Turbo boost: kPa versus inches

IndyCar, IndyCar commentary — By on July 5, 2012 8:33 am

[Editor's Note: On last week's podcast, Steph blathered on aimlessly trying to explain the current boost levels and eventually (in an attempt to save face) blurted out, "I'm used to talking about boost levels in inches!"

Our friend Shane Rogers -- the International Superstar himself -- heard this and decided to give a hand to the less technically inclined among us. We're glad to feature Shane's insights here at More Front Wing any time he's interested in offering them.]


For us old-school kids who measure boost in inches (inHg = inches of mercury):

125.28 kPa = 37 inHg (CART in 2002)
130 kPa = 38.39 inHg (Indy 500 Race 2012)
135 kPa = 39.87 inHg
135.44 kPa = 40 inHg (CART 1997/98/99)
140 kPa = 41.34 inHg (Indy 500 Quals 2012)
140.52 kPa = 41.5 inHg (what the Champ Car Cosworth ran in ’04 without Push to Pass)
148.98 kPa = 44 inHg (what the Champ Car Cosworth ran with Push to Pass in ’04)
150 kPa = 44.29 inHg (INDYCAR 2012 – Road courses from Toronto on without Push to Pass)
152.37 kPa = 45 inHg (Indy 500/CART, excluding stock blocks at the Indy 500)
155 kPa = 45.77 inHg (INDYCAR 2012 – Road courses before Toronto)
160 kPa = 47.25 inHg (INDYCAR 2012 – Road courses from Toronto on with Push to Pass)
186.23 kPa = 55 inHg (Indy 500 stock blocks in the early ’90s)

You may also have heard about “bar.” Bar and pascal (Pa) is one of those strange thing in the SI (metric) system where we have two things that describes one measurement. Bar isn’t exactly an SI unit — it’s an imperial (British) unit that happens to roughly equal 10^5 pascals, so it fits nicely in the metric system.

So, to get from bar to kPa, you go three decimals places forward to get Pa (x 1000), then five decimals places back to get bar.

130kPa * 10^3 = 130000 Pa / 10^5 = 1.3 bar

Now you understand why those Menards went Kesha/Kerblammo a lot!