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Propulsion Gel Crouch Boost Glitch

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Discoverer(s) S.
Games Portal 2
Engine Source 2011

The Propulsion Gel Crouch Boost Glitch, or PGCBG is a Glitch, discovered by S. It is used to gain speed on Propulsion Gel over a much shorter distance. This makes the glitch useful to perform flings and longjumps with a much shorter runway.



When walking on propulsion gel, the player's top speed is 800 ups. When crouching on propulsion gel, the player's top speed is 267 ups. This means that crouchspeed is 1/3th of walking speed. However, when changing crouchstance, the engine does not use these numbers. Rather it seems to use a relative number of the topspeed. So if you're crouching at 100% the topspeed (267 ups), after uncrouching, your speed will still be 100% of the topspeed. However, the topspeed has now changed to 800 ups. As a result, the speed quickly skips from 267 ups to 800 ups. Another example: If you're walking on gel with a speed of 600 ups, or 75% of the top speed, and then start crouching, your speed will quickly jump to 200 ups, in order to remain at 75% of the topspeed. This basically means that upon uncrouching, your speed gets tripled very quick, almost instantly.


Acceleration from 0 to top speed will always take 1.25 seconds, regardless of whether you're crouching or not. This means that the glitch does not directly save time, because it takes 1.25 seconds to hit 800 ups, whether the glitch is used or not. This acceleration is linear, except for the beginning.
PGCBG Acceleration Chart.png
During the first quarter of a second, walking relatively accelerates faster and then slows down, continueing to be linear. Crouching, on the other hand, has a lower acceleration at first. It then increases dramatically, followed by the linear increase. Take note of the plotted image as well.

This means that when one lets go of crouch too early, the glitch works against them and is not beneficial at all. This means that one has to crouch forward for at least a quarter of a second in order for the glitch to be of any benefit.


Upon pressing or letting go of the crouch button, the player's stance doesn't change immediately. It plays a short animation first where the screen moves up or down. Acceleration still happens during this animation, but the glitch won't activate until the animation is finished. As soon as the animation is done the speedchange will apply. So there's a slight delay between letting go of crouch, and the speed being tripled. This is important to know when you're trying a fling. If you let go of crouch too late and you'll already be in the air before the animation is finished and nothing will happen.


The glitch does not directly save time, because it takes 1.25 seconds to hit topspeed no matter what. However, because you're going slower when crouching, you can hit the topspeed over a much shorter distance. Therefore you can do large flings with a much shorter runway. Therefore, the glitch indirectly saves time in that less time is needed to create and set up for a running start.


The glitch is simple to pull off. Crouch while on orange gel, start moving forward. After about a quarter of a second, let go of crouch. If you're still on the gel by the time you completely stood up, the glitch will apply.


  • The glitch was discovered by S. on august 27th, 2011
  • A common misconception about the glitch is that it instantly boosts you to topspeed. As seen earlier, this is not true, it doesn't boost you to topspeed unless you crouch for more than 1 second.
  • It is possible to achieve a speed of up to 700 ups with just one blob of gel. This is usually enough, especially since most jumps are scripted in Portal 2 anyway.
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