Nogyro

My Feedback: (10)

I've been running a 3w80Xi on a 3w LL canister for a few months now. I feel like I've pretty well got all the engine idosyncracses figured out. Needles are set right, and engine is pretty well broke in I believe with 39 hrs of run time on it. Running 93 octane with Mobil Racing 2T at 50:1. The problem I'm having is right at the rpm that I'm trying to harrier at, it acts like its on a full length pipe and picks up 800 rpm with just one click of throttle. I've tried several different throttle servos, worked on a throttle curve in the transmitter till I'm blue in the face. All that does is move the location of the throttle stick where it comes up on pipe at. I tached it on the ground today, and when I'm at 3800 rpm, one more click on the tranny makes a jump to 4600 rpm.[:@] I've tried 26x10 Bolly wood, Menz S, and NX props, and I get the jump in rpm with all three. In the air, once in a while you can give it one click of throttle in level flight, and it might take 3 seconds or so, but it gradually picks up the 800 r's, not instant like when you're trying to harrier. This is getting very frustrating. It's also at the rpm that I do (attempt) rolling harriers at. Just can't do them the way the throttle is. This is my first canister setup, and I've never used a full length pipe on anything either. Is this normal? It's killing my 3D. I really like the quietness of the canister, but I can't live with this touchy of a throttle at that particular point in rpm. I can fly IMAC all day long and it's not a problem, don't even notice it.

Anyone have any suggestions?

Here's a pic of my setup.

flyinrazrback

My Feedback: (69)

Mine was not peaky at all, really smooth and awesome in the middle. Something is not right....hmm.

Nogyro

My Feedback: (10)

I had the same problem with the 3W aluminum ? header also. Just figured I could get it out with the throttle curve. It's not going to happen. I set up a mock setup in my shop with the transmitter and servo. I had my curve set to where the first half of throttle only moved the servo arm 1/4 of the total throw. Got my ATV's at 100% both ways..........you can barely see the arm move where it's jumping in rpm.....My needles always seem to be turned in a bit much to me, but this is my first 3W.........low needle is set where 12 o'clock would be 3/4 turn open, I'm at 2 o'clock. High is at 3/4 open. If I go any richer on low, it loads up and won't idle. It never sags, I can hold a TR or hover for a minute in 95 degree heat, punch it, and vertical as far as I want to go....great transition.......plug is showing just a tad on the rich side...........Elevation 530'.............

flyinrazrback

My Feedback: (69)

I am not sure, what are your temps like? Is it possible to pull the can out and shake it to see if something is loose inside?

Nogyro

My Feedback: (10)

I checked the head temp the other day with the infra red gun about 30 seconds after landing and it showed 169 at the base of the plug. Not an ideal reading, but I figured the heat would rise after shut down....Normal restarts on a hot engine........just don't think it's over heating.

I can get the canister out, but have to remove engine to do it. It would be easier to pick the plane up and shake the thing.

rmh

likely:
you are hitting a resonant point
I hate negative comments but -I have yet to see a long header/ tuned canister setup which was NOT peaky

Nogyro

My Feedback: (10)

No more than I know about pipes, but that's what it sounds like to me. A buddy of mine runs the OS 160 on mous cans, and he said that's what it sounds like to him also.

That was my next question. I know you always set yours up with the engine tilted at 7:00 or 8:00 o'clock postion, then a real short header. If I had to do over again, this is how I would have mounted mine, but to do it at this stage of the game would be a real PITA........So in essence the long header is acting like a tuned pipe correct?

I really don't want to go to a 27" prop, but do you think this might help calm down the touchy spot?

rmh

It is the long header that is also about -1/2" to 1" from a reflector
The cans I use have no reflector - there is about 5" of wide open can
essentially my setup is a bit like a simple megaphone-
The can does provide a littl backpressur for excellent low end but as far as I can tell -there is not a detectable resonant point
on longer headers it just decreases power - directly with increased length
this is from a sh-t load of test bench work with telescoping tubes and readjusting for max power on 40cc/50cc/60cc/80cc ZDZ's
RCShowcase was very co operative in allowing me to test different versions of cand and pipes and tuned cans .
Some -I sent back a few I use .
My favorite is the simple large JMB muffled can fitted to appropriate sized engines

small cans also worked with no peakiness - but power wwould go down a bit
I tried a lot of tuned cans
None was WAS in my book (worth a darn)
they either had a flat spot or simply reduced power- I also bought a selection of KS tuned cans
Honestly I did not find any I liked . same problem - the worst being th front outlet types
I am not trying to knock em - I simply did not like them when I compared results with the stuff I did like.
I could get increased rpm when adjusted right -in most cases but in flight mid range would annoy me
I am a grouchy guy

Nogyro

My Feedback: (10)

Dick,

Thanks for enlightening me on the reflector being that close to the header. There's no substitution for experience when working with these things. You've spent many many hours with these things and it shows. I'm not sure what I'll do at this stage. I can't live with what I have, that's for sure. Guess I'm too grouchy also. It may be time to put a side dump muffler on it, and chalk it up to experience until winter time or my next project. Then I'll mount the engine at 8:00, a short "J" header, and a different can....................

