## What is Wheel Horsepower?

**Wheel horsepower** is the actual power available at the driving wheels of a car. Unlike the engine or crank horsepower, which manufacturers often highlight, wheel horsepower accounts for energy losses in the drivetrain during power transmission.

### Bhp to whp Calculation Formula:

The formula for wheel horsepower (WHP) is given by:

*WHP*=*ηdvtr*⋅*EHP*

Where:

*WHP*is the wheel horsepower.*ηdvtr* is the efficiency of power transmission of the drivetrain.*EHP*is the engine horsepower (also known as crank or brake horsepower).

### Drivetrain Systems:

Cars can have different drivetrain systems:

- Front-wheel drive (FWD)
- Rear-wheel drive (RWD)
- All-wheel drive (AWD) or Four-wheel drive (4WD)

## Drivetrain Loss Calculation

The drivetrain introduces losses in power transmission due to various components. Drivetrain loss depends on the efficiency of these components.

### Front-Wheel Drive Efficiency Formula:

*ηFWD*=*ηgbx*⋅*ηdif*⋅*ηfdrs*

Where:

*ηFWD* is the efficiency of the front-wheel drive system.*ηgbx* is the efficiency of the gearbox.*ηdif* is the efficiency of the differential.*ηfdrs* is the efficiency of the front drive shaft.

### Rear-Wheel Drive Efficiency Formula:

*ηRWD*=*ηgbx*⋅*ηprs*⋅*ηdif*⋅*ηrdrs*

Where:

*ηRWD* is the efficiency of the rear-wheel drive system.*ηprs* is the efficiency of the propeller shaft.*ηrdrs* is the efficiency of the rear drive shaft.

### Drivetrain Loss Calculation Formula:

Drivetrain Loss=1−*ηdvtr*

Drivetrain hp loss=(1−*ηdvtr*)⋅*EHP*=*EHP*−*WHP*

## Efficiency of Drivetrain Components

### Gearbox Efficiency Formula:

*ηgbx*=*Nbrg**ηbrg*⋅*Ngrm**ηgrm*

Where:

*ηgbx* is the gearbox efficiency.*ηbrg* is the bearing efficiency.*Nbrg* is the number of bearings.*ηgrm* is the gear mesh efficiency.*Ngrm* is the number of gear meshes.

### Propeller Shaft Efficiency Formula:

*ηprs*=*Nuj**ηuj*⋅*Nbrg**ηbrg*

Where:

*ηprs* is the propeller shaft efficiency.*ηuj* is the universal joint efficiency.*Nuj* is the number of universal joints.

### Differential Efficiency Formula:

1*ηdif*=*Nbrg**ηbrg*⋅1*ηgrm*

Where:

*ηdif* is the differential efficiency.*ηbrg* is the bearing efficiency.*Nbrg* is the number of bearings.*ηgrm* is the gear mesh efficiency.

### Drive Shaft Efficiency Formula:

*ηdrs*=*ηtrp*⋅*ηrzp*

Where:

*ηdrs* is the drive shaft efficiency.*ηtrp* is the tripod joint efficiency.*ηrzp* is the Rzeppa joint efficiency.

## How to Calculate Wheel Horsepower?

**Determine Drivetrain Efficiency:**- Use the wheel horsepower calculator to find the drivetrain efficiency.

**Multiply with Engine Horsepower:**- Multiply the drivetrain efficiency with the engine horsepower to obtain wheel horsepower.

**Verify with Calculator:**- Confirm the result using the wheel horsepower calculator.

## How to Use the Wheel Horsepower Calculator?

**Select Drive Type:**- Choose between Rear-wheel drive or Front-wheel drive.

**Enter Engine Horsepower:**- Input the vehicle’s engine horsepower.

**Enter Component Efficiencies:**- Fill in the efficiencies for gearbox, propeller shaft, differential, and drive shaft. Advanced mode allows entering individual efficiencies.

**Get Wheel Horsepower:**- The calculator will provide the calculated wheel horsepower.

## FAQ

### Q: What is the wheel horsepower of a 660 bhp rear-wheel drive vehicle?

**A:** The wheel horsepower is 539.4 hp. Multiply brake horsepower by the assumed drivetrain efficiency (0.8173).

### Q: What is the drivetrain loss of a 118 bhp car if the wheel horsepower is 95 hp?

**A:** The drivetrain loss is 23 hp. Subtract wheel horsepower from brake horsepower.

### Q: Which drivetrain system has maximum efficiency?

**A:** Front-wheel drive systems generally have the highest efficiency due to fewer power transmission components.

**Note:** This information is provided in simplified terms for better understanding. For precise calculations, the wheel horsepower calculator is recommended.

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