The term is called scavenging. It's where the low pressure component of an exhaust pulse is used to increase the velocity of the next exhaust pulse. The length of each primary tube is important for the timing of each exhaust pulse, and when they are done right you do a better job of getting the scavenging you want. The same concept works with Y and X pipes. As soon as an exhaust pulse reaches a collector, Y pipe or X pipe, it creates a low pressure because the increase in space (diameter of tube), which in turn helps pull out the next exhaust pulse.
While Edelbrock's headers don't appear to be "tuned" headers, it doesn't necessarily mean they're not providing good scavenging. Conceptually, you should be able to take the firing order of the Viper engine, and with a bit of calculation, figure out a ball park figure on how much a difference there needs to be between the primary tubes to ensure 2 or more pulses don't meet at the collector, Y pipe, or X pipe at any given time. Ideally, you want that designed around hard accelleration (where you want the most power gains), which means you need to factor in the assumption that each exhaust pulse is moving faster than the previous pulse (due to increasing RPMs), and ensure the distance is so that the pulses don't catch up with eachother. It's possible the Edlebrocks are a good header for the Viper.
Any math experts/engineers want to give it a try?
Just my $.02.
Jason
While Edelbrock's headers don't appear to be "tuned" headers, it doesn't necessarily mean they're not providing good scavenging. Conceptually, you should be able to take the firing order of the Viper engine, and with a bit of calculation, figure out a ball park figure on how much a difference there needs to be between the primary tubes to ensure 2 or more pulses don't meet at the collector, Y pipe, or X pipe at any given time. Ideally, you want that designed around hard accelleration (where you want the most power gains), which means you need to factor in the assumption that each exhaust pulse is moving faster than the previous pulse (due to increasing RPMs), and ensure the distance is so that the pulses don't catch up with eachother. It's possible the Edlebrocks are a good header for the Viper.
Any math experts/engineers want to give it a try?
Just my $.02.
Jason
... The tuning is so that the sonic waves and exhaust pulses meet at specific times in the collectors causing a suction in front of the next cylinder's exhaust pulse.
...
The Edelbrock headers have no effort made towards equalling tube lengths and therefor obviously make less power than tuned headers...
Ted