Shike 10-15 engine?
)
! I have a .15 LA on a wonder that could need some fine tuning 
10-27-2005, 06:03 PM
#29
Senior Member
My Feedback: (9)
Join Date: Dec 2002
Location: South Bend,
IN
Posts: 145
Likes: 0
Received 0 Likes
on
0 Posts
RE: Shike 10-15 engine?
Ok fellas....I'll try to get you what I know and I hope you find it useful. I learned these tips from some of the other guys I race with. The first thing you want to do is get a good glow plug. It's been my experience that the K&B 1L plug works best with these engines. I noticed an increase in top end rpm right away with this plug over the OS A3. In bigger engines, I have not noticed any increase in high rpm when I changed to the K&B plug. You will also want to increase your compression ratio. There are two methods for doing this, you can use one or both, you might want to experiment. You can remove the head shim or head gasket, whatever you want to call it. When you take the head off, you'll see a circle under the head where it touches the top of the cylinder, it may appear there is nothing there, but there is, with a small flat blade screwdriver, you can get under the shim and remove it. The other way to increase your compression ratio is to not install the copper washer under the glow plug. If you're using the K & B plug, you won't have issues with the plug hitting the piston at TDC. There are also some mods you can do on the exhaust system, but please understand, these engines do rely on back pressure to force fuel into the carburetor, anything you do to the exhaust system may have an effect on fuel flow. You should do the things I have already mentioned first, tach your engine, and then work on the exhaust if you want to try for more RPM. Ok, we all know about baffles. The OS 15's baffle is unique in that if you remove it, you actually shorten the muffler. Try removing the baffle first, you may find you have to place washers on the bolt that holds the muffler together to get the retaining nut on far enough. If you don't want to remove the baffle, you can take it out and expand the hole in it using a drill with an all purpose high speed bit and then put the whole thing back together. You may also, use a tapered ream and venturi out the stinger, that's the little thing where the exhaust exits the muffler. I have never reamed a stinger myself, I have had other people do it for me. I and other racers in my club believe this helps suck the exhaust out of the engine more efficiently, this is only an opinion. If this is done properly, the stinger will be wider at the end and tapered as you go further inside of it. Other things to consider would be to assure that you have no air leaks. Place a piece of fuel tubing over the high speed needle valve to help seal it in the housing. Place small zip ties around the nipples where the fuel line hooks to the engine. If you can get ahold of a carb from on OS 15fp, but it on the LA in place of the rear needle carb as this will also help reduce air leaks. Please understand, these mods are done to increase top RPM, they may have an adverse effect on engine idle and midrange performance. I would try one mod at a time, starting with the K&B glow plug, it has been my experience that this is single best way to pick up 500 to 700 rpm without having to do anything else. Get a reliable tach and check your engine from behind the airplane. I usually use the top of the fuselage as a rest for the hand holding the tach. It's important that you check the engine's RPM readings from the same point all the time to get reliable readings. The master airscrew 7 by 5 prop is my prop of choice and a high quality fuel with 15% nitro content is my fuel of choice. I have also experimented with higher nitro contents with not much more success. It's my opinion that the higher nitro fuel doesn't boost RPM enough to justify it's higher price. One last thing, don't try to get more RPM by leaning the engine too far. Using your tach, get max RPM just before the engine falls off, then back the needle out to a point were you give back a couple hundred RPM or so. This will help fuel flow in light of decreased back pressure and assure proper lubrication. Well, that's alot of info, I hope it helps. Happy flying
