Harley Davidson V-Rod Forum banner
1 - 1 of 1 Posts

· Ghost Rider
549 Posts
We have a similar phenomena on old carbureted race engines, longer stacks are better for higher rpm ranges and vice versa. It depends on where you expect to have your normal operating range or your shift points.

As a practical example, on my racecar we use long stacks as the peak torque and HP goes from 6700 to 8500 RPM and we then geared the transmissions to take advantage of this accordingly. The settings being that when you upshift at approx 8250 RPM the next gear comes in at 6700 RPM thus in the thick of the power band.

On my application all stacks are equal length as are the exhaust headers.

In some modern cars, the intake runners are variable in length to take advantage of boundary air layers applicable at different engine speeds. The idea being maximizing intake velocity and thus the volume of air being drawned in.

Hope this helps. Juan
1 - 1 of 1 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.