle completly closed and kills the engine (I also have a FO kill on another channel). Setting the center point so that I get equal throw on either side has been difficult and the last time I went through this I didn't bother -- I simply set the center where the arm is perpendicular to the servo...

The servo is mounted 6 or so inches back from the carb in the engine box. I'll have to measure the amount of rotation of the servo arm from fully closed to fully open, but it is pretty close to 90 degrees...

Seems like most of my carb rotate about 60-65 degrees from idle to full. Maybe another 7-10 degree to full closed. Say 75 degrees at carb and maybe up to 140 degree on servo.
I'm trying to get max EP on throttle channel to correspond with carb rotatation. This one, though glow, gives an idea of how I came up with some additional adjustment in linkage. Initially forgot about travel needed for throttle kill switch but will tweak more later.

GalenB--That sounds very reasonable to me. I have set-up a few throttle curves on my 9z and some times it is just trial and error till you find what you want. I had a flattened spot on one of mine just below mid range to help with hovering. Still can't hover worth a hoot, but that is just me not the curve.

Tell you what I do with my 9C.
I know what idle is 1500rpm and WOT 6100 rpm.
I take the difference and get 4600 rpm.
I know that my mid point should be 4600/2+1500 or 3800rpm (position 3)
I do this same kind of calculation for position 2 and 4.
When you fly it will be linear. (real close to it)

WOW....What Geistware says just makes sense. I just experiment with my 9C to remove the flat spot at WOT but and this would sure take some of the guess work out of it. On the other side, I know I have mentioned a throttle curve at the field and some of the guys look bewildered and have had replies like....what would you want that for? OH WELL.......Bill

Throttle curves and my opinion. I've tried total linear throttle curves and they really don't work for me. Forget about RPM's. They work so much different in the air depending on props etc. Fly the airplane and see where you feel comfortable for cruise speed. While your doing that, look, or have someone look at where the stick is. Make a note. Now, when you get it on the ground, go ahead and tach it where your stick was. Use that RPM reading for your center throttle stick position. Then start working on your curves above and below this point where you feel comfortable with it. If you're into 3D, do the same thing.. where YOU feel comfortable to have that center stick position.

I'm sure there are people who have different ideas, but I like to have the throttle center in a position where I can work up or down from there, but most of the flying done is at that position.

John, what you describe is what I do with my IMAC planes.
I move the stick to mid throttle then adjust the curve to give me the speed I want. I then fly a 45 up, move the stick to 3/4 then adjust. Fly 45 down, move the stick to 1/4 then adjust. It works good.

I also have a memory set to allow for fun flying.
In this memory, I use the throttle setting described in the previous post.
In the air, I find that the speeds remain linear.
Don't know why this works for me and not you but it does.
Maybe because I never fly WOT at straight and level but on an incline or vertical.
You can also use the above setup as a start and then adjust it in the air to make it perfect.