I like your method. The only snag is that mechanical gauges see the most inaccuracy at low pressure, as your standard air line gauge built to read up to 150psi or whatever. I think the suggestion of using a boost gauge is a good one, as they generally only read up to around 30psi so the chances of being accurate at a low pressure of 6psi on that gauge are 5 fold the 150psi gauge.
Its cheys03's method
would have been lost without it.
etches69 - I just pumped the tyre up to a random pressure, say 10psi. then like cheys03 says, used a t-piece with the main part going to the tyre, then the other 2 bits to the boost switch and boost gauge. I used ptfe tape on the boost switch and tightened it up as it was leaking being just hand tightened. Then cable tied everything else.
Then with it all connected, I let the pressure out of the tyre slowly, watching the gauge until it read 6psi. Then with the screw of the boost switch fully in, released it until it was on the border of reading the contacts as open/closed. Then did the minor adjustment so that they were closed at 6psi i.e. 0.00 on the multimeter.
Then tested it by pumping up the tyre again, and slowly releasing the pressure. As soon as it hit below 6psi, the switch opened again [i.e. 1 on the multimeter] as there wasn't enough pressure to close the contacts.
Correct me if I'm wrong??
Only problem I can see is, the boost gauge doesn't seem to sit exactly at '0' ?? nor does the new one in my car.
How accurate should the boost switch be calibrated? Would a chip not just be set to read a boost switch, and it just runs on a signal from the switch closing its contacts? I mean, is the chip set to fuel at 6psi or is the chip set to read a signal from the boost switch closing its contacts whether it be 6psi or 6.2psi for example?