Advanced Calculator
Formula Used
The calculator treats drivetrain loss as a percentage loss between the engine and tires. Fixed loss is subtracted after percentage loss. This helps model extra drag from tires, accessories, or testing load.
How to Use This Calculator
- Select crank-to-wheel mode for engine horsepower conversion.
- Select wheel-to-crank mode when starting with dyno wheel power.
- Choose a drivetrain preset or enter a custom loss percentage.
- Add fixed loss only when you need extra load modeling.
- Enter RPM when you want a torque estimate.
- Click calculate to show results above the form.
- Use CSV or PDF buttons to save the report.
Example Data Table
| Vehicle Setup | Crank HP | Loss % | Fixed Loss | Estimated WHP | Efficiency |
|---|---|---|---|---|---|
| FWD manual compact | 250 | 10% | 0 | 225.00 | 90% |
| RWD manual coupe | 450 | 15% | 0 | 382.50 | 85% |
| AWD automatic sedan | 600 | 25% | 5 | 445.00 | 74.17% |
Crank Horsepower and Wheel Horsepower Explained
Why the Difference Matters
Crank horsepower is measured at the engine. Wheel horsepower is measured at the tires. The two values are not the same. Power is lost as it moves through the clutch, transmission, driveshaft, axles, bearings, differential, tires, and fluid systems. This calculator helps you estimate that gap with a practical drivetrain loss method.
Better Planning for Builds
Tuners often compare crank horsepower and wheel horsepower during upgrades. A turbo kit may advertise engine output. A dyno chart usually shows power at the wheels. Without conversion, the numbers can look confusing. This tool makes both sides easier to compare. It also adds correction factor control. That helps when weather, dyno type, or testing standards affect the reading.
Loss Percent Selection
Drivetrain loss is not fixed for every vehicle. A light front wheel drive manual setup may lose less power. A heavy all wheel drive automatic setup may lose more. Tire size, gear oil, torque converter slip, and bearing drag can change the result. Use presets as starting points. Then adjust the loss percentage when better data is available.
Advanced Output Review
The calculator also estimates torque, kilowatts, lost horsepower, efficiency, and planning horsepower. The safety margin is useful for conservative tuning targets. The fixed loss field is useful for extra load modeling. CSV and PDF downloads help store results with customer notes or build records. Always treat the result as an estimate. Real dyno testing gives the best proof.
FAQs
1. What is crank horsepower?
Crank horsepower is power measured at the engine crankshaft. It is measured before drivetrain parts consume power. Manufacturers often publish this number.
2. What is wheel horsepower?
Wheel horsepower is power measured at the tires. It is usually lower than crank horsepower because the drivetrain absorbs energy before power reaches the road.
3. What drivetrain loss should I use?
Use 10% to 12% for many front wheel drive cars. Use 15% to 18% for many rear wheel drive cars. Use 20% to 25% for many all wheel drive cars.
4. Is drivetrain loss always accurate?
No. It is an estimate. Real loss changes with transmission design, tire weight, fluid temperature, gear selection, dyno type, and vehicle condition.
5. Why add fixed accessory loss?
Fixed loss helps model extra drag that is not percentage based. Use it for added tire load, accessory load, or conservative testing assumptions.
6. What is the correction factor?
The correction factor adjusts horsepower for testing conditions or standards. Use 1.00 when no correction is needed. Higher values increase corrected power.
7. Can I estimate crank HP from dyno WHP?
Yes. Select wheel-to-crank mode. Enter wheel horsepower and drivetrain loss. The calculator estimates the crank horsepower needed to produce that wheel output.
8. Should I use this instead of a dyno?
No. This calculator is for planning and comparison. A calibrated dyno test gives better evidence for tuning, racing, and verified performance claims.