Fractured Connecting Rods
- Thread starter Shel_B
- Start date
If this is what I'm thinking, usually this allows for the rod cap to be broken where it wants to be broken along the grains of the metal and makes for a stronger assembly, versus cutting the rod cap.
mitchell1.com
Fracture-split Connecting Rods – No, That’s Not a Broken Part
Fracture-split Connecting Rods – No, That’s Not a Broken Part Actually, a fracture split connecting rod is a technology used in some of the very latest engine designs on the market. Usually, connecting rods and their adjoining end caps are separately forged and machined. Rods may also be forged...
mitchell1.com
Yes and it’s easier to manufacture along with being more of an accurate fit.
I’m not sure how new that is, my old 1994 BMW used them 30 years ago.
I’m not sure how new that is, my old 1994 BMW used them 30 years ago.
Less machining and manufacturing cost.
With a traditional rod: Cast or forged the rod, machine the hole in the big end, cut the cap, machine and dowel the rod and cap, resize the big end (because cutting the cap made the big end hole slightly undersize and oblong).
With a fractured rod: Cast or forged the rod, machine the hold in the big end, score the cap, fracture.
There's also machining on the small end and drilling for bolts or studs on the big end, but that's the same for both.
I'm sure someone will tell you that fractured caps are stronger but the reality is, they're easier to manufacturer. They cost less. Less cost always wins the day.
With a traditional rod: Cast or forged the rod, machine the hole in the big end, cut the cap, machine and dowel the rod and cap, resize the big end (because cutting the cap made the big end hole slightly undersize and oblong).
With a fractured rod: Cast or forged the rod, machine the hold in the big end, score the cap, fracture.
There's also machining on the small end and drilling for bolts or studs on the big end, but that's the same for both.
I'm sure someone will tell you that fractured caps are stronger but the reality is, they're easier to manufacturer. They cost less. Less cost always wins the day.
Yes they are easier to manufacture but you do not have to try and account for the kerf. The fit is superior.
I thought the grain structure of the metal is kept intact making for greater strength.
Superior cap registration and less tendency to walk. The use of Forged powdered metal played into this fracturing process, also.
Yes there are multiple advantages.
You are correct and I apologize. I was going off an old article I read about the BMW rods. What it actually said was that it was easier to and more accurate to machine a round hole (that was subsequently fractured) than machining the two half pieces. According to that article though, it was machined prior to fracturing at least for the process at BMW.
And for what it's worth they used this process even earlier than my '94.
They are all about cheap manufacturing costs. If they are so easy to fracture is that a good thing?
All the talk about great for cap location? Never saw a problem with the old way of doing it, in normal every day use applications.
Cracked caps is nothing new, its been done long before auto engineers discovered it.
If a mechanic drops a rod or cap that have been separated from each other, and it lands on that rough cracked area, and there is a small imperfection to any of it, the parts are then junk.
The other not so cool thing is most all of them are made from sintered metal. Saying that is a good thing is like saying plastic is a great thing to use all over an engine, you know the famous Ford oil pans, the thermostat housings that break etc.
All these various parts made from junk materials are all talked up by the manufactures as something wonderful, but the real reason for their use is $ for the company not for you and I. The use of these materials just helps contribute to the planned obsolescence, and disposability of the over priced low quality engines they build.
All the talk about great for cap location? Never saw a problem with the old way of doing it, in normal every day use applications.
Cracked caps is nothing new, its been done long before auto engineers discovered it.
If a mechanic drops a rod or cap that have been separated from each other, and it lands on that rough cracked area, and there is a small imperfection to any of it, the parts are then junk.
The other not so cool thing is most all of them are made from sintered metal. Saying that is a good thing is like saying plastic is a great thing to use all over an engine, you know the famous Ford oil pans, the thermostat housings that break etc.
All these various parts made from junk materials are all talked up by the manufactures as something wonderful, but the real reason for their use is $ for the company not for you and I. The use of these materials just helps contribute to the planned obsolescence, and disposability of the over priced low quality engines they build.
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My goodness.
Shel_B
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My Goodness x 2
Nothing wrong with powdered metal rods, Many LSx engines with stock Gen IV rods putting down 800+ horsepower while handling 20 psi of boost, Try that with a stock small block Chevy forged rod.
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Someone needs to do some reading about metallurgy....
That's quite understandable!
Not stronger. Weaker, less ductile, prone to fatigue, and shorter life than forged. He's not wrong - cheaper wins. The "benefits" are always made up to obfuscate the real reasons - welcome to business 101
