Technex

Hello guys,

Just got a new piston and liner, bushing, con rod and bearings installed on my O.S. 21VG PX.

I'm going to break it in again tomorrow.

Instead of using the crappy way it shows in the manual (which made my last piston and liner last just about half a gallon with good idling and starting, hot starts were never possible) I am going to use my own method.

I've avoided moving the piston hardly at all, only coated all parts with ARO.


Here is my idea:

Heat head with hairdryer to max temp I can get it. (only problem is I don't know how I'm going to do this at field... If I do it at home then I can't run it around!) Perhaps heat it up at home and then leg it to the field near by?

Bring foil paper out with me and apply around head (not top, just sides shiny side in).

Start up and allow it to idle for about 30 secs without the glowstarter (Only going to use it for starting) on reving a little.

Run at a little bit richer than ideal tune (more richer than normal just to get rid of any metal parts if they are created and to provide a bit more lube)

Drive it around on grass without shell but with foil around head.

Using various throttle ranges, no WOT for longer than a few secs not idling much.

Keep checking on temps, aiming for around 220-240F. If any lower add more foil (if at max foil it can take I shall lean out the mixture or put the shell on?)

At end of tank (8 mins or so) move piston to BDC by feel. (Is that okay? Or do I have to mark out the precise BDC? Does it have to be below the inlets?)

Wait for engine to cool down to air temp then start again without hairdryer (or shall I just let it cool down a little then start again? Or shall I just fill it up and start again straight away?)




Is this a good plan? Or shall I just forget the foil and just run with the shell and leaner?


I am after max engine life, and reliable idle, not worried about performance at all.


Thank you. Please respond ASAP, I am hoping to do this tomorrow but don't want to take any chances.

[]TEX[]

[link=http://www.johnnycoolguy.com/JCGR/main/tech_break-in.html]Heat cycle[/link]

Technex

Thank you, I'll add that to my list of methods. I've been reading up a lot. I just was wondering if running a little bit richer while keeping the temps up (by covering fins) would help even more? That way you've got the benefit of more oil flowing through taking all the particles with it and giving more lube while still keeping the temps up to keep that pinch at bay when running.

Or am I just being silly?

Thanks again!

[]TEX[]

You won't get temps up while running it rich.

I use on board temp units to tune my engines.

duratraxrc

I Will give it a try the next time that I rebuild my engine Thanks

Technex

So what is the difference (if I don't put a sock/foil on head) between this and normal running? Because you let the engine cool down at BDC after every tank? (Do you let it cool down to ambient temp (being harder to start next time? Or just let it cool down a bit?)

Technex

I'm going to use this method.

http://www.rcuniverse.com/magazine/a...article_id=397 But going to get the temps up to ~220F


Edit:

Can you belive it??! After setting it all up, trying to start the thing I was wondering why it wasn't starting. Worried about wearing the engine down (I preheated it to 160F) I checked the glowplug, nope not working, checked another nope not working. Damn glowstarter is dead. Stupid self discharge....

Hopefully in about 30 mins it's enough to get it going.

[]TEX[]

Use a heat gun to heat it up, it will start much easier.

motoman827

I think it's best to use a heat gun, a hair dryer doesn't get as hot as a heat gun will or as fast. Use a temp gauge and check it as you heat it. You're not going to be able to heat it and carry it to a ffield unless it's in your back yard. If you don't have the room at your house to run it, do you know someone that has more room? You don't need a huge area to break it in.

Technex

I used a hair dryer with no problem, got it to around 170F.

Well done it

You know the best part? The engine didn't cut out once and started up great each time (other than the first run)

Apparently I've finished the break in now according to the instructions. I think I'll take it steady for the next 5-10 whole tanks but keep the temps up to 220-260F.

Will put the shell on from next tank.

No WOT throttle banging until then.

I used the hairdryer for the first 6 tanks. After that I had to go to the field for the medium-high speed running.

Great, now I have a headache, poor ears this motor is just too loud to be close to for 40 mins .

I'm also not going to use ARO from now on, unless I'm storing for a month or more. (keeping glowplug in as long as possible, to avoid dirt) I want to know how the piston looks, but not going to look .

Technex

Well bit of a problem to do the first start today for some reason, same as yesterday but after that it ran great. Very, very powerful for the first 1/4 tank, first of all I thought this new liner and piston or the break in is giving crazy power, the wheels were spinning with a touch of throttle, then realised I had it just a touch to lean (temps were around 240-250F 260 if I left it I guess) richened it up back to how it used to be (a lot richer than it used to be which is strange) and it's got a little more power than it used to have but it idles a lot better. I'm more of a big field user so I have it pretty rich.

Kept temps at 220-240F.

Just hope it lasts.

mozzzy_2000

I know everyone is chiming in but most of what you have said I actually employ when running in my engines. I have run in a few now and there are some basics that everyone should be doing.
Yes use a heat gun to get it as hot a possible. Start her up and then you need to get the engine upto 200F & above as soon as you can. You can really only do this by driving the vehicle around on the ground whilst the engine is under load. Do not idle it. Drive it around gently and with each tank, slowly lean it out to raise the temps and use more and more throttle range. You dont need to run it overlly rich as its already been said that you will have trouble getting it upto operating temperature. The otherthing I find very useful is try using a hotter plug than normal. This helps to burn the excess fuel as its running richer whilst running it in. I always stick with the same fuel from beginning as well.
Also a thing about temperatures. Dont be too concerned about them. The hotter the better to a certian point. Some engines will run their best at 250F, some at 270F and I have had some like running 290-300F and as long as they are not tuned lean. ie there is enough fuel & hence oil getting to the engine, the engine should be ok. There is no "perfect" temperature as such. Every engine behaves differently. As soon as you realise this, tuning becomes way easier and you'll have more fun, less concern. After all these are meant to be fun!!

Technex

Hehe, I know I forget sometimes!

It's just getting close to 300F I've never done that before, I suppose I should stop worrying yes, I will try that then. I tell you what I won't take my temp gun out .


I tune it for WOT for about 4-5 seconds pretty rich as I only really have a open field to run it, pretty boring. Going to tune the LSN today hopefully it'll idle longer (it still dies down a little after 10 secs, I guess because it's to rich on factory LSN).

Thank you!

mozzzy_2000

Yeah when I say "The hotter the better" it goes without saying that is the case upto a certain point. For me 300F is about the limit I would suggest. If your engine "normally" operates much cooler than this and then all of a sudden it shoots up to 300F you know something is going wrong. Air leaks and a lean tune is the likely cuprit in that case.

With your LSN, if the car idles down after 10 seconds its actually probably only a touch rich. I wouldn't lean the LSN out too much from that point. If you lean it too far you will find that your idle stays constant and does not idle down, you know thats the sign of a lean tune. It should idle down after about 20 seconds perhaps. It can be a very touchy needle and easy to throw your tune out so go easy on it.

hrdcoreglf

I will start by saying you are putting to much load on the engine for a heat cycle break-in by running in grass. You need to find a nice big paved area and run figure 8 or large circles during the first 6-8 tanks. You could start a couple of tanks earlier if you have no patience and can't wait. If you have to wait until the weekend and do it during the day when it is less likely to make your neighbors angry, that way you can run an extension cord for the hair dryer and heat the engine up and start it. Getting the engine as close to 200% F as possible is best for break-in and makes the engine easier to start.


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, but it 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.

sjschwarz

Thanks for this information. How can one tell whether the engine is tuned "slightly rich"? I'm fairly new to this. BTW, I'm breaking in a V-Spec.