DA85 on pipe! Results please.

[Steve]

	Quote: Originally Posted by ejohn18
	here is my first run on my DA-85 on a K&S 1090 Eddy

Is that a 26 or 28 X 10 prop?

[ejohn18]

28x10 mej

[avi8freak]

I also have a 110" EF Yak...My 85 on greve pipe pulls this 28.5lb plane around with ease. I am running a 28x10 mej and it seems perfect also...I will be flying mostly IMAC in the Southeast with it, but is set up for a good mix between 3D and IMAC. I couldnt be any happier with mine at this point...only have 20 flights so far...weather has not been ideal here.

[Ground Pounder]

OK, a number of us who fly the 85 and 1090 pipe have "seen the light" and are sold on the Mej 28 x 10 which turns roughly 6600 in many cases. My 29.5 lb 110" flys like a foamy.

Has anyone tried the 29 x 10 and reported the rpm and flight performance?

[Royster]

Can anyone suggest a fix for the following issue:

Have a DA85 in a Wild Hare 35% Sukhoi and the motor surges (RPM changes) between inverted and upright at mid throttle. Plus when I do a 45 downline positive snap on idle the motor dies. The idle is up so its not from too low an idle.
Also the motor seems fine when over 50% throttle. Anything below mid is where the problem lies.

Have check fuel lines, changed plug, changed to a higher Mah pack on the ignition (Fromeco LiPhe) and also checked clunk and throttle servo and linkage.

Some have said its a tuning issue but rather ask guys who own the 85

[krayzc]

richen that low end up

[Royster]

	Quote: Originally Posted by krayzc
	richen that low end up

Really? What makes you say that?

Most have said lean it out

[krayzc]

the motor is surging and it dies its surging because its not getting enough gas......

[pe reivers]

??
Please explain that.
Engine surging means either the engine is going on or off resonance with carb and / or muffler system, or there are some external reference changes, so the carb will not stay tuned to provide the mixture that the engine needs. Each failure mode has it's own set of cures, but you cannot mix them and hope for a solution. That would be like groping in the dark until you touch something you recognise.
Hardly the way to solve problems in a constructive way.

[Royster]

I beleive in "trial by elimination".

So what do I need to eliminate?

[pe reivers]

first off, this does not sound like a DA problem, unless caused by fuel puddling that the DA is known for.

first elimination: change engine (mostly not an option, and not needed if you know what to look for)

second, there is the orientation of the fuel metering diaphragm that responds to G-forces due to it's mass. With the membrane in vertical fashion (on edge), this issue should be non-existent.

third, the air pressure that the hole in he cover of the metering system "sees" changes wildly due to plane attitude and airflow speed changes. You may need to fit a static air pressure reference tube to solve that. (this would be the first cure in my book) Using this system, static and in flight mixture strength are the same.

Last but not least, the carb tuning may be way off. Follow the book, or the many good advices provided here.

[dbcaster]

Someone else just went through this issue and it turned out to be pressure in the fuse. You can easily try to cut a small opening in the rear of the fuse to see if that makes a difference.

[customjrod]

Plain and simple, RICHEN THE LOW END.

[Royster]

Thanks for the info guys.

I really do hope it is simple as richening it up but since it was tuned by DA Australia staff I doubt it very much however they have closed shop for the year so I have to sort this one out my self.

The pic bellow was taken during the build. As you can see it doesnt really open into the fuse.

Question: What if the side holes on the cast were seal with duct tape (as an experiment) to see if that affects pressure on the diaphram?

[Ground Pounder]

First go back and triple check your needle settings.

Then read through this thread. Camss and I have done a lot of work on this issue (using pitts and pipes). We tried "blue tape", false firewall air boxes and a other approaches. One at a time they were not enough put applied collectively, it final cleaned up the mid range.

http://www.flyinggiants.com/forums/f...5-burbles.html


Worked for us and may be of help to you.