Help with Part Identification please

[Armitageshanks]

Hi,

trying to find reason for an error code on the car'17964' boost pressure negative deviation. anyhow i was tryin to identify problems with any hoses for the turbo(not that i've identified it) and found a partially cut/eroded hose connected to a black box on the drivers side of the engine,almost parallel to the EGR valve , with several other hoses going into it. The hose in question dissapears down the back and possibly connects to a plastic pipe,another hose goes to the EGR, i think, but could'nt verify as the missus took the car away. Any ideas as the remapper told me my turbo was sufferin from a lot of lag. My cars an Ibiza Mk4 pd 100. Is this box the boost pressure solenoid?


Cheers!!

 

[Muttley]

Don't have a PD so can't match your description to specific bits. A picture or two would help.

Can't work out what this black box is with several other hoses going into it. The solenoid valves I see in my engine bay have two or three pneumatic hoses, narrow tubes, going in to them as well as an electrical connector.

Any narrow hose going down behind the engine is almost certainly the turbo vane control line. The turbo vanes should be preloaded to the fully open position, appropriate for high revs/high exhaust volume. Vacuum is applied to the control line to such the vanes shut for low revs.

 

[Armitageshanks]

Ok , will try and get pics up ,soon as missus returns(hate sharin MY car). But yes, i think theres one plug on one side of box then around six black pipes connected on the other. Bought a handheld scanner off the 'bay 'and set about using it today,and thats when it gave me the fault code. After reading a few threads I thought about seeing if there where any dangling hoses and then saw a leaky/puntured lookin one halfway down the side of engine. Im taking my car back to remapper tomorrow as the I found my torque figures rather modest compared to some. If i could sort out a new hose it would make things better im sure ,as mapper said things would get rather smokey as my car was slow to pick-up/boost.

 

[Armitageshanks]

just seen the part in another thread, and now know it's the vacuum control assembly!!

 

[cheshire cat]

the black box controls boost/egr/antishudder valve and can't remember what else, another pipe goes to the vac reservoir the pipe in question is undoubtably the turbo pipe and I would have thought if it was shot you would suffer from high boost as vac is applied as the revs rise to reduce the vane pitch a "lot of lag " in boost suggests that the diaphram/actuator may well be stuck and I would have thought no one would try to reprogramme a "faulty " engine it needs sorting before you go back keep us posted

 

[Armitageshanks]

I was also thinking the engine was starting to shudder a little on 'engine turn-off' too. Ok, so do you think i should try and replace this torn hose/pipe , is it easy enough. Would be good idea to upgrade with silicone hose?

 

[cheshire cat]

high boost as vac is applied as the revs rise to reduce the vane pitch a "lot of lag " in boost suggests that the diaphram/actuator may well be stuck

may have this arse a bout face someone please confirm, terrible getting old an daft

 

[Muttley]

From everything I have read, the boost control systems on the turbos on VAG cars fail safe - if control input is lost then the boost control goes to the wide-open, lowest boost condition. On a wastegate turbo the wastegate stays open, on a VNT turbo the vanes go to fully open, lowest augmentation. At engine startup, the ECU signals the N75 valve to apply low pressure and the actuator pulls the vanes from wide open to the other extreme, the narrowest opening, to get the low gas volume to speed up and spin the turbo.

In the case of a worn hose, the effect may be to slug the response, as the ECU will measure boost pressure at the MAP and apply what it thinks is the appropriate control input to the turbo only to have to apply more - the leak haveing affected the vane movement.

 

[Muttley]

Aha! found a diagram of the vac hoses for an ATD engine, which is what yours is I think. There is indeed one solenoid box which takes on the functions of the individual N75, N18 and N239 valves in my old-fashioned TDI 110. Six pneumatic control hose connections (I'd say vacuum, but one of them isn't). Reading from top to bottom of the diagram, we have

1) Turbo boost control
2) Vacuum reservoir
3) Airbox connection (not vacuum, this provides the clean "ambient pressure" that the solenoid valves mix with the vacuum to provide an intermediate pressure)
4) Antishudder flap control
5) EGR valve control
6) Vacuum source (goes to a T-piece on the connection between the vacuum pump/tandem pump on the end of your camshaft and the brake servo)

 

[Armitageshanks]

OK,
Little update, replaced the piping at no1 position(the turbo boost control) as named by Muttley, and the car is now flying. The error code no longer comes up after thrashing the car a few minutes down the dual carraigeway, so im almost there. I did have a remap done when the faulty pipe was there, can't say if the mapper ignored any eror codes at the time, but he did say my standard car was underpowered compared to some.
Anyway, he got my BHP upto 144 and 169ib/ft. The 144 sounded good for a PD100 but 169ib/ft was low to what i know about remaps, reason being that the car would smoke too much.
Now with everything fixed he's going to tweek my map this afternoon, so hopefully even more joy!!

Oh yes, must confess, when fitting the slighty smaller bore pipe on ,i broke the fixing nozzle on the vac box , but being an ever resourceful type, I fashioned an airtight joint using small metal tubing from a bicycle v-brake noodle and some plumbers tape .Im confident it'll hold forever but im made enquiries about second hand bits just in-case