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Old 09-27-2009, 07:11 PM
Jaketab is offline
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United States, WV, Charleston
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DA-150 Surges at Mid-Range

Hello,

Have a well run in DA 150 with MTW 110 Canisters. Has excellent top end and idle. Good transition. It runs very well and has never quit. At mid throttle the engine surges very noticable. If you hold at mid throttle on straight and level flight it continues to surge until you reduce or increase the throttle. Same for knife edge or inverted.
The surging will go away if you pull an upline.
The surging sounds like the engine is transversing from rich to lean and back at 1/2 second intervals. Leaning or richening the needles has little noticable effect.

Any suggestions or advice please??? Is this possibly a chacteristic of this engine and cannister set up????

Thanks - Jaketab
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Old 09-27-2009, 07:43 PM
SmoothFlying is offline
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Re: DA-150 Surges at Mid-Range

My best friend has this same issue. It will even cut off and cut back on at times. The cutting off only happens on the very first flight. But the surging continues. Maybe a DA tech can help us out. Richenning and leaning of the needles has not helped.
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Old 09-27-2009, 08:19 PM
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United States, AZ, Scottsdale
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Re: DA-150 Surges at Mid-Range

A friend of mine has been dealing with the same issue. We found that it had an air leak at the sealing surface from the reed block to the case. We noticed some fuel residue in that area. We re-sealed that area and the problems is gone.
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Old 09-27-2009, 08:48 PM
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Bennington VT.
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Re: DA-150 Surges at Mid-Range

I just installed Chip Hydes canisters on my 100cc plane and it does the exsact same thing.Ides great transisions great on the ground and top end is sick,It's also very quiet.But surges something awfull in the midrange.I put the factory mufflers on it and it went away and ran great.I think it has to do with the header length.I think I have to make the headers longer increasing the overall length of the exaust system.anybody have any ideas.Not to highjack your thread but I think we're in the same boat.
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Old 10-01-2009, 09:23 PM
Jaketab is offline
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Re: DA-150 Surges at Mid-Range

Problem solved.

Upon examining my DA-150, I found 3 areas, or combination of, that may have been causing the surging at mid-throttle.
  1. There was a very slight seepage of fuel on the underside base of the right can. One of the cylinder bolts had began to work its way loose. All bolts were re-torqued to 70 in/lbs.
  2. The spring was disconnected on the throttle lever. Additionally, the throttle servo was getting sloppy. The slop was most noticable when the servo arm was at 90 degrees - which corresponds to mid-throttle position. I reconnected the spring to give enough back tension on the linkage.
  3. After re-tuning, I discovered the needle settings were on the rich side - both high and low. I set the low for best transition and leaned the high slightly. My needle settings ended at low - between 1/2 and 5/8. High ended up at 2-1/16.
Running a Mejzlik 3-blade 28.5 x 12 prop, after retuning, static ground rpm was 5850. Upon flying -I flound the mid-range surging was eliminated.

In a nutshell, some combination of air leak, throttle servo slop, and rich needle settings were to blame for the surging at mid throttle.

Thanks - Jaketab
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Old 10-02-2009, 07:50 AM
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Re: DA-150 Surges at Mid-Range

Good news .... thanks for sharing.
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Old 04-30-2017, 01:47 PM
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Mine was doing same thing. It has KS 1090 tuned pipes.

SO then, while I was at the field, I searched and found this thread. I tried the one thing that was most easy, which was to lean the needles, did that in a step wise fashion, and now, it runs way better in mid range. still has just a tiny tiny bit, which I take it to mean, it is still slightly rich, and I will leave it that way for now.
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Old 04-30-2017, 05:23 PM
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I had that same issue years ago on cans and pipes. I cut the headers to the DA recommended length and it was still a light-switch at mid range. Just drove me nuts in hovers. Off came the cans and on went the in-cowls. Grrrrrrrrrrrrrr.........
I'm sure there's ways to fix it through header length, throttle curves and tuning, but I don't have the patience, and thankfully we have no noise issues around here. That was my only foray into cans/pipes.
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