HELP!! Throttle Curves and Engine Tuning

[lperagallo]

OK, so I have the new Bergen Muffler. After installation I see a loss in power and climb out. I'm also running GV-1. Chris suggests that I turn off the GV-1, richen the needles back to 1 3/8 and tune the engine. I do as Chris suggests. I also watch the Gary Travis set up video again just to be sure. I even went back and re-adjusted my throttle linkage so I'm at half throttle at 90 degress on the servo.
I go to the field today to see if I can tune the engine and get it set up again. It's about to be winter here so it's turning cold and windy. I try to tach out the head and can't seem to get it right at all. Seems like head speed is to high. It also is shaking like crazy on lift off :arggg: The back of the canopy and tail are dancing. The canopy cheeks are also jumping around. In fact so much vibration the rear canaopy bolt departs. This shaking is new. It was pretty smooth before I started messing around with it. I figure head speed is way off and too fast. I didn't have help to read the tach at lift off. To keep head speed down I bring the curves way down. I lift off and the shake is bad. I land lean slow jet and try again. I punch it to see what happens and boy does it pop. I then bring it back down quick and the engine cuts out a second. I richened the slow jet whihch fixed that. The engine doesn't sound bad, it starts off 4 cycling then smooths out at half stick (0 pitch). Head speed picks up as I lift off. The curve I have set now is 29-45-47-50.5-77. Does this sound reasonable :dontknow It's way too cold and windy to do much more today, but I am stumped in how to reign this in. Any suggestions on figuring this out is appreciated. Is it better to start with a low head speed and work up or start higher and work down. I trying to fly at 1650 in normal and 1750 in Idle-up. This is on an Intrepid EB running 720s and a Hanson G26. I'm looking for a logical way instead of trying a bunch of things. Mechanically, nothing has changed since the last flight and I checked everything again when I got home and things seem smooth and aligned. Pitch curve in normal is +9,0,-5, linear.

[cbergen]

When you readjusted your throttle linkage, did you also clear out your Throttle curve in the radio?

Oh and please tell me that you're not out flying by yourself....

[lperagallo]

Chris, Yes I did redo the throttle curves. The numbers in my posting above are what I have now. I have a new DX7, so I have been resetting everything up. No, I wasn't alone, I had my daughter with me. The issue was that she is inexperienced and couldn't get a reading when I lifted off. The wind made it hard to keep in one spot and I didn't want to keep it in the air with the vibration. I could tell from the sound that head speed was increasing to quickly. I'm just surprised that the I am getting such an increase in head speed and have such a close curve. Maybe tomorrow will be less windy so I can try again. I am still concerned with the vibration. Is a high head speed a source of vibration? Could it all be in tuning? The last time I flew with the GV-1 on I had zero vibration.(I also didn't have much power either, that's why I'm playing with it) Even though I have a DX7, I left the antenna mounted on the landing skid to see vibration.

[cbergen]

Good, I feel better!!

Ok, I think we need to start from scratch here. There are too many things changing at once.

Too high of a headspeed can certainly cause the violent vibes you saw, but so can the mistuned engine.

The muffler will require richening of the needles, which may require a change in the throttle and pitch curves.

Getting a clearer idea of the headspeed will certainly help to know which way to go. The different tone of the muffler makes it more difficult to tell headspeed by sound alone.

The curve I have set now is 29-45-47-50.5-77.

Does this include 0 at the bottom and 100 at the top?

[lperagallo]

Chris, I wrote a reply but see I must have screwed up on the posting. This is the set up. Stick at bottom, pitch at -5, throttle curve at 29%, stick at 1/4, pitch at -2.5, throttle at 45%, Headspeed at 1,600, stick in middle, pitch at 0, throttle at 47%, headspeed unknown, stick at 3/4, pitch at +4.5, throttle at 50.5%, headspeed high, stick at maximum, pitch at +9, throttle at 77%, head speed sounds really high. I agree that changing a bunch of things make it harder, but prior to the DX7 my throttle curve in the Futaba was, 28,46,55,57.5,92.5. Those worked pretty well.
I started with the needles at 1 3/8. When I was done I leaned the slow needle a blade with and opened the high needle a blade width.
Maybe I need to bite the bullet and take a three hour drive and visit you. Is it possible to fly up there in the winter or do I have to wait till spring. Can this be done on a weekday?
Let me know what you think.

[cbergen]

Sounds like a very good idea, we do fly all winter long.

