beeftip

Here's a total newbie question. But that's because I'm a total newbie. How do I make sure the piston is at the bottom of it's stroke, or bottom dead center, when I stop the car? I'm sure that if I had a new RTR or kit to look at, the instructions would tell me how. But as my MT does not yet exist (at least not in my posession) I am curious. Is there a marking on the flywheel or something? I know on my real car that TDC is clearly marked on the damper, or is it the thing the damper is connected to? I probably have no business owning a nitro engine....

mecky33

There is no marking on a nitro engine though you could put one. If you ever take your flywheel off, the mark could get misaligned though. The easiest way to do it is to take off th glow plug and look at it. Also, you could take off the glow plug and practice feeling with the pullstarter to get a feel for the bottom of the stroke, then you dont have to keep pulling out the glowplug. Also on your real car, there is a timing degree marking set on the front of the engine block and there is a timing mark on the damper that you line up with the apropriate degree of timing on the engine block. And as for not owning a nitro engine, everyone can own one. you just need to ask if you have questions, that is what we are here for.

beeftip

Thanks for the answer and for your patience.

I bought myself the "Ultimate Nitro Engine Guide" book from Radio Control Nitro magazine. It's a very well written book and I'd recommend it to any newbie. Unfortunately, after they tell you to make sure that your piston is at BDC they don't explain how to to do it. So I thought it would be good to ask those in the know.

Thanks again.

caseyddr

My Feedback: (13)

actually the easiest way is just make sure the flywheel has lots of play going either way unless its at the top. No need to take the glowplug off at all, thtas way to much hassle.

mecky33

Remember casey, he's new to nitro. And instead of guessing, pulling the glowplug is the easiest way to tell. Also the flywheel will only have play one direction due to the one way bearing. Thus, if you play with the fly to much, it will not sit at the bottom of the stroke anymore.

caseyddr

My Feedback: (13)

Didn't think about the pullstart, I was going by what I do on my O.S. RZ-r I see your point mecky!

cyclejerk

Why do we need to know BDC? I'm a newbie too.

mecky33

It help when you are heat cycling the engine during break-in. read the FAQ for newbies at the top of the MT section, it will answer your questions.

caseyddr

My Feedback: (13)

definately not why.


The reason is because if you dont have it at BDC after running (break in or regular running) if the piston is at TDC or near, the sleeve could lose its pinch by cooling around the piston, ruining your new engine.

mecky33

Exactly, it helps when you are heat cycling the engine during break-in. Heat cycling is the heating and cooling of the engine to properly seat the sleeve in the cylinder, and the piston in the sleeve.

Casey, maybe you should read and understand a post before saying someone is wrong. I did not feel a need to get into the particulars since it is explained in the newbie FAQ.

caseyddr

My Feedback: (13)

my aplogies then, use different lingo here

cyclejerk

Thanks guys, this must be for abc motors.

mecky33

I would assume its the same for ABN's as well. the piston sleeve will cool the same in either engine.

cyclejerk

you are prob... rite, although my savage directions said nothing about this. (the engine manual either).

mecky33

It is a part of break-in that has come from the more experienced people in the nitro community. If you look at the construction and the way that the nitro engine works, it makes a lot of sense.

caseyddr

My Feedback: (13)

also, the chances of a motor stopping at TDC is very unlikely, its just a safety measure so you dont mess up your engine

RobH

I personally just put a mark on the flywheel with a sharpie. It can get messed up if you take the flywheel off, but you can remove the mark from a sharpie with denatured alcohol real easy.

BUGGIES_R_US

If the engine machining process were immaculately PERFECT, and if it takes into account all the possible forces present at all RPMs, then you wouldnt have to break in the engine. So as you probably guessed, we are literally trying to "sand down" the rough points of the engine with the break in process.

