Originally posted by stefan
Now, please tell me if it is advisable to change the conrod after break in or if the people that had problems did something wrong during break in.
Also, do you know if the cut out below the boost port is ROAR legal, or is it considered an additional port?
The new sleeve and piston set is very tight. It will let the rod have to take a very big stress during breaking in. And make the bushing worn fast even break if you make the rpm too high. So don't make the rpm too high when the sleeve and piston still tight. The most important thing is let everybody know that when the break-in process through. Then they just know when they can lean it to their heart's content.
We have ever changed the conrods production-line to make the bushing more thicker. So all the newest Dragon have upgraded conrods. I prefer to let every customer know what can be happened rather than hide them. Maybe my way make you worry. But to my consumer viewpoint(I'm still a customer to other manufactories
),I rather know every truth if they can tell me in advance.
Read the Instruction Manual,
1. Install a new glow-plug (Hotter rated plugs will be better for the rich settings used during break-in)
2. Use normal fuel, 5%~15% nitro is best.
3. First tank of fuel: Start your engine, idle for 2 minutes then stop and let it cool down. Whenever you stop the motor please ensure, by rotating the flywheel by hand (careful it can be hot), that the piston is NOT at Top Dead Center (TDC), let cool. Repeat the "start-idle cycle" 6 to 8 times. If idle rpm is too high, adjust the slow needle. Make sure the temperature is under 80C (176F), it is good if some raw fuel is spitting from the exhaust.
PS:This way we call it cold run in. The piston expand when hot and shrink whan cold down. This way let piston adapt the change of temperature and also let the piston get tempered and the correct clearances. If you have done the "start-idle cycle",you will find the engine is more easy to break-in.
Idling a engine can let it clean itself without hurt(least) if there is any internal impurities. So I usual let my engine idle for a while if I have ever opened it. All parts need run in for a while including conrod;bearings;crank...etc. So if I change any part I will let it idle for a while,too. Any engine needs warm up a while after started. One is for hot expand another reason is for lubrication. So don't full throttle when the engine still cold...
4. Next several tanks of fuel: run the car on the track at low speed (50% to 80% throttle). Avoid using a constant throttle position; keep blipping the throttle to vary the rpm, slow-fast-slow-fast etc. Check the temperature regularly and keep it between 80 oC (176 F) and 100 oC (212 F), if you can not measure temps make sure smoke is always being generated out the tuned pipe.
PS.This way we call it hot run in. Avoid using a constant throttle position let piston can be rubbed on all sides. During this step,the temperature control and rpm control are very important. If you make the rpm too high,you will find some vertical lines on the sleeve internal. It is not caused by some dirts enter your engine,and it may make the engine lose some compression. Temperature control for sure your engine have enough lubrication.
5. After about 1~2 liter fuel through it, take out the glow plug and turn the flywheel by hand, let the piston pass the top dead center in the sleeve. When you don't have any significant friction or just a little snug, you can start leaning the main needle incrementally in small steps, and keep it around 100~120 oC (212~248 F).
PS.Yes,you need about 1~2 liter fuel through for sure that you can start to lean it. STS's piston is harder than Novas. If you have more patience to break in our engine,you will find our engine more lasting. Mine D3 borrowed to my racer for racing last weekend,he still win the A-champion. In fact I got that engine about half year ago.(practice plus 4 times races) I guessed about 4 gallons through it already. But still have unbelievable compression.
I have a special way to check the break-in. Put a white tissue outside of the tail pipe. Let the smoke spray on it and open the throttle a bit. If you can't find any impurity but only oil,that means your engine is clean and no more fine metal particles out.
After break-in process,I will take apart it thorough. First I will check the con. rod bushings and pins. If there is a play,I will replace with new parts. Then I will check the bearing and crankpin. If there is any play,I prefer to spend some money to replace with new parts. I don't want to bet with full engine life and guess it still ok. In my opinion,I spend valuable time to run it a engine or you can say I bring it up like a pet. He/she have to work hard for me,I don't want he/she feel any uncomfortable. Have you ever run with a over-size shoes? Yes,it dose uncomfortable and maybe you will fall down.
About the engine operating temperature I want to do some additional remarks.
20-30C max about 120C (68-86F max 248F)
10-20C max about 100C (50-68F max 212F)
0-10C max about 80C (32-50F max 176F)
About under 0C??? Sorry I have no chance to do the test.
With Lola body,the engine should run colder because heat leave fast.
A working fine engine can drink all of the fuel in the tank and keep stable temperature;stable idle;never singing. When you feel the engine not fast enough but working fine,first thing you should think about is ....
1)If the tyres stick?or the track is clean without many sand?
2)If you should change the gear ratio?
3)If the clutch is ok?
4)If the transmission or bearing smooth?
5)The last way is to lean a bit your engine.