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Engine Horsepower Calculator

HP/Liter Reference

Economy NA60-80 HP/L
Sport NA90-110 HP/L
High-Rev NA110-130 HP/L
Mild Turbo100-140 HP/L
Performance Turbo150-200 HP/L
F1 Engine500+ HP/L

Common Engines

4-Cyl 2.0L150-200 HP
V6 3.5L250-300 HP
V8 5.0L350-450 HP
V8 6.2L (Supercharged)650-700 HP

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Understanding Engine Power

How Engine HP is Calculated

Engine horsepower depends on displacement (size), RPM (speed), and volumetric efficiency (how well the engine breathes). Forced induction (turbo/supercharger) significantly increases power by cramming more air into the cylinders.

Basic HP Formula

HP = (Displacement x RPM x Volumetric Efficiency x BMEP) / 792,000
Where BMEP is Brake Mean Effective Pressure (typically 125-200 psi for NA engines)

Key Factors

FactorDescriptionTypical Range
DisplacementTotal volume of all cylinders1.0L - 8.0L
Peak RPMEngine speed at max power5,500 - 8,500
VE (Naturally Aspirated)Volumetric efficiency80% - 100%
VE (Forced Induction)With turbo/supercharger100% - 200%+
Compression RatioCylinder volume ratio9:1 - 13:1

Power vs Torque

Horsepower

  • Measures rate of work
  • Determines top speed
  • Higher at high RPM
  • HP = Torque x RPM / 5252

Torque

  • Measures rotational force
  • Determines acceleration
  • Usually peaks at mid-RPM
  • Measured in lb-ft or Nm

Engine Types

Naturally Aspirated

Relies on atmospheric pressure. Linear power delivery, typically 70-110 HP per liter.

Turbocharged

Uses exhaust-driven compressor. Can achieve 100-200+ HP per liter.

Supercharged

Belt-driven compressor. Instant boost with no lag, 100-150+ HP per liter.

Hybrid/Electric Assist

Adds electric motor power. Fills in torque gaps, improves efficiency.

Dyno vs Advertised HP

Manufacturer ratings are often at the flywheel (gross HP). Real-world dyno numbers measure at the wheels, which is typically 15-20% lower due to drivetrain losses. FWD loses less than RWD, and AWD loses the most.

Frequently Asked Questions

How is engine horsepower calculated?

Engine horsepower depends on displacement (engine size), RPM, and volumetric efficiency. The basic formula is: HP = (Displacement x RPM x VE x BMEP) / 792,000. Turbocharged engines can exceed 100% volumetric efficiency by forcing more air into cylinders.

What is the difference between horsepower and torque?

Horsepower measures the rate of work (how fast power is delivered) and determines top speed. Torque measures rotational force and determines acceleration. They're related by the formula: HP = Torque x RPM / 5,252.

Why is dyno horsepower lower than advertised?

Manufacturers measure horsepower at the flywheel (crank HP), while dyno tests measure at the wheels. Drivetrain losses account for 15-20% reduction. FWD vehicles lose less power than RWD, and AWD loses the most.

How many horsepower per liter is normal?

Naturally aspirated engines typically produce 70-110 HP per liter. Turbocharged engines achieve 100-150+ HP per liter, while high-performance forced induction engines can exceed 200 HP per liter.