Heres a Quick reference that i learned to aid in helping others in the future

Okay So a Bar is simply a Pressure measurement

A 1 bar Map sensor is what you would run on a N/A car But to stay within 1 Bar "Zone" and run right it has to stay below Stoich which it 14.7:1 which is 100% efficiency so on a N/A car you would not need anything more than a 1 bar Map sensor

Now this is were Boost comes in to play. when you boost a car it Becomes more efficient By Using exhaust gases to to force air in to the cylinder which intern increasing cylinder filling.
so that would be were you want to upgrade a From a 1 Bar map sensor

So you take The Amount Of boost you are going to run a and add it to Stoich
(EXAMPLE) 14.7 + 10 psi of boost = 24.7 PSIA (Pound per Square Inch Absolute)
Here a chart


1 Bar 14.7 PSIA
2 Bar 29.4 PSIA
3 Bar 44.1 PSIA
4 Bar 58.8 PSIA
5 Bar 73.5 PSIA

When yo add your amount of boost to Stoich lets say it when you added it all up it was 27 you would go with a 2 bar map sensor. Go with the next highest number from your total.
hope this all helps


And yes i understand you can grab a 5 bar map and be fine no matter how much boost you run just wanted to let everyone know how to decide which bar map sensor to use.


-Sakasaku

 

hahaha the reason its "stoich" has nothing to do with any of that bullshit its purely coincidence.
normal ambient air pressure is is right around 14.7 psi which also happens to be the ratio of fuel to air we want according to stoichiometry

 

as well as different elevations have different starting points in air density. the higher the elevation the less vacuum the engine will create as well as boost from lack of oxygn in the air.

That being said choosing a map sensor is a simple as how much boost you want to run. 14.7 plus the amount of boost with a little extra. stock map sensors are 1.7 bar or are good for about 10 psi boost.

 

Edited...thanks for the correction, 808. Sorry, Justin

 

1.7 bar absolute. or 10 psig.

 

agreed, OP has stoichiometry confused here. Stoich would be a 14.7:1 AFR.

also. 1 bar = 14.5 psi not 14.7 but hey who's counting

 

yeah i always forget that the actual pressure here is always just a hair above 1 bar. I said around 14.7 to simplify my explanation

 

Hehe the stoich comment made me LOL. Good tech thread tho.
My contribution would be to choose the smallest "bar" MAP sensor that meets your needs with a little bit of room for growth. It will give you more resolution in the pressure ranges that you will be operating at. Another words dont get a 5bar if you plan to boost 10psi...