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