What are the benefits of a polished crank

obi_waynne

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What have you discovered to be the benefits of a polished crank?

What other crank mods are worth thinking about doing?

What is a nightrided, knife-edged crank?
 
What have you discovered to be the benefits of a polished crank?

What other crank mods are worth thinking about doing?

What is a nightrided, knife-edged crank?


Polishing a crank removes small imperfections, tiny surface scratches and cracks and reduces the amount of oil that sticks to it. It also looks pretty on the bench.

A knife edged crank reduces weight slightly and allows the conterweights to slice though any oil that gets in the way.

Nightrided was a programme with KITT and Hasslehoff. Ohh, you mean nitrided :-)

Nitriding is done in an oven. The crank is suspended in a closed chamber which which is lowered into the furnace for heating. At a determined temperature ammonia and nitrogen gas are introduced into the chamber. The heated gas reacts with the carbon on the surface of the crank to a depth of approx 0.010", making the surface hard.

Nitriding treats the crank evenly from top to bottom and side to side. It sets up a surface tension that stiffens the crank and increases the fatigue life by 18-20%..




 
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If the crank is knife edged in it's direction of rotation does it not reduce 'splash' lubrication? Or am I about fifty years out of date by asking this question?
 
Maybe a tad :-) If your tuned engine is relying on splash for lubrication then you don't know what you are doing.
 
Maybe a tad :-) If your tuned engine is relying on splash for lubrication then you don't know what you are doing.

Clearly so. I only asked. Bit severe to imply in the public domain that I don't know what I am doing. I am not stupid.

Then again I am not the retired person who delivers packages in their spare time and makes handbrake turns on icy roads to impress bystanders.
 
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Clearly so. I only asked. Bit severe to imply in the public domain that I don't know what I am doing. I am not stupid.

Then again I am not the retired person who delivers packages in their spare time and makes handbrake turns on icy roads to impress bystanders.

That's the main problem with text, the wrong end of the stick is very easy to pick up. I wasn't referring to you, Paul, when stating an engine builder doesn't know what he is doing if he is relying on oil splash these days to lubricate a tuned engine. You should know me better than that by now! :-)

I apologise for failing to make that clear.

Never done a handbrake turn on an icy road, asking for trouble as there is no grip and only grief will ensue. I only play in snow.
 
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Fair enough. It is a problem with written communication - no inflexion can be conveyed.

Just re-read my post and it too looks pretty confrontational.

Sorry chaps
 
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Polishing a crank removes small imperfections, tiny surface scratches and cracks and reduces the amount of oil that sticks to it. It also looks pretty on the bench.

A knife edged crank reduces weight slightly and allows the conterweights to slice though any oil that gets in the way.

Nightrided was a programme with KITT and Hasslehoff. Ohh, you mean nitrided :-)

Nitriding is done in an oven. The crank is suspended in a closed chamber which which is lowered into the furnace for heating. At a determined temperature ammonia and nitrogen gas are introduced into the chamber. The heated gas reacts with the carbon on the surface of the crank to a depth of approx 0.010", making the surface hard.

Nitriding treats the crank evenly from top to bottom and side to side. It sets up a surface tension that stiffens the crank and increases the fatigue life by 18-20%..

Treating a crank to this, does it clear up any imperfections on the crank then? Can this type of treatment be a form of balancing aswell?
 
Treating a crank to this, does it clear up any imperfections on the crank then? Can this type of treatment be a form of balancing aswell?

Polishing removes tiny imperfections in the surface and minor stress inducers but neither this or nitriding will cure internal structural faults.

A crank is balanced once all mods are completed but before nitriding.
 
Fair enough. It is a problem with written communication - no inflexion can be conveyed.

Just re-read my post and it too looks pretty confrontational.

Sorry chaps

No problem. Handbags put away for another day :-)
 
Polishing removes tiny imperfections in the surface and minor stress inducers but neither this or nitriding will cure internal structural faults.

A crank is balanced once all mods are completed but before nitriding.

