Nissan GT-R Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
100 Posts
Discussion Starter · #1 ·
Alright, i've had my 2010 car for about 4 months now, and i LOVE everything about it.

This could be a very dumb question to you, but i have to ask out of curiosity: on the MFD, why does the Boost gauge start at -15 , and not 0 ??
 

·
Premium Member
Joined
·
1,485 Posts
Vacuum before boost...
 

·
Registered
Joined
·
48 Posts
It is an absolute gauge. Pressure absolute takes into account the atmospheric pressure where as "gauge pressure is pressure above absolute. Atmospheric pressure (1 bar) is 14.7 PSI. So on an absolute gauge one PSI of "boost" is 16PSI absolute. Whereas a "gauge pressure" gauge would read 1 PSI.
 

·
O_o
Joined
·
1,656 Posts
actually its the suction from the engine running that causes the negative pressure. With the throttle plates closed and the car running the engine is pulling in more air than what is in the plenum meaning the air pressure inside the chamber is actually negative.

If it was reading absolute atmospheric pressure it would read negative with the ignition switch "on" and the car not running
 

·
O_o
Joined
·
1,656 Posts
the negative on the gauge can help determine if you have a vaccum leak as well
 

·
Happy in Hermosa
Joined
·
1,534 Posts
Gawd, I wish I understood this stuff.
 

·
Happy in Hermosa
Joined
·
1,534 Posts
simple. at low enough RPM, intake airflow > charge air movement, hence vacuum. eventually, charge air > intake air thereby, boost (positive pressure).
Hahaha! I spent my entire career manipulating the English language. You beat me in one sentence.
 

·
Happy in Hermosa
Joined
·
1,534 Posts
1 - 13 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top