hrdcoreglf
Posts: 759
Joined: 5/2/2007
From: Boca Raton,
FL, USA
Status: offline
|
Here is the os chart so you can check plug selection http://www.osengines.com/accys/glowplugs.html
I was able to squeeze a hump pack in my radio box, but ofna does sell a syick pack cover for the side of the radio box. If you are not sure what to look for just let me know. Here is a good break-in procedure for heat cycling.
Heat cycling for stress relief
Stress relief is accomplished by repeatedly heating and cooling the engine-short engine runs followed by complete cooling repeated many times. ABC engine break-in involves such heat cycles, betit is not the same proceedure as is used for non ABC engines.
ABC break-in the inside story
Abc engines require a shorter break-in (heat cycling) than engines of the past- less than 45 min. for most. To attain and maintain maximum power levels, however, requires adherence to an entirely new set of break-in rules.
The primary objective of ABC break-in is to maintain the delicate top of the piston pinch zone while allowing the internal engine components to heat cycle with some minor smoothing and allignment (crankpin, wristpin, rod journals, etc.).
Here is how this is achieved:
FUEL- Use the same fuel for break-in as you will for normal operation. If you break-in your engine with low nitromethane fuel, e.g., 5% and then jump to 20% for actual running, the piston / cylinder fit will be too loose. Five % nitro doesn't generate as high a combustion temp., so the cylinder won't expand as much, and the pinch zone will wear more than if the cylinder had pulled away farther, as it would with the hotter burning, higher nitro fuel.
2- vs. 4-cycling operation
If you run a 2-stroke engine then you have heard of 4-cycling. When a two stroke engine is operated very fuel-rich or at somewhere below 1/2 throttle, it begins to fire on alternate crankshaft revolution. As the mixture is richened at wide open throttle, the ehaust sounds like this as it breaks from 2-cycling to 4-cycling: " RRREEEAAAHHHHHHH."
As the throttle is reduced to about 1/2, the exaust sounds like this, as it breaks from 2-cycling to 4-cycling: "RRRRREEEEETAT-TAT-TAT-TAT."
With both examples comes a simotanios loss of rpm with the change in exuast sound. This is 4-cycling. Learn to avoidit. Because the ABC-type engines were originally designed as WOT racing engines, their pistons and cylinders operated happily. Today, ABC engines are also expected to idle and throttle reliably. Unfortunatly this allows them to cool excessively, especially below 1/2 throttle, where poor cylinder scavenging (clearing) causes them to 4-cycle and wear away the critical pinch zone as the piston sleeve cools and tightens around the piston
Throttling is a necessary phase of running nitro engines in cars, so you can't simply eliminate it from your routine, but do not allow the engine to 4-cycle during break-in. Afterward, when engine components have been stess-relieved and bedded in through heat-cycling, the wearing effect of 4-cycling will be minimized.
Tight ABC piston/cylinder assemblies
Some new Abc-type engines are so tight at TDC that for the first few times the engine is cranked over and run, the possibility exist of damaging the connecting rod, crankpin, and piston. To avoid this, preheat the cylinder and the head with a heat gun or a hair dryer. This preheating expands the piston sleeve, and that minimizes the potential for stress on all the engine components during initial startup.
. ABC break-in in the car
Set the main needle according to the manufacturer's specifications (e.g., 2 to 3 turns counterclockwise from closed). Open the idle needle several turns so the engine shuts off when abruptly throttled back.
-Start the engine
-Advance the throttle to 1/2. Listen for 4-cycling. Lean the mixture to a rich two cycle operation.
-Run the car in a 100 foot diameter circle or figure 8. Keep the throttle at 1/2 and listen for 4-cycling. Don't let this happen! If it does, immediately lean the main fuel needle a little at a time until the engine produces a clean, steady 2-cycling sound. Run your car in a cicle/ figure 8 for about 1 minute. When the minute is up immediatly check the head temp.
Keep a log of run time, head temp, estimated rpm and your perfomance comments.
The goal is to keep the head temp. at above 200 degrees F. and less than approximately 230 degrees F. If the head temp. is less than 200 degrees F. lean the high speed needle slightly, and try again after the engine has completely cooled. When the engine stops, using the fly wheel turn the piston to BDC.
-Perform the 1 minute run at least three times while you adjust the head temp. by "tweaking" the needle valve as needed.
-Now run the car around for 2 minutes at least twice. Remember: 1/2 throttle and no four cycling. Same game : check head temp., allow it to cool, record data.
-Don't be tempted to open the throttle wide! The mixture settings will probably be all wrong for wide open throttle(WOT)(. There is plenty of time for that later.
-The rest of the 1/2 throttle break-in runs will be 3 minutes long. When they tottle 35 minutes(minimum), you have successfully heat-cycled your engine and break-in is properly complete. If you like you can run it another 10 minutes or so it won't hurt.
-Tune the engine for WOT and idle operation.
To read " Super Engine Tining" by Steve Pond go to ( rcnitro.com/artcles/index.asp )
_____________________________
Wisdom is only as good as the person you give it to.
|
Printable Version
All Forums >> RC Cars, Buggies, Trucks, Tanks and more >> RC 1/8th Scale Buggies >> RE: !!!!!!Official Ofna Ravager Thread!!!!!! 
RE: !!!!!!Official Ofna Ravager Thread!!!!!! - 
. I'm re living my child hood 
Back in 1985 I had the Tamiya Frog with a Futuba control and a 7.2 volt 
Many questions...