## Does Revving the Engine Help Jump Start a Car?
Introduction
Jump-starting a car is a common roadside emergency procedure that involves using another car’s battery to provide temporary power to a dead battery. While revving the engine of the assisting car is a popular practice, its effectiveness is often questioned. This article aims to delve into the science behind revving the engine during a jump start and explore its potential impact on the process.
The Jump Start Process
To jump-start a car, the following steps are typically followed:
1. **Connect the jumper cables:** Connect the red positive cable to the dead battery’s positive terminal and the black negative cable to the assisting car’s negative terminal.
2. **Start the assisting car:** Start the assisting car and allow it to idle for a few minutes.
3. **Attempt to start the dead car:** Turn the ignition in the dead car and attempt to start it.
The Role of Revving the Engine
Revving the engine of the assisting car during a jump start is a practice that has been used for decades. Its supposed benefits include:
* **Increased voltage output:** Revving the engine increases the engine’s revolutions per minute (RPM), which in turn drives the alternator to produce more electricity. This can provide a higher voltage boost to the dead battery.
* **Reduced strain on the assisting car’s battery:** By revving the engine, the alternator can supply more power to the dead battery, reducing the drain on its own battery.
* **Faster starting:** The increased voltage output can help the dead battery recover its charge more quickly, potentially shortening the time it takes to start the car.
Scientific Evidence
While revving the engine during a jump start has been common practice, there is limited scientific evidence to support its effectiveness. Some studies have shown that revving the engine can indeed increase the voltage output of the alternator, but others have found negligible differences.
A study published in the Journal of Power Sources examined the effect of engine speed on alternator output. The results showed that increasing the engine speed from idle to 2,000 RPM resulted in a significant increase in alternator output. However, at higher engine speeds, the increase in output was minimal.
Another study published in the IEEE Transactions on Vehicular Technology compared the effectiveness of jump-starting with and without revving the engine. The results showed no significant difference in the starting time or the voltage supplied to the dead battery.
Potential Risks
Although revving the engine may have some potential benefits during a jump start, it also carries certain risks:
* **Overheating:** Revving the engine for extended periods can cause it to overheat, especially in hot weather.
* **Engine damage:** If the engine is not properly maintained, revving it at high RPMs can put unnecessary stress on its components, potentially leading to damage.
* **Alternator failure:** In some cases, excessive revving can overload the alternator, causing it to fail.
Best Practices
Based on the available evidence and potential risks, it is generally not recommended to rev the engine of the assisting car during a jump start. Here are some best practices to follow:
* **Ensure the jumper cables are properly connected:** Loose or poorly connected cables can impede the flow of electricity.
* **Allow ample time for the dead battery to charge:** Do not attempt to start the car immediately after connecting the jumper cables. Allow the dead battery to charge for a few minutes to improve its chances of starting.
* **Use jumper cables with sufficient gauge:** Thicker jumper cables with a lower gauge will allow for better current flow.
* **Disconnect the jumper cables in the reverse order:** Disconnect the negative cable first and then the positive cable. This helps prevent any potential electrical spikes.
Conclusion
While revving the engine during a jump start has been a common practice, there is limited scientific evidence to support its effectiveness. It may provide some benefits in certain situations, but it also carries potential risks such as overheating, engine damage, and alternator failure. It is generally recommended to avoid revving the engine and instead focus on proper cable connections and allowing the dead battery to charge for ample time before attempting to start the car.
