Dodge V10's found in Vipers and the heavy duty pickups from 94-03 have a unique sound that you can instantly recognize upon start up all the way through the rev range. It is so unique that it is easily distinguishable from other V10's found in many exotics and Ford trucks. To explain the unique sound, we will be looking at the various firing intervals and block angles of production V10's.
To start off we will cover a few definitions:
Firing interval - the degrees of crankshaft revolution between cylinder firing events
Block angle - Angle between cylinder banks
Split journal crank – When a pair of cylinders in a V engine do not share a common crank journal but are rather split into two separate journals
Balance shaft – Internal crank driven shaft with counterweights to balance engine harmonics
In a 4-stroke engine all cylinders need to fire within 720 degrees (2 rotations) of crankshaft revolution. This means a single cylinder 4 stroke engine will have a firing interval of 720 degrees where a 2-stroke engine fires every 360 degrees. When adding cylinders, to find the ideal firing interval divide 720 degrees by the number of cylinders. The result is the ideal design interval for easy balancing. For example, a typical push rod V8, take 720 / 8 = 90 degrees. For a V10, the firing interval is 72 degrees.
In traditional engine design, the block angle on multi cylinder “V” engines is determined by the firing interval for ease of balancing. For example, a typical V8 would have a block angle of 90 degrees. This allows for the use of shared rod journals. Many exotic cars with V10's, the block angle is 72 degrees. Both Dodge and Ford strayed from traditional engine design by using a 90 degree block angle for their V10’s. This resulted in unique design challenges to balance their V10 engines. Using a block angle of 90 degree was likely to keep tooling costs down, as either engine is loosely based of existing V8 architecture. Ford balanced their engine by keeping the 72 degree firing interval with a split journal crankshaft with counter weights and the addition of a balancing shaft. By keeping the 72 degree firing interval their engine sounds very similar to a traditional V10.
Dodge took a different approach to balancing their V10 with a 90 degree block. The shared rod journals were retained in the Dodge design and an unequal firing interval of 90 and 54 degrees was used. This allowed the crankshaft counter weights alone to balance the engine. This means that as the engine progresses through the firing order the intervals between firing events are unequal. Starting with cylinder 1, the engine fires rotates 54 degrees to fire cylinder 10, rotates 90 degrees to fire cylinder 9, and so on through the rest of the firing order.
Dodge V10 Firing Order:
1 , 10 - 9 , 4 - 3 , 6 - 5 , 8 - 7 , 2
Comma = 54 degrees
Dash = 90 degrees
This uneven firing interval creates the unique sound of Dodge V10's.