tooter's manifold adventure... - Toyota Yaris Forums

ljming99 · 07-20-2012, 01:18 AM

Given the long runners, and my limited knowledge of VGIS used in chevy cars.

Im guessing probably ~ +3% torque and a ~ -3% decrease in top hp assuming that vvti doesnt do something funny =P

""VGIS stands for Variable Geometry Intake System. In this system, the length of the intake manifold is varied according to the rpm of the engine. (using a set of flaps that are automatically activated, maybe).

"To provide a smooth power delivery and torque across all engine speeds, the air intake system needs to be narrow and long at low rpm and short and wide at high rpm. Since these are conflicting requirements, most inlet systems are a compromise between low and high rpm performance. Varying the inlet tract gives the best of both worlds and variable intake systems in which the inlet tract length varies depending on the rpm is now increasingly common in many cars.
The Optra 1.6’s Variable Geometry Intake System (VGIS) uses a valve to alter the length of the air intake tract, making it longer when the engine is running low revs and shortening the path of air when the engine is running at higher rpm. This improves throttle response and offers a flatter torque curve and is the main reason for the Optra 1.6’s good driveability.""

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07-20-2012, 01:18 AM	#11
ljming99 Drives: Yaris '06 Join Date: Apr 2011 Location: Singapore Posts: 73	Given the long runners, and my limited knowledge of VGIS used in chevy cars. Im guessing probably ~ +3% torque and a ~ -3% decrease in top hp assuming that vvti doesnt do something funny =P ""VGIS stands for Variable Geometry Intake System. In this system, the length of the intake manifold is varied according to the rpm of the engine. (using a set of flaps that are automatically activated, maybe). "To provide a smooth power delivery and torque across all engine speeds, the air intake system needs to be narrow and long at low rpm and short and wide at high rpm. Since these are conflicting requirements, most inlet systems are a compromise between low and high rpm performance. Varying the inlet tract gives the best of both worlds and variable intake systems in which the inlet tract length varies depending on the rpm is now increasingly common in many cars. The Optra 1.6’s Variable Geometry Intake System (VGIS) uses a valve to alter the length of the air intake tract, making it longer when the engine is running low revs and shortening the path of air when the engine is running at higher rpm. This improves throttle response and offers a flatter torque curve and is the main reason for the Optra 1.6’s good driveability.""