Charge Motion Delete Plates

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The intake manifold features charge motion control valves (CMCV) which look like small throttle plates placed in each intake runner path. The pivoting butterflies are processor-controlled, closing off all but a small portal to accelerate and tumble incoming air at low rpm, and then swinging wide open as the engine's demand for air increases. They reputedly help to homogenize the air/fuel mixture for thorough and squeaky-clean combustion at idle and just off-idle.
The problem is that they present an obstruction to ultimate airflow and therefore rob power. The solution is to remove the original CMCV system from the intake manifold and replace it with a pair of charge motion delete plates (CMDP). Steeda's CMDPs cost $280 but a cheaper solution is to buy a used CMCV system that was removed from another Mustang and perform a DIY conversion to custom CMDPs.
When the Mustang GT's Spanish Oak processor is recalibrated with a custom tune that compensates for the revised airflow characteristics of the CMDPs, the result is a 7-10rwhp gain from 3200-6700rpm and a 10-15rwtq gain from 2500-4500rpm. Two more dyno tests showed virtually identical peak-to-peak gains of 6rwhp & 9rwtq. Very worthwhile for such an inexpensive upgrade.

CMCVs

The original charge motion control valve (CMCV) assembly. Despite the relatively low mileage of the engine, the internal passages and valves/shafts were coated with thick crusted oil deposits. Nasty!
Oil vapours are scavenged from the crankcase by the vacuum in the intake manifold via the hose and PCV valve from the driver's side valve cover. Over time oil vapours can become deposited on the CMCVs and the intake valves causing them to stick, thus degrading performance.

Degutted

The easy solution is to delete the CMCV system altogether by separating the actuator system, shafts, and valves from the original assembly.

CMDPs

The custom set of DIY charge motion delete plates are bolted back onto the intake manifold, and the engine's ECU reprogrammed with a custom 91 US octane tune uploaded from my SCT X3 handheld tuner courtesy of Brenspeed. The rev limit was also raised to 6500rpm to take advantage of the engine's improved mid-range and higher rpm breathing ability.