Drilling a drain hole in the intercooler plumbing

JasonG · Jan 6, 2015

Ran a few numbers:

A 3/32" hole at 20psi will flow 3.6 cfm.
A CR170 would run around 330 cfm at that pressure.

[Edit]
A1/16" hole at 20psi will flow a hair over 1cfm.
[/Edit]

I'm not even sure the maf could detect a 1% difference.

psrumors · Jan 6, 2015

What will small insects with access to the clean side of the air filter do to an engine? Insects love small holes and many carry different types of grit with them to build nests.

flyboy320 · Jan 6, 2015

My concern is this pipe always under pressure when the engine is running, or are there some circumstances when it's under vacuum (perhaps coasting to a stop)? If there are times when it's under vacuum, then it's drawing unfiltered air into the engine (albeit a very small amount, but still)...

VeeDubTDI · Jan 6, 2015

afarfalla said:
I fixed all posts should be .3cm hole, I'm getting old!

So 3mm. Gotcha.

2011tdiproject · Jan 6, 2015

JasonG said:
This looks like a perfect fix.
Just to clarify as people are getting hung up on a minor point.

1/8"=0.125"
3mm=0.119"
7/64"=0.1093"
3/32"=0.0938"=2.38mm

I believe the OP stated he used a 3/32" drill bit. A 2.5mm would be the nearest equivalent.

I did not use a 3/32" bit.
As I wrote in response to afarfalla, I believe the hole I drilled is approximately .05", or about half the size of his 3mm hole. It was the smallest bit the drill would still hold. I had originally written, before I did this, that I thought I would drill a hole about 1/32", but .05" is bigger than that.

2011tdiproject · Jan 6, 2015

Rolyak said:
No automotive engineer would approve drilling a hole in the intake system.

Based on 30 years of Cummins experience and my turbo Volvo it essentially can be a vacuum leak. Under a load, fuel creates boost, let off the throttle it's back to vacuum.

My Volvo can blow 10 psi under full load but will cruise at 12"/HG (vacuum).

Truckers liked to cut holes in the intake pipes to spray a shot of ether, doing an overhaul they got a new intake pipe or voided their warranty.

Oh yeah, the Volvo has a factory intercooler drain plug.

12" of mercury is only 5.89 psi.
http://www.convertunits.com/from/inch+of+mercury/to/pounds+per+square+inch

For a diesel to be cruising at 5.89 psi absolute manifold pressure, it would have to losing an astonishing 8.81 psi across the turbo compressor and intercooler, which is obviously completely impossible.

5.89 psi absolute is only .4 of an atmosphere (.4 x 14.7) but is within the realm of possibility for a throttled gas motor going down the highway, although my old turbo honda cruised with a little higher manifold pressure than that.

Next, since what you're describing requires a throttle plate, you are also incorrect in describing any vacuum created by that as vacuum in the charge air piping. The vacuum is in the intake manifold, after the throttle, not before it, in the charge air piping.

2011tdiproject · Jan 6, 2015

psrumors said:
What will small insects with access to the clean side of the air filter do to an engine? Insects love small holes and many carry different types of grit with them to build nests.

Funny stuff right here. I don't know, mazda had a problem with "gasoline loving spiders" infiltrating the evap canister/purge system (I swear I am not making this up, google it!) But in general, I can't imagine any insect crawling through a .05" hole coated with crankcase ventilation residue and water to lay eggs or something in the charge piping. And if it did, the motor sure wouldn't notice inhaling it.

2011tdiproject · Jan 6, 2015

flyboy320 said:
My concern is this pipe always under pressure when the engine is running, or are there some circumstances when it's under vacuum (perhaps coasting to a stop)? If there are times when it's under vacuum, then it's drawing unfiltered air into the engine (albeit a very small amount, but still)...

I cannot imagine any scenario where the VW diesel would have anything less than atmospheric pressure in the charge piping. Going down the highway, according to another poster on here, the turbo is putting out a low level of boost, 5-8 psi. I have not verified this myself, I don't have any way of doing so currently.

flyboy320 · Jan 6, 2015

Rolyak said:
Based on 30 years of Cummins experience and my turbo Volvo it essentially can be a vacuum leak. Under a load, fuel creates boost, let off the throttle it's back to vacuum.

