What wonders a tune up makes! BPV question...

[Boxerfan]

Well I managed to get the correct 3B rotor, and a new cap installed along with a set of NGK 7 series plugs. An oil change and a new fuel filter and PRESTO! What a happy car!

I am pretty sure the Bosch BPV is pooched though. The engine is a 7A with all the 3B turbo plumbing and an RS2 replica turbo. The car builds boost nicely now but it doesn't hold and there is a tell-tale "Wooooooosh" after about 5PSI that sounds like a completely open hose. Sometimes it feels like it totally lets go of the pressure. Worse still... today it stalled coming to a gentle right turn.

The car has a cone filter and the BPV is closed circuit. I may be hearing the BPV even though it sounds totally open.

I remember hearing that the Bosch BPVs were known to open under idle vacuum. Does anyone have a good BTDT for an aftermarket replacement? Any other comments or suggestions?

I am just dying to put my foot down and get that freight-train-in-the-back feeling once again!

Cheers all!

Boxerfan

[UrS4boy]

BPV info as it relates to UrS Motronics

Oh, so it is a turbo coupe quattro. (!!)

Anyway, the Bosch 710N BPVs have been shown to be good and cost effective.

Here is some BPV info:

http://forums.quattroworld.com/s4s6/msgs/20994.phtml

[Boxerfan]

Bingo.

Here's another question... The WG operated differently on the 20VT motors as to the 10VT motors. Can anyone describe the symptoms of a torn WG diaphragm in the 20VT setup? I am not sure what to guess will happen.

If the Diaphragm is torn and the exhaust pressure bleeds off into the upper chamber it will then vent to atmosphere through the open nipple. There is still the spring pressure attempting to keep the WG closed.... dunno... will the valve begin to float?

I seem to hit about 5 PSI and then I hear a real woosh as if the BPV is ventoing to atmosphere. It doen't look like the path is opn though. All seems tight. Once upon a time I did see the intake manifold vac/boost nipples on the rear of the 10VT manifold come loose from the manifold. under vacuum and at rest the hose pressure kept things sealed up. Under boost eventually the tube would pop out, then when the throttle relaxed it would pop back in. Took forever to uncover that issue. I am wondering if the 20VT has a similar Achilles heel.

Running the standard 3B software I am expecting it to try and make 10-12psi as per the norm. Hence the crazy amount of octance booster and 94 octane pump gas. Will knock detection rtard the boost to about 5PSI? Does it automagically dump the boost using the BPV in that case? Perhaps the woosh I hear is coming from/through the cone filter when/if the BPV is operated by the ECU?

My next step is to remove and replace all the vac/boost lines one by one. Painstaking task but often yields good results.

[UrS4boy]

I thought I saw a diagram yesterday that showed that you were trying to control the WG with boost lines to both sides of the WG diaphragm. Can't find it maybe it was somebody else.

How did you lower the compression on the 7A before you added the 3B goodies? 10.3 is very high for a turbo'd engine and could be the cause of many of your boost issues.

[Boxerfan]

I bought the car with the mods in place. I am still trying to sort it all out. I am not sure if a compression dropping HG was installed.

The WG control is stock 3B.

I am using super high octane to compensate for the high CR while I trouble shoot. 94 Pump gas with a LARGE bottle of octane booster and half a small one.

I expect to try and limit the boost to just 5 PSI, but this is trying to get higher and then something is giving way. Gotta hate when plumbing gets old!

[my2000apb]

this may help

[Boxerfan]

Hmmm... I'll have to find a similar one for the 3B. Thanks.

[Boxerfan]

Well... I just learned the engine is an AAN block! So... the CR isn't an issue... I just have boost problems!

[Ruffiano]

Well... I just learned the engine is an AAN block! So... the CR isn't an issue... I just have boost problems!

how did you discover that? it is sort of hard to distinguish blocks, there isn't a stamp on them that say "AAN"

[Boxerfan]

I managed to contact the garage where the work was done. The guy selling the car didn't seem to know much. Just asked for turbo and got turbo. LOL.

Soooo... it's an AAN with the 3B goodies and an RS2 turbo. That makes me feel so much better. if I get ambitious this summer I may go ARP studs and a new HG just to be safe.

I'm glad the CR is in good turbo territory now.

[my2000apb]

Hmmm... I'll have to find a similar one for the 3B. Thanks.

everything other than crankcase breather is the same

[UrS4boy]

Crankcase Ventilation (PCV) system info

Hmmm... I'll have to find a similar one for the 3B. Thanks.

Those diagrams come from my PCV system FAQ post on quattroworld. There is ABY/ADU and 3B infor there as well:

http://forums.quattroworld.com/s4s6/msgs/22506.phtml

[UrS4boy]

Soooo... it's an AAN with the 3B goodies and an RS2 turbo. That makes me feel so much better. if I get ambitious this summer I may go ARP studs and a new HG just to be safe.

If that is true:

a) assuming that you also have appropriate MAP sensor (in the ECU) and injectors and the MAF are good, you can get tunes up to about 380 hp on 94, around 26-28 psig boost. This assumes that your entire engine system is working well, e.g. PCV system, intake and boost hoses have no leaks and your complete ignition system is in top shape.

b) with just an RS2 turbo, you don't really need ARP studs to hold the head down. Stock head bolts are fine. However, if the head gasket has never been done, you can keep driving until it blows (starts to leak coolant) and when you replace the head gasket, sure go for ARP head studs.

To learn more about the AAN, you might want to visit (and bookmark) this engine bay device map and click on the all the live link labels, e.g. PCV system in the lower right corner:

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

Dave F (in Vancouver)



Good luck.

[Boxerfan]

Cheers Dave. How's things on the Left coast?

[UrS4boy]

Cheers Dave. How's things on the Left coast?

Sunny and warm (18 C), green grass and cherry blossoms.