Is the manifold air presure coming off the turbo? I know boost is. Is the MAP a good indication of proper turbo operation? I run about 12psi MAP ideling and about 20 to 22 on cruse. 0 psi boost on idel and about 8 or 9 psi on cruse. All stock settings. Thanks

 

The MAP sensor is plugged in on top of the intake manifold plate roughly in the middle of the plate to the rear of the intake horn. The MAP and the boost gauge should be very close to one another as they are reading the same thing. Your boost gauge being a closer to correct reading. 22psi on cruise from the MAP? that is only a few psi away from max for your turbo and you'd have to have it floored for that.

More info is needed, but at first glance I'd say the MAP sensor is whacked. How are you measuring this to get those readings? Are you sure that is what the MAP says and your are interpreting correctly?

 

Yes, my MAP is usually 20 to 22 when on cruse, while by boost shows 7 to 8 on cruse. I'm reading these through my Edge CTS.

 

Ok, I don't know about the CTS and how it works... I would have to guess the issue is there.

IMO, what you are seeing is just readings and not what actually is going on. I know you aren't cruising at 22 psi. 7 to 8psi is a little high (normal is closer to 4-6) unless you are over 2k rpm cruising. Your MAP and boost should show about ~1psi idleing.

Where are you tapping to read the boost?
Is the CTS plugged into the MAP sensor or is it reading the ECM? That make a difference.

 

Since I see the a/c in soulezoo 1st sgt. map pressure is barametic pressure at sea level it lowers with elevation , if you are familuer with piston a/c static map is 29.92" at sea level. the engine will draw vacumn until you get enough boost to start pressurizing te engine. On the p/w r2800 eng. we pulled 48" 0n the DC 6 p/w 2800 we pulled 52" with ADI (water alcohol) you will not read same boost / map readings.

 

Common confusion with boost sensors and gauges[edit]

MAP sensors measure absolute pressure. Boost sensors or gauges measure the amount of pressure above a set absolute pressure. That set absolute pressure is usually 100 kPa. This is commonly referred to as gauge pressure. Boost pressure is relative to absolute pressure - as one increases or decreases, so does the other. It is a one-to-one relationship with an offset of -100 kPa for boost pressure. Thus a MAP sensor will always read 100 kPa more than a boost sensor measuring the same conditions. A MAP sensor will never display a negative reading because it is measuring absolute pressure, where zero is the total absence of pressure (it is possible to have conditions where negative absolute pressure can be observed, but none of those conditions occur in the air intake of an internal combustion engine[citation needed]). Boost sensors can display negative readings, indicating vacuum or suction (a condition of lower pressure than the surrounding atmosphere). In forced induction engines (supercharged or turbocharged), a negative boost reading indicates that the engine is drawing air faster than it is being supplied, creating suction. This is often called vacuum pressure when referring to internal combustion engines.

In short: most boost sensors will read 100 kPa less than a MAP sensor reads. One can convert boost to MAP by adding 100 kPa. One can convert from MAP to boost by subtracting 100 kPa.

 

MAP sensor checks absolute pressure with has to do with your altitude and weather conditions (barometer) so the engine knows air density and can adjust fuel to keep it in perfect tune.

I know on some of the older vehicles the ECU took a reading at start up and that was it. So if you were traveling and ended up in the mountains without shutting the vehicle off you could be out of tune as you climbed altitude.


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