I see. Thanks for the information! Out of curiousity and lack of knowledge in this area, can you do the same for pistons, rods or cams?
 
You can certainly treat conrods, valves, camshafts and piston rings. Pistons are treated differently due to being mainly aluminium and subjected to a lot of heat.
 
I've been having a read up about the engine in my current car - the engine model is BMW M52TUB28. I thought that apart from crank throw and cylinder bore the 2.0, 2.2, 2.5 and 2.8 litre derivatives were identical.

Apparently mine (2.8) has a forged crank whereas the others do not ! ! ! I am not sure if the information is correct, but, is it normal for manufacturers to make 'small' internal engineering changes like this?

Surely it would be better and cheaper to use the higher quality components across the engine family?

I'm not complaining mind, at 131,000 miles the engine is working perfectly and still gets below measurement threshold CO (ie 0.00%) at MoT time. I uses no oil at all and the HC reading was 9ppm. This is all with the original cats and lambda sensors.

Any thoughts? Would it be just as durable with a standard crank?
 
Again - very interesting point. What does cryogenic chilling (at a molecular level, or even atomic level) do in terms of metallurgy?
 
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Again - very interesting point. What does cryogenic chilling (at a molecular level, or even atomic level) do in terms of metallurgy?
Fun go to the 2nd site and click on "racing" for all the info.
NASSA also use the process on some of their spacecraft parts.

FWIW i have my gearbox parts and driveshafts including the CV joints treated this way That cost me $88.00 AUD app 3 years ago.
If I was to do a motor rebuild absolutely everything including the block and head would be cyroed for greater reliability and less wear.
when my discs need replacing they will be treated along with the pads for far better wear resistance the cost of doing this will be repaid by a much longer service life.
 
For brake info go to the 2nd site and click on "brakes" and read the results of the wear and crack resistance when tested on one side of the dump truck and stock untreated brakes on the other side.
I have been told by my local cyro workshops that most if not all of the V8SUPERCAR teams use this process.

The process is also great for cutting tools and rifle barrels for longer life and more consistent grouping for target shooters.
 
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Good links indeed yet totally uninformative.

You've not answered my question though. What happens on a metallurgical/molecular/atomic/sub atomic level?
 
Good links indeed yet totally uninformative.

You've not answered my question though. What happens on a metallurgical/molecular/atomic/sub atomic level?

The second site has a couple of books named in the first few paragraphs so hopefully they contain answers to your questions ???

I am just an old retired chippie (carpenter) so am unable to answer your queries so would suggest you direct them towards people far more qualified than me.:embarrest::confused:

PS To call call them " good links and then totally uninformative" seems a bit harsh but i guess it all depends on what info you are seeking ??.

PPS Don't shoot the messenger.I posted the links to share information as I am guessing that most drivers do not seem to be aware about cryogenic treatments or their benefits.
 
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I've been having a read up about the engine in my current car - the engine model is BMW M52TUB28. I thought that apart from crank throw and cylinder bore the 2.0, 2.2, 2.5 and 2.8 litre derivatives were identical.

Apparently mine (2.8) has a forged crank whereas the others do not ! ! ! I am not sure if the information is correct, but, is it normal for manufacturers to make 'small' internal engineering changes like this?

Surely it would be better and cheaper to use the higher quality components across the engine family?

I'm not complaining mind, at 131,000 miles the engine is working perfectly and still gets below measurement threshold CO (ie 0.00%) at MoT time. I uses no oil at all and the HC reading was 9ppm. This is all with the original cats and lambda sensors.

Any thoughts? Would it be just as durable with a standard crank?

Cast cranks are cheaper to produce than forged ones and they have deemed them necessary on the larger engine only thus saving millions of Euros, is my guess.

There would be no difference in reliabilty or longevity as long as engines are left alone. The fact that they have fitted a forged crank to the bigger engine suggests that the cast items aren't up to the job in the more powerful lump. I am sure thst a cast crank would work fine, but I am guessing that the safety margin wasn't sufficient for their engine designers to use it.
 
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