Intake Manifold Runner Control (IMRC) is a feature employed by OEMs in which electromagnetic actuators block off the ends of certain intake runners, either reducing or diverting airflow through those runners.
The primary intent of intake manifold runner control is to prevent individual cylinders from receiving inadequate amounts of air during transient and wide-open throttle operation. The ECU generally controls the IMRC system via solenoid valves.
The basic function of intake manifold runner control is to reduce or divert airflow through certain intake runners for better high-rpm performance and reduced emissions. In practice, many aftermarket ECUs disable the solenoid valves responsible for the IMRC system.
How Do Variable Intake Manifolds Work?
The most basic intake manifold runner valve utilizes a single pair of opposing actuators to reduce or divert airflow through all idle and part-throttle intake runners (i.e., low cylinder flow). However, many production engines offer more complex systems that direct the flow of certain cylinders during only high-load/ wide-open throttle conditions.
Variable intake manifolds work with the powertrain control module to improve engine performance by matching the incoming air to the available engine vacuum, increasing torque, and providing more horsepower. A VIM does this by independently controlling the position of the throttle valve in relation to each cylinder.
It uses a complex design that incorporates multiple cam-like lobes, each with its own throttle blade, on a common spindle to move the throttle from fully closed to fully open.
The VIM has two distinct sections: an upper and lower manifold. The upper manifold contains multiple intake runners that are stacked in series; adjacent runners share one throttle body. This allows more air flow through each runner because no runners share one throttle blade.
The lower manifold comprises a single large runner that extends to just before the exhaust ports on each bank. When the engine is cold, low pressure in front of each intake port provides positive suction, sucking air through the open valve and into the cylinder head.
As RPMs increase, the lobe rotates further, closing the valve and blocking the port. The lobe then opens a passage between an upper and lower runner (the ones that share throttle blades) by rotating to align them into one larger opening. This creates a more direct path for air flowing through each intake runner, which reduces the vacuum in front of each cylinder.
By matching RPMs to available engine vacuum, horsepower is increased from a wider powerband. Torque is also increased with the reduced restriction at the manifold. The amount of positive or negative displacement an engine can produce per revolution is referred to as its volumetric efficiency (VE). A VIM maximizes VE by matching it to RPMs and throttle position for optimal performance.
One misconception is that the IMRC actuator changes the engine’s displacement; it does not make an engine bigger or smaller. It merely adjusts how much time (by moving the throttle valve) for intake air to enter each cylinder at a given RPM.
Symptoms of a Bad Intake Manifold Runner Control
Following are the major symptoms of a bad intake manifold runner valve:
- Check Engine Light
- Poor Engine Performance
- Poor Fuel Economy
Let us see these symptoms in a bit detail:
1. Check Engine Light
Check engine light will come on when you have a bad intake manifold runner control valve. The symptoms you notice, like rough idle or loss of power, may depend on how badly the part has malfunctioned. Another problem with your car can also cause it, so you should have your engine checked for a vacuum leak by a mechanic.
2. Poor Engine Performance
When the intake manifold runner control goes bad you will experience poor engine performance and low engine speed. The engine may run rough, hesitate under load, and not perform as it should.
Driving along suddenly, your engine loses power, especially when under load (going up hills); most likely, your intake manifold runner control has failed. What happens is that the valves inside the intake manifold either stick or they don’t open at all.
3. Poor Fuel Economy
A bad intake manifold runner control will result in poor fuel efficiency because the engine’s cylinders aren’t delivering the same amount of air when under different amounts of demand due to vacuum leaks.
A slight difference in airflow can result in a loss of power and less than optimum MPG, and this is why people notice an increase in fuel consumption after performing modifications such as chip tuning, intake, or exhaust work.
Replacement Cost of Intake Manifold Runner Control Valve
The replacement of the intake manifold valve is estimated to range from $300 to $1,000. The replacement cost depends on the type of car and the model year. The older the car, the more expensive it is to replace intake manifold valves.
Here’s a helpful breakdown of average intake manifold valve replacement costs:
Newer luxury cars with overhead cam engines tend to have very expensive intake manifold valves. The average cost is $800 to $1,000 per valve and $3,000 for a set of four.
Domestic cars with overhead cams and newer model years tend to fall in the $300 range. Some domestic vehicles can be cheaper than this or more expensive, depending on the model year and size of the engine.
Replacing intake manifold valves is necessary because it helps maintain the car’s performance and prolong its life span. If left unrepaired, these problems might even cause more damage making the vehicle irreparable. Intake manifold valves are crucial in the vehicle’s engine, and it’s important to change them when needed.
The Benefits of Intake Manifold Runner Control IMRC has been used in production vehicles from General Motors, Fiat, Volkswagen, and others. It was originally employed to meet U.S. emission control requirements by reducing the effective length of the manifold runner and, therefore, the intake manifold’s cross-sectional area.
However, IMRC also has benefits for high-performance engines because it allows them to perform at their peak in any crankshaft position. The major benefit of having individual intake runners controls is that it reduces restrictions imposed by the intake manifold. This gives an engine the capability to achieve a desired low-speed torque and high rpm power.
Frequently Asked Questions
Can you drive with a bad intake manifold runner control valve?
You cannot drive with a bad intake manifold runner control valve in most cases. A bad intake manifold runner control valve can cause a misfire that could affect the car’s drivability.
The car may go into limp mode or stall out while driving on the highway, or it may be hard to start when cold. If you are not getting enough engine power with the engine light on, your intake manifold runner control valve may be at fault.
Is a variable intake manifold the same as a turbocharger?
VIM technology has been applied to single and twin-turbocharged engines with great results. The turbochargers work in conjunction with the VIM by forcing more air into the engine, increasing power even further. A downside of this technology is that it requires changing or re-tuning fuel maps to accommodate the change in airflow.
Can a variable intake manifold affect the valve timing of the engine?
A common misconception is that this technology is like variable valve timing (VVT). VIM technology does not change the timing of the valves. It is simply a mechanical device that moves the throttle valve to allow for optimum airflow into the engine, which maximizes torque and horsepower under different engine loads.