I've been wanting to play with a DX7!!

[lperagallo]

Chris, Do you fly out your back door or do we need to travel to a site? Does a weekday work for you? Since I am trying to fly all winter, I'd like to set something up soon.

Thanks,
Lou

[Bobs]

Lou, your throttle curve is a lot different (higher) than mine. I have a std Intrepid, G26 with 720mm V-blades and my transmitter is a 9303. My pitch in normal mode is -4 0 10 which is 37 42 48 54 69 85 100 with a throttle curve of 10 26 29 31 34 38 100. I'm hovering at exactly 1650 with lift off at between points four and five (about 66%) on the pitch curve and that's about 33% on the throttle curve. Your throttle curve sounds more like a nitro setup. I just wanted to mention the huge difference in our two setups. Gary's video talks about how different nitro and gasser setups are. Chris didn't mention anything out of the ordinary, though, so I guess that's just the way it is. Good luck.

[lperagallo]

Bobs, Our curves aren't really that different. I have a 5 point curve while yours is a seven point curve. Since everything is relative on the curve, your center point of 31 is about equal to my 47 when you account for the difference between your point one of 10 and mine at 28. That difference of 18 points is the difference between our linkage set ups. So if you add the 18 points to your mid point of 31 you come out at 49 while mine is at 47. After checking things out again I think I might have had a pitch curve issue where I was not at the points I thought I was and didn't load the head. Since winter decided to show up I haven't had a chance to test the set up again.

[Bobs]

Makes sense to me, Lou. Must admit, though, I didn't think of it that way. Winter's been here for a while now in Minnesota so I know how frustrating it is not to be able to fly when trying to make changes in setups. We never got above zero for several days last week. We're actually having a heat wave today, it's 14 above zero, but it's snowing. I've been giving a lot of thought to heading southwest for the Las Vegas funfly but the 1700 plus mile drive is not very appealing.

[rbort]

My gassers don't fly with that much throttle curve...

I setup my curve as 0% on the low side and 100% on the high side. That leaves 3 points in my tx. 1/4 stick. 1/2 stick and 3/4 stick.

At 1/4 stick in normal mode its about 20%, at 1/2 about 25% and at 3/4 about 27.5%.

I also fly at 1650 in idle up 1 and 1750 in idle up 2. I think you have WAY too much throttle and too much head speed. The way to find out is to use the GV-1 to your advantage, not turn it off completely.

Hover your machine and then toggle the gv-1 on. If the rpms drop then you had too much throttle and too much head speed. I know you are trying to tweak it without the gv-1. but use the gv-1 as an indicator and a tach. You don't need a skytach once you have a gv-1 installed. Turn on and off the gv-1 to find the target rpms and then adjust the curves.

If you are climbing like a rocket you are also probably screaming 2000 rpms in a hover. :shock:

-=>Raja.

[lperagallo]

Raja, On my new DX7, I set point 1 for idle. This keeps a nice idle. I trim up when I start and down a bit when it's warm. I push the trim to the bottom to stop the engine by closing the carb all the way. The next point is 1/4 stick and so on. While I haven't been able to test it because of weather, I think I must have had my pitch curve screwed up :arggg: I think that I was way off and there was no real load on the engine which in turn gave me way too much head speed. I am now not running the GV-1 on advice from Chris so I can tune the engine back in with the new muffler. When I put on the new muffler I lost the great engine performance I had. I guess that's what I get when I changed too many things at once (new radio, new muffler, adjust throttle linkage to be 90 degrees at half throttle) I do have idle 1 at 1650 and idle 2 at 1750 in the GV-1. I couldn't go to idle up 1 when testing becuase it was windy and too out of control. I didn't want to crash :bomb: Oh well, the best I can do is wait for the weather to break a bit, but it doesn't look good for the next week. :dontknow

[SeaHawk]

did you ever sort this out?

[lperagallo]

Seahawk,

This was resolved ages ago. I just had a bad throttle curve set up. It's all good now and I'm running a GV-1, so my throtlle curves are on close to ideal. I did go up and see Chris and it was worked on all day. I learned a tremendous amount of tricks and correct set ups so I now have some real nice flying machines. I've progressed to light areobatics and the Gasser flies like a dream.

Lou

[SeaHawk]

Good. I've been to their shop a few times myself. I would love to go there too as I've not mastered the art of tuning yet. But, I know Chris will be too busy testing setups for my Tazer:) I'll have to do a bit more re(search).