Exhaust Diameter Calculator
Calculate optimal exhaust pipe diameter for maximum engine performance
Calculation Mode
Calculate Optimal Exhaust Diameter
RPM where engine produces maximum torque (typically 2000-6000 RPM)
Total engine size (e.g., 2.0L, 1800cc, 110 cu.in.)
Common: 4, 6, 8 cylinders
Alternative: Direct Single Cylinder Volume
If known, enter directly (overrides calculation from total displacement)
Example Calculation
1.8L Four-Cylinder Engine
Total displacement: 1.8 liters (1,800 cc)
Number of cylinders: 4
Single cylinder volume: 1,800 ÷ 4 = 450 cc
Peak torque RPM: 6,500
Step-by-Step Calculation
Cross-section = (RPM × V) / 88,200
Cross-section = (6,500 × 450) / 88,200
Cross-section = 2,925,000 / 88,200 = 33.16 cm²
D = √(4 × Area / π) = √(4 × 33.16 / π)
D = 6.50 cm ≈ 2.56 inches
Exhaust Size Chart
*Chart shows outer diameter ranges for reference
Exhaust Facts
Diameter affects torque across RPM range
Larger pipes favor high-RPM power
Smaller pipes improve low-end torque
Match diameter to engine characteristics
Peak torque RPM is critical for sizing
Understanding Exhaust Diameter
What is Exhaust Diameter?
Exhaust diameter is the internal diameter of an exhaust pipe, critical for optimal engine performance. The right diameter ensures proper exhaust gas flow while maximizing torque at your engine's peak torque RPM range.
Why Does Size Matter?
- •Affects engine torque curve and power delivery
- •Influences backpressure and scavenging effects
- •Determines optimal RPM range performance
- •Impacts fuel efficiency and emissions
Formula Explanation
D = √(RPM × V × π) / 88,200
- D: Optimal exhaust diameter (cm)
- RPM: Peak torque RPM
- V: Single cylinder volume (cc)
- 88,200: Mathematical constant
Measurement Formula
Internal Diameter = Outer Diameter - (Wall Thickness × 2)
Pipe Size Effects on Performance
Too Small
- • Restricts high-RPM flow
- • Creates excessive backpressure
- • Reduces peak power
- • May improve low-end torque
Optimal Size
- • Balanced flow characteristics
- • Maximum torque at peak RPM
- • Good overall performance
- • Efficient scavenging
Too Large
- • Reduces velocity
- • Poor low-end torque
- • Inefficient scavenging
- • May help at very high RPM