Velocity Stack Comparison

Summary

In this video, Ryan from Air Force Velocity Stacks demonstrates the impact of different stack lengths on motorcycle performance. Through dyno testing, he compares a traditional snow bike intake with an Air Force stack, showing how the latter boosts torque and horsepower, especially in real-world riding conditions. The video emphasizes that stack length is crucial for optimal performance, highlighting the power gains achievable with proper tuning. Ryan also explores the science behind airflow, pulse waves, and stack design, offering insights into motorcycle engine dynamics and the importance of using the right stack for different engines.

Takeaways

• 😀 Intake stack length plays a crucial role in engine performance, particularly in improving torque and horsepower.
• 😀 The Air Force stack shows significant improvements in torque delivery, especially at mid-range RPMs, compared to traditional stacks.
• 😀 While more airflow might seem like it would lead to more power, the dynamics of pulse waves and air compression are key factors in performance.
• 😀 Even though the Air Force stack flows more air than the traditional snow bike intake, the longer stack design is more effective in capturing and compressing air for higher torque.
• 😀 The importance of proper stack length is emphasized for different engine configurations, with specific recommendations for 550cc, 520cc, and 490cc motorcycles.
• 😀 Testing results show that the Air Force stack provides better overall horsepower, even though the peak horsepower is nearly the same as the traditional stack.
• 😀 Proper tuning and setup, including considerations for throttle body size and cam configuration, are essential when testing intake stacks for optimal performance.
• 😀 Stack modifications can lead to dramatic improvements in torque, especially when riding through tough terrains like snow, where consistent power is crucial.
• 😀 The dyno runs reveal that the longer stack design helps maintain a steady, usable power curve across various RPMs, making it ideal for snow bikers.
• 😀 Research and feedback from riders are essential in fine-tuning stack designs for different motorcycle models and engine sizes, as demonstrated with KTMs and other bikes.

Q & A

What is the main purpose of the video?

The main purpose of the video is to demonstrate how different intake stack lengths can impact motorcycle performance, specifically focusing on horsepower and torque gains from various stack configurations.

Why does the narrator emphasize the importance of the correct stack length for each motorcycle?

The narrator emphasizes that different engine sizes require specific stack lengths to optimize performance. By selecting the correct stack length, significant increases in horsepower and torque can be achieved, ensuring better performance for different motorcycles.

What is the key difference between the traditional snow bike intake and the Air Force stack?

The traditional snow bike intake is primarily designed for shedding snow, and it provides decent performance. However, the Air Force stack is designed to improve both horsepower and torque more effectively, making it the better option for performance-focused riders.

How did the Air Force stack compare to the traditional snow bike intake in terms of power?

The Air Force stack resulted in better overall performance. While the horsepower numbers were similar, the Air Force stack delivered more torque across the entire rpm range, especially at lower to mid-range rpms, which are crucial for real-world riding conditions.

What was the performance result when the Air Force stack was installed on the motorcycle?

When the Air Force stack was installed, the motorcycle showed a significant increase in torque and horsepower at lower to mid-range rpms, providing better overall performance, particularly in off-road conditions like riding through trees.

How does the fuel-air ratio (AFR) compare between the traditional snow bike intake and the Air Force stack?

The AFR gauge indicated that the Air Force stack was allowing more air into the engine, making the engine leaner compared to the traditional snow bike intake, which had a richer mixture, resulting in less optimal performance.

Why doesn’t simply increasing airflow lead to more power?

Increasing airflow doesn't always result in more power due to the complexities of engine dynamics, such as pulse waves and air stacking. The air must not only flow in but also create pressure within the engine, and too much airflow can disrupt this balance, affecting performance.

What role do pulse waves play in intake stack performance?

Pulse waves are crucial in intake stack performance. A longer stack helps trap and compress the air during valve operation, contributing to increased power. The right stack length can optimize these pulse waves to improve engine performance.

Why does the narrator state that stack length is crucial and not just the intake design?

The narrator points out that stack length directly affects the engine’s power curve. Even though a stack might have a good design for airflow, if the length isn't suited to the engine size and type, it can result in significant power loss, especially in real-world riding conditions.

What does the narrator mean by saying 'stack length does matter'?

By stating 'stack length does matter', the narrator means that the specific length of the intake stack is crucial for optimizing engine performance. A stack that is too short or too long for a particular engine will not produce the best torque and horsepower results.