Engine map with load curve in 5th gear:fuel consumption varies weirdly

In summary, the load curve in 5th gear shows that at 5500 rpm, there is a lower fuel consumption of 270g/kWh compared to 4000 rpm at 280g/kWh. This may seem counterintuitive, but it is due to the engine operating more efficiently at high load and low speed. This is commonly seen in engines, as they tend to work most efficiently at high load and low speed, resulting in a lower specific fuel consumption.
  • #1
marellasunny
255
3
http://imageshack.com/a/img824/2641/1cpe.png

The black curve I drew there represents the load curve in 5th gear. Why is it that at 5500 rpm(160kph), I have a lesser fuel consumption(270g/kWh) than at 4000 rpm(280g/kWh)?

Intuitively,if I produce more power at 180kph(ie 5500rpm),I should consume more fuel,right? But,this is not the case here.Why?
 
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  • #2
It is consuming more fuel at 5000rpm, it's a specific fuel consumption map.

4000 rpm = approx. 20kW
5000 rpm = approx 50kW

We can set a steady run for 1 hour (to remove the h term from kWh)

So in an hour:
At 4000rpm we burn
20 kW * 280 g/kWh = 5600 g fuel

At 5000rpm we burn
50*270 = 13500 g fuel


Per unit of power, it's using less fuel because that engine combusting more efficiently. The specific reasons are not described by the map. Typically engines work most efficiently at high load low speed, it's why cruising gears are chosen to keep the engine operating in the 2000-3000rpm band at higher throttle openings (ie low specific fuel consumption)
 

1. What is an engine map with load curve in 5th gear?

An engine map with load curve in 5th gear is a graphical representation of how an engine performs at different levels of load and in 5th gear. It shows the relationship between engine speed, load, and fuel consumption.

2. Why does fuel consumption vary weirdly in 5th gear?

Fuel consumption can vary weirdly in 5th gear due to a number of factors such as engine efficiency, driving habits, road conditions, and vehicle weight. It is important to properly maintain the vehicle and drive efficiently to minimize fuel consumption.

3. How does load affect fuel consumption in 5th gear?

The load on the engine in 5th gear plays a significant role in fuel consumption. Higher loads require more fuel to maintain speed, while lower loads require less fuel. This is why fuel consumption may vary at different levels of load in 5th gear.

4. What is the significance of an engine map with load curve in 5th gear?

An engine map with load curve in 5th gear is important for understanding the performance of an engine and how it consumes fuel. It can help drivers make adjustments to their driving habits to improve fuel efficiency and reduce emissions.

5. How can I use an engine map with load curve in 5th gear to improve fuel consumption?

By studying the engine map with load curve in 5th gear, you can identify the most fuel-efficient range for your vehicle and adjust your driving habits accordingly. This may include maintaining a steady speed, avoiding rapid acceleration and deceleration, and properly maintaining your vehicle to ensure it is running at its peak efficiency.

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