Lightweight Pins worth it?

[user-23911]

Most people have no idea about piston or pin weight and only use them due to "flock of sheep syndrome".

In fact they've got no idea about pretty much anything.
Thanks to the internet and car forums.


Lets use a 4G63 as an example?
Go buy one........jump on the net?
Jump onto evolution M.
It's the biggest joke ever.......people with a 7 year olds mentality giving advice to kids with a 5 year old mentality.......they all end up broken because they do the same modifications wrongly.

[user-30257]

If you were starting off with a japper turbo engine, stock pins are thick wall and never give trouble.

When you upgrade / downgrade to forged pistons from Ross, JE, wisec etc, you end up with the thin wall pin.
They bend and break and are unfit for use,
The fix is to go back to the stock pins.


Or better still, stick with the stock pistons and tune it so there's no knock.

What's stopping you from running a lighter piston with a heavier pin?

Exactly, or of you want a light pin, how about a smaller diameter but same wall thickness, shorter pin. Bottom line is talk to the guy that designed the piston.

I would rather have a smaller counterweight and a strong piston/rod assembly. But then again you are doing nothing if you stuff a 14" converter behind it.

[user-23911]

Exactly, or of you want a light pin, how about a smaller diameter but same wall thickness, shorter pin. Bottom line is talk to the guy that designed the piston.

Weaker, not stronger.


Stronger would be bigger in diameter.
Bigger in diameter won't usually work due to the conrod.

[Warp Speed]

Exactly, or of you want a light pin, how about a smaller diameter but same wall thickness, shorter pin. Bottom line is talk to the guy that designed the piston.

Weaker, not stronger.


Stronger would be bigger in diameter.
Bigger in diameter won't usually work due to the conrod.

Really, please explain.

[David Redszus]

Exactly, or of you want a light pin, how about a smaller diameter but same wall thickness, shorter pin. Bottom line is talk to the guy that designed the piston.

Weaker, not stronger.


Stronger would be bigger in diameter.
Bigger in diameter won't usually work due to the conrod.

Really, please explain.

Joe is right.
Diameter, not wall thickness is what really matters in pin design. For a given diameter, a thicker wall is stiffer but the
weight gain is considerable. By increasing the diameter we can reduce wall thickness, while increasing stiffness and reducing weight.

Pin stiffness is also a function of the material modulus of elasticity (E modulus); all ferrous materials have virtually
identical G mod values.

If cost and technology were not limitations, a wrist pin should be made of boron carbide. It is twice as stiff as
any other material and weighs only about one fifth as much.

Steel
Pin 3" length, 19mm OD, 3.0mm Wall, ,237mm flex, 0.20 lbs.
Pin 3" length, 22mm OD, 1.5mm Wall, .232mm flex, 0.13 lbs.
Boron carbide
Pin 3" length, 22mm OD, 1.5mm Wall, .107mm flex, 0.04 lbs.

In addition to material, wrist pin shape is an important design factor.

[statsystems]

Isn't boron carbide fracture prone?

[digger]

Weaker, not stronger.


Stronger would be bigger in diameter.
Bigger in diameter won't usually work due to the conrod.

Really, please explain.

Joe is right.
Diameter, not wall thickness is what really matters in pin design. For a given diameter, a thicker wall is stiffer but the
weight gain is considerable. By increasing the diameter we can reduce wall thickness, while increasing stiffness and reducing weight.

Pin stiffness is also a function of the material modulus of elasticity (E modulus); all ferrous materials have virtually
identical G mod values.

If cost and technology were not limitations, a wrist pin should be made of boron carbide. It is twice as stiff as
any other material and weighs only about one fifth as much.

Steel
Pin 3" length, 19mm OD, 3.0mm Wall, ,237mm flex, 0.20 lbs.
Pin 3" length, 22mm OD, 1.5mm Wall, .232mm flex, 0.13 lbs.
Boron carbide
Pin 3" length, 22mm OD, 1.5mm Wall, .107mm flex, 0.04 lbs.

In addition to material, wrist pin shape is an important design factor.

In the real world the wall thickness matters because a 2.5" pin .866" isn't really a simple beam due to the dimensions of it . Local flexibility in the Diametral direction due to it ovalizing is important with thin wall pins

Also When you look at how the pressure is distributed on the contact surfaces the shear characteristics are important to. Shear is predominantly an area thing deformation is not just a second moment of area thing as it's combined bending and shear etc .

It's the same as a 12" square tube with 1/16" wall has good section modulus and second moment of area but is pretty useless structurally

Simple calculations only get you so far

[David Redszus]

Isn't boron carbide fracture prone?

I don't know.
It is the third hardest material known; often called Black Diamond. It is used in nuclear reactors and body armor.

My concern is how to machine it and how much does it cost?

As with most exotic materials, it would probably be banned by most race sanction groups.

[David Redszus]

Really, please explain.

Joe is right.
Diameter, not wall thickness is what really matters in pin design. For a given diameter, a thicker wall is stiffer but the
weight gain is considerable. By increasing the diameter we can reduce wall thickness, while increasing stiffness and reducing weight.

Pin stiffness is also a function of the material modulus of elasticity (E modulus); all ferrous materials have virtually
identical G mod values.

If cost and technology were not limitations, a wrist pin should be made of boron carbide. It is twice as stiff as
any other material and weighs only about one fifth as much.

Steel
Pin 3" length, 19mm OD, 3.0mm Wall, ,237mm flex, 0.20 lbs.
Pin 3" length, 22mm OD, 1.5mm Wall, .232mm flex, 0.13 lbs.
Boron carbide
Pin 3" length, 22mm OD, 1.5mm Wall, .107mm flex, 0.04 lbs.

In addition to material, wrist pin shape is an important design factor.

In the real world the wall thickness matters because a 2.5" pin .866" isn't really a simple beam due to the dimensions of it . Local flexibility in the Diametral direction due to it ovalizing is important with thin wall pins

Also When you look at how the pressure is distributed on the contact surfaces the shear characteristics are important to. Shear is predominantly an area thing deformation is not just a second moment of area thing as it's combined bending and shear etc .

It's the same as a 12" square tube with 1/16" wall has good section modulus and second moment of area but is pretty useless structurally

Simple calculations only get you so far

Yes, I agree. When aspect ratios are taken to extremes the resulting physical performance may no longer be adequate.
Ovalizing deformation is a factor to be sure. At what loading does the pin ovalize compared to the aluminum piston boss?

Of equal importanceis the determination of actual loading points with a tube in bending since we could be applying area loads and not just point loads. Nonetheless, equations are available that cover almost anything automotive.

But for incremental dimensional modifications, simple beam bending calculations provide a wealth of insight to improve performance.

[Mark O'Neal]

Jesus.


Can't we stick to just guessing?

[modok]

The wall thickness of the pin should match the piston it lives in. It's a system.

[user-17438]

looks like i have a lot of engines to recall for using .866 and .927 pins. I should have read this. Good write up.

[swampbuggy]

Mark O'Neal----I can't stop laughing----great one man!!!! Mark H.

[user-30257]

Wow. ... lol less competition than I thought

[289nate]

I can't think of any reason why I'd spend a dime on light weight pins for the motor and rpm you're describing unless you were class racing with a very well set up car. I MIGHT be convinced differently IF you were willing to spend money on a better (not necessarily lighter) piston with a better/ thinner/ more modern ring pack. Even then I think it would be a moderate dyno gain not felt on the street.