Will your engine actually pull 100 percent of the value of the barometric pressure under WOT? Say I flip my key on w/o starting the engine and my map KPa is 99.16. How close can an engine get to zero pressure inside the intake? Does this represent an intake restriction?

 

Intake tract, cam, exhaust all play huge roles.
Takes alot of work to get to near 0.
I've had a car that was steadily 96s, with a mild cam.
You can trick and engine with plenum volume, and runners, but it's just as good to not worry about the MAP as much as ET.

 

Wise words. Thank you.

 

i ve seen as high as 100 kpa and 4.7 volts in a boat. naturally aspirated of course.

 

What was the atmospheric pressure that day? couldn't have been 100kpa?

 

i dont rememeber. the boat had a Tunnel ram intake. this period of map reading is very breif for about 1500 rpm of the power band. it start at 3500 and continues to 5000 rpm. tunnels rams have the ability to create inertial supercharging.

 

I find the kpa rating while in WOT is about 2 kpa less than the kpa reading if I have my scan tool running and JUST turn off my engine.

EG. On the WestCoast, at sea level. The MAP sensor reads 102 kpa when I turn off the engine (and leave the scan tool running). While in WOT I never get over 100.

At Kamloops, where I currently live, I usually read 97-98 kpa on the "flats" (depending on weather) with the engine turned off. But in WOT I get 95-96 kpa.

So I get a consistent 2 kpa difference between WOT and a "turned off engine".

 

So the west coast has more pressure. My car would run faster there?

 

It has more pressure because it's at sea level. The higher you go (elevation) the less the maximum MAP reading.