Piston after break in
 

Hi,

I am new in nitro, one engine I use for races successfully. Recently I start break in my second new Picco torque edox .12 and here's the question, after about 0.8l of fuel on the box and last 2 tanks gently driving, I checked the engine. There are small scratches, one quite clearly visible, what could have caused this and whether it will affect performance. Obviously, the engine was heated to around 90 degrees celsius with each start, I added Castor oil to the fuel, I looked at the engine before starting it for any dirt/filings from machining, fresh air filter and engine was very very rich and still heating to 90-100 degrees. If such scratches are normal I would like to avoid it.
https://cimg2.ibsrv.net/gimg/www.rct...ea1af8d8bc.jpg
https://cimg3.ibsrv.net/gimg/www.rct...2fc2770185.jpg
https://cimg4.ibsrv.net/gimg/www.rct...c38d76af00.jpg

that is not normal. something scratched the piston. the scratch seems goes thru all the way to the top thru 2 rings. you may try to see if the idle is stable in your upcoming run in.

i will warm up the engine with your temperature, and "make sure" the chassis has shared the same temp before i put it on track to "run in" and prevent the engine stopped without fuel. i will refuel, say 3 mins or some laps.

No good, it's a shame that I pay so much attention to the break-in process and there are problems anyway. I also heated the chassis with a heat gun. Only bearings for the break in time, I use non-original ones, and then I change them to the original ones, which were with the engine, after about 4 liters. The engine still has a big pinch so I'm hopeful that it will run fine after full break in anyway.

You put old bearings in the engine for break in?

The small scratches on the last pic is from a low lubrication and maybe also going to quick on the performance.

The long scratch does not match with a steady point on the sleeve so I expect some dirt or a chip chrome from the edge of a port.

But these scratches will do nothing to the performance, the oil will do its work to close the gap. And the piston probably still needs to finish the break in so the tiny scratch will be polished a tiny bit smaller..

When you break in a motor you're not JUST breaking in the P/S. You're breaking it in as a unit, P/S , piston and conrod, bearings to crankcase. Using "break in" bearings is a bad idea IMO. You're going to have to do break in when you put on the OG bearings.

How much castor oil did you add. If using 9-12% oil lube fuel You will need to add a lot. 5 oz castor oil per gall only raise 2% more lube per gallon.

That isn't a lot. But what % oil lube did you start with???? You only added only 2% more lube to fuel.???? And what's his face said you didn't have enough oil lube which caused the scratches?

Roelof you mean? Not hard to keep up with the people in the thread...

If the adding of a lot of castor oil and running of almost a liter is true then the piston looks too clean!

That piston looks like it comes from an oilbath lookin at the polished part above the small oil ring.

If you're new to nitro, then you probably haven't dealt with a ringless piston engine before. The entire side of the piston contacts the cylinder sleeve, and tiny scuff marks are inevitable. This is not "piston slap" like you would see in a ringed engine. Remember, aluminum is a soft metal, much softer than the chrome plating inside the cylinder sleeve.

It was probably caused by tiny bits of chrome flaking off the edges of the ports. I always clean the edges of the ports with a diamond jewelry file, and then wash the sleeve, before the first run to minimize these scratches, but there are always a couple scratches anyway, because nothing is perfect. Are the scratches deep enough to catch your fingernail? If not, then they're just cosmetic and won't result in any measurable change in engine performance. Such a tiny scratch, especially when filled with oil, will present so much resistance to leakdown that the scratch may as well not exist at all. You can worry about it if you want, and some people will be happy to help you in worry about it, but your driving skill, suspension tuning, and engine tuning will have orders of magnitude more effect on your lap times than these tiny scratches will.

I have older engines with year's of fuel run threw them and they look just as clean like new condition. It's the castor oil that cleans the engine. No castor oil then you will get discoloration.

Castor oil leaves a black surface

In my opinion you're fine. But I agree that the piston is way too clean, should be almost coated in a dark brown color. I would richen it up a tad if that's what it looks like after running it.

Any discoloration (brown, gold or black) means you're not running castor oil. I run castor oil in all my engines 2% and they are clean just like new condition. Castor oil promotes better engine life.

Yeah, but 2% is no 6% as the topic starter mentioned. Or he has a very well degummed castor oil or his castor was realy a (half) synthetic.

It's been my experience that castor oil in nitro fuel leaves your piston a dark honey color. The more castor the darker the color.

Totally WRONG! castor oil has a real high flash point ICSC 1452 - CASTOR OIL (inchem.org) Any discoloring is from the lack of castor oil. Les oil lube will causes burring color with no castor oil 8-12 % oil lube. I run 15% nitro with 18% oil lube and 2% castor and get no burning or discoloring.

