Engine braking lets you slow down without using your vehicle’s brakes.
And, more importantly, why should you use it?
In this article, we’ll answer those questions after we briefly explain what engine braking is. We’ll also talk about the three common types of engine braking and mention a few limitations of using it to slow down your car or truck.
This Article Contains:
- What Is Engine Braking?
- How To Perform Engine Braking
- 3 Types Of Engine Braking
- 4 Reasons Why You Should Use Engine Braking
- What Are The Limitations Of Engine Braking?
Let’s get started.
What Is Engine Braking?
Engine braking is a process where you decrease vehicle speed without engaging your brakes.
Here, instead of pressing down on the brake pedal to engage the brakes to slow your car or truck, you simply take your foot off the accelerator pedal (or gas pedal) to reduce your speed.
However, it’s crucial to remember that engine braking only works if your vehicle is in gear. In other words, you should lay off the clutch pedal for the engine brake process to work.
Pressing down on the clutch pedal disengages your clutch.
Yes, pressing down on it disengages it, not the other way round!
And when the clutch is disengaged, the engine braking effect isn’t passed on to the vehicle’s wheels. As a result, the wheel speed stays constant.
However, when you release the clutch pedal, your car goes into gear, allowing you to decelerate using engine braking.
Now, if you want to increase the engine braking effect further, simply downshift right after you release the accelerator pedal.
You’ll need to be very careful about downshifting, though.
If you’re going at a high vehicle speed, an abrupt downshift can damage your clutch plate and transmission system.
Now that you know what engine braking is, we’ll tell you how to use your engine brake:
How To Perform Engine Braking
Engine braking is more commonly used in manual transmission vehicles since the effects of engine braking are less pronounced in automatic transmission cars.
And while engine braking involves only a few simple steps, it could take you a while to master it and do it the right way.
Here’s how you can perform effective engine braking in a manual transmission car:
Step #1: Take your foot off the accelerator pedal (or gas pedal).
Step #2: Press down on the clutch pedal and downshift.
Step #3: As you take your foot off the clutch pedal, apply a slight pressure on the gas pedal for jolt-free engine braking (this is known as rev-matching).
Perform these three steps the right way, and you should be able to reduce vehicle speed using the engine brake process.
Next, let’s check out the different types of engine braking:
3 Types Of Engine Braking
There are generally three types of engine braking, depending on the mechanism used to decelerate your car or truck.
A. Manifold Vacuum Braking
In a gasoline engine, engine braking works by creating what is known as a manifold vacuum.
How does a vacuum brake work?
During engine braking, the throttle valve (or throttle body valve) in your vehicle’s engine shuts off, creating a vacuum inside the engine cylinder. The vacuum gets created because the throttle body valve controls the airflow into your engine.
The vacuum that the closed throttle valve creates will impede the movement of the engine piston, causing the piston to decelerate.
As the piston decelerates, your engine speed (revs) declines. As a result, the rear tire set (in a rear-wheel-drive car) or front tire set (in a front-wheel-drive car) begins to slow down.
B. Exhaust Braking
The exhaust brake process is more commonly found in diesel engine vehicles than in gasoline engine vehicles. This is because a diesel engine usually doesn’t have a throttle body like a gasoline engine, so it can’t create a vacuum.
As a result, a diesel engine vehicle will need to rely on mechanisms like exhaust braking to activate its engine brake.
How does an exhaust brake process work?
When you use this braking method, a butterfly valve inside the engine causes a restriction in the exhaust. This restriction leads to back pressure build-up, which in turn decreases your engine speed and vehicle speed.
C. Compression Braking
Compression braking (aka Jake Braking) is typically found in diesel engine trucks.
How does a compression brake work?
Compression braking works by opening the exhaust valve of the engine at the end of the compression stroke.
When the exhaust valve opens, the compressed air (and energy stored in it) gets released into the atmosphere. Since this compressed air no longer provides power to your engine, your engine speed will drop. As a result, your vehicle will slow down.
We’ve now learned about the different types of engine braking.
But why should you use engine braking in the first place?
Let’s find out.
4 Reasons Why You Should Use Engine Braking
Engine braking is beneficial to your vehicle because it helps:
A. Reduced Brake Wear
Your service brakes (main brakes) use frictional force to slow down your vehicle.
With repeated usage, your primary brake system components like the brake pad (in a drum brake system) or brake shoe (in a disc brake system) and brake drum or brake rotor will start to wear due to friction.
