Comparison of "Base" 1.5T and "Si" 1.5T Connecting Rods

D-RobIMW

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For anyone wondering if the different part number connecting rod the Civic Si engine got makes it any different, I ordered a "base" 1.5T rod and a Civic Si unit.

As far as my dial calipers can tell, they're dimensionally the same. The bushing for the wrist pin on the Si rod has a visibly smoother finish than the base model rod, but other than that, I don't see a difference. If I get real nitpicky, the color and sheen of the Si rod is SLIGHTLY different, but that may just be a result of the batch each rod was manufactured in.

There has been a handful of accounts of "base" 1.5T rod breakage, so I decided to have the material of each rod tested for hardness.

The results are:
Base = 22 HRC
Si = 28 HRC

The Civic Si rod is definitively harder on the Rockwell scale than the "base" 1.5T rod.

I would also like to note that the rod thickness is just 1.3mm thinner than a K20A2 "PRB" connecting rod at the thinnest parts.

I hope this comes in handy for everyone.

Thanks!

Honda Civic 10th gen Comparison of "Base" 1.5T and "Si" 1.5T Connecting Rods 28164435_2030051937261521_1942652561793776438_o


Honda Civic 10th gen Comparison of "Base" 1.5T and "Si" 1.5T Connecting Rods 28161852_2030051520594896_6161611196574426197_o


Honda Civic 10th gen Comparison of "Base" 1.5T and "Si" 1.5T Connecting Rods 28161417_2030051410594907_8376034772913084933_o


Honda Civic 10th gen Comparison of "Base" 1.5T and "Si" 1.5T Connecting Rods 28238902_2030051563928225_6906486491000744294_o
 

charleswrivers

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For anyone wondering if the different part number connecting rod the Civic Si engine got makes it any different, I ordered a "base" 1.5T rod and a Civic Si unit.

As far as my dial calipers can tell, they're dimensionally the same. The bushing for the wrist pin on the Si rod has a visibly smoother finish than the base model rod, but other than that, I don't see a difference. If I get real nitpicky, the color and sheen of the Si rod is SLIGHTLY different, but that may just be a result of the batch each rod was manufactured in.

There has been a handful of accounts of "base" 1.5T rod breakage, so I decided to have the material of each rod tested for hardness.

The results are:
Base = 22 HRC
Si = 28 HRC

The Civic Si rod is definitively harder on the Rockwell scale than the "base" 1.5T rod.

I would also like to note that the rod thickness is just 1.3mm thinner than a K20A2 "PRB" connecting rod at the thinnest parts.

I hope this comes in handy for everyone.

Thanks!

28164435_2030051937261521_1942652561793776438_o.jpg


28161852_2030051520594896_6161611196574426197_o.jpg


28161417_2030051410594907_8376034772913084933_o.jpg


28238902_2030051563928225_6906486491000744294_o.jpg

The talk was about someone doing a GoFundMe me or something for this info. PM me your PayPal and I'll send you a few bucks.

It is very appreciated. The harder rod will be more brittle... have higher strength... but technically less toughness. It'd be more adept to break outright than bend. It does bode well for the Sis.
 


maddmatt02

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That's weird (and proves that pic I posted was a base rod) that the SI has "5PA" but the base has "9BJ". I actually didn't even look that hard until somebody else pointed it out and then I was skeptical that the pic I found of the base rod was real. I'll kick in a few bucks too since that's what stopped me from buying a couple. Pm me your info if you want and thanks for the comparison..
 
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D-RobIMW

D-RobIMW

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While I appreciate the kind gesture of wanting to pay me for this, it's really no problem. The rods were inexpensive enough for me to source and it satisfied my own curiosity on them.

The Rockwell test would indicate roughly a 10-11% increase in implied tensile strength, but I'm not into metallurgy enough to say much more on it.

I plan to have them stress tested if I can find someone locally in a reasonable time frame to do it.
 

maddmatt02

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how much harder is 28 compare to 22?
112,000 to 129,000 psi tensile strength.

Of course Wikipedia can't always be trusted but I got this from there. "When testing metals, indentation hardness correlates linearly with tensile strength"

And found an online tensile to hardness scale.
 

17siturb0

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Thank you for spending your own money to give us some insight on the rods! Much appreciated! I was thinking of doing it, but figured someone already pulled the trigger.
 


davemarco

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While I appreciate the kind gesture of wanting to pay me for this, it's really no problem. The rods were inexpensive enough for me to source and it satisfied my own curiosity on them.

The Rockwell test would indicate roughly a 10-11% increase in implied tensile strength, but I'm not into metallurgy enough to say much more on it.

I plan to have them stress tested if I can find someone locally in a reasonable time frame to do it.
Much gratitude sir. I know that this was something that everyone really wanted to see.

Visually, they appear to be identical - could the SI rod be a different composite alloy?
 

3925blue

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Could be different alloy, or could just be shot-peened. Any difference in mass?
 

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I'm not sure if this is any explanation for the difference, but from the Honda press kit for the SI:

"Lightweight, high-strength steel connecting rods are heat-forged in one piece and then "crack separated" to create a lighter and stronger rod with an optimally fitted bearing cap."

http://hondanews.com/honda-automobiles/channels/Model-Press-Kit/releases/honda-civic-si-powertrain
Actually if you look at the press kit for the 2016 Civic sedan, Honda describes that cars connecting rods with the exact same wording:

http://hondanews.com/honda-automobi...s/2016-honda-civic-sedan-press-kit-powertrain

"Pistons and Connecting Rods
The 1.5-liter engine's pistons help maintain stable combustion and contribute to improved efficiency with "cavity-shaped" crowns. The lightweight pistons have a carefully optimized skirt design to minimize reciprocating weight, which minimizes vibration and increases operating efficiency. The pistons are cooled by twin oil jets directed at the underside of each piston crown. Ion-plated piston rings help reduce friction for greater operating efficiency. Lightweight, high-strength steel connecting rods are heat-forged in one piece and then "crack separated" to create a lighter and stronger rod with an optimally fitted bearing cap."
 
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maddmatt02

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the plot thickens...
Sponsored

 


 


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