griff851
As I was doing the cbr carb sync, I decided to have a play. It has Short stacks on 1&4 and longer stacks on 2&3. I assume the stack length is tuned to first and second harmonic as the Japanese aren't stupid. I use a Morgan Carbtune, engine rpm around 8k rpm. I did runs, with no stacks, stacks, stacks and filter with air box.
The stacks increased cmHg by ~ 2. The longer stacks decreased the cmHg by ~2 over the shorter stacks. The filter and air box decreased the cmHg by ~2.
I read somewhere years ago the velocity stacks would generate about 4% power over no stacks. So say I got lucky and my rebuilt eng is 45hp ( very optimistic) at Max Hp, stacks are going to contribute 1.8Hp in a laminar flow environment. Scary hey!
Interestingly knowing that a short inlet runner length gives more torque and longer gives more rpm, I assume the jap boffins used short 1&4 and longer 2&3 combined with larger 2&3 main jets to balance out crank loading and help cool 2&4 cylinders.
Well there you go velocity stacks.
