Just fitted an electronic boost gauge to the cosworth, rather than a tube running all the way to the gauge it has a boost sensor that mounts under the bonnet. I spliced into a vacuum tube running from the inlet manifold as describded in the instructions. A tee piece is installed and a small lenght of tube runs to the sensor. The sensor is then connected to the gauge by wires.
When at idle the gauge reads about -21 psi (vacuum) when revved it climbs towards the 0 mark on the gauge but will not surpass this point, no matter how hard I rev the engine it will not register any +psi (boost).
I thought the gauge its self might be fautly so I connected a vacuum gauge in place of the boost sensor and found the same readings, when I connected a small compressor to the boost sensor it measured up to the full 30psi
Anyone any thoughts? Am I missing somthing here? :-?

 

Boost pressure will not register until you are driving it. The correct way to test it is to drive in 4th gear at 3500 rpm and then apply the brake (momentarily) while keeping your foot on the gas

 

I thought the same when I installed my boost gauge the other month.... but gave her a pasting and she's running a mere 9 psi !

 

try driving the car not just sitting in it reving as i am sure you wont get boost till its under load.cheers mark

 

as has been said above, the car wont make positive boost unless under load..... so that means driving it

 

Thanks for the info guys, just had me worried there for a while, incidently how would you test boost pressure without driving the car?