What is a jake brake? What is engine braking?

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Mohammad Saad Jebrini (Rotary Fanatic and V8 Enthusiast)

Isn’t engine braking is when you downshift without rev matching? this way you force the engine to slow the car down to match its low revs? or am i missing out on something?

05/11/2016 - 16:50 |
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Engine braking is using that vacuum that naturally reduces the RPMs, to decelerate. The downshift process helps mantain the engine in the revs necessary to stay on.
Think of it this way: When you’re off the throttle, your car loses speed by rolling and the RPMs go down. Right? So, what do you do to compensate and keep the car on without being on the clutch? You downshift. When you do, the RPMs peak and, if you’re off the throttle, they’ll keep going down until you either lose momentum or go back on the throttle.
It’s the same process, being explained but without the gears in context

05/11/2016 - 17:24 |
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You’re exactly right, this video is just explaining in more detail how that happens.

05/11/2016 - 19:20 |
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No that’s the friction of your clutch, engine brake can be use even if you Rev match

05/11/2016 - 20:07 |
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It’s just coasting. Let your foot off the accelerator and you’re engine braking.

05/11/2016 - 20:24 |
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No that just fcks up your clutch

05/11/2016 - 21:08 |
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Roi Nieto

As always, very interesting stuff, thanks Jason! Keep it coming

05/11/2016 - 19:00 |
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Engineering Explained

In reply to by Roi Nieto

Happy to hear it Roi!

05/11/2016 - 23:20 |
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Jake Menesse

Where does overrun come into all of this? Injecting fuel with no ignition to cool the cylinders but with no air sounds like the fuel would sit in the cylinders surely? How is the fuel contacting the manifold when there is no airflow?

05/11/2016 - 20:10 |
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In overrun the engine is being powered by the wheels essentially. This is caused shifting into a lower gear, causing the engine to exceed RPM’s. When you close the throttle plate it creates a vacuum. Thus sucking the atomized fuel into the combustion chamber. Also the pcm will recognize that there is not a load inside of the engine. Which in turn will tell the fuel injectors to spray less fuel. I hope this answers your question. :)

05/11/2016 - 21:14 |
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Phil Rad

Jake brake: AKA the loud ass engine noise trucks make to slow down, especially at 3am in the morning when you are fast asleep and then jolt out of bed.

05/11/2016 - 20:13 |
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Turbo_Man

is engine braking bad for your engine? isn’t it healthier to use your brakes instead, for example going down a hill?

05/11/2016 - 20:21 |
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You are sooo wrong m9

05/11/2016 - 20:25 |
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No it isn’t. It’s the opposite. When you’re going down a hill, you should shift down a gear or two, to use the engines brake power. If you’ll use your brakes to long, they’ll overheat and lose their braking power.

05/11/2016 - 20:26 |
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It isn’t bad if you don’t let your RPM fall too low. However, it increase the clutch wear if you don’t rev match. All in all, changing brake pads is easier and cheaper than changing clutch. So engine braking is needed only in a long downhill

05/11/2016 - 20:54 |
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Matt Bailey

This guy always makes my brain hurt. Keep it up!

05/11/2016 - 20:57 |
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Anonymous

Do not mistake it with Engine Breaking from Volkswagen!

05/11/2016 - 20:57 |
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Engineering Explained

In reply to by Anonymous (not verified)

Very different beast, but often just as loud!

05/11/2016 - 23:19 |
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Anonymous

In reply to by Anonymous (not verified)

What’s the case with VW? Tell more, dude!

05/12/2016 - 10:04 |
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Irimescu Vasile

In reply to by Anonymous (not verified)

its funny because old 1.9 tdi engines are the most reliable engines ever.imature people still making jokes they’ve seen on google

05/12/2016 - 12:11 |
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Anonymous

I’m not sure if I’m being mislead here or people don’t understand the concept, but engine braking is literally coasting in a lower gear. The only way you’ll wear out the clutch is if you’re riding it or being a nugget with downshifting.

05/11/2016 - 22:18 |
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Anonymous

Engineering Explained how does engine braking affect the life of a dual mass flywheel? I’ve always engine braked and do it without thinking. My current car is the first I’ve owned with a DMF and I’ve read that it is bad to cruise slowly in too high a gear, which is another habit of mine for economy (i.e. from 25mph in 5th etc), is engine braking also harmful to the DMF?

05/11/2016 - 23:01 |
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Engineering Explained

In reply to by Anonymous (not verified)

I’m not sure, I wouldn’t think there would be negative effects. Cruising in fifth at 25 mph puts your engine at a massive gearing disadvantage though, not much torque available that low so it may struggle.

05/11/2016 - 23:21 |
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Anonymous

for GODS SAKE! TELL US WHEN ITS THIS DOUCHENOZZLE! I REFUSE TO WATCH HIM!

05/12/2016 - 00:30 |
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Anonymous

In reply to by Anonymous (not verified)

Well considering he’s the only guy that post videos on engineering explained I feel like that’s your fault

05/12/2016 - 01:30 |
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