MBC pressure setting idea, will it work?

[scr8pdo]

Say I pumped up a tyre to a set pressure ie 18 psi and got a length of hose attached to an old say foot pump connector and the other end to the mbc, wind the mbc right up, connect the hose to the tyre, then unwind the mbc until it starts to let air out, do you think this would be accurate, ie set at 18 psi, iam talking about the ball and spring type mbc not bleed valves

[p fandango]

yes it should do, but it does depend how accurate your gauge is

[MC_Bob]

Connect the foot pump to your mbc and pump slow and firm, you'll begin to see it let go at certain pressures.

[daveforber]

I may be talking rubbish here - sure someone will point it out if I am, but I *think* MBCs are base boost plus the setting, so if base boost is, say, 4psi and you set the MBC at 10psi, boost ends up as 14psi?

(just want to avoid you hitting 22psi and boomage in error , but not 100% sure)

[BruceT]

Dave, the MBC will keep the wastegate shut, till the required boost level is reached to move the spring and ball, which then will open the wastegate.

If the mbc is set too weak, the car will boost to 'base' boost as per the actuator pressure.

[nobananas]

The way I set mine up was similar but I used a length of hose with a tee piece in it, one end of the tee went to the MBC the other end to a boost gauge that I happened to have kicking around then started to pump the pressure in. I did have a proper pump with a one way valve but you could do the same with a footpump if you get an old schrader valve from a car tire , strip off all the rubber down to the brass tube then use that between your foot pump and tubing to make a one way valve then pump in air till the mbc 'blows off' and read off the pressure on the boost gauge and adjust as required.