Stop the crap, your 2% castor is falling into nothing with your 18% oil and basically that is no fuel any competition engine will see. Any normal fuel with a large content of castor will give a brown to black color in any competition engine. And another thing, what is your experience with real onroad racing engines? The higher comperssion and the hotter combustions compared with any RTR engine is also making a difference.

You stop your crap with the fuel I use. I use Omega fuel off the shelf .with 2% castor oi. It isn't going to leave any brownish color in any nitro engine. I have been running nitro for 30 yrs. with no affect running castor oil. Low oil lube will burn any nitro engine up fast and cost you more money. Fuel is fuel It all burns. What really matters is the oil lube to protect the life of the engine.

You didn't bother to look at the facts! castor oil flash point 229C, nitro flashpoint 35c and methanol flash point 12C How can castor oil burn if nitro and methenol have a low flash point????????

I've been playing with nitro motors for 60 years. so what? The more castor you have in there the browner it gets... your 2% castor doesn't amount to nothing. Put enough castor in there to do some good and you'll see brown on your piston.

So it is all of us having the wrong experience compared to yours?

You can provide us with all kind of scientific numbers but the one castor oil isn't the other. Take Shell Racing M, the best performing oil I have seen due itts SAE30 specs but the engine will turn totally black inside. I also have runned Castrol M50 (later named to Racing M as well) and Eurol Racing-1. They seem to be the same with the same results like a pretty clean light brown color.
And sometimes it is not the oil itself causing the black layer but from the polution inside the oil, it is hard to get castor 100% clean. It is the synthetic oil that is made to give a clean combustion for less engine maintenance.

And talking about your flashpoint numbers..... How hot does it become inside the engine? You do not know.... I can only say that our 48.000 rpm and higher compression will give our engines a much higher combustion temperature than your monster truck engine.

Hello 1995 Monster T,

Castor Oil flash point is at 229ºC. But as Roelof said that the heat at the combustion point/center surely exceeding 229ºC.

I had the experience of using Runner Time fuel for some time. It has full 9% Castor Lubricating Oil, and the Piston Head comes out brown to black after 60 minutes Final. At the moment I am running VP Tessmann Edition Fuel that run propretiary 7% Full Synthetic Lubricating Oil and the Piston Head is not as brownish as with Runner Time.

Cheers.. :)

Both of you can drop???? Castor oil doesn't burn at operating temperature not even under compression. Your engine would melt down before it would reach 229C. The discoloring if from something else burning. Castor oil doesn't burn until 229C.

Huh? melting point of aluminum is at 660C, brass even much higher so how would it melt at 229C

About combustion temps: http://fluid.wme.pwr.wroc.pl/~spalan...combustion.pdf

Yes, the oil is not the the one that combust but because it is within the mixture and on the surface of the piston it will be in the flame of the combustion and burn.

Aluminum expands @ 229 C to remove engine bearings easy But a engine will never get that hot under normal operating temperature. Not even close. Fuel without castor oil will discolor after burning. So it isn't castor oil that burns. It's the ingredients that the manufacture puts in the oil lube blend that is causing the burn. I have used may brands of fuel with and without castor oil . Sig, Redmax, Omega, Byron(crap) Wildcat and S$W. Non of these I nave never seen burning.. So it comes down to the brand and blend! So you can keep on blaming castor oil for the burning but it doesn't BURN under operating temperatures! I have even started making my own blend of fuel. Only 3-4 ingredients. No burning yet.

Can you please make up your mind...

There is always fighting on this forum for some reason.
By the way more castor you have in fuel more darker piston gets. It's 2+2 = 4.

Well you can call it fighting but this guy (look in his post history) knows it better, even if he is wrong. And we all know our experiences with castor oil based fuels and this "punk" says we all have it all wrong and tries to get his right by throwining in some technical details that has nothing to do with what is happening inside the engine. Not to mention the high chance he never have run a high competition engine.

I think he's not getting the brown color because he's only using 2% castor and thinks that's a lot. I've been running 8% castor and 4% synthetic. A friend makes the fuel so I know what's in there. It runs real good and my pistons are a deep honey brown. Not enough castor is the only thing I can think of that would explain why he's not getting a brown piston.

For years I have mixed my own fuels with 7% synthetic and 3% castor and even with that the pistons did get a color. But yes, just 2% castor on a total of 18% (or is it 20%?) lubrication is nothing. Beside that, it is way too much lubrication

OS recommends 18% but that's way too much in my opinion. I like my 12% blend with 25% nitro. Runs good doesn't get hot you just have a bit of castor goo but I know how to clean that so not an issue.

Ah, yes! Good that you did mention that, now I remember another very stupid discussion with this guy.
https://www.rctech.net/forum/offroad...ubleshoot.html

Well, he does seem to have an opinion. Unfortunately I don't agree with it but what the heck.. :smile: