Sorry if this has been discussed before, I searched this forum and other forums, as well as google but couldn't find the answer I'm looking for.

How does boost work ?

I know the basics of supercharging: increasing the pressure in the intake a few psi over atmospheric pressure, therefore increasing power of the engine, compared to a normally aspirated engine which uses only atmospheric pressure.

My question is why does my boost gauge reads -10 to 10 psi and why is in the negative most of the time ?

I would understand if it read 0 to 10, 0 meaning no boost (atmospheric pressure) and 10 meaning 10 psi over atmospheric pressure. But why is it negative ?

Thanks

 

Because when boost isn't being formed, then the engine is running as a vacuum, which is the negative numbers.

It's not technically negative boost, but the vacuum reading, until you start getting air pushed through.

 

To sum up a lot of info:

Engines run off of vacuum. The gauge reads -10 to +10. 0 would be atmospherically balanced. Anything over 0 is boost, anything under is engine vacuum. It reads "negative" cause it is not producing boost at that given time.

 

Ah I understand now.

Thanks guys !