Boost issues

**jimnielsen** · 25-08-07, 22:31

I've had a few opportunities to take the Q4 out for a spin now. It runs very well and very smoothly, but I don't think that the boost system is working properly. The car has been fitted with a boost gauge that shows that in 2nd, 3rd and 4th gears the car is producing approx .45 boost. From what I've read in the manual and on various posts on this site I believe that it should be able to produce .7 - .8 in 2nd and 3rd and 1.1 in 4th. So it looks like I have a problem.

What is the most logical way of going about trouble shooting this issue? How can I rule some of the components in the system in / or out as possible culprits?

thanks, jimN

**wrinx** · 25-08-07, 22:37

From what I've read here "base boost" is about the figure you're quoting.

I asked a similar question and some of the answers may help you...have a search further down this lounge

wrinx

**wrinx** · 25-08-07, 22:51

http://forum.berlinasportivo.org/showthread.php?t=588

http://forum.berlinasportivo.org/showthread.php?t=595

These might help....

wrinx

**jimnielsen** · 27-08-07, 03:19

I have started having a look at the low boost issue. I have removed both of the small bore hoses that go between the peirburg valve and the wastegate accutator / turbo body. They both had very bad air leaks. The one to the turbo housing actually had a split that you can see in the picture, but both also have small holes just along from where the small hose clamps were. I still haven't figured out how this peirburg valve controls the action of the wastegate but it would have difficulty doing anything with big air leaks I think.

www.nielsen.org/alfa155Q4/smalhoses.jpg

**Steve Webb** · 27-08-07, 06:38

Jim, as far as I can remember the pierburg valve bleeds pressure from the turbo to the 'atmosphere' side of the wastegate, reducing the pressure differential across the wastegate and keeping it closed. This allows the turbo to make more boost than the wastegate base level is set to.

**Steve Webb** · 27-08-07, 11:23

Originally Posted by Steve Webb

Jim, as far as I can remember the pierburg valve bleeds pressure from the turbo to the 'atmosphere' side of the wastegate, reducing the pressure differential across the wastegate and keeping it closed. This allows the turbo to make more boost than the wastegate base level is set to.

Right ignore that one, I've remembered how it works properly now. The pierburg valve is inserted into the small bore hose that goes from the compressor side of the turbo to the wastegate. Normally when the overboost isn't activated boost from the turbo is presented to the wastegate. However when overboost is activated, some of the boost from the turbo is vented back into the inlet manifold so the wastegate doesn't see it and stays closed for longer, letting the turbo make more boost.

Common problems are the electrical connectors on the pierburg valve, as the plug can be connected the wrong way round. Result is no overboost. The other problem is a split in one of the smallbore hoses, resulting in no pressure at the wastegate, and loads and loads of boost, only halted by the ECU when it reaches 1.45 bar

Neither of which are your problem, could be a knackered re-circ valve. The original ones are plastic and fail fairly regularly.

Partialy stuck wastegate could also be the problem. As could any of the small bore hoses, also the rubber elbow that attaches the plenum chamber to the metal pipe that runs between the head and battery has a habit of splitting. So if its rubber and its under the bonnet, give it the once over.

**jimnielsen** · 27-08-07, 21:51

thanks Steve. Thats disappointing! I was hoping I could just fix the small bore tubes and it'd be ok, but from your description I'll have to look further.

Um, where is the plastic 'recirc valve'?

Thanks, JimN

**wrinx** · 27-08-07, 22:19

It's under the hoses to the intercooler and airbox. If you remove the battery and it's tray you can get to it much easier...underneath the two hoses. Little black cylinder with two 25mm hoses and one vaccum hose attached.

wrinx

**jimnielsen** · 28-08-07, 00:01

Ok, I removed the battery box, and a couple of million hoses that were in the way and discovered that the small bore hose that connects that antistall / blowoff valve to the inlet manifold was not connected. it was just dangling in the breeze (so to speak).

www.nielsen.org/alfa155Q4/bovalve.jpg

Also it was very split at the rubber boot. I have tested the bov (using the suck method..) and it works fine. Hopefully I can get it back together today and test it tonight. Any opinions on whether this could contribute to me having only seen the base level of boost?

JimN

**AlfaJack** · 28-08-07, 08:30

Yup all these split hoses certainly are not helping, think you may have found your fix - that small pipe that comes off the dump valve is where my boost gauge reads from (much further up the line though) - If yours is the same - it would explain your bad reading too.

