It seems to me that if the CAC were under a vacuum at idle, the water in the CAC wouldn't have been dripping before he revved the engine. I'm of the opinion that the CAC is always at atmospheric pressure or under boost as evidenced by the video that I posted.

Anyway, I don't want anyone to get their feelings hurt over this. It's a great discussion with tons of cool input.

I'm not touching my truck unless I actually do have a recognizable symptom that makes me uncomfortable. In the first 58K+ miles, nothing has happened except the occasional ping from the injectors at hard take off.

 

Tim, I too was of the same mentality. Truck always ran strong except for a few repeatable instances. Merging onto the highway from work is one of those times...it's a 35 mph lead into a near wide open throttle run to 65-70mph. Often the truck felt like it was holding itself back...almost like the traction control wanted to interfere, however it would do the same thing with TC turned off. It got me thinking about condensation, and we all know it gets humid here in VA (although not as bad as some place like Houston TX).

Anyway, since drilling that hole I've not had ANY of the same feelings no matter how hard I run the truck. Since drilling I've added a mild tune, increasing the boost pressures slightly, and still cannot get the truck to replicate the pre-drill symptoms. I've also pulled the front and rear blocker plates that Ford added as a "fix".

The truck consistently spit a watery oily solution for a little more than a week, and I still find the back of the airdamn and the CAC lower support with residue on them. Somethings working...as scary as it might be.

 

The IC is IN FRONT of the throttle body. There is vacuum behind the throttle body, not in front of it. On a turbocharged engine there is none in front of it just like there is NO VACUUM on a turbo diesel that has no throttle body. Why do you think gas engines have a BOV and diesels do not? When the TB closes after a hard acceleration (creating vacuum behind it), the boost has nowhere to go. On a diesel, the boost just pushes through the engine all the time (except for a very brief moment when the throttle is let off when under very high boost and the turbo loses drive pressure).

 

Something worth looking at...disregard the catch can routing...it's the only diagram I could find to show the proper air flow path.

 

Okay, so you're saying the turbos are providing positive pressure the entire time the engine is running?

On a N/A engine negative pressure from the throttle body sucks air though the intake tract. This negative pressure would also suck unfiltered air through a leak in the intake system

 

this is the basis of my question.


we know the manifold is in vacuum under deceleration. with very little exhaust flow and heat to spool the turbos (and with them not being needed), do the turbos still create positive pressure in the CAC?


or does the air demands of the engine exceed the supply created by the turbos creating a situation where air is drawn through the CAC, rather than being driven by pressure.


if the former, then the hole presents no realistic danger of letting unfiltered air in the system.


if the latter, then there may be cause for concern.

 

Sorry for the late response, but I've never seen the water accumulation problem in this way.


I agree that this is the way that the CAC is supposed to work, but I think that's the problem.


Imagine a vehicle driving for hours on end collecting water the whole time (due to prevailing conditions), then exits the freeway and shuts down. When did this water get a chance to get blown out of the CAC?


Add to this that the next time the driver takes off easily and never really gets into the boost, that water is sitting there collecting. Do this often enough and you can collect a large amount of water.


Personally, I think that is what is going on. People like me who never really get into it are collecting small amounts of water over large periods of time, then when the do finally step into it, the large volume of air at full boost does what it is supposed to do and cleans out the CAC. but if you only do that once in a great while, then you are running the potential for problems. or so it appears to this guy.

 

If the butterfly in the TB is closed, and we know the IC is in front of it, where would vacuum be coming from IN FRONT of the TB? Especially with turbos there even spinning at idle speed moving air INTO the space in front of the TB?

EDIT: AND.... What does it mean when the throttle is at a position where there is neither boost nor vacuum showing on the gauge?

 

Excellent couple of posts, wish I could rep ya.

 

Interesting thread. It got me thinking... I have 3 Cat C9 generators that I maintain at work. The C9 has a "condensate drain valve" on the intercooler, which is essentially a ball check valve with a light spring holding the valve open. The theory is, when the engine is shut down or in a no-boost load condition, the spring holds the valve open and any condensate in the intercooler drains away by gravity. As soon as boost is present, the valve seats and there are no air leaks.

I believe the valve seats in both directions, so if there were a vacuum in the intercooler, there wouldn't be any unfiltered air introduced to the intake (and more importantly, air not registered by the MAF sensor).

I wonder if a similar off-the-shelf component could be had for a decent price? I'd see what the Cat part is worth, but I'd bet a body part a cheaper solution could be had. I'd feel a lot better about something like that, instead of just drilling a hole in the intercooler.

 

The manifold. The throttle blade doesn't actually close all the way. It has to be open some or the engine would be starved of air and stop running.

I have no conclusion about this matter but what I have noticed is that articles that discuss "Intake Boost Leak" all have a common theme that when the manifold is in vacuum, then the entire intake tract is in vacuum. None of those articles were Ecoboost related but the theme appears consistent across different turbo car enthusiast groups.

 

Yes, there is either a very small hole in it, or it doesn't close completely. Either way, it's still not enough to overcome the amount of air the turbos push in even at idle. Below is what my old 7.3L turbo looked like at idle -- do you think a tiny hole allowing just a slight bit of air through a TB is enough create a vacuum behind something like that? I know this is the 7.3, but I also know the turbos in the 3.5 are spinning similarly, and pushing more than enough air than what is going past the TB. It makes no sense even at idle, and ESPECIALLY during deceleration when the TB is closed, that vacuum is magically being pulled past it and overtaking the air being pushed in by the turbos. So yes, there is enough heat, even at idle, to drive the turbos enough to fill the intake tubes when the TB is closed. It would be easy enough to install a boost/vacuum gauge temporarily if you don't believe the numbers already posted.

 

The numbers posted are at the manifold. Nobody disbelieves those numbers, but we're not talking about drilling holes in the manifold.

 

Ya, what numbers posted? That's what we want if you got it!

 

I've been out in the field, so I haven't read every word of the thread -- thought someone posted numbers. I'm about to order a set of ScanGauges, so hopefully they will be able to read the pre-TB pressure.

I'm still curious what you guys then about when you're going down the highway and get the throttle just so you 0psi of boost/vacuum...