My Volvo can blow 10 psi under full load but will cruise at 12"/HG (vacuum).

2011tdiproject said:
I cannot imagine any scenario where the VW diesel would have anything less than atmospheric pressure in the charge piping. Going down the highway, according to another poster on here, the turbo is putting out a low level of boost, 5-8 psi. I have not verified this myself, I don't have any way of doing so currently.

I assumed Rolyak was saying his Volvo's intake sometimes runs in a vacuum.

ihatespeed · Jan 6, 2015

a 3mm hole probably wont suck up enough trash to cause an issue in an engine that spends most of its life under boost. the vast majority of air going through the engine will be properly filtered. path of least resistance says it will suck air readily through the filter and full intake before going through the hole. if you are turning say 3krpm going down hill (coasting) that's 3000lpm, not sure what a 3mm orfice flows at say 14psi, but it can't be a lot. Plus a few grains of sand are way friendlier than a cup of water.

Softrockrenegade · Jan 6, 2015

I would think any water not drained through a tiny hole (slowly) only while the car is not running will still take the path of least resistance (through the engine) when under boost.

afarfalla · Jan 6, 2015

my hole is working!

no cel's or stored codes after 3 days of driving and no water but its been in the 60"s here, maybe not good conditions to create water?

afarfalla · Jan 6, 2015

OMG! my hole is under attack

https://www.flickr.com/photos/37674324@N07/sets/72157650097686256/

2011tdiproject · Jan 6, 2015

afarfalla said:
https://www.flickr.com/photos/37674324@N07/sets/72157650097686256/

Lmao!

Also that pic definitely shows the hole you drilled is like 2x the size of what I did.

I drove today for about an hour and 20 minutes, no problems. Also let the car idle for at least 20 minutes, drove and shut it off multiple times, restarted after eating dinner and doing some shopping, which should have resulted in some ice melting. It was also pretty cold out, about 0 degrees. Definitely cold enough to form ice in the intercooler.

2011tdiproject · Jan 6, 2015

ihatespeed said:
a 3mm hole probably wont suck up enough trash to cause an issue in an engine that spends most of its life under boost. the vast majority of air going through the engine will be properly filtered. path of least resistance says it will suck air readily through the filter and full intake before going through the hole. if you are turning say 3krpm going down hill (coasting) that's 3000lpm, not sure what a 3mm orfice flows at say 14psi, but it can't be a lot. Plus a few grains of sand are way friendlier than a cup of water.

Again, you may not need to drill the hole 3mm, like I wrote who knows how many times by now, haha, the hole I drilled was like .05". But with the coasting at 3000 rpm down a hill thing, you're hypothesizing that the compressor of the non spooling turbo coupled with the very slight flow restriction of the intercooler will create enough of a vacuum in the intake tract to pull in air through the hole? Interesting. I wonder what the vane position on the turbo is under coasting like that.

I suppose I could just measure the pressure and be done with any speculation..

Dirtracr95 · Jan 6, 2015

2011tdiproject said:
Again, you may not need to drill the hole 3mm, like I wrote who knows how many times by now, haha, the hole I drilled was like .05". But with the coasting at 3000 rpm down a hill thing, you're hypothesizing that the compressor of the non spooling turbo coupled with the very slight flow restriction of the intercooler will create enough of a vacuum in the intake tract to pull in air through the hole? Interesting. I wonder what the vane position on the turbo is under coasting like that.

I suppose I could just measuring the pressure and be done reading all this speculation..

Just so you know your thread was merged with afarfalla's.

Probably depends if its DSG or not on the vane position might be mostly closed to provide some engine braking to make it feel more like a conventional automatic gasoline vehicle. I'll hook up my scan tool tomorrow and watch boost and n75 and report back tomorrow.

VeeDubTDI · Jan 6, 2015

Dirtracr95 said:
Just so you know your thread was merged with afarfalla's.

Probably depends if its DSG or not on the vane position might be mostly closed to provide some engine braking to make it feel more like a conventional automatic gasoline vehicle. I'll hook up my scan tool tomorrow and watch boost and n75 and report back tomorrow.

If it helps, I see no vacuum ever on the ScanGauge in the Passat. I wouldn't be too worried about the unfiltered air thing.