**wrinx** · 28-08-07, 08:43

I also have a split in the DV elbow but the other end, it's been taped up

...where can they be bought from, couldn't find much on ebay?

wrinx

**AlfaJack** · 28-08-07, 08:52

You mean the small bore stuff like in the pic Jim posted? That rubber bit connects on to a long plastic line which leads round to the top of the engine

If so, just get some of this stuff in the right size:
http://cgi.ebay.co.uk/3mm-ID-VACUUM-...QQcmdZViewItem

Also, change all the other small bore hoses for this stuff - saves a job when the original stuff does finally perish!

On mine someone has fitted a good quality hose connecting the MAP sensor to the inlet plenumn (very had connection to get to) - You never want this splitting as its an absolute pig to drive!!

**jimnielsen** · 29-08-07, 03:00

Can somebody please tell me if this is the correct way to connect the lead to the pierburg valve. This is the way it was connected when I got the machine, but I have no reference for it, and the thing can be connected either way around. The green wire is closest to the engine, the white closest to the radiator.

www.nielsen.org/alfa155Q4/pierburg1.jpg
www.nielsen.org/alfa155Q4/pierburg2.jpg

Thanks, jimN

**q4fatboy** · 29-08-07, 06:00

Similar to my problems but I think mine are now a bit worse

Looks like the Turbo has finally lunched itself, oil seems to be getting into the induction tract and a distinct lack of serious boost. Will have a look at weekend to see how bad it is.

Anyone know of any good turbo suppliers ?

**Steve Webb** · 29-08-07, 06:49

Originally Posted by jimnielsen

Can somebody please tell me if this is the correct way to connect the lead to the pierburg valve. This is the way it was connected when I got the machine, but I have no reference for it, and the thing can be connected either way around. The green wire is closest to the engine, the white closest to the radiator.

www.nielsen.org/alfa155Q4/pierburg1.jpg
www.nielsen.org/alfa155Q4/pierburg2.jpg

Thanks, jimN

I'll take a look for you this morning Jim, I'm down in the garage doing stuff.

**Steve Webb** · 29-08-07, 06:54

Originally Posted by q4fatboy

Similar to my problems but I think mine are now a bit worse

Looks like the Turbo has finally lunched itself, oil seems to be getting into the induction tract and a distinct lack of serious boost. Will have a look at weekend to see how bad it is.

Anyone know of any good turbo suppliers ?

Sounds like the bearing oil seal on the compressor side has failed letting oil back into the inlet.
There are 3 options, get a do it yourself bearing kit, send back to a turbo recon place, or buy a new one. I think Wrinx mentioned he was going to look into recon kits, not sure how far he got. I had mine rebuilt with a different turbine to give better response, I'll see if I can dig out who did it.

Or you can go the modern route and get something like a new GT28 or the like. Getting one for those from the States is good value these days.

**Steve Webb** · 29-08-07, 06:58

Originally Posted by AlfaJack

You mean the small bore stuff like in the pic Jim posted? That rubber bit connects on to a long plastic line which leads round to the top of the engine

If so, just get some of this stuff in the right size:
http://cgi.ebay.co.uk/3mm-ID-VACUUM-...QQcmdZViewItem

Also, change all the other small bore hoses for this stuff - saves a job when the original stuff does finally perish!

Totally agree with you Jack, this stuff is far better than the regular rubber small bore hose. Doesn't perish and stays where it is put without hoseclips etc.

Originally Posted by AlfaJack

On mine someone has fitted a good quality hose connecting the MAP sensor to the inlet plenumn (very had connection to get to) - You never want this splitting as its an absolute pig to drive!!

I had this pipe split just as I came out of the Blackwall tunnel one day. When it goes you know about it, as far as the ECU is concerned the engine isn't making any boost at all, but in reality it is, as such the engine runs very very lean on anything other than the smallest of throttle openings. Not much fun.

**jimnielsen** · 29-08-07, 07:03

Thanks Steve, I really need to know if I have that connector on correctly!

Thanks, JimN

**Steve Webb** · 29-08-07, 08:25

Jim, just been down to the garage and on mine the white/black stripe wire is connected to the pin closest to the radiator. So it sounds like yours is connected correctly too.

**jimnielsen** · 29-08-07, 10:43

Thanks Steve, I have tested the system now and the boost works fine now that I have fixed the hoses that were broken etc. Thanks for checking the pierburg wiring for me. Um, now I have uncovered a more complex problem however with the clutch, that I will outline in a new topic.

JimN