If the wear becomes excessive, your primary braking system may get compromised.
On the flip side, engine braking doesn’t depend on frictional force to reduce your vehicle speed. And using the engine brake can decrease your reliance on your service brakes (or friction brakes), allowing you to prolong the life of your main brake system components.
B. Prevents Brake Fade
Brake fade is the loss in stopping power of your friction brakes (main brakes) due to the excessive frictional heat generated from heavy or sustained braking.
For example, you may engage the friction brakes continuously for extended periods when driving down a long and steep hill. As a result, your brake pad (or brake shoe), the brake disc (or brake drum), and other brake system components will likely overheat.
Overheated drum and disc brake system components won’t generate enough frictional force, potentially leading to brake failure.
Fortunately, you won’t need to use the friction brakes as much if you use the engine brake while driving downhill. And since you’re not engaging the brakes all that much, the likelihood of brake fade decreases, reducing the chances of a decline in braking system performance.
C. Increased Fuel Economy
Engine braking can offer better fuel efficiency than traditional brakes if your car or truck uses a fuel injection gasoline engine.
During engine braking, the throttle valve to your engine cylinder gets cut off. As a result, combustion can’t occur, and most fuel injection vehicles shut off the fuel supply at this point.
On the flip side, when using your service brakes, the engine is still running as is, and the fuel consumption doesn’t stop.
While fuel savings due to the occasional engine braking may not seem like much, remember that these savings can add up over time. For example, during a long trip, your fuel economy or fuel efficiency can improve quite a bit when you rely on the engine brake process.
D. Improved Vehicle Control
Engine braking also helps you gain better vehicle control.
While the braking force generated by your primary braking system can be inconsistent, the engine braking effect is a lot smoother, giving you better control over your car or truck. This improved vehicle control during braking is helpful when you’re driving in icy/wet conditions.
If the road’s slippery and you engage the brake pedal (or foot brake), there’s a high chance that your wheels lock up and the car or truck starts to skid. And when it skids, you may lose control of the car or truck, compromising your road safety.
Fortunately, engine braking will allow you to slow down without using your brakes. As a result, you’ll have better vehicle control when slowing down on wet or icy roads.
However, does engine braking result in any negative consequences?
What Are The Limitations Of Engine Braking?
Unlike clutch braking, engine braking is usually encouraged for most vehicles. But engaging the engine brake does have a few disadvantages, like:
A. High Engine RPM
When you downshift for better engine braking, your engine’s RPM (revolutions per minute) could shoot up. And driving your vehicle at a high RPM for long durations can cause the engine to overheat, placing heavy demands on your cooling system and radiator.
However, as long as your RPM stays well under the redline, your engine shouldn’t experience any problems.
B. There’s A High Strain On The Transmission System
Downshifting abruptly during engine braking can place a large amount of stress on the gears of your manual transmission system and the clutch plate.
If this stress is excessive, your transmission system and clutch plate might get damaged. And the cost of fixing your transmission system can exceed any savings from prolonging the life of your brake components.
To counter this, you’ll need to do a proper rev-match while downshifting.
C. The Brake Light Doesn’t Turn On
Another problem with using the engine brake is that it doesn’t illuminate your brake light.
And so, when you’re using the engine brake at night, we recommend that you occasionally press down on the brake pedal (foot brake). This way, your brake light would turn on and alert the driver behind you that you’re slowing down.
D. Loud Noise
Loud noise is usually applicable if you’re driving a diesel engine truck that uses a Jake brake.
Remember, in a Jake brake, compressed air from the diesel engine truck is exhausted towards the end of the compression stroke. This often results in an extreme amount of noise being generated.
To combat this, some interstates and toll roads in the United States may place restrictions on engine braking if you’re driving a truck with a Jake brake installed. For example, there’s a ban on engine braking by trucks in Colorado Springs and Vail.
While engine braking helps you slow down your car without the help of your main brakes, you must know how to do it right. Perform engine braking the wrong way, and you could damage your transmission system and clutch plate.
However, engine braking does offer some excellent benefits like reduced brake wear and fade, fuel economy or fuel-efficiency, better handling, and more.
Now, even though engine braking can help you prolong the life of your drum and disc brake components, they’ll still need replacement at some point.
And when that time comes, just get in touch with RepairSmith — a convenient and hassle-free mobile auto repair solution.
When you book your repairs with RepairSmith, our ASE-certified mechanics will come to your driveway to take care of all your vehicle repair, maintenance, and service requirements.