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> This is commonly called power braking, usually called up in an emergency. I've never heard it called power braking, always engine braking or j-braking. It i
by shkkmo 5y ago
> This is commonly called power braking, usually called up in an emergency.
I've never heard it called power braking, always engine braking or j-braking.
It isn't just useful in emergencies but also in steep descents with heavy loads to make sure your brakes stay cool enough to be useful. It may be obvious, but the other technique that really helps keep your brakes cool is descending more slowly.
- adonovan 5y agoAlso known as "jake braking". It's useful if you're a dump-truck driver who thinks midtown Manhattan is too quiet.
- cartoonworld 5y agoJake Brake is engine braking, its really similar but not the same. Theres a difference between the kind of power braking/engine braking that a car does and a commercial truck. I typed a lot about this elsewhere, but essentially trucks have crappy brakes because of reasons (thermal ones, in large part) and as a result, in order to gather enough brake performance to not be extremely hazardous, they often must apply their engine brakes/jake brake/engine compression release brake in order to safely navigate with their loads in normal traffic or an emergency braking scenario (such as being cut off in midtown by some a-hole). https://en.wikipedia.org/wiki/Compression_release_engine_brake https://en.wikipedia.org/wiki/Compression_release_engine_bra...
- deleted 5y ago[deleted]
- MisterTea 5y agoA real "Jake brake" (Invented by Clessie Cummins) slows a truck down by turning the engine into an air compressor. It does this by modifying the exhaust valve timing to open at top dead center while cutting fuel. Once turned on all you do to engage it is to take your foot off the accelerator. That staccato popping sound is the compressed air blasting out of the exhaust valves. On old rigs like my '61 Mack the jake brake is switched manually. You have to be sure to turn it off once you get close to engine idle rpms otherwise the engine will stall. A quieter version called a bleeder brake which does the same thing though it leaves the exhaust valve slightly open during the entire compression stroke eliminating the popping sound. There is also the exhaust brake which puts a butterfly valve on the exhaust line creating back pressure when closed. Though the exhaust brake is known to cause problems with some valve train setups.
- rootusrootus 5y agoTalking a little bit out of my ass here making some assumptions, but I'd guess that in this context, 'power braking' refers to grabbing an low gear and letting out the clutch to assist the front brakes when you're trying to stop really fast and maintain the handling dynamics of the car. It's hard to explain, but if you've driven a manual sports car for a while it's easy to learn. And it isn't the same as simple engine braking, which is usually done in higher gears to add moderate resistance, not to actually try to slow the car significantly. And you do have to be careful not to grab too low a gear and/or don't let the clutch out too fast, or you can mechanically overrev the engine. IMO compression braking (jake brake) would be a better analog.
- hunter2_ 5y ago> And you do have to be careful not to grab too low a gear and/or don't let the clutch out too fast, or you can mechanically overrev the engine. A.k.a. the "money shift" as it results in spending lots of money, typically from grabbing 2nd instead of 4th (each being relatively down and to the left).