# where do you read psi?



## CERBERUS XE (Feb 2, 2004)

Does anyone know where you would read how many psi goes into your car. I was thinking about putting in a supercharger into a car, and I was think that if I wanted to read how many psi it was putting out where do you read it from. The psi would change with the size pipe that you would use. If I was to run compressed air into a 4" pipe it would read lower psi from the middle of the pipe as compaired to the same amount of air thrown through a 3" pipe. Thanks for any info you can spare.


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## James (Apr 29, 2002)

you read psi on the boost gauge.


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## chimmike (Oct 17, 2002)

lol!


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## lshadoff (Nov 26, 2002)

CERBERUS XE said:


> Does anyone know where you would read how many psi goes into your car. I was thinking about putting in a supercharger into a car, and I was think that if I wanted to read how many psi it was putting out where do you read it from. The psi would change with the size pipe that you would use. If I was to run compressed air into a 4" pipe it would read lower psi from the middle of the pipe as compaired to the same amount of air thrown through a 3" pipe. Thanks for any info you can spare.


The size of the pipe matters if there is gas continuously flowing through the pipe. The pipe to a gauge is a dead end pipe which only has flow in it when the pressure changes. The size would determine how fast the gauge responds to a change in pressure. Ordinarily boost gauges use small diameter pipes (1/8" OD) to minimize the amount of air which has to be compressed before the gauge reads the pressure correctly.

Usually the boost is read from a port in the intake manifold (I use the port to the charcoal canister).

Lew


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## Jasper (Apr 2, 2004)

chimmike said:


> lol!



my thoughts exactly, after i read it a 3rd time and made sense of the grammar.


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