matador_24

Hello guys,

I have a DLE 20cc and having no knowledge about gas engines, I chose this one to be my first one.
I have some questions about the throttle configuration. What I did is that I set 50% throttle to the center position of the free movement of the throttle arm of the DLE 20cc then I set up my ATV to get the maximum and minimum throttle travel, so far everything was good. Now I do not understand how the throttle arm works because having the throttle at maximum throttle (thus, carb completely open) the engine gives me 8600RPM (with APC 17x6) thus, pretty good. However, I decrease the throttle to 50% and even though I see the throttle arm moving in the carb, the RPM decreases only to 8400RPM!!!!! (thus almost no change from 50% throttle to 100%), why????? I have to decrease throttle to 40% to start noticing considerable change in throttle (i.e. 40% throttle = 7500RPM, 25% throttle = 6500RPM, 10% = 4000RPM)..... why is that???? I thought the power of the engine would be even with the throttle arm movement ?

Also, I am running IDLE at 1800RPM, if I lower IDLE the engine dies..... is it ok or I should move the needles ?????

Also, how many RPM I should have set in my transmitter when being at 50% throttle?

P.S. My engine is still in breaking phase thus, I am not sure if that has any impact.

Thanks for the help!

w8ye

My Feedback: (16)

Your observations are typical - plan accordingly

That's the way the throttles are on most gasoline model engines.

w8ye

My Feedback: (16)

Set your throttle linkage up like this mechanically before you go monkeying with the throttle program in the radio

Image from Jedijody

matador_24

Thanks a lot!
I thought it was the same thing than nitro! it is my first gas engine. Thanks a lot for the pictures, they are going to help a lot!

Another question..... if my IDLE is 1700RPM and my max is 8600RPM.... how many RPM should I have at 25%, 50% and 75% throttle????

thanks!

ahicks

My Feedback: (2)

The top part of that diagram - throttle stick and carb arm in idle positions, servo arm is pointed nearly straight at the engine. Extreme mechanical differential for sure, but it's just what the doctor ordered for these gassers! I start my setup there at the idle, then work out from there. Might be a little easier than starting at half stick/half throttle?

You're doing good! Took me a LONG time to figure out that engine is pretty much all in by time the throttle is only maybe half open. That was the hard part, but I screwed with this issue quite a while, trying this and that prior to coming across these diagrams. After studying them for a minute, it made perfect sense. Been using them since!

w8ye

My Feedback: (16)

Probably the best answer to this is after you get the carb linkage set up as in the picture, fly the plane and decide for yourself what 25% 50% qnd 75% are.

Typically the transmitter throttle stick is almost near half way at 75% power.

There are just too many variables

speedracerntrixie

My Feedback: (29)

Although the guys are right about this being typical of Walbro carbs, the pictoral published will only make your situation worse. IMO it will be much better to stick with the setup you started with and employ a throttle curve provided your TX has that feature. With a little work it is possible to make your throttle response almost liniar. Looking at the picture you can see that point 1 would be idle. Using the curve you can drag down points 2, 3 and 4. Point 4 being half stick. In this particular application point 4 is roughly 30% carb opening. What I like to do is set this point up so that when I am at half stick it is a nice cruise speed between manuevers. This will be a taste thing and will differ slightly from pilot to pilot. Once that is set you can fine tune all other points to give a smooth transition. This is pretty much what 98% of TOC and IMAC pilots use.


Pictures are not as clear as I had hoped. Looking at the pics, the vertical line in the middle of the graph is half stick and point 4. Idle and point one is to the left, full throttle and point 8 is to the right.

av8tor1977

My Feedback: (6)

Look on your camera and see if it has a "Macro" setting. That's what you need for close ups. Makes all the difference in the world, especially for photos here in the forum where you are trying to show someone something in detail and close up.

AV8TOR

matador_24

Thanks a lot guys.... I really appreciate your comments and advices.

ahicks: Actually it was not that easy to come to this forum and learn that the throttle worked that way (compared with nitro is different). It took me to fly with a 10oz tank for 10mins at 40-50% throttle stick thinking that I was flying at actually 50% throttle carb (when I was actually flying at full throttle all time and burning all my gas!) and running out of gas just before landing and crashing. hehehehe [&o] Now I replaced the tank by a 12oz tank but I think I should be fine for a 9mins flight flying at different throttle openings and not full throttle since the beginning!.

I have a Heli DX7 and it has the throttle curve function for the helis setup but I think it doesn't have it for the airplane set up. I was looking for it yesterday and nothing. Thus, I think I will go for the diagram linkage set up which makes sense and I will try to play around with the ATVs to fine tunning.

BarracudaHockey

My Feedback: (11)

DX7 doesn't have a throttle curve in acro mode.

