Quote:
Originally Posted by BR3W CITY
Is there a negative side effect from having 4 cylinders push air 3ft to the turbo, wherease the other 4 push the air 4 inches to the turbo.
|
I found out the answer to my own question lol so I figured I'd put it here.
Equal length runners from head to turbo will almost always make a little more power, and do so a little more efficiently....but this effect has somewhat of a diminished return on a big v8....why?
Exhaust leaves the head in a pulse, not a single stream of air. These pulses have a certain amount of force inside a pipe, and thusly take a certain amount of time to travel the distance to the turbo. On a small engine like a 4 cyl turbo, there are only 4 pulses being generated, so if one runner has a significantly longer path, it has a greater effect on the amount of air being delivered to the turbo. From what I can find its similar to the idea of scavenging exhaust in terms of squeezing the maximum effort from the air. The more cylinders and larger engine, the more frequent and larger the pulses, making the issue of equal runners less imperative.
I still think its weird to force air towards the outlet of a head, but at least the runner length thing has an answer.