There are two MAP sensors. One in the intake and one pre intercooler. Where is the pre intercooler sensor actually located? If it is between turbo and intercooler then this should be an easy proof.

I might be able to check sensor readings with my diagnostic scanner or maybe the X4 tuner with LiveLink. We already know for certain the manifold is in vacuum but there is a nearly closed throttle blade that is causing that vacuum.

By the way, water can still drip with vacuum so don't assume there is no vacuum just because you see it drip.

 

Remember that water in the CAC is there for an extremely short duration. It accumulates over time when driving under steady throttle state, and is blown out the instant you apply moderate to heavy throttle. It's not something that accumulates over weeks or months.

 

When is it in vacuum?

 

The intake manifold is in vacuum when the turbos aren't making boost.

 

A whole lot of the time.

Seeing is believing so here is a data log of me driving around town. The graph is manifold pressure and anything under about 100 kPA is vacuum. You can see the engine is in vacuum the majority of time I am driving.

Remember, the engine is an air pump and the throttle body is basically a restrictor plate. The pistons can pull vacuum when the throttle blade is low enough.

 

Is the cac under vacuum?

That is what really matters to this discussion.

 

I don't know. I need somebody to tell me where the pre-cooler MAP is located.

 

Yup. Only one way air can move through the CAC, and that's across a pressure gradient. If the turbos are supplying positive pressure the CAC would be at higher pressure than the surrounding atmosphere. If it's being sucked by manifold vacuum it would be at a lower pressure. The real question is whether or not the turbos are supplying positive pressure 100% of the time the engine is running, and my guess is they aren't. Just a guess though, I'm not an engineer.

 

Was out playing with torque scan.
At idle we had~6lbs of pressure.
It would dip a little if you hit the gas hard.
Lowest I could get was 2.9 by doing a high rev and taking my foot off.
All this was sitting in the driveway in park.

The PID I was reading is labeled "intake".

 

6 psi is less than atmospheric pressure so there you go, you answered your own question.

 

You really want to go with that?
Your losing credibility here.

 

It is manifold ABSOLUTE PRESSURE.

 

When I turned the truck off, it dropped to 0 psi, it did not rise to 14.7 ( I am at sea level).
Enjoy your thread... I am out.

 

The manifold is located after the throttle body in the air intake system. There's nothing between the manifold and the cylinders to meter air, it's certainly not under pressure all the time.

The pistons move the same amount per stroke, meaning the volume of the intake air charge is always the same in a given stroke. Pressure is what changes the amount (mass) of air that enters the cylinder, and that's regulated by the throttle body. Atmospheric pressure in a N/A engine only enters the cylinders at WOT, and there's absolutely no way you could hold an idle with that much air going into the engine.

There certainly is a vacuum in the manifold at idle and low throttle levels, there's no debating that. The question is whether or not there is positive or negative pressure before the throttle plate, not after.

 

That's not a 0 psi measurement. That's a zero out of the gauge because you lost the data feed when you keyed off.

Nobody has been difficult with you. Leave if you want but don't blame us!