RE: SK ENGINES

RE: SK ENGINES
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RE: SK ENGINES - 9/30/2007 1:05:28 AM

spad4mebaby

Posts: 65
Joined: 8/14/2007
From: Bull Head, AZ, USA
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Thank you TURK1 I will search for Downunders posts.

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Post #: 401

RE: SK ENGINES - 10/4/2007 8:25:27 AM

XJet

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From: Tokoroa, NEW ZEALAND
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The SK50 has had around 3 hours running now and isn't getting any stronger.

The transition isn't improving any either -- while it's not "bad" it's still not an engine I'd use for 3D -- with a definite tendency to load up in the mid-range and cough a little when the throttle is snapped open after being throttled back for more than a few seconds. The SK50 isn't unique in this, lots of 2-stroke engines do it and it's only the real gems like the OS, TT, Webra and a few others that have the truly snappy response that is essential for true hard-core 3D flying.

The bottom end is as lean as can be without the engine threatening to die from fuel-starvation when the throttle is opened and the hi-speed needle is 200-300RPMs off peak. However, the mid-range remains rich and the engine will drop in and out of a 4-stroke at half-throttle -- which makes flying 3D *very* difficult because it means the power level is constantly going up and down.

One thing I noticed today was that drilling out the muffler exit by just 1mm made a *huge* difference to the engine's power and transition (and not much to the noise).

I gained over 800 RPMs on a 10x6 prop after drilling.

This weekend (if the weather allows) I'll first try a Tower/GMS muffler and then one of my mousse-can pipes along with a range of other props to see what this engine is really capable of.

The reviewing continues...

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Post #: 402

RE: SK ENGINES - 10/4/2007 11:33:53 AM

rainedave

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From: Greensboro, NC, USA
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quote:

ORIGINAL: XJet

I gained over 800 RPMs on a 10x6 prop after drilling.

I thought I read here that this engine's personality changes dramatically when spinning a 12x5. I could be mistaken, but I seem to recall reading that it doesn't like small props, either.

I know what you're going to say, "What good is an engine that is limited to one size range of props?" but that may be the case with the SK.

David

(in reply to XJet)

Post #: 403

RE: SK ENGINES - 10/4/2007 3:07:08 PM

spad4mebaby

Posts: 65
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From: Bull Head, AZ, USA
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I drilled the muffler output hole waaay larger and used a piece of fuel line from an automobile supply house. I handed the hapless autozone clerk my muffler and told him I wanted a tail pipe ----for a chinese import-----and a spring clamp. Cost for four setups about $4.00 Two feet of tubing and 4 clamps.

I also use a pressurized bladder style tank..
A Poor mans jett tank.
a tower pillow pak plastic bag in a clear 16 oz pop bottle.
A check valve from a windex bottle.
Good fuel flow at any angle.
A little hard to fill.

I use the recommended 12-5 APC prop.

My next step is porting and polishing the sleeve . Which to me seems a simple way to obtain more power.
Next is to try moving the sleeve. up or down slightly

The stock muffler could be the key to more power for you.
My plane engine (SK-50) does not change power levels at any angle now. and is smooth enough for me to attempt hovering and other things.( trimming trees, etc).
I just have to be sure that the wind is blowing away from me. Very Close in slow flying up and down. Did I say Very close in.

< Message edited by spad4mebaby -- 10/4/2007 3:26:49 PM >

(in reply to rainedave)

Post #: 404

RE: SK ENGINES - 10/4/2007 6:07:30 PM

playntraffic

Posts: 124
Joined: 3/20/2006
From: Alabaster, AL, USA
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spad;

can you snap some photos of your muffler? I am not following your discription. How would Tower's .46 muffler work?

My SK50 is running pretty well. I am going to take an RPM reading with the stock muffler and then a Macs one piece and see if I get positive results.

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Post #: 405

RE: SK ENGINES - 10/4/2007 7:01:10 PM

Turk1

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Joined: 10/8/2004
From: Istanbul, TURKEY
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Some friends use lesser props on SK 50 with high revs(10x6-11x6) and there seems no overheat problem.Also I have tried 11x8 APC without a problem. So my opinion is to try as many props to find best suitable combination for an individual model.

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Post #: 406

RE: SK ENGINES - 10/4/2007 7:37:28 PM

spad4mebaby

Posts: 65
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From: Bull Head, AZ, USA
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This thread reply's are confusing not the topic . Please address to whom you are replying to.

Play

My muffler is stock except for a drilled out exhaust piece. My muffler has a front with manifold, then a middle aluminum tube, and finally an end piece that I drilled out.

This is what it cost me to get back into this hobby. So a Webra, Rossi, MVVS, engine is not needed.
A used 4 mm coro realtors sign cost $0
Sk 50 engine $60.00
Futaba faast radio $203.00
5 hitec 425 servo's $75.00
aluminum tubing, pool noodles, blue electrical boxes, super glue and assorted hardware $50.00
A very fine 3d trainer
I was so impressed
I needed more.

I use for example per plane
$10.00 worth of 2mm and 4mm coro
Sk 50 engine $60.00
Futaba faast radio reciever $90.00
5 hitec 425 servo's $75.00, or 5 chinese metal gear mini-servos $100.00
aluminum tubing, pool noodles, blue electrical boxes, super glue and assorted hardware $50.00
A very fine trainer or plain old plane.
Plus the usual fuss and bother

(in reply to playntraffic)

Post #: 407

RE: SK ENGINES - 10/5/2007 3:00:37 AM

XJet

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From: Tokoroa, NEW ZEALAND
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quote:

ORIGINAL: rainedave
I thought I read here that this engine's personality changes dramatically when spinning a 12x5. I could be mistaken, but I seem to recall reading that it doesn't like small props, either.

