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Midrange adjustment

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Posted

I'm going back and forth with my midrange performance. Here are my stats:

 

Rotax 618,

WOT cruise set to 6800

Rotax Rick 50hrs TSMOH

 

My current installed Jetting:

PTO main jet 165

MAg Main jet 175

2.72 needle jets with 15k2 needles

45 idle jets and 2 turns out

 

I'm about to readjust idle after I install the clutch, so we will leave that be for now.

 

WOT on takeoff, I'm getting good smooth power and 950deg

 

Cruise: so here's the deal. Up till about a month ago, oat temps were in the 90's and the clip on the 2nd from the bottom was giving me a perfect colored plug and good egt temps hovering around 1050-1100. Now that the oat temps are down to 80 and below, I have been noticing my temps increase as they should. Checked my plugs and sure enough, too lean for me. So I dropped the clip to the bottom option. No good. She runs way to rich and pops and burps in cruise (5600rpm). I had a 45min flight toady with those conditions. landed, shut down, pulled the carbs and adjusted the needles back down. Off to the next landing site.... Engine runs soooo nice. But temps were at 1150 and any decrease in cruise rpm and the temps go up. as expected, but I don't like it.

I need a needle that allows me to use a middle clip option and be a bit richer than what I have now with the 15k2 on the 2nd clip.

Or am I missing something?

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Posted

Can you put a hacman on it?  Its kinda nice to be able to dial in your temps.  950 on take off seems a bit low, but your also keeping it from burning down so thats cool.  I run around 1100-1150 on take off and cruise, but I have inflight prop and mixture.  Turning 6800 WOT level is probably your issue.  I have mine set so I turn 65-6600 WOT level.  anything more than that and I get high EGTs in cruise even with the inflight mixture.  I would be tempted to up the pitch a little, and drop a jet size on the main to get your take off EGTS better yet still not unload the engine too much in the midrange as your doing now.  The high  EGTS in midrange are due to the engine not being loaded enough.

 

:BC:

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Posted (edited)

I can do that. I'll go with 160/170 mains and pitch it to 6600. I need to verify the WOT. I'm thinking it is 6700-6750 I think I was chasing high water temps this summer so I was moving the pitch to 6800 for a baseline assessment.

 

I thought the Hackman and the 618 didn't play well together?

 

I can run at 5800+ rpm and the temps stay cooler, but the fuel consumption increases of course

Edited by Deejayel

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Posted

you could be right, dont quote me on the 618.. im going off a basic 2 stroke principals and the 582 :lol: 

 

:BC:

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Posted

I have the arctic sparrow in flight adjustable needles on my 582 so I am not a HACMAN guy, just tossed that one out there as a possible fix.

 

:BC:

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Posted

Ill start by increasing the pitch a degree or two and report back

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Posted

A little more pitch will really help to bring the temps down especially in the mid range.

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Posted

What gear ratio are you running?

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Posted

Here is another thought that I have used with success. I put a small washer of the right thickness under each circlip that would move the needle half the distance from one groove/notch to the next. Just wondering what your static rpm is @ full throttle? Others mentioned adding pitch and that makes sense also. Jim Chuk

[quote name="Deejayel" post="15493" timestam

I need a needle that allows me to use a middle clip option and be a bit richer than what I have now with the 15k2 on the 2nd clip.

Or am I missing something?

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Posted

Interesting ideas. Thanks for opinions

I have a 3:1.

I haven't gotten to the clutch or repitching yet. Busy week. I promise to report findings

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Posted

The reason I ask is that I went from 3:1 to 2.6:1 gearing and the wild swings in egt temps went away. I think 3:1 doesn't put enough load on the engine. Bryce

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Posted

Absolutely perfect day to fly in south Louisiana today. Got my t-crate and legend cub flying pals out of the hangar and we spent the day burning gas.

 

Ok, here are my new stats.

 

I have not yet changed the main jets. Probably should have done that prior to this testing.

 

I adjusted the prop for the first run. Just tossed a few degrees at the blades. Static run was at 5750. Ok, a bit low, but lets see what she will do. On the takeoff run, I noticed the rpm actually decreasing! Ok, back to the barn. Too much pitch

Set the pitch again and got a 6100 static. BTW, my static is consistently 600rpm lower than WOT. So I knew I was going to get 6700 WOT. Test flew. No love yet. Temps still running up to 1200.

Adjusted the pitch yet again, and I think I hit the sweet spot. 6000 static and 6600 wot. Much better. Mid-range temps stayed in check below 1150. CHT is at 125. Interestingly enough, my CHT has indicated 125 throughout all this testing.

 

So here I am. I think at at the end of my props efficiency. Either I change the prop for a longer blade, or go with a harder set of gears.

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Posted

Man! I had the same problem as you before, and 2 things, I never EVER considered and were causing problems.....

 

1.- Ignition; mine is a Rotax 532; had the engine overhauled from a certified workshop, with papers and all, they told me is spot on, WELLLL, NOOOOO...... I had to do that myself. check and recheck, in your case is electronic, so it won´t be a problem however "CHECK"

 

2.- Propeller; initially, I had a 3 blade GSC, very common, as per book, pitch diameter, all very good..... took me more than 6 months, trial and error.. NOTHING couldn´t get it right......

 

but trying another propeller, 2 blade lighter, the engine perform way better, and sounds smother too. EGT are now spot on, all the time, and actually very difficult to change them for hot or cold in all ranges, is almost as stable as I ever seen it.

 

the #2 item, my mechanic friend said that perhaps the gear box is not tip top and need replace, but I will leave that alone by now, and hope to get a new one when I buy the 582.

 

Regards

Dimi3

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Posted

Here is another thought that I have used with success. I put a small washer of the right thickness under each circlip that would move the needle half the distance from one groove/notch to the next. Just wondering what your static rpm is @ full throttle? Others mentioned adding pitch and that makes sense also. Jim Chuk

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