I'm just curious..
I dont know where to get this information... But would someone post the "Rate of expansion" for the following metals PLEASE?
Aluminum (Al)
Iron (Fe)
Copper (Cu)
Tin (Tn)
Nickel(Ni)
Chromium (Cr)

This is to see if there is any difference in the rate of expansion between ABC and ABN engines.. and just to know
From what I know.. Chromium is definitely more slick compared to Nickel and its definitely more Touch. Thats one reason why ABC engines should be superior. But Nickel might have other properties that make it more durable etc..


Ram

jwan

another way to tell if your at bdc I found is to listen for it. I can usually hear a light sort of pop as the piston moves back down.

fhm101

During new engine break in, your average nitro engine will stop at TDC more times than not because it's still so tight. It is always a good idea to check this during break in.
The simplest way to put the piston at the bottom of the stroke is to move the flywheel with your finger until resistance is felt, stop and turn it the other way until resistance is felt, making sure to watch the distance the flywheel moves between the two points of resistance. Now turn your flywheel back half the distance between where it got tight the first and second times and you will be close enough to BDC to avoid any problems.

fhm101

What should be actually happening during break in on an ABC or AAC engine is more of a shaping of the piston to the sleeve by getting it hot and forcing it to conform to the taper of the sleeve. This is more a reshaping of the piston taper than a material removal process. While some scuffing can't be avoided, too much scuffing will result in short service life. That is why it's so important to get a new engine up to operating temp as quickly as you can when heat cycling. Running an engine at idle, so rich that it won't get hot will give you the "sanding" effect, and short engine life. It was great when engines had iron pistons and/or sleeves, but for modern engines (even ABN engines) the "blubbering rich, idle a few tanks before you run it" school of engine break in will do more damage than good.
Because nickel is softer than chrome, break in of an ABN engine will be a process of shaping the sleeve to the piston taper rather than the piston to sleeve as in chrome plated bores. This allows an ABN engine to be run in much quicker than their chrome plated counterparts. While it is generally thought that an ABN engine will not last as long as an ABC, this something of a myth. An ABC engine will run a longer single session without going soft than will an ABN, but with proper care and feeding the ABN will give a longer service life. I know guys that have ABN OS 12's that predate the CV series (CZ series, I think???) and these little engines are still running like tops. I know one guy that has this engine and has replaced the crank, rod, and bearings a few times through over 20 gallons of fuel, but the original piston and sleeve are still going strong.

BUGGIES_R_US

Oh.. I've always done the "idle for a tank" routine.
I was thinking that if the part thats to blame isnt corrected, running it lean/high(er) rpms might cause the high amount of localized "scuffing" to produce a LOT of heat and maybe causing the engine to sieze after cooling due to uneven heat distribution.
So theoretically even thought the engine is running "cool" (above 150-175 at least though), there is still a lot of localized heat for the first tank.

I'm not sure how it works with R/C cars, but diesels usually start out with about 22:1 compression ration when theyre new and that goes UP to 22.5:1 as they go through their break in period (~2000 miles).

Just defending my perspective, even thought it may be flawed
I'm not conviced that its either way.. the search continues!

Ram

BUGGIES_R_US

Reliability:

Well heck as long as the piston is forced straight DOWN with NO sideways motions, I think theres very little wear.
The piston, after a while is literally "gliding" on a coat of oil which actually acts like a "ring" (again.. theory)

So unless you give the engine a 30G shock, I dont see why it shouldnt last a nice long time!
The problem is people dont know how to tune.. or they just dont care.
With our 1:1 cars, the "conservative tuning" is done for us (the ECU, O2 sensor, MAF, injectors etc) so we dont have to worry about it.

But theres a very thin line between a " well running R/C motor that will last long" and a "run lean and crazy motor that has a gallon left".
I'm willing to bet that your friends are mechanically minded and they probably know what theyre doing
Ram

mecky33

FHM, just to let you know. Those of us with pull start motors cant spin the flywheel both ways. The one way bearing does not allow it. And again, for new people the easiest and most failsafe way to determine if the piston is at the bottom of its stroke is to remove the glow plug and look at the piston position.

caseyddr

My Feedback: (13)

thats also what i said about the flywheel, but as mecky pointed out, most ppl dont run engines w/o pullstarts or electric starts.