There can be no replacement without displacement, especially when it comes to the racing world.
More power means more speed. Have you ever wondered why nitrogen oxide and turbo are so popular? Well, it is simple they burn more oxygen which means more power. There are three ways of increasing power in an engine.
- Increase the stroke of the crankshaft.
- Increase the number of cylinders.
- Increase the bore size of cylinders.
However, in this case, we are going to focus on how to increase the stroke of the crankshaft.
Increasing the stroke of the engine – Why Do You need a Connecting Rod?
When increasing the stroke of a racing engine, look at two things – the dynamic and physical features.
When you increase the stroke of a crankshaft, the journal will rotate on a larger diameter. The big end of the connecting rod needs to be connected to the crankshaft, while the smaller end to the piston.
The bigger end travels in a rotating motion while the smaller end rotates in a reciprocal motion. This is where the connecting rod comes in and converts the reciprocal motion into rotational. It is in this case that the top dead centre (TDC) is equal to the bottom dead centre (TDC). Racing connecting rods can help you make things easier, what we will take a look at below.
Guide to connecting Rods
Rod length varies, and this affects the piston’s acceleration and distance. It is crucial to note that piston acceleration TDC and BDC are at zero at all points. The piston archives maximum velocity when the rod axis is 90 degrees and the crank angle does not exceed 70 to 75 degree.
Rod length as a tuning component – Long rod vs Short Rod
Experts recommend the rod length to be 1.7-1.9 times the stroke length. This will allow some more power to it. However, it should be noted that rod length should be able to measure up to the race car’s application. Longer rods tend to increase the piston dwell time at TDC. It also reduces side loading in the piston, therefore less pressure. Holding a bit more combustion for half a degree of crankshaft rotation will add a bit more power. The longer the rod, the more will be the power for mid-range.
However, long rods have a disadvantage. The velocity and force will decrease meaning lesser revolutions per minute( RPM)which is not good for everyday driving but really advantageous for race car drivers. Short rod length means that the height of the piston is shorter which results to less weight. This means that there will be a low vacuum at RPM leading to low force. Actually, this is really good for everyday driving.
So you might be asking yourself which is the best rod length?
The answer depends on what you are looking for. The variables are many, from the difference in cylinders, designs, turbo heads and valves. For instance, the BMW M3 has a rod length of 1.48 which is not a good number. On the other hand, it has a horsepower of 2.4 per cubic inch.
Many people worry about how rod length will affect performance. Sure, horsepower and force matter, but they aren’t the only things to look at; you cannot ignore a connecting rod when it comes to engine performance.