Truckracer

My Feedback: (19)

While the illustration shows an extreme case, mechanical differential on throttle can come very close to what a radio throttle curve can provide. I used differential long before throttle curves existed on radios and still use it today .... only using the throttle curve to fine tune the throttle feel.

speedracerntrixie

My Feedback: (29)

Yes you are correct, taking the time to get it close mechanically is best before you start fooling around with a curve. A few years ago I had a 3W 170 on an Aeroworks Extra 260. This was the first airplane I had 2.4 in and it was with a DX7. That 3W had the worst throttle transition of any engine I have ever had and the DX7 did not help any not having a throttle curve. What worked best for me was to set the servo arm at 8 o'clock at idle and 11 o'clock at full throttle. In this case full throttle was 7/8 open. I was able to adjust the carb opening at 1/2 stick with the sub trim. By offsetting the throws between high and low ( less travel on low then high 80% vs. 100% ) I was able to soften the response just off idle. Took some fiddling but I eventually got a pretty good throttle response. There are a few things that are going to influence all this. In this particualr case the DLE 20 comes with an ignition that has a more agressive timing curve then others. This could account for some of the problems. Retarding the timing a couple of degrees could help. The choice of prop can help too. If you want to soften the spool up just off idle, you may want a heavier prop such as a CF or APC over wood. The OP seems to have a fairly good grasp of what he wants, I hope he tries a few things mentioned on the thread and report back what worked best for him.

octanehuffer

Once you leanit out and the engine breaks in, you should have at least 25 minutes of flight. I get 22-25 from 8 oz on a DLE30. Tune the engine from out of the box, run a rich oil mixture for break in, not needles and run a loop of fuel line behind the tank then to the cowl for a vent to atmoshere

matador_24

Thanks a lot guys!!!!
I am using an APC 17 x 6...... I haven't been able to try the plane yet as I was fixing it from the last incident (running out of gas). Yes, I thought I would get about 15mins with a 10oz tank but again, I didn't realize I was flying full throttle for 10mins! and I guess that is why I run out of gas before expected (my fault because I should have flown before) but I actually was trying to land before 7mins but I was approaching too fast! (and it is because I was flying full throttle!!!!!!) anyway, as I thought I was flying at 50% throttle, I just thought that the engine had lots of power, lollllllll..... anyway.... it is my first gas and I have learned much now with this missap! I appreciate all the help and comments and I will post back when I fly again!

I will try the mechanical settings and I will try to set an IDLE of 1700RPM to land and an IDLE of 2000RPM to keep a steady IDLE during flight.....

I will use the 12oz tank for the moment and as octanehuffer mentions, if after breaking in the engine consumes less, then I might go back to the 10 oz tank as I never fly more than 10mins.....

what should be a good temperature in the head of the engine during flight? I checked mine and it was about 190F after 6mins flight (my first flight before the missap).

ahicks

My Feedback: (2)

Just me, but I wouldn't spend a lot of time with a different "flight" idle speed, and a "landing" idle speed. I prefer to keep it simple, not have to deal with which one I'm on, or supposed to be on. One less thing to think about? They can both be the same speed.

Just remember if it's quitting in the air, it's probably too lean, and if it's sitting on that "high idle" for more than a second or 2 prior to dropping down to where you expected it to be, that's too lean as well.....

matador_24

Hello, you are right, I set the idle at 1750RPM and it is pretty stable (below that it seems to hesitate).... I'll keep it that way...
landing was very nice.... I had 2 flights and in the third one, one of the servo arms stripped (dubro heavy duty) and I not only lost one of the aileros controls but the aileron stayed down and it was pretty hard to control and stay leveled.... I had a rough landing and I called it a day.... not damage, just the landing gear came off..... I wonder why happened? vibration??? the arm was not touching any surface... should I use alum servo arms? or it bas just due to the fact that the plane has been flying for 3 years????

About fuel consumption, now that I set up the throttle properly (thanks guys!) I was able to fly nicely and for a 10mins flight I think I used about half a tank of the 12oz.... which makes more sense now! overall very happy with it!!!! need to fix and have it flying again this weekend!

[&o]

darrolair

I've not seen a heavy duty Dubro servo arm strip out. Might not be the proper brand name servo arm on the same servo name. As an example JR arms will fit on Hitec servos, but the splines don't line up. One can tighten the servo screw, but the arm will slip. Just an idea.

matador_24

Now that I think, I had JR servos in the ailerons and I replaced them with Hitec but kept the same arms as I found they fitted properly.... it seems it was not the case!
I knew futaba was different from hitec, but I didn'T know JR and hitec were different....

ahicks

My Feedback: (2)

Geez....that's usually how I learn stuff. The hard way! At least that lesson wasn't one of those REALLY expensive ones...

Nice to know though, why what happened did.

matador_24

Yes, I know!
I didn't know it! and they seem to fit very well but apparently they don't!
I was thinking about puting alum arms but I'll keep them heavy duty dubro as it is only a 20cc...

what do you think?

ahicks

My Feedback: (2)

The HD plastic/nylon have been working fine on anything I've flown/am flying (20-30cc).

matador_24

yes, I will do that
thanks!

matador_24

Coming back from the field....... 5 happy flights of 9mins each!
The picture posted helped a lot now! that plus playing a bit with the ATVs and I got 8600RPM at full throttle, 6600RPM at half throttle and 1700RPM at IDLE....

I think it is pretty cool! with so many fixes... my plane weights now 10lbs..... not too bad, the engine pulls it pretty good..... I am using APC 17 x 6. I haven't tried hovering yet but I am not expecting a lot..... however, it looks with lots of power.... after 9mins of sport flying, I go back down and have about 1/4 tank left of my 12oz tank... I think it is pretty good and I will keep it that way.....

Overall, very happy with this DLE 20cc..... and thanks guys for all the help!

ahicks

My Feedback: (2)

Nice job!

rtmusic

I was wondering if using exponential on the throttle servo would be a way to even out the throttle curve on the DLE 20. I have the same problem with my SBACH 342 Profile and DLE 20. I am basically WOT at 50% stick. From 50% to WOT there is little RPM change. Frustrating! Since I am new to RC gas engines I can only conclude that the carbs are the problem, (since I've always driven cars with carburetors and adjusting was only a matter of getting the air/gas/idle mix right). Is there an aftermarket carb that works for these?