|Sep 10, 2012, 10:03 PM|
Running and flying the SV-17cc gasoline RC engine
I accidentally deleted the entire thread by mistake. So I recreated it here again. Sorry.
A while back I had acquired a SV-17cc engine. At the time the reviews weren't all that good for it either. But the price was right, so I couldn't resist.
When I first ran the engine, I found that I couldn't lean it out enough to run at its top speed. It stayed blubbery rich even with the needle valve all the way out, ready to fall out even. So when I looked at the carb I found that it had a Walbro WT-694 carb on it with a 12.7mm venturi bore, which I thought was way too big for a 17cc engine. As I have seen them a carb with around a 9mm venturi is about right. A 12.7mm carb is big enough to run a 35cc engine or even some 50cc engines too. So I rummaged around and found a WT-520 carb with a 9.53mm venturi and I put it on the engine. Now the engine ran great, easy to adjust, throttle response good, nice RPMs and I could lean it out good too.
At that point I didn't see any reason to not use the engine as it was performing good now.
Using a 14x6 prop on the engine
Using a 15x6 prop
using a 13x8 prop
A 13x6 prop didn't gain anything with the engine
here is a pic of the engine running'
Of course then the muffler on the engine doesn't do anything to quiet down the engine either. That big exhaust outlet just lets the engine be horrendously loud.
So I made a baffle insert to help quiet the engine down more. The insert worked great. It knocked off about 10 db of noise off the engine when it is running. It only cost maybe 500 RPMs off the top end too.
Here is a video clip of me test running the engine after mounting the WT520 carb on it.
Here is a video clip with the engine being run with the DIY baffle insert. At the end of the clip I put in a short clip and alternated it showing the different in noise levels with the baffle and without the baffle insert.
My iPhone Db meter was showing a touch over 90db when standing on top of the plane, much more close than the recommended 20 feet from the exhaust side of the engine too. So the baffle insert does work well.
Getting more close to the engine resulted in about a 95 db noise level, but that is getting too close really.
|Sep 10, 2012, 10:06 PM|
After that I mounted the engine on my Great Planes Escapade .60 RC plane. The plane flew quite well with the SV 17cc engine on it. It could use a little more power, but otherwise it flew really well. The engine and carb tends to be a bit cold blooded in that you have to warm it up before you can go full throttle and fly it of course. The WT-520 carb doesn't have a choke either. But it doesn't really need it so far. It does have a external primer bulb though, and that is pretty handy.
The baffle insert makes the engine less noisy than many glow engines with nicer mufflers too. When flying it around it is not very noisy or annoying at all.
I also weighed the plane and it weighs in at 9 pounds 4 ounces with the fuel tank empty. I am thinking about changing the two NMH battery packs to a single LiFePo4 battery pack too. This would save a little more weight. Using a Tech Aero Ultra IBec would also work as it regulates the voltage for the CDI unit and also serves as a ignition cutoff switch too.
Here is a video clip of me flying the Escapade plane with the SV 17cc engine on it.
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