Inside case polishing

[Old standup rider]

Just wondering if anybody has polished the inside of their cases? Is it helpful? Is there a drawback? Or just a waste of time?
My season on this ski is over, just looking to do some mods for next season. It’s already ported and epoxied and finger ramps filled.

 

[mikidymac]

My understanding is you don't want to polish the cases, in fact you want them rough to help the flow and mix the air and fuel. It is only the exhaust path that you want polished.

 

[Old standup rider]

My understanding is you don't want to polish the cases, in fact you want them rough to help the flow and mix the air and fuel. It is only the exhaust path that you want polished.

But billet cases are polished Inside, so I don’t think it would hurt!

 

[Quinc]

Polish the outside instead so it looks cool.

 

[bored&stroked]

But billet cases are polished Inside, so I don’t think it would hurt!

Its a well known problem. You never polish the intake ports on 4 cylinders otherwise the flow causes the fuel to pull out of atomization and become liquid again adhearing to smooth port walls. Ruff texture creates turbulence which keeps the fuel atomized.

 

[Storbeck]

I would be very impressed if anybody has done an actual test that showed a difference. I suspect it would be difficult test to do and reach any actual conclusion.

 

[Old standup rider]

Its a well known problem. You never polish the intake ports on 4 cylinders otherwise the flow causes the fuel to pull out of atomization and become liquid again adhearing to smooth port walls. Ruff texture creates turbulence which keeps the fuel atomized.

I was going to swirl polish

 

[Big Kahuna]

But billet cases are polished Inside, so I don’t think it would hurt!

I think if you look really close it is not as smooth as you think. You do not want any of the fuel mixture to "stick" to the cases, if you polish, this will happen. Just like taking a sheet of glass and sticking it in water, then pick up flat, water will be stuck to the underside.........

 

[bored&stroked]

I would be very impressed if anybody has done an actual test that showed a difference. I suspect it would be difficult test to do and reach any actual conclusion.

No, its not difficult, and yes, its been done countless times in the world of engines. 2 strokes are not unique in this case.

I was going to swirl polish

It won't help anything.

 

[Old standup rider]

If it won’t help I won’t waste my time!! Thanks for the input all

 

[Storbeck]

No, its not difficult, and yes, its been done countless times in the world of engines. 2 strokes are not unique in this case.

It won't help anything.

Point me to one?

 

[wmazz]

It looked like there was aluminum pieces sitting inside your cases?
Did you have an engine failure?


Bill M.

 

[Old standup rider]

It looked like there was aluminum pieces sitting inside your cases?
Did you have an engine failure?


Bill M.

No engine failure I had to drill out a broken intake manifold bolt! The stud snapped when I was removing it. They are metal shaving just haven’t hot tanked the cases yet.

 

[Storbeck]

Point me to one?

Or even just describe in general how one would test this?

 

[bored&stroked]

Point me to one?

I don't have these things stored for reference.
To test you can put a camera inside the port. You can monitor air/fuel ratios which the atomization will affect due to difference in combustion efficancy. Or you can study laminar flow theory which deals in exactly this.

 

[Storbeck]

I don't have these things stored for reference.
To test you can put a camera inside the port. You can monitor air/fuel ratios which the atomization will affect due to difference in combustion efficancy. Or you can study laminar flow theory which deals in exactly this.

You either know a lot more about testing and laminar flow than I do, or a lot less, because none of that sounds like easy testing to me, (do you have a lot of experience with testing this sort of thing?) nor does it sound like it's something that has any obvious relevance to a two stroke crankcase, and aside from the really obvious "turbulent air probably keeps the fuel in suspension better" I have no idea what laminar flow theory would tell you about this. Is the flow in a two stroke crankcase in any way behaving like laminar flow?

 

[Storbeck]

Let's put it this way, would you bet $100 that you could pick which motor was going to make more power, if somebody built two "identical" motors, one with a polished crankcase, and one without?

 

[Big Kahuna]

Let's put it this way, would you bet $100 that you could pick which motor was going to make more power, if somebody built two "identical" motors, one with a polished crankcase, and one without?

I would say the one that was polished would seize sooner at WOT!

 

[wmazz]

They are metal shaving just haven’t hot tanked the cases yet.

I don't know what they use in Hot Tanks these days, but when I was a kid we used
caustic soda and we used to throw beer cans into the sump and watch them dissolve
within a few minutes.

Bill M.

 

[bored&stroked]

You either know a lot more about testing and laminar flow than I do, or a lot less, because none of that sounds like easy testing to me, (do you have a lot of experience with testing this sort of thing?) nor does it sound like it's something that has any obvious relevance to a two stroke crankcase, and aside from the really obvious "turbulent air probably keeps the fuel in suspension better" I have no idea what laminar flow theory would tell you about this. Is the flow in a two stroke crankcase in any way behaving like laminar flow?

I went to auto machining school and have been building engines for friends for 20yrs. I used to do r&d for a performance company specilizing in J series Honda v6's. My idea of easy to test is not something a guy can do in his garage, but from a manufacturer and high end performance company [or race shop more likely] stand point these are fairly simple things to do.
Laminar flow has everthing to do with this, it deals with liquid, smooth surfaces, and their interactions.