Every now and then, you find something new and interesting about cars, bikes, or automobiles in general. While sifting through random automotive forums, I came across a new term. The discussion was regarding “exhaust brake”. I read about it a little and found it interesting enough to write about it here so others who are new to automobiles can learn something new as well.
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As the word ‘brake’ in ‘exhaust brake’ might hint, it is about slowing down the vehicle. Simply put, the exhaust gases are used to slow down the vehicle. It is one form of engine braking. In engine braking, you let the lower gear combined with closed throttle to decrease the speed of the vehicle. However, exhaust brake goes a different route to solve the same issue. The system closes the path of the exhaust of a vehicle to slow it down.
First of all, you must know that the exhaust braking system is used in vehicles running on diesel fuel. Almost all heavy duty diesel pickup trucks Like Dodge RAM 3500, Ford F-350 Super Duty, and GMC Sierra HD now come equipped with exhaust braking. You will find exhaust braking system in Toyota’s Coaster van as well. Exhaust braking is also known as Jake Brake in many international markets but companies like Dodge have their own clever way of engaging the exhaust brake which I will mention below.
So how does the exhaust braking system works? It closes the exhaust of the vehicle with a valve. And this causes all the exhaust gasses to accumulate in the manifold as well as the engine cylinders. The accumulated gasses then start to compress inside and reduce the fresh inflow of the fuel because there is no more space in the cylinder for a fresh charge. The back pressure caused by restricting the exhaust outflow of the engine significantly decreases the speed of the vehicle. Keep in mind the butterfly valve in the path of exhaust won’t shut down the path complete. Some amount of exhaust gasses keeps on flowing even when the system is fully engaged. The exhaust braking system engages as soon as the driver takes his foot off the accelerator. And as soon you get back on the race pedal, the system disengages.
As mentioned above, this system is now available in pickup trucks as well. The reason is that over time, the towing capability of pickup trucks has gone up significantly. And trying to stop the tons of weight with the regular brakes of the pickup alone can be quite dangerous. The brakes are going to overheat; you are going to have a lot less control and a lot less confidence going down the road.
But the exhaust brake is a complete opposite of that. The exhaust brake is basically helping you in saving your normal brakes. It can give you 30% more life to your normal vehicle brakes and gives you a lot more control and a lot more peace of mind going down the road and especially when you are descending down a hill with an extra load. It raises the safety standard a whole lot higher.
I previously mentioned that it is also called Jake Brake. The Jake Brake, developed by Jacobs Vehicle Systems, itself has improved a lot with the passage of time. It isn’t as simple as restricting the exhaust flow. Now there is valve timing involved as well in order to find the same result. In newer Jake brake systems, the exhaust valve timings are manipulated to control the compression of the engine. The system disrupts the usual 4-stroke power cycle of the engine and opens the exhaust valve right at the end of the compression stroke. There is no full compression and expansion stroke like you get in the normal 4-stroke cycle. The energy is released into the exhaust system. It helps in controlling the downhill speeds of a truck.
Jake Brake System Off
Jake Brake System Off
Also, above I mentioned that Dodge has employed a different type of exhaust braking compared to regular Jake brake. The thing about Jake brake is that will clog up the exhaust. As pressure builds, the untreated exhaust would bleed off in the atmosphere, and it is not that great for the environment. However, the automobile companies have developed new and much more environmentally friendly options of doing the same thing. For example, Dodge can now use their variable geometry turbochargers to control the exhaust gasses and accomplish the same thing where they are restricting the exhaust and making the engine to brake while making it more polar bear -environmentally- friendly.
There are various methods of achieving the same thing, i.e., the exhaust braking. In older models of trucks with simple exhaust braking, if you had engaged the exhaust brake, the engine would simply stall and shut down. But now the automotive technology has improved immensely. The Newer iterations of exhaust brakes use variable geometry turbochargers as well as exhaust gas modulation to continuously vary the braking depending upon the towing load and downhill road. That was just a synopsis of this otherwise quite fascinating topic. I hope you learned something new today. Happy motoring!
