Is there a certain point at which a longer intake manifold runner hurts air flow potential? How much does a longer runner, say 3" vs 10", intake runner boost power or does increase in runner length have minimal effect on upper rpm power?

Also does intake port velocity matter as much as intake cylinder head runner port velocity?

Thanks
Jeremy

 

In theory, the runner could be 10 feet long, but the diameter of the runner would have to be large enough to support the airflow you need. For practical purposes, this wouldn't work and you wouldn't need it to.

The longer you make intake runners, the lower the torque peak moves in the operating range of the engine. This subsequently moves your peak power output lower into the rpm range.

When you look at a dual plane manifold vs a single plane or tunnel ram, one thing is obvious, the manifolds designed to make the most torque and power in the lower RPM ranges have longer runners, while the ones made to make peak power at 7000 rpms have short runners.

To my knowledge runner length doesn't affect actual power production, just where it is made. Runner diameter is what decides how much air can be flown through the runner and then this decides your power output.

Intake runner velocity and cylinder head intake runner velocity would go hand in hand I think. You want velocity to be high to promote good fuel distribution, and to help with the interial ramming affect to help fill the cylinders. I would try and got for the smallest diameter runner that can support the power level you want. This would keep the velocity as high as it can be without restricting the airflow, resulting in a loss of power.


Hope that helps you out, I am sure OldSStroker or SStroker will chime in as they know this stuff well.

Hunter