Piston Scratched - Exhaust side
#1
Piston Scratched - Exhaust side
Hi,
When pistons have scratch marks on them, its usually on the exhaust side. Why is this so?
I just had a race last weekend, my nova flash PT siezed. I thought the rod broke. But when I took the engine apart, the whole exhaust side of the piston was badly scratched. Why?
Sam
When pistons have scratch marks on them, its usually on the exhaust side. Why is this so?
I just had a race last weekend, my nova flash PT siezed. I thought the rod broke. But when I took the engine apart, the whole exhaust side of the piston was badly scratched. Why?
Sam
#3
Hi,
When pistons have scratch marks on them, its usually on the exhaust side. Why is this so?
I just had a race last weekend, my nova flash PT siezed. I thought the rod broke. But when I took the engine apart, the whole exhaust side of the piston was badly scratched. Why?
Sam
When pistons have scratch marks on them, its usually on the exhaust side. Why is this so?
I just had a race last weekend, my nova flash PT siezed. I thought the rod broke. But when I took the engine apart, the whole exhaust side of the piston was badly scratched. Why?
Sam
#4
It is the hottest side of the piston so the material will expand more at that side. In a simple way the piston will shape as an egg rounding and so the it will run a bit tighter at that side.
Indeed a good rinning-in proces and a good warming up or pre-heating will prevent scratches.
Indeed a good rinning-in proces and a good warming up or pre-heating will prevent scratches.
#5
Thank you to all for your inputs and comments. Another expensive lesson for me.
Engine had at least 10 liters thru it before this happened. Fuel used was O'donnel speed blend. Below are the pictures of the aftermath Any other insights or thoughts most welcome.
Engine had at least 10 liters thru it before this happened. Fuel used was O'donnel speed blend. Below are the pictures of the aftermath Any other insights or thoughts most welcome.
#6
Ah, a Novarossi. This problem was a hot issue 2 years ago with the Flash with the Microcasted piston (also seen with 35-plus models and even a JP P7L) ans some .12 models.
The Flash did get a follow up model called the Flash Special with a CNC piston.
That is why Novarossi has made some kind of transfer ports comming out just under the exhaust port, fresh fuel will splash against the piston cooling it down.
The Flash did get a follow up model called the Flash Special with a CNC piston.
That is why Novarossi has made some kind of transfer ports comming out just under the exhaust port, fresh fuel will splash against the piston cooling it down.
#7
Ah, a Novarossi. This problem was a hot issue 2 years ago with the Flash with the Microcasted piston (also seen with 35-plus models and even a JP P7L) ans some .12 models.
The Flash did get a follow up model called the Flash Special with a CNC piston.
That is why Novarossi has made some kind of transfer ports comming out just under the exhaust port, fresh fuel will splash against the piston cooling it down.
The Flash did get a follow up model called the Flash Special with a CNC piston.
That is why Novarossi has made some kind of transfer ports comming out just under the exhaust port, fresh fuel will splash against the piston cooling it down.
#8
An engine maker here in Holland thinks a pinch (hot piston and cold sleeve during warming up) in combination with current race fuels with a low amount of oil could create a short time cold weld and due the rotation forces again tear it appart damaging the surface.
The PT should have a black coated piston or hasn't it? That coating should give a lower friction.....
The PT should have a black coated piston or hasn't it? That coating should give a lower friction.....
#9
An engine maker here in Holland thinks a pinch (hot piston and cold sleeve during warming up) in combination with current race fuels with a low amount of oil could create a short time cold weld and due the rotation forces again tear it appart damaging the surface.
The PT should have a black coated piston or hasn't it? That coating should give a lower friction.....
The PT should have a black coated piston or hasn't it? That coating should give a lower friction.....
Well.. I will be extra careful and take special note of warm up process in the future. Just ordered a p/s/r set for the PT and will see how it goes.
Thanks Roelof for taking the time to share your insights. Appreciate it.
Happy racing.
Sam
#10
While it is damaged already you can give it a try to smoothen the piston with a fine waterproof sandpaper, be sure you do not touch the upper side of the piston arround the rings and give it a try. I have done this with 2 engines and they were able to run on.
And for the future it is wise to get an engine heater like the new RB, competition heat or other devices you can click on.
And for the future it is wise to get an engine heater like the new RB, competition heat or other devices you can click on.
#11
Tech Fanatic
iTrader: (20)
had the same thing happen to my jp 6 months ago - spent a gallon breaking in the engine with maxy's and had no problem, but during a race in which a I ran out of fuel, I purchased Vp power master fuel and after approximately 5 tanks of running this fuel, the piston seized with those same marks on the exhaust side people suggested that it was the fuel
#13
The scratches come from the engine not being broken in all the way.
If you do not run at least a gallon threw the engine this can happen.
I had the scratch issue 6 years ago when the plus 35 first came out.
Started break in my engines longer and the problem went away.
I have not had that problem in the last 15 engines I've bought since.
If you do not run at least a gallon threw the engine this can happen.
I had the scratch issue 6 years ago when the plus 35 first came out.
Started break in my engines longer and the problem went away.
I have not had that problem in the last 15 engines I've bought since.
#14
Castor definitely helps, especially with low castor fuels like the OD speed blend and 9% Byrons.
#15
Would a bad exhaust manifold gasket cause this too? Overheating due to leak?