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Discussion Starter #1 (Edited by Moderator)
Hi,

I'm trying to diagnose lack of boost on a 2008 Fabia 1.4 TDI with the BNV engine. I've worked out that the VNT actuator works in the opposite direction to all others I've come across in that it pushes the rod out which springs back rather than the way more common pull type. Also it appears the actuator needs positive pressure in the pipe rather than the usual vacuum. Looks like the actuator and VNT mechanism are fine as the VNT lever moves easily and the actuator rod moves out under pressure (from a bicycle pump). But there's no movement when connected to the valve block.

The valve block has three connections that look relevant - numbers 1,2,3 which are connected to the pre turbo intake air pipe, the VNT actuator and what looks like a tap off the turbo outlet (boost side) pipe flange.

So the question is, where does the positive pressure come from that is supposed to push the rod out and hence move the VNT lever to the higher boost position?

I have VCDS and have run the basic settings test. There is no change in charge pressure when the VNT is on or off and the rod doesn't move at all.

I have a huge amount of experience with the 1.9 TDI PD engine and know the VNT system inside out on these, I'm just confused and can't find any information on this 'reversed' system.

Thanks.
 

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You probably have a waste gate type turbo rather than a vnt, they just open a vent to allow excess gases to bypass the turbine instead.
 

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Discussion Starter #3
Yeah, I think that's the conclusion I've come to after a lot of googling. The car is supposedly a 80hp 'BNV' though, which should have a Borg Warner VNT turbo but the actuator I removed today certainly has a Garrett (GT15?) label on it and the whole actuator mechanism looks nothing like any VNT I've worked on before (horizontal actuator rod and lever near the exhaust downpipe connection) It's starting to make sense now!

ECU is correct for a BNV engine so looks like a right mishmash of parts on the car.

Am I right in thinking the vent/waste gate is opened by pressure from the turbo outlet pipe tap? Is the correct turbo (BorgWarner VNT) likely to be a plug and play fitment?

TIA :)
 

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Manufacturer: Skoda, Date(s) Used: 01/2007-03/2010, Model: Fabia, Engine Code: BNV, 59Kw, 80PS, 1.4 Ltr, 3 Cyls, Remarks: Turbocharged Direct Injection Pumpe Düse (TDI-PD) Timing belt

Any problems search TDI Wiki as that covers write ups and forum posts.
 

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Discussion Starter #6
According to this site it should be a borg warner vnt turbo, maybe that's why it's lacking boost. Maybe someone fitted the wrong one not knowing what they were doing

http://www.btnturbo.com/parts/model/skoda/fabia.aspx
Yep, I found that page too! However this link shows a BNV engine with the non VNT turbo that I have.

https://workshop-manuals.com/skoda/fabia-mk2/power_unit/1.4/51;_59_kw_tdi_pd_engine/exhaust_turbocharger_g-charger/charge_air_system_with_exhaust_gas_turbocharger/exhaust_turbocharger_summary_of_components/

Everything looks factory fitted, it doesn't have the feel of a bodged up car. Plus, the intake, boost and vacuum piping is different for the VNT turbo (different routes and connectors) and so, I would imagine, is the ECU programming. The exhaust flange look completely different too.

I think I've come to the conclusion that that's just the way it is. A non VNT engine is always going to feel sluggish at low revs. It's a friend's car who previously had a 1.9 PD100 so he's used to an extra cylinder and a VNT!

Will chuck it back together, get some boost logs and see how it's actually performing. Probably should have done that to start with!

Thanks for your help.
 

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I had the 2000 plate seat Cordoba estate, it had the AGR engine which is basically the ALH 90 with a waste gate turbo. That thing was very peppy with the waste gate turbo.

Should be as peppy as a vnt version with the same poke
 

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Discussion Starter #8
This is a 1.4 80hp. Went to Skoda dealer today and they confirmed that the wastegate turbo is the correct one for the BNV engine (or at least it is in this car). Did some boost logging, sure enough boost does build but nothing of note until 2,000rpm and then about 2 bar absolute is held. Told my friend the bad news that this is how it is supposed to go.

Then lucky turn of events, found a same age 2008 Fabia 3 with all the toys and the 4 cylinder 100bhp VNT PD engine. Picked it up for just £800 and it's driven 50 miles home without a hiccup. Plenty of low down grunt and sounds a lot less like a tractor that's missing a cylinder or two.

Friend is happy again!

Live and learn...
 
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