kevinbell

My Feedback: (2)

Hi all,

I have a DA 50 in a 80" span CM PRO Extra 330. I had a canister type silencer made for it as our field is a bit noise sensitive.
Is the silencer restricting the power?

It has a Just Engines wooden prop 20x10 and run at @6200rpm, still being run in though, 32:1 on HR1 Bel ray oil. I think it may well be a little rich to protect it. There is very little amount of oil residue down the bottom of the fuz, an indication to me with my limited experience that it's running not too rich. Enough to wipe off with a hand wipe.

As far as elevation goes, it's 400ft absl and usually about 20'C.
Have a look at my exhaust and see if you think it's restricting the power at all. I think it might because it's very quiet, quieter that than some small .60 sized engines. These inlet and exhaust pipe measurements are ID, not OD.

The exhaust has one baffle mid way, it's a disk with holes drilled in it, don't know what size the holes are though.

mtwister

32.1 :1 is still pretty rich. I think as you get it broken in a couple gallons later, and switch up to 50:1 or better you will start to see it come alive. Just an opinion though.

Mike.

kevinbell

My Feedback: (2)

Ok,
I was planning on putting a menz 22x8 on it. I fly smaller models with saito's and run a 6" pitch on that it has really thrust to weight ratio. Do you think running an 8" pitch would be ok without exceeding the revs? What would be the maximum revs?

Kevin

Hans Meij

Yes the silencer creates this problem, it has nothing to do with the amount of oil.

rmh

from the picture your muffler setup is quite restrictive -- here is one I did for a ZDZ50 which is more in line with size required
the can is an all steel, one pint (16 ounce volume) container. It may not be pretty but should be much better at breathing than the device you are using.
.

kevinbell

My Feedback: (2)

Without changing the whole system what would you say would help? Is it the volume and the exhaust exit size?
Hmmm.... dilemma... Do I start again?
I do love power..
Kevin

Tired Old Man

My Feedback: (1)

Considering that you're using a prop that's 2" too small for the engine your rpm level is pitiful. I would be expecting something in the 7,600 area. A 22-8 should be turning up around 7,100-7,200. Get rid of the exhaust system, change the oil mixture to 50-1, and set the needles correctly. You're killing that engine very early in it's life.

kevinbell

My Feedback: (2)

Wow, so many helpful replies so quickly. A bit disappointed that the exhaust cost me so much money and basically wrong.. I did ask for it to be quiet but not hamper the power too much. Just Engines told me that I will loose a little but it sounds like I'm loosing a lot of power.
The model weighs 15lbs and will prop hang on about 2/3rds to 3/4 power, I would have expected at least 1/2 power..
Kevin

Hans Meij

Buy a BMB, MTW, Krumscheid etc. muffler

Tired Old Man

My Feedback: (1)

Go with what Hans just told you.

Panzlflyer

My Feedback: (15)

One difference between Dicks and yours is the way the bends are formed...his are nice and smooth, gas likes to flow.
you could mabe get a larger pipe to replace the small one on yours or try cutting it down a little...its all things combined that will get you.
I have a brand new DA with a 22/10 that does better than that although with a Pitts style Jtec. Outlets are probably 2x yours x2 but the Hogs and Turkeys nearby dont care

rmh

.

rmh

actually- the volume of my setup is considerably more.
The initial expansion makes a huge difference in power
as for oil to fuel - my 32-1 setups make most power -for me
My 50's (ZDZ) like large systems and tuned systems .
good systems run 7500-7700 rpm on 22x8 Mejzlic
the DA will do about the same.
Most in cowl mufflers KILL power
The header in the pic of the DA is way to close on initial bend at exhaust flange but the other sharp bends really don't do much harm For decent flow the first bend should not be nearly so sharp see pic attached

kevinbell

My Feedback: (2)

Where did you get that manifold/header from? It looks nice. I've had a look at BMB, MTW, Krumscheid systems, there doesn't ssem to be a nice curved pipe like Dick's. Is the length of the header critical like small 2 stroke engines with tuned pipes? The total length is a problem, the wing tube is in the way. The total distance from the engine exhaust port to the tube is 400mm.
Here's a photo before I cut anything, Ive moved the rudder servo closer to the tail. There's a shroud around the exhaust and the fuel tank is above it.

Kevin

Hans Meij

Mine,

is from MTW
Perhaps the one from Dick too.

bodywerks

My Feedback: (4)

Yep, that exhaust is killing your power. My Da, on a stock in-cowl muff, turned a PT 22X8 at 7200 within the first 2 minutes of running...

kevinbell

My Feedback: (2)

Hmm... I looking into getting a MTW exhaust system, might have to seriously modify the layout to accept a longer exhaust system.

You know it's funny to hear you abbreviate muffler to muff, it means something different here... Funny

Prapan

Hi Kevinbell, I am Prapan from Bangkok and started to fly gas engine airplane size 80 inch wingspan since last year and enjoy it very much. I have seen you just purchased EXTRA 330 from CMP product.
There is supplier here in Bangkok who supplies this one as well and please let me know about the performance with DA-50. I am looking for this one also.

Thanks.

kevinbell

My Feedback: (2)

It's mega! Not had enough time with it yet to say if it will harriar well,I would say the wing area isn't enough for the weight, it's bang on 15lbs. For the price it's well worth it!
It stalls flat does most of the aerobatics nicely. Knife edge is superb, flat spin, prop hang, blenders and flying inverted requires very little down.
I need to move the c of g back to have a go at harriars.

Kevin

kevinbell

My Feedback: (2)

Hi all,
Just to let you know that I've changed my exhaust system, I've kept the silencer, gutted it, ie, took the baffle out and the other crap, got a KS manifold like the ones in the photo's I received, well had to silver solder it up but the bends are so nice and smooth.....
Well.... huge difference!!! The silencer was a 600rpm increase and the manifold was a 700rpm increase!!! Now I'm seeing 7600/7700... Wow!!! Huge difference.... I have six pounds more thrust!! Only thing now is that it's noisy... well noisy tips, I'm running a wooden 22x8... crap I know... Not sure now if I should get carbon 20x10 or a 23x8 prop???

mrbigg

My Feedback: (21)

23x8 carbon.