JasonG · Jan 7, 2015

2011tdiproject said:
I did not use a 3/32" bit.
As I wrote in response to afarfalla, I believe the hole I drilled is approximately .05", or about half the size of his 3mm hole. It was the smallest bit the drill would still hold. I had originally written, before I did this, that I thought I would drill a hole about 1/32", but .05" is bigger than that.

Wow, that's around a 1/16"
Sorry for my mistake.
Recalculated that comes to a hair over 1 cfm. Not enough to do anything to the computer as both of your driving histories have shown.
Great, easy fix

Afarfalla,
Be careful, that's one of them sludge ants.
He'll chew right through the plastic to get to that tasty oil/water mixture

SilverGhost · Jan 7, 2015

There is a MAF and MAP and several differential pressure sensors. A boost leak this small will take time to be noticed, and may never set a DTC.

These engines are extremely sensative to air flow and can do all kinds of weird crap when even minuscule damage is present.

Jason

elitegunslinger · Jan 7, 2015

Crazy idea, what about drilling, tapping, and plugging once finished?

VeeDubTDI · Jan 7, 2015

elitegunslinger said:
Crazy idea, what about drilling, tapping, and plugging once finished?

You'll need a plug that is easily removable, as water accumulation needs to be drained regularly (every couple of weeks to every couple of months). A petcock would do nicely, as would the suspension air line valve shown in a post above.

If you do a valve, the best way to get the water out would be to open the valve, go for a drive around the block, let it sit for a little bit, then close the valve.

Chris · Jan 7, 2015

SilverGhost said:
There is a MAF and MAP and several differential pressure sensors. A boost leak this small will take time to be noticed, and may never set a DTC.

These engines are extremely sensative to air flow and can do all kinds of weird crap when even minuscule damage is present.

Jason

Are these sensors upstream or downstream of the hole?

STRANGETDI · Jan 7, 2015

Subscribed.

VeeDubTDI · Jan 7, 2015

Chris said:
Are these sensors upstream or downstream of the hole?

MAF is upstream, I believe MAP is also upstream. Differential pressure sensors are in the exhaust, before and after the DPF.

volks27 · Jan 8, 2015

How would the car behave if you're stuck in traffic in a huge puddle of water? I assume the engine will suck up some (lots) of water through this hole ? Hard to hide after the engine is hydro locked and you're sitting at the dealer.

Chris · Jan 8, 2015

volks27 said:
How would the car behave if you're stuck in traffic in a huge puddle of water? I assume the engine will suck up some (lots) of water through this hole ? Hard to hide after the engine is hydro locked and you're sitting at the dealer.

Only if you assume that the duct goes into vacuum.

Slurry Pumper · Jan 8, 2015

Has anyone ever been stuck in traffic sitting in a foot deep puddle? I haven't, but if I did drill a hole, I would make sure I didn't park my car in a pond.

Revpeach · Jan 8, 2015

The question is not if the turbo creates a vacuum. The question is if the moving air moving past the hole creates a venturi effect that would draw outside air/junk into the system.

2011tdiproject · Jan 8, 2015

I see the idea of a valve is till being brought up, but no one who brings it up addresses any of this, what I wrote earlier.

2011tdiproject said:
I really want to emphasize one thing here that has been brought up repeatedly. I do NOT want a valve on that pipe. The reason why the people who've said things along the lines of "it's okay as long as you plug it back up", is psychological, not based on engineering. They think because the hole "isn't supposed to be there" that a valve is better, without looking at how the idea of the hole actually works. With a valve, you're not going to know when to open it. You won't know when water is accumulating, or when ice that is going to melt later is forming. You might never open it at the right time, you might open it when the water is still ice, and think there's nothing there. You might forget to open it. You might have to open all the time, way too often.

With the hole, it drains any time water is there. Whether you're driving, whether the car it parked, whether you're there or not. Therefore the hole is a much better idea. Human effort and error factor is out of the equation.

VeeDubTDI · Jan 8, 2015

With a valve, the idea would be that you drain the system on a regular basis to prevent water from accumulating enough to be ingested. Is that every day? Every week? I think that depends on your driving conditions, but most people who have experienced this should have some idea of how often it happens in various conditions.

Drilling a drain hole in the intercooler plumbing

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