Double acting pistons open slowly

We are using double acting pistons on our robot. We are not using a pressure regulator, for the air is just directly fed to the solenoids. Closing the piston (pulling the piston towards itself) is perfectly fine and fast, but when we try to open it (pushing the piston away from itself) it goes VERY slowly, releasing the air into the piston VERY slowly. We have tried changing the solenoids and listening some bolts to remove friction but the slowness is still apparent. How might we fix this?

Are you guys using the 90 degree fittings? Those fittings are also flow controls that limit the flow of air going out of the cylinders. You can try turning the screw on the flow regulator all the way out to see if it speeds things up.

That wouldn’t make much sense though would it? Because isn’t that the airflow that closes the piston?

yes, however if there is more pressure it effectively lowers the amount of air trying to close it. Think about it like an equaiton. closing power is equal to xpressure-ypressure=closing power. y presssure is one side of the piston, and x is the other

You may find the attached information to be a helpful supplement to the sketchy pneumatic instructions provided by VEX.
pneumatics information.pdf (313 KB)

which fittings are you using? i had the same problem using 90 degree solenoid fittings, but if you switch to straight gold fittings of your solenoids it might fix it. (sorry for the terrible explanation, click on the link, and use those)

We have found that the 90 degree fittings can be adjusted by turning the screw on the inside of the fitting, controlling how fast the piston retracts or pushes out.

Dont use the 90 dgree fittings for the pistons. They either leak or restrict airflow. The straight gold fitting do not leak and do not restrict airflow.