Dump Valve observation/question

968 Views 6 Replies 3 Participants Last post by PSM20VT, Jul 21, 2004

PSM20VT

Discussion Starter · Jul 18, 2004

I changed my DV for a Forge item the other day when i had the car chipped and found/observed a few things:

1. The OE DV spring was so weak that i could activate it by just a light push with my finger ( could push the valve all the way in), could only just unseat the Forge unit.

2. I found the boost pipes quite oily inside, is this normal, i have read a few threads/topics that say it is, but have also read some that say its bad ?

3. Those bastard clips that Vw use to hold the pipes on are a nightmare to get off, ended up using my dremel with a cutoff wheel.

4. Someone had previously replaced a clip with a hoseclip on the car but the screw head area of the hoseclip had been rubbing against one of the boost pipes and has worn quite a gouge out of the pipe, not all the way through though but i guess this is now a weak spot in the system, should i replace the pipes, if so can you suggest a aftermarket kit or just OE replacements?

5. Its a very easy job to do once you get the bellypan off and deal with those bloody clips, i would say anyone could do it, so don't waste your money getting someone to fit it for you, get your hands dirty.3

Makes a nice sound now when it dumps the boost.

Thanks

Peter

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pete1

· #2 · Jul 20, 2004

(2) some oil residue is normal. Your intake is a garbage disposal for the crankcase breather, evap system, and such. If surfaces are lightly coated with oil, that's okay. If the oil is actually dripping and runing out, that's a sign there is a problem -- probably overfill.

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PSM20VT

Discussion Starter · #3 · Jul 20, 2004

pete1 said:
(2) some oil residue is normal. Your intake is a garbage disposal for the crankcase breather, evap system, and such. If surfaces are lightly coated with oil, that's okay. If the oil is actually dripping and runing out, that's a sign there is a problem -- probably overfill.

Thanks for that Pete.

Yes it only seemed to be a light coating of oil on the pipes.

So do you think that is a deliberate design fault or is it to do with emissions, as it causes several problems?:

1. Oil and rubber don't mix well, the oil breaksdown the rubber overtime, so making the parts fail, so that you have to re-new the parts, i guess thats why the OE DV's with the rubber diaphram fail so often.

2. A crankcase breather in the intake system of a turbo car must effect the intake temperatures quite a bit i would have thought?

3. I guess also that the crankcase breather must reduce the oxygen content of the intake charge as its pumping exhaust gases straight back in?

4. Are there any sensors that can be buggered up by oil in the intake system.

I remember reading a write-up in an Audi magazine as regards cleaning out the intercooler on Diesel Turbo's due to the amount of oil that used to collect in them due to the crankcase breather pipes.

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pete1

· #4 · Jul 20, 2004

(0) I'd imagine it's deliberate, due to ever-increasing emissions standards. The crankcase and evap have to go *somewhere*. It might as well be back through the engine to burn up some of the hydrocarbons.

(1) Not sure if there's a connection. Everything about the OE DV screams "Light and Cheap as Possible".

(2) Probably a drop in the bucket compared to the heat added by the turbo. The crankcase air is at, maybe 300F? ...with a fairly low flowrate.

(3) not really exhaust gasses... IIRC the crankcase air is the air from around the non-combustion areas of the engine. Any oil in this air is from the engine oil being tossed around during normal engine operation.

(4) the only two sensors that plug in to the intake are (A) the charge air pressure sensor on the hose port on the upper side of the intercooler, and (B) the intake air temperature sensor at the throttle body. (A) is only present in AWM engines, IIRC. The pressure sensor should not be affected by oil residue. The temp sensor is a thermistor (resistance changes with temperature) as long as the oil does not thermally insulate the temp sensor, it should be fine.

(5) you could pop the lower hose of the intercooler and stick a clean lint-free shop rag in there... it would likely soak up most of the excess oil residue using gravity alone. Not sure if it's worth it, however.

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PSM20VT

Discussion Starter · #5 · Jul 20, 2004

:thumbup: Thanks Pete1

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the_dread

· #6 · Jul 21, 2004

Note: Intake air pressure sensor also present on APU engine (euro spec).

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PSM20VT

Discussion Starter · #7 · Jul 21, 2004

the_dread said:
Note: Intake air pressure sensor also present on APU engine (euro spec).

Thanks, i have a 98 AEB engine (euro spec)

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