Customers should pay close attention to the horsepower rating, as it is a direct indicator of the vehicle’s performance. Vehicles with higher horsepower and torque are more reliable when towing and have quicker acceleration, both of which are useful for those who frequently utilize highway on-ramps.
In this article, we’ll compare horsepower in two forms: wheel horsepower (WHP) and conventional horsepower (HP). There is a close relationship between these two terms, and knowing how to convert WHP to HP is an essential element of comprehending engine powers.
Why is Calculating The Horsepower Important?
The strength of the car’s engine is a crucial factor to consider when making a purchase. Engine power is typically expressed in terms of horsepower. A higher horsepower rating means more strength and faster acceleration.
How does that affect you as a car buyer, though? The amount of work that your car’s engine is capable of depends on its horsepower. Better acceleration is a key component of a car’s performance, and a high horsepower engine is a key component of that.
Engine Horsepower
The flywheel is the standard measurement device for determining an engine’s horsepower. This is also known as brake horsepower or power “at the crank,” which refers to the engine’s rotating crankshaft. Manufacturers typically flaunt this figure when describing a car’s horsepower.
If you don’t know your engine’s horsepower, then you most probably know its capacity (CC). In this case, check our article that helps you determine your engine HP from its CC.
Wheel Horsepower
The wheel horsepower of a vehicle is defined as the amount of power delivered to the road via the wheels. In other words, WHP describes the horsepower that actually reaches the wheels. This is after drive-train loss is taken into consideration. It refers to the total power output of the vehicle, not simply the engine.
Difference Between HP And WHP
While HP refers to the actual horsepower output of the engine, meanwhile, wheel horsepower is a crucial metric that indicates how much power is transferred from the engine to the wheels.
The difference between the engine and wheel horsepower is typically 20%-45%. The reason for this is that the engine’s output power is affected by a wide variety of factors beyond the engine itself, including the transmission, drivetrain, vehicle weight, tire and wheel size, gear, and environmental factors, including weather, altitude, and the type of dyno used. WHP refers to the amount of power that a vehicle produces when it’s actually moving.
Convert WHP to HP
The following equation is used to determine the horsepower (hp) of the engine from the horsepower of the wheels (WHP).
HP = WHP / (1 – DL )
Where,
HP is the engine horsepower
WHP is the wheel horsepower
DL is the drive train loss
The drive train loss is 0.10 (10%) for front-wheel drive, 0.15 for rear-wheel drive, and 0.25 for all-wheel drive.
Example
Suppose the wheel horsepower is measured to be 350 HP. First, figure out what kind of drive train it has. In our case, we’re looking at a car that is rear-wheel driven.
Next, use the type of drive-train to figure out the system’s drive-train loss. In this case, 0.15 is the DL. Last, use the above formula to figure out the HP from the WHP and DL:
HP = WHP / (1 – DL )
HP = 350 / (1 – 0.15 )
HP = 411.76 horsepower
Convert HP to WHP
The amount of horsepower actually going to the wheels of a car can be determined using the following formula.
WHP = EHP / DTLF
Where,
WHP is the wheel horsepower
EHP is the engine horsepower
DTLF is the drive train loss factor
The drive train loss factor (DTLF) is 1.1 for front-wheel drive, 1.15 for rear-wheel drive, and 1.2 for all-wheel drive.
Example
Determine the total engine horsepower output. Suppose the engine of the car can output a maximum of 800 horsepower (hp). Now, determine the drive train system. In this example, the drive train is a rear-wheel-drive system.
Next, determine the drive-train loss factor. In this case, the loss factor is 1.15, as shown in the formula above. Finally, calculate the wheel horsepower:
WHP = EHP / DTLF
WHP = 800 / 1.15
WHP = 695.65 horsepower
Or,
You can simply use the below calculator for the conversion;
FAQs
How do you convert HP to WHP?
To go from horsepower to wheel horsepower, you’ll need a calculator to know how your car’s drivetrain works. The drivetrain loss can be used in the formula. For front-wheel drive, the drive train loss is 10%, for rear-wheel drive, it is 15%, and for all-wheel drive, it is 25%.
Does HP stand for horsepower?
Yes, in the field of auto mechanics, HP stands for horsepower, which is the amount of power that the engine puts out. There are different types of horsepower, like wheel horsepower, braking horsepower, and crankshaft horsepower. You’ll find that engines with more power have more horsepower.
What Does The HP At The Wheels Mean?
The HP at the wheels is the power from the engine that gets to the wheels. Drivetrain losses, mostly caused by friction, usually make it less than the HP.
How much HP do you lose from the crank to the wheels?
Some of the power is lost when the transmission system sends power from the crank or flywheel to the wheels. Depending on the drivetrain, you lose 10% with a front-wheel-drive car, 15% with a rear-wheel-drive car, and up to 20% with an all-wheel-drive car.
Is manual more powerful than automatic?
Yes, the manual transmission is stronger in some ways than the automatic transmission. Its strength comes in part from the fact that it loses less power due to parasitic power losses. This kind of loss can happen in the torque converter and clutches of an automatic system. This isn’t as good as a manual transmission, which sends all the power to your wheels.
Does a transmission increase horsepower?
No, the transmission does not make the horsepower go up. In fact, it may make the horsepower go down. It is more of a stabilizer than anything else because it sends power from the engine to the wheels. But making changes to the transmission unit can help speed up the car or make it go faster.
The Bottom Line
Power output, measured in horsepower, is an important factor to consider while purchasing an automobile. Go for a higher horsepower car if you want greater power. You now know that by the time the power from the engine reaches the wheels, it has been greatly reduced. A WHP to HP converter reveals how much power is lost due to the vehicle’s drivetrain.