Scoubidou

My Feedback: (17)

Hi Nogyro
Did you use 28mm or 25mm diameter for the KS header and where did you buy the KS exhaust flange? AI and DA do not have in stock the 28 mm exhaust flange for the 3W80.

Nogyro

My Feedback: (10)

Scoub,

I used 25mm and I got all the fittings from AI.

Nogyro

My Feedback: (10)

Just an update guys,

I yanked the KS stainless steel header, 3w canister, and mount out the yak and put on a Johnson side mount muffler. I removed 13 oz. in the process! My Yak ended up just a tad bit more tail heavy but I needed it anyways. Now for the good part. No more peakyness!! Very solid even transition. When I first cranked it, the engine wouldn't even throttle up it was so lean. I had to open the low over a 1/4 turn to get it to transition. It also solved my problem of a film of oil inside the fuse from carb over spray. There must have been considerable backpressure, because after two flights it was bone dry. The noise level was very tolerable doing IMAC, but I haven't done any low TR's yet since the needles aren't set just right yet. I couldn't get any WOT rpm's for you since I was flying by myself, but it appeared to have the same vertical, just a bit louder. All and all I couldn't be happier.

I haven't given up on a canister yet. I'm sure I'll try it again in my next project, but you can bet the engine will be mounted in the 8:00 position with a very short header going to can.........

rmh

Too bad you had a setup which was no fun -
I was lucky enough to get the chance to first sort out most of this on a bench .
So far - I have still never seen a can setup which is as smooth as the short header JMB large can muffler.
I have some smaller cans (the tuned variety ) that I am going to get rid of KS, etc..- Simply tired of trying to get them to add power and still have perfect transition
I get close --but no cigar.
The picture shows a JMB and a "tuned" can for same engine -I tested against each other a while back
The little one put out good power but was cranky

Nogyro

My Feedback: (10)

It sounds like the canister design has as much to do with performance as the length of the header. How's a guy to know going in what is what? Will my 3w canister be "peaky" regardless of the length of the header?.................

On a side note. If I was having problems with a smooth mid-range with my setup, how's this one work.............
http://www.rcuniverse.com/market/item.cfm?itemId=207890

Scoubidou

My Feedback: (17)

I am using the KS-95 with 10'' header on a super ZDZ-80 and transition is not peaky at all. I prefer a lot the throttle transistion from my canister than a Pitt muffler.

Nogyro
I ordered the 33% AM Yak with 3W-80XI but i'll probably go with BMB 70mm XL canister and engine monted at 8 oClock with short header.
Good luck and thanks for posting your info.

Daniel

Nogyro

My Feedback: (10)

How do you guys measure the length of your header? Seems to me the measurement could really vary depending on how you measure it.

Scoubidou

My Feedback: (17)

total header equal=elbow+straight lenght .

You can calculate the header lenght in elbow by using the maths:


elbow=2*pi*radius sq/4=pi (square)*radius/2=3.1416*3.1416*elbow radius/2

Nogyro

My Feedback: (10)

I'll give it a try with the math and see what I come up with.

Thanks!

rmh

length needs no math-just eyeball c/l of the pipe - that is close enough
the peakiness shows up worst -on hover and trying to do minute power variations
getting pipe matched - mix and carb adj right makes a big ifference too.
I can put a piece of wire inside a can and tell instanly if it is /is not tuned type.
That is NOT the whole story but the proximity of the end of head pipe to a baffle is a really big clue. close = tuned
5" away = NOT tuned

Nogyro

My Feedback: (10)

I'll check mine tomorrow and see what it is.

Thanks

Nogyro

My Feedback: (10)

I measured my header(eye ball method down center of pipe) and it is 11" long. I also checked out my 3W LL canister and there is no baffle in it. I can run a rod all the way down to the end of the canister. Visual inspection also shows no baffle so I guess it's not a tuned can.

rmh

No - you also must know where the pipe ends inside the can -- put a little hook on the end of the wire - then see where the pipe ends relative to total length inside
look at this drawing -note the two end points possible
I made these cans for my own use and ran a sh-it load of tests on diameters and lengths -

Nogyro

My Feedback: (10)

Ok.