User Guide

48—Dyno2000 Advanced Engine Simulation
known for its ability to boost low-end power.
The divided plenum is another common feature of dual-plane manifolds that fur-
ther boosts low-end power. Since each side of the plenum is connected to only one-
half of the cylinders (4-cylinders in a V8), each cylinder in the engine is “exposed”
to only one-half of the carburetor. This maximizes wave strength and improves low-
speed fuel metering (these effects are much less pronounced with throttle-body fuel-
injection systems). However, the divided plenum can become a significant restriction
at higher engine speeds, limiting peak horsepower.
The main benefits of the dual-plane design are its low-speed torque-boosting
capability, compact design, and wide availability for use with both carburetors and
injection systems. However, not all engines are capable of utilizing a dual plane
configuration. Typically, engines that do not have an even firing order or have too
many cylinders to generate a resonance effect will not benefit from a dual-plane
manifold. While there are some exceptions, engines having 2 or 4 cylinders work
best with this manifold. Since most V8 engines are basically two 4-cylinder engines
on a common crankshaft, even-firing V8s also benefit from the resonance effects of
the dual-plane manifold. Motion’s simulation does not prevent choosing a dual-plane
manifold on engines that will not develop a full resonance effect. For example, you
can install a dual-plane manifold on a 5-cylinder engine, but the results—a low-end
power boost—are not reproducible in the real world, since an effective dual-plane
manifold cannot be built for this engine. The simulation is best utilized by modeling
Dual-Plane vs. Single-Plane Design
The basic differences between single- and dual-plane manifolds are clearly illustrated
here. The dual-plane (left) divides the plenum in half, with the runners grouped by
firing order. Each cylinder “sees” only one-half of the carburetor, transferring a strong
signal to the venturis. This manifold design is said to have a 2
nd
degree of freedom,
allowing it to reach a unique resonance that makes its short runners boost low-speed
power. The single-plane manifold (right) has short, nearly equal-length runners with
an open plenum, much like a tunnel ram that is laid flat across the top of the engine.
The manifold has excellent high-speed performance, but its design prevents full-mani-
fold resonance. That reduces low-speed torque, driveability, and fuel economy.
Dual-Plane Manifold Modeling