You sit down with your favorite magazine and open it up to find this advertisement. As the average-Joe truck buyer, you may not know what a connecting rod is, but if it’s bigger, then it must be better right? Well, if the connecting rod is bigger, then you imagine all the other components in the engine are also bigger. Well, the advertisement says to compare doesn’t it? Well, is it really better? Let’s let some basic math tell us if it really is!
The diesel engines offered by the “big three” are relatively similar in size. The Dodge Cummins at 6.3 liters, the Ford Power-Stroke at 6.0 liters, and the largest of the three, the Chevy Duramax is at 6.6 liters. Horsepower figures are also the similar, with the Ford and Dodge engines producing 320 horsepower, and the Chevy Duramax producing 340 horsepower. So, with all these numbers being the same, what’s up with the bigger part from the Dodge engine? Did they just feel gracious to give us bigger, stronger parts? Well, sort of, but it doesn’t really make the engine that much better.
Huh? It’s stronger but not better? Well, yes. The important number to look at is the number of cylinders each engine has. The Power Stroke and the Duramax both are 8 cylinder engines, and the Dodge is a 6 cylinder engine. Okay, so what does that funny connecting rod part have to do with cylinders? Well, without going into a huge explanation on how diesel engines work, it’s easier to say that there is a connecting rod for each cylinder.
With that statement, it perhaps just hit you what is up with the larger part in the Cummins engine. There are 6 connecting rods in the dodge Cummins engine performing the same work that 8 connecting rods would be performing in the Duramax or Power stroke engines.
We can look at the numbers in a little more detail and show exactly why the connecting rod is bigger. The Power stroke engine is 6.0 liters, divided by 8 cylinders, so there is .75 liters per cylinder. We can do the same with the Chevy. 6.6 liters is divided among 8 cylinders which means each cylinder is .825 liters. Okay, so what about the Cummins? Well it’s 6.3 liters are divided by only 6 cylinders, so each cylinder is 1.05 liters in size…much bigger.
We can divide up the horsepower as well. The Ford Power Stroke produces 320 horsepower with 8 cylinders, so each cylinder is producing 40 horsepower. On the Chevy engine, it’s 340 horsepower is also being produced by 8 cylinders, meaning each cylinder is producing 42.5 horsepower. The Dodge, however is producing 320 horsepower with only 6 cylinders, meaning each cylinder is being asked to produce 53.3 horsepower.
It’s quite obvious by these numbers why the part in the Dodge engine is that much bigger. I am glad it is too, if the connecting rod was in fact similar in size to the 8 cylinder engines, I would be worried about the durability of the engine. Now, this is in no way belittling to the Dodge Cummins engine, but has been done to demonstrate that the different engine design produces different results. The wording of the advertisement is very slick however….It does not tell you the Cummins engine is any better than the other two…it just says to COMPARE them…which, as you can see, has been done quite well!