Pierburg Valve

[Alfa Patch]

Whilst trying to work out why boost was dropping off above 4.5k i checked through various pages on here and read through the manual a bit. The Pierburg valve kept cropping up and how it might cause similar affects so i though I'd have a look at it. Well ive been looking for about an hour now and come to the conclusion that it's not there?

Am i right in thinking that they're usually mounted to the slam panel?

On my car the pipe comes from the bottom of the turbo, into a bleed valve (not fitted by me) and then straight into the actuator. The Pierburg should be plumbed in there somewhere right?

Would the lack of this valve cause my boost to drop off? It boosts up to just under a bar and then tails off at 4.5k to about 0.6 / 0.7 bar (due to the location of my gauge its really hard to look whilst not crashing).

I know people remove these valves but why? If you want more boost can you not fit a bleed valve into the system in the same way it does without the valve?

So many questions......

[wrinx]

By "bleed valve" I guess you mean manual boost controller (MBC)? If so it should be adjustable to gain more boost and as they replace the Pierberg it could easily have been removed from where it's located on the slam panel.

wrinx

[Alfa Patch]

Yes I guess it is an MBC, I have just always called them bleed valves?

I understand that I can raise the boost using the mbc but I'm curious as if it would maintain the boost all the way through the rev range or allow it to drop off as I'm experienced?

Would I not also lose the overboost features in 3rd, 4th and 5th gear?

TBH I would rather have it controlled by the pierburg because as I understand it that would effectively act as an ebc (allowing me to change the boost) once (or if) I had access to the ecu maps?

[SteveNZ]

A bleed valve effectively does the job on the PBV only it's manual and not controlled by the ecu. Generally you would install a bleed valve in place of the PBV. Using bost is not a good idea. The ecu will try to compensate for changes made by the bleed valve.

[wrinx]

Boost still drops off...can't be sure of the exact behaviour without driving mine and making a mental note.

wrinx

[Evodelta]

If you were to correctly describe a 'bleed valve' it has 3 legs and an adjustable knob.
It bleeds boost off to the atmosphere via one of the legs, because you are wasting boost which could be used they aren't very good and should be binned.

They have been largely superseded by a similar type which only has two legs, known by a few names I simply call it 'ball & spring' type. They are much better and your engine will produce boost in areas (of rpm and throttle position) where it didn't before.
They don't waste any boosted air.

Both types do away with the original Pierburg which is sluggish in its operation, but in doing so the ECU is not controlling the boost any more so if it needs to cut it it can't.

If you've got a problem as you describe you've got a fault somewhere, it may be the valve itself, I would start there and work back.

[SteveNZ]

If you were to correctly describe a 'bleed valve' it has 3 legs and an adjustable knob.
It bleeds boost off to the atmosphere via one of the legs, because you are wasting boost which could be used they aren't very good and should be binned.

They have been largely superseded by a similar type which only has two legs, known by a few names I simply call it 'ball & spring' type. They are much better and your engine will produce boost in areas (of rpm and throttle position) where it didn't before.
They don't waste any boosted air..

Both types are still bleed valves that bleed off air. The only difference is one has the ball and spring also. The use of a restrictor in the inlet will dramatically reduce the volume of air required to be bled off. The volume of bled off air is insignificant.

[Evodelta]

That's incorrect, take this ad for instance, it's good because it's got diagrams with it.

http://www.ebay.com/itm/NXS-BOOST-CO...-/260356025810

If it's bleeding off air and wasting it exactly how is it doing this and where is it going?
It's got two legs (inlet/outlet) one gets it supply from the turbo, the other goes to the wastegate.

[Alfa Patch]

The MBC on my car was basically the same as that ad. One prong in, one out and a hole that bled the excess pressure out of the back of it.

I found my main boost leak today, it was the recirculating valve. I didn't even think my car had one as it 'chattered' when I changed gear or lifted off. It just appeared not to be there as it was basically doing the complete opposite of what it should have.

I pressurized the intake system using compressed air and there was such a big leak the system wouldn't even hold 3psi pressure with even that escaping in less than a second. I could hear the air escaping as quickly as I was putting it in.

There was a small split in the dump valves diaphragm and it was holding so little pressure when shut I could blow through it.

I took it out, plugged up the holes and went for a drive. I was accelerating cautiously but immediately hit 1.5 bar and the boost cut. Pretty terrifying so crawled back.

What seems to have happened is that at some point the dumpvalve split and the owner at the time fitted the MBC and wound up the boost to compensate. I took the MBC out and that appears to be knackered as well.

With the waste gate connected straight to the boost feed from the turbo I am now seeing a fairly stable .6/.7 bar of boost. The car is running so much better at top end now but lacks the punch it had mid range due to less boost. I guess that will be back once I fit a new boost controller and wind it back up to 1bar.

I'm considering one of these:

http://item.mobileweb.ebay.com/viewi...id=86127786605

Has what I want but is almost certainly Chinese crap. I'm not sure this is an area I should be cutting costs?

[SteveNZ]

That's incorrect, take this ad for instance, it's good because it's got diagrams with it.

http://www.ebay.com/itm/NXS-BOOST-CO...-/260356025810

If it's bleeding off air and wasting it exactly how is it doing this and where is it going?
It's got two legs (inlet/outlet) one gets it supply from the turbo, the other goes to the wastegate.

