RPM Air Gap Runner Length (SBC)

[77cruiser]

Probably depends on the runner measured, looked like 4 1/2 to 6 inches.

[Stan Weiss]

Measurements by another forum member have yielded some mixed results. As was pointed out, the irregular shape of the runner(s) where they enter the plenum make an accurate assessment difficult.
As it is, it was somewhat determined that the runner length is about 4 1/4". While that may be the value, as was also pointed out, the behaviour of the pulses follow a different path. With a 4 1/4" runner and a 5 1/2" port, that works out to less than a typical single plane induction length of 11 1/2".
So, in conclusion, I guess it's a case of run what you brung and if it doesn't work, go to plan B.

Kevin,
There are different wave refection and the smaller the number the stronger they are. DV wanted Torque Master to calculate the 2nd 3rd and 4th. 9.75" total track length, 5th refection would be 5538 RPM.

Stan

[skinny z]

Probably depends on the runner measured, looked like 4 1/2 to 6 inches.

They're certainly not all the same.

[skinny z]

Kevin,
There are different wave refection and the smaller the number the stronger they are. DV wanted Torque Master to calculate the 2nd 3rd and 4th. 9.75" total track length, 5th refection would be 5538 RPM.

Stan

Thanks for that Stan. Even though the impact might only be from the 5th reflection, in the case of the engine I've entered into TM, that plays well into the cam that TM generated using CFM as a data point. Peak HP RPM was calculated to be around 5500.
I'll revisit TM and fiddle around further with induction lengths.
Thanks again.

[SchmidtMotorWorks]

I have measured this with a scope.
5th is so weak and distorted in anything other than a perfectly straight tube it is not worth considering.

CFD illustrates how contorted the waves get in turning ducts with non square openings.

There can be some benefit to a curved duct or non perpendicular opening but nothing designed prior to the past few years could have optimised that with anything beyond guessing.

[skinny z]

Much like (or exactly like) the pulse reflected back from the tip of a full exhaust system. It's not worth much from a tuning perspective but it is offered as a dimension in Pipe Max.
That said, it looks to be that there is no real value that can be assigned to the AG dual plane manifold runner length. Run it and see what you get.

[6.50camaro]

Just read back thru my early post . Miss wrote 1.46 csa it should have been 2.46 sq.in. IMHO that is the "magic" of the rpm ag sized large enough to carry a health small block to 6500 rpms and small enough to get velocity up to make peak torque in the 4000-4500 range . Length has little to do with it . Must modern single plane have runners close in lenght but csa of well over 3 sq.in. many 3.25 to 3.5 .Dan

[skinny z]

Just read back thru my early post . Miss wrote 1.46 csa it should have been 2.46 sq.in. IMHO that is the "magic" of the rpm ag sized large enough to carry a health small block to 6500 rpms and small enough to get velocity up to make peak torque in the 4000-4500 range . Length has little to do with it . Must modern single plane have runners close in lenght but csa of well over 3 sq.in. many 3.25 to 3.5 .Dan

I'm hardly in your territory with respect to breathing capacity but the AG manifold certainly seems to have the legs to support my modest platform from what you've reported and others.
As far as length, the late Joe Sherman demonstrated that gains were to be made with the dual plane as he proceeded to add up to 4" of open spacers and power kept on climbing. While that's more of a plenum thing than length, it goes to show that there's some tunability after the choice has been had to run the dual plane.