I own a DLE170 (I suspect first generation) with only +/- 60 minutes of running time. It is mounted on a Extreme Flight 125" Extra 300 with Mtw RE3 tuned pipes and Mejzlik 30x12 prop.

On the ground it runs completely fine, but as soon as the plane gets airborne, it runs very rough.

I've already tried a 3W inlet and filter, but the engine doesn't run great with them, so I removed them.

Any ideas? I'm running out of ideas at the moment. While browsing this forum, I found some people who had replaced the original carb, is the stock carb a bad one perhaps?

Thanks

hello Alex
I have had the same plane and engine.
I think your prop is a little small, I use a 30x13 PT. To have the good tuning with RE3 you must have 35 cm headers. With this the needles must been open 1 1/2 on low and 1 3/4 high.
The DLE carb works well I have tried a WB27 (as DA 170) with no better résult.
May be you have to change the diaphragm.
Yves

Could be turbulence getting to the diaphragm plate.

Originally Posted by papy69

hello Alex
I have had the same plane and engine.
I think your prop is a little small, I use a 30x13 PT. To have the good tuning with RE3 you must have 35 cm headers. With this the needles must been open 1 1/2 on low and 1 3/4 high.
The DLE carb works well I have tried a WB27 (as DA 170) with no better résult.
May be you have to change the diaphragm.
Yves

Hi Yves!

The 30x12 is only for breaking in the engine.

Have you done anything on the engine cowl or on the carb itself? (maybe a picture of your setup?)

Thanks man.

Hi Alex
I have just put baffles as usualy.
I have no pictures at this time.
Yves

Originally Posted by papy69

Hi Alex
I have just put baffles as usualy.
I have no pictures at this time.
Yves

Good to know. You left the hole open in the cowl? (beneath the cilinders)

And no filter on the carb and/or put a fuel line on the pressure nipple? (some people do that to get the pressure from inside the fuselage)

Thanks mate.

Yes I let the hole open and I use it to put the choke directly with the fingers.
I take off the filter inside the carb and I put a big one on the line between the tank and carb
Very important I use in the tank a clunk like this
https://hobbyking.com/fr_fr/felt-fue...large-2pc.html
no fuel line in the pressure nipple.
friendly
Yves

Not likely related but since you have the filtered clunk get rid of all other filters at least until you get it running right. Keep it simple while troubke shooting.

Rough running makes electrical jump out at me at the moment. Eliminate all devices between a known good battery and the ignition and try again.

Please discribe us the trouble with th engine. does it cough, cut , lose power and so on.
I am ok with KMatch about electricals problems. You must have a power supply at mini 6 V (4.8 is not enought). On all my gas engines models (8) I use a 2s lipo batterie with a Ubec (out 6 v) killswitch Rcxcel and a signal booster between the Rx and killswitch..
Like said by KMatch may be you have a faulty connection on th line. Use a 6v batterie directly on the input of the ignition.
At least replace the sensor .
Yves

Thanks guys,

When taking off with a full tank, the engine rpm decreases heavily, also when I fly inverted, so I don't trust it very much. Midrange is horrible as well, but only in the air.

With filter I meant airfilter.

For the ignition I use a 2s lipo connected to the Powerbox Digiswitch 5.9V.

The first two things I think of is turbulence affecting the pump diaphragm
Or the vent line is creating a vacuum by how it is placed in the air stream

You described a clunk issue perfectly. Start by pulling the line out of the fuel tank. I don't care if it's new and installed yesterday. I've heard that before when lines were off or cracked. Look there first. If you absolutely can't find anything wrong, look into the carb vent mod as boothg-3 is hinting at. You can solder a tube to the plate on the carb and run the vent line into stagnant air. This is a common fix for a semi common problem.

I had a similar issue with my DLE 170 (although it wouldn't always run good on the ground). I tried numerous things; adjusting the DLE carb, replacing the DLE carb with another DLE carb, replacing gaskets on all the intake items (carb & heat block) and retightening the carb bolts. What fixed it after 4 weeks of adjusting was a new ignition and Walbro carb from DA. I believe the issue was the ignition pickup sensor but I was so tired of taking out the 21 bolts on the Hangar 9 Sukhoi cowl that I replaced the DLE carb with a Walbro carb at the same time as the ignition system.

When I checked the timing, it was sometimes firing at 48 degrees BTDC and other times at 32 degrees. I searched online and found if a pickup goes bad, sometimes it will fire as the magnet starts going under the pickup instead of after it leaves the pickup. I wasn't going to only replace the pickup as I was fed up with messing with this engine.

When I replaced the ignition I set the timing at 29 degrees BTDC and it now it runs like a champ!

One more time I am ok with KMatch for fuel line, there is already a nipple on the plate of genuine DLE carb, and with T-ster for ignition sensor. I have seen several time sensors giving two sparks,one before and one after the good timing. If the engine had too much advance it loose power and overheat. But it will do also on the ground.
I have had this kind of trouble with clogged tuned pipe (but after more than 300 fligts) .Too smalls extenders (not advised) at the output of exhauts can give same thing.
Yves

Air filter... I didn't catch that. Why an air filter? Is that a carb air filter or fuel tank breather filter? If it's on the carb, get rid of it for a test. Having airflow disrupted in flight with something like that could throw weird kinks we don't normally see since no one uses air filters on the carb. If it's on the tank vent, it's likely not a problem but make sure it's clear.