Does Conrod Length Affect Torque in Engines?

In summary, the conversation discusses how the length of a conrod in an engine can affect torque production. The speaker mentions how a longer wrench can increase torque when loosening a bolt, but their friend argues that the conrod's motion is linear, not rotational like a wrench. However, the speaker brings up how using longer conrods in racing engines can slightly increase power through increased mechanical advantage and lighter reciprocating mass. They provide links to forum discussions and articles on the topic for further information.
  • #1
Mikesaa309
3
0
Hi,

Sorry if this is in the wrong thread I'm new to the forums. I was recently talking my mate about how engines produce power and torque and how there's so many factors in it. I mentioned the length of conrod would be a factor but my mate disagreed that it has no effect on torque. To my understanding this is why I see it effects torque.

If you have a bolt and you have a short wrench it's difficult to undo the bolt. If you increase the length of the wrench you increase the torque and less force is required. However he made a valid point that the conrod is pushing or pulling the crank not twisting it as it's still linear motion. So with the example of the wrench and bolt does the length of conrod still effect torque in the same way? If not what is the effect of different length conrods I've struggled to come across any decent information online.
 
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  • #2
this question comes up from time to time
go into Search and type in con rod length and you will find several threads posted here
short reply is - we run longer con rods to take advantage of a slight increase in power gained by mechanical advantage. The piston remains at Top Dead Center slightly longer in crank shaft degrees. You must use custom pistons with wrist pin located closer to the deck ( top of Piston) and this means the piston is lighter Mass. We use a smaller wrist pin than usual so the over all reciprocating mass is lighter and spins up RPM quicker. You are not making more power as such, you are making more effective use of the power that is available as the leverage is slightly better. There are longevity issues as sidle loading and long life will be reduced but you are spinning past 5000 RPM so what the hey-hay??
thats racing!

http://www.f1technical.net/forum/viewtopic.php?t=1261

http://www.strokerengine.com/RodStroke.html
 
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FAQ: Does Conrod Length Affect Torque in Engines?

What is a conrod and how does it affect torque?

A conrod, short for connecting rod, is a crucial component in an engine that connects the piston to the crankshaft. It plays a vital role in the combustion process by transferring the linear motion of the piston into rotational motion of the crankshaft. This motion is what creates torque, making the conrod a key factor in determining an engine's torque output.

How does the length of a conrod impact torque?

The length of a conrod can affect torque in two ways. Firstly, a longer conrod can increase the leverage on the crankshaft, resulting in a higher torque output. However, a longer conrod also increases the reciprocating mass, which can negatively impact the engine's ability to rev quickly or smoothly. Therefore, the length of a conrod must be carefully considered to optimize torque output.

What is the relationship between conrod angle and torque?

The angle of a conrod, also known as the rod angle, is the angle between the piston rod and the crankshaft. A larger rod angle can result in a longer stroke length, which can increase the torque output of an engine. However, a larger rod angle can also increase the lateral forces on the piston, leading to increased friction and potential engine damage. Therefore, the rod angle must be carefully balanced to optimize torque output.

Can changing the conrod material affect torque?

Yes, the material of a conrod can significantly impact torque output. A lighter conrod made of a strong material, such as titanium, can reduce the reciprocating mass and allow the engine to rev more quickly, resulting in higher torque. However, using a weaker material may not be able to withstand the high forces and can result in engine failure, ultimately reducing torque output.

Are there any drawbacks to increasing torque through conrod modifications?

While increasing torque through conrod modifications can provide a more powerful engine, there are potential drawbacks to consider. These modifications may increase engine stress and wear, leading to reduced longevity and potential engine failures. Additionally, increasing torque too much can also make the engine more difficult to control, resulting in reduced drivability. Therefore, careful consideration and balancing are necessary when making conrod modifications for increased torque.

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