orthobird

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 I have a dynaflite super decathlon, with saito FG 36
no maiden flight yet,
almost earlier today,
except, engine conked out on runway when i fully accelerated.

i have a problem.

engine has been run in my backyard for over 1 1/2 hours
using 20 to 1 oil mix, as prescribed by Saito.

I was set to fly plane today.

I built cowl with a total of 3 air inlet holes on the cowl front face.
  the outlet areas are much larger area thab the three intake holes.






took plane to airfield, turned on engine, and it was revving fine,

i then taxi'ed plane on runway, and walked behind it, warming up engine, and little up and down revving.  right before take off, i put full throttle whilst still holding the plane, just to do one last check.
it appeared to hesitate very minimal, once i let go of plane, full throttle, and it began to lose speed and engine almost shut off, i decreased throttle, and 

aborted flight.


while cowl was still on, i tested again,

i turned on engine, then began to throttle, and on doing so, it sounded like engine wants to die 
if i do not decreased throttle, it would shut off for sure.

i can throttle from iddle to about 1/4 speed, past this, and it wants to die.

i know engine is hot by now

so it sounds to me like there is an issue with airflow in the cowl, or warm air, or turbulunce issues.


does anyone have any suggestions,.

i do not want to fly plane with out the cowl.

if the cowl is off, the engine runs fine
and i can get 7800 rpm with a 18 x 8 prop

Mein Duff

Maybe you could post a few pics of the size and placement of the 3 cooling holes? It might be a good idea to install some baffles which would deflect more cooling air to the cylinder head area.

Ernie Misner

It may be tuned slightly too lean and / or is tending to get hot with the cowling in place. If it runs fine without the cowling then there is definitely something wrong with the air flow when the cowling is in place. It may need more break in time as well. You can try increasing the size of the openings or fly it without the cowling altough you don't want to for some reason. Try richening it up a little and see how it goes. Keep us posted.....

Ernie Misner

orthobird

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i have to fly with cowl, because i added 6 ounces of weight in it
this is necessary, since plane is tail heavy,
and with these weights, the CG is at where dynaflite wants it,
i have already put weights under the gas tank, about 5 ounces there as well.

Sharpeye22

I had the same problem with my FG30. I had to retune the engine so that it was a bit richer with the cowl off. When I installed the cowl it would lean out.It took some trial and error till I got it right. This is the same problem I have had in the past with some of my 2 strokes when they are tightly cowled.

orthobird

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here is the pic

any suggestions would be great

orthobird

My Feedback: (1)

here is the pic

any suggestions would be great

hsukaria

well, most of the cylinder and the whole cylinder head is out in the airstream. I can't see how that is causing the problem. Is it possible that a fuel line is getting pinched by the cowl?

orthobird

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i will check that

Ernie Misner

Gasoline isn't going to give you the cooling effect that an alcohol burning engine receives. If the problem persists and it still runs great without the cowling, I would absolutely open up those cooling holes larger and larger as necessary. And you are correct that the exit opening needs to be 2 - 3 times more area than the entrance openings. It helps that the cylinder is mostly exposed but gasoline can run very hot. How does the plug look when it dies? It should be just tan in color, not whiteish. And once again make sure it is plenty rich especially until you get more time on it.

Ernie Misner

orthobird

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Thank you Ernie

orthobird

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update

i opened the three front openings up more on the cowl
then i made 4 small holes on the top of cowl, where i could see the high speed needle and use a special thin screwdriver, with which
i could adjust HSN with engine and cowl on.

took plane to my back yard, this time, with cowl still on.

turned engine on, within a minute of allowing engine to warm up, i tried to rev engine up, and it was doing same thing as yesterday.
i brought out my screwdriver, and
i did have to richen the flow of gas by about 1 1/2 turns
and then it had power
i got 7950 rpm with a 18 x 8 master airscrew prop
and was able to run it for about 20 minutes, no conking out
howeverthe only thing is that once in a while, it would hiccup, but would not turn off.

i wonder if i need to make an airscoop that will flow air near to carb opening?

orthobird

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[youtube][/youtubehttp://www.youtube.com/watch?v=6ChTLNYWHdI

Ernie Misner

The air inside of the cowling should be fine for carb intake unless the cowling is ridicously close to the carb intake and restricting it some how which isn't likely. You are making good progress. I think the hicup will go away when you get more time one it and are able to lean it out slightly from where you are at this point. Keep us posted, good work.

Ernie Misner

SrTelemaster150

^^^^X2.^^^^

Tune it on the rich side.

orthobird

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update, flew the plane today, maiden flight

the engine did great

had a 18 x 8 nylon prop

prior to flight, it was a warmer day than any other day i had the plane,

i made the gas flow richer again by 1/2 turn

got 7800 rpm on the tach

whole flight, not a single problem with engine,

very strong throughout.

thanks guys for all the help.

Mein Duff

The sweet smell of success ! Congrats !

Ernie Misner

Did you use about 25 cents worth of gas?.....

Ernie

orthobird

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thanks again Ernie,
engine is a dream!!!

SrTelemaster150

I guess I should be happy W/my (spark ignition) FA 150 running on E85/Klotz turning a nylon 18X8 @ 7500 RPM.

It turns the same 7800 RPM W/the 18X8 as your FG 36 when I run 15% Cool Power on the electronic ignition but it burns through 16oz of fuel in 12 minutes @ WOT.

I ran the E85/Klotz @ WOT for 15 minutes & only used about 8oz of fuel.

I need to put a pump/regulator on the glow carb as it is erratic as far as tuning. ST Engines has been developing the P/R as a less expensive, lighter, more compact alternative to going to a Walbro carburetor.

SrTelemaster150

deleted

KenD

My Feedback: (65)

What's the chance of seeing some pics of your 150 with the ignition pickup installed?
Thanks

Rudolph Hart

C'mon you guys it's the nitro that puts the bark in the dog,hang the extra fuel costtomorrow may never come

flycatch

My Feedback: (26)

I recently purchased a Saito 220 NIB and it has a problem. I'm not new to Saitos but have never experienced this particular problem and need some advice. The problem is when I move the throttle past 1/2 it backfires and throws the prop assembly. NV setting is according to the instructions for break-in and it idles fine and runs up to half throttle with no problem.

Garthwood

So true......................if you don't spend it your kids will after we're gone.


Last week i ran in my SAITO 125A the one that seized up on me last fall. Got it back from Horizon......it is installed on a TF Sea Fury. With a 3-Blade Graupner it tached around 7000-7200 rpms. It still needs more running in. The high speed needle is 3 full turns out. The idle speed needle has not been touched yet, but it sitting 1mm below from flush. The weather turned cold again, so it will be a while for the next run.
Total weight of the Sea Fury (empty) is between 13-14 lbs. I'm wondering if at those rpms/prop combination if it will be able to take off. What is the formula if there's any ? This prop generates more torque. Any comments from the warbirds guys ?