## 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=EHPWHP

## Efficiency of Drivetrain Components

### Gearbox Efficiency Formula:

ηgbx​=Nbrgηbrg​​⋅Ngrmηgrm​​

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​=Nujηuj​​⋅Nbrgηbrg​​

Where:

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

### Differential Efficiency Formula:

1ηdif​=Nbrgηbrg​​⋅1ηgrm​​

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?

1. Determine Drivetrain Efficiency:
• Use the wheel horsepower calculator to find the drivetrain efficiency.
2. Multiply with Engine Horsepower:
• Multiply the drivetrain efficiency with the engine horsepower to obtain wheel horsepower.
3. Verify with Calculator:
• Confirm the result using the wheel horsepower calculator.

## How to Use the Wheel Horsepower Calculator?

1. Select Drive Type:
• Choose between Rear-wheel drive or Front-wheel drive.
2. Enter Engine Horsepower:
• Input the vehicle’s engine horsepower.
3. Enter Component Efficiencies:
• Fill in the efficiencies for gearbox, propeller shaft, differential, and drive shaft. Advanced mode allows entering individual efficiencies.
4. 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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