That's also what I read but *my* Sk50 is very lackluster with larger props -- read back a few posts and you'll see my tach figures.

It is *much* better with smaller props -- which is why I'm wondering if it's ported differently to the ones that Kange are importing into the USA (although I can't see why it would be).

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Post #: 408

RE: SK ENGINES - 10/12/2007 8:44:14 AM

XJet

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Well I think I've found out how to make an Sk50 really sing.

Tonight I fitted a mousse-can pipe to my SK50 and the difference in performance (albeit only subjectively at this stage) is quite stunning.

I would say (just by ear) that the engine has gained at least 1000 RPMs over the stock muffler with a drilled-out tailpipe.

The transition is also very snappy on the relatively small prop I'm using -- and it really pulls hard now.

I hope to get time to accurately quantify the true effect of the MCP tomorrow when I'll throw a tach on the motor but it looks as if (at least the engine I've got) really responds well to a better design of exhaust system.

To be honest, I've never been a fan of that generic Chinese two/three-part muffler. They're restrictive and really kill the performance of most engines they're fitted to -- but it looks as if this power hit is even greater on the SK50.

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Post #: 409

RE: SK ENGINES - 10/12/2007 4:37:06 PM

Ed Cregger

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From: Ringgold, GA, USA
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quote:

ORIGINAL: XJet

Well I think I've found out how to make an Sk50 really sing.

Tonight I fitted a mousse-can pipe to my SK50 and the difference in performance (albeit only subjectively at this stage) is quite stunning.

I would say (just by ear) that the engine has gained at least 1000 RPMs over the stock muffler with a drilled-out tailpipe.

The transition is also very snappy on the relatively small prop I'm using -- and it really pulls hard now.

I hope to get time to accurately quantify the true effect of the MCP tomorrow when I'll throw a tach on the motor but it looks as if (at least the engine I've got) really responds well to a better design of exhaust system.

To be honest, I've never been a fan of that generic Chinese two/three-part muffler. They're restrictive and really kill the performance of most engines they're fitted to -- but it looks as if this power hit is even greater on the SK50.

---------------

I'm with you. Mousse can pipes are really the best all around exhaust systems for most applications. They're broadband devices which come close (sometimes exceeding) open exhaust rpm figures. They are almost always quieter than a stock muffler, lighter than a stock muffler and they are inexpensive to make at home. The most expensive part of the set up is the tuned pipe header, which most of us buy at one point or another if we really like the engine.

If anyone wants to know how to construct them and wants to read up a bit on them, do a Google groups search for Bob Adkins, mousse can pipe, rec.models.rc.air. Bob has a vast amount of knowledge gained by experience, plus he's no dummy at engineering either.

Ed Cregger

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Post #: 410

RE: SK ENGINES - 10/13/2007 2:21:33 AM

spad4mebaby

Posts: 65
Joined: 8/14/2007
From: Bull Head, AZ, USA
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Xjet

Glad to hear you got your engine running good.

Your post
"Well I think I've found out how to make an Sk50 really sing.

Tonight I fitted a mousse-can pipe to my SK50 and the difference in performance (albeit only subjectively at this stage) is quite stunning.

I would say (just by ear) that the engine has gained at least 1000 RPMs over the stock muffler with a drilled-out tailpipe.

The transition is also very snappy on the relatively small prop I'm using -- and it really pulls hard now.

I hope to get time to accurately quantify the true effect of the MCP tomorrow when I'll throw a tach on the motor but it looks as if (at least the engine I've got) really responds well to a better design of exhaust system."

Good for you.

Post details for example, header pipe, diameter of can, length of system, output tube, thanks in advance.

(in reply to Ed Cregger)

Post #: 411

RE: SK ENGINES - 10/13/2007 6:22:52 AM

XJet

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The weather wasn't so good today but if it's better tmorrow I'll take some tach readings and pictures -- although I've had my picture-posting privileges removed from RCU so I won't be able to post them here :-( MODERATOR - ARE YOU READING THIS??? -- WHY???

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Post #: 412

RE: SK ENGINES - 10/13/2007 10:27:45 AM

TestPilot6

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Joined: 9/18/2005
From: San Francisco, CA, USA
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Interesting to know what kind of original SK muffler you have, XJet. I read in some place about a year ago that they changed from the "old" muffler to new mousse can type muffler and iruns much better. I wonder if my muffler is actually a "mousse can" type muffler. I got my SK-50 from Kangke about a year ago. Mine is about 7" long, 1.25" in diameter one chamber construction made from 3 parts.

My SK-50 runs over 12000 rpm with 5% Cool Power. It's been through about 2 to 3 gallons of fuel. I remember it started to run almost as good as now after a few tank full of fuel.

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Post #: 413

RE: SK ENGINES - 10/13/2007 10:44:56 AM

XJet

Posts: 3453
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From: Tokoroa, NEW ZEALAND
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The muffler that came with my engine is the same as pictured here:

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Post #: 414

RE: SK ENGINES - 10/13/2007 3:47:46 PM

blw

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Joined: 3/15/2004
From: Auburn, AL, USA
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xjet- yes, we are reading. Looks like your privileges weren't removed.

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