Falcon32

I’ve done quite a good job of setting up my throttle linkage, equal throw on the servo but I’m getting full RPM on about ¾ stick movement and would like to set up a throttle curve. The programming bit is easy on my Aurora transmitter but I’d like to know how you would relate stick position to RPM.
If for example idle was 1800 and max was 6800, that’s 5000 RPM difference would you set ¼ stick to ¼ RPM (3050) and ½ stick to ½ RPM (4300) and so on, or would that be way too linear.

Thanks

closetguy

My Feedback: (13)

i got the Aurora 9 transmitter also,but i do not use the throttle curve,i make the throttle servo arm shorter than the throttle arm on the carb.that way you will not be at full throttle at 3/4 stick.

DaleD

In addition to the suggestion above, set up your throttle linkage geometry as per the attached diagram.

DaleD

Truckracer

My Feedback: (19)

I would never relate stick position to RPM but would instead relate stick position to how the airplane responds to the stick position. Set up a mild curve in the Aurora and fly the plane. Then readjust the curve to your liking. This is one of those things that have to be done by feel, not by using a tach. Thrust and airplane performance do not directly relate to RPM!

I use to just use mechanical differential in the throttle linkage to create a curve but with the Aurora or similar transmitters it is very easy to just make the linkage linear and set a curve in the transmitter for the desired effect.

av8tor1977

My Feedback: (6)

Setting up a good throttle geometry that allows you to use the full range, (or more) of your servo throw is the first thing to do. Set your radio to 120 to 140 percent throws, and try to get the geometry set up so that gives you full low idle and wide open throttle. Use a long arm on the carb and a shorter one on the servo.

I use exponential sometimes on engines that just won't respond well without having the idle mixture too rich. I think on the Aurora you can choose two curve points, like idle and full throttle. Then just add exponential and it will add it between those two points. Play with it till it responds how you like it.

AV8TOR

Truckracer

My Feedback: (19)

For radios that have the feature, a throttle curve is extremely easy to set up. I could never get exactly the same effect with expo. so just used mechanical differential setups before curves were commonly available.

acerc

I measure the distance of throttle throw and then measure which hole on the servo best fits. Some time's having to make my own hole. That will get the linkage as close as possible. Then if needed adjust the throttle curve. More often than not the center is to high so I take the servo arm off and move it one notch toward'sclosed. Of course adjusting endpoint's as well.I also use subtrim to move center, but as little as possible. And as said before most of these adjustment's come after fly, see, adjust, repeat.

krayzc-RCU

My Feedback: (31)

pic of a jr deal

captinjohn

Anyone that looks at that last post...should get the picture!!!! Smile!

Falcon32

Hi Guys
Thanks for the info so far.
Something I should mention I already have a good geometry on the throttle linkage, I have a long arm on the carb short arm on the servo with well over 100% throw.
The problem is that I get max revs with the carb butterfly at about ¾ open and no further increase in RPM when the butterfly is fully open. I guess this is more to do with how the cheap Walbro copy works than the throttle linkage itself.
Thanks for the photos, that's pretty much what I’ve done on the Aurora and will now have to fly it and fine tune it as necessary.


Thanks

Truckracer

My Feedback: (19)

Non linear throttle responses are common to all butterfly type carburetors, not just the Walbro clones. Also has quite a bit to do with carb venturi size in relation to throttle valve size and engine displacement. You can get a very quick lesson in throttle response by driving a race car with a small carb compared to a large carb on the same basic engine. The small carb is much more linear throughout the whole throttle range where the large carb shows very little throttle "feel" up towards full throttle. Throttle differential is useful on these engines also just like on our rc gassers. Barrel valve and slide valve carbs are a completely different animal.

Antique

My Feedback: (4)

Nothing much changes on a gasser carb from a little over 3/4 to full open...If you look into the carb you will see that the effective size of the venturi changes very little after 3/4..
The size of the prop has an effect too, a smaller prop will show morre difference than a large one....

Falcon32

So what I have is probably normal for our engines.
Thanks for the replies.

Falcon

Truckracer

My Feedback: (19)

Normal and correctable using mechanical differential and / or a throttle curve in the radio.

Falcon32

Thanks Guys
Got the throttle curve done as suggested and works great.

Falcon

krayzc-RCU

My Feedback: (31)

ur welcome glad we all could help....