There will be a small port drilled in it somewhere to bleed off some air. It would not raise the boost if it wasn't, it's just physically impossible.

I've have many manual boost controlers, with and without the ball and spring, over the years. They all have the small bleed somewhere and they all work even if you remove the ball and spring. The ball and spring is not there to control the boost pressure, it's there to reduce wastegate creep, make the boost come on faster. It's still the bleed function that actually raises the boost.

Electronic boost controlers are exactly the same too, they are essentially a bleed valve that is just electronically controlled. Like I said before, any air bled off is totally insignificant. With the right restrictor, the volume of air we are talking about is miniscule.

There are a lot of myths floated about to make one product sound better than another. Don't get sucked in.

[SteveNZ]

I pressurized the intake system using compressed air and there was such a big leak the system wouldn't even hold 3psi pressure with even that escaping in less than a second. I could hear the air escaping as quickly as I was putting it in.

It's great you found a leaking blow off valve, but it may have been only by chance.

Did you pressurise the other side of the blow off valve at the same time? From the description of your test procedure above, you didn't. The BOV will always leak under those circumstances. The springs are usually rated for around 2-3psi only so any more pressure than that and it will leak. You need to also pressurise the other side of the diaphram via the vacuum hose to keep the valve shut.

[Alfa Patch]

It's great you found a leaking blow off valve, but it may have been only by chance.

Did you pressurise the other side of the blow off valve at the same time? From the description of your test procedure above, you didn't. The BOV will always leak under those circumstances. The springs are usually rated for around 2-3psi only so any more pressure than that and it will leak. You need to also pressurise the other side of the diaphram via the vacuum hose to keep the valve shut.

I pressurized the system from the airbox hose. Thinking about it logically though the valve should have been venting the pressure as you describe. However the fact that after removed boost went through the roof shows that it was indeed fit for the bin. But as you say, I got lucky.

I have a ball and spring controller on the way to me and am also curious about how it differs from a bleed valve. Either way can't wait to get the boost back up to 1bar. The car runs so much better than it used to above 4.5k rpm now and power delivery is generally more linear.

Still need to find the smaller boost leaks but will do this once I have a new hose kit. Someone has fitted various silicone bits and they are all wrong. The elbow that goes to the throttle body is a massive samco item which is cool but has caused a big kink in the hose from the intercooler which is now about half the diameter it was.

I have been finding lots of odd bodges on the car. Someone had blocked the idle control valve. I have no idea why you would do that? Somewhat unsurprisingly it idles much better and more consistently now it's getting its data!!

[SteveNZ]

Some, lets say older, simple boost controllers that worked by bleeding air off were (correctly) called bleed valves but the name sort of stuck to these older type controllers. A "bleed valve" is not a type of boost controller but a pneumatic principle of how they work. All pneumatic type boost controllers, no matter what they are called, what they are built with, still use this basic bleed off principle to work.

For some reason bleed valve became a dirty word, so new names were invented to make products seem better.

Before you could just easily buy something called a "bleed valve" from a corner store or ebay, I had no choice but to build my own with simple pneumatic valves. You soon learn if you create a restriction to the bleed valve, I used a seperate ball tap, the bleed valve becomes far more sensitive, less air needs to be bled off to change the boost. If you keep restricting the flow to the bleed valve, the smaller and smaller the bleed needs to be. You can get to the point where the bleed is so small, it's too sensitive to adjust so it's better to fix the bleed (just drill a small hole) and adjust the boost by adjusting the restriction. This is how some modern boost controllers work and it is a far better way of adjusting the boost. They can usually be setup to achieve a maximum boost. As you open the restrictor, the boost will only decrease. This is why most boost controllers state a boost range, e.g. "up to 30psi".

The ball and spring is essentially a pressure valve that acts as a total restriction. No air will pass to the bleed or the actuator untill there is enough pressure to push the ball off the seat. This pressure point can be adjusted by preload on the spring. Once the ball is off the seat it becomes irrelevent to the system.

[Alfa Patch]

So a ball and spring will only adjust wastegate opening time by delaying the p eu attic signal rather than allow you to adjust what is bled off and therefore vary the boost?

Thats a pain if true as I'll have to reinstate my old bleed valve in order to do so?

I was fairly sure I knew about these before I started with this. As with most things speaking to other people has confused this nicely

I'm hoping the thing I bought has arrived today, if so I'll fit it and update on my progress / destroyed head gasket!!!

[SteveNZ]

So a ball and spring will only adjust wastegate opening time by delaying the p eu attic signal rather than allow you to adjust what is bled off and therefore vary the boost?

That is correct however you wont need a seperate bleed valve to adjust the boost as every "ball and spring" boost controller will incorperate a bleed valve into it also.

[Alfa Patch]

That is correct however you wont need a seperate bleed valve to adjust the boost as every "ball and spring" boost controller will incorperate a bleed valve into it also.

I re read your post and now understand what you mean. The restriction (in this case the ball) is already so large that the bleed itself does not need to be regulated and doing so would be very difficult. Therefore the restriction is regulated (by adjusting the tension on the ball via the spring) and this in turn regulates the boost.

The controller does have a drilled 'fixed bleed' as you suggested. I am fitting it tonight and will update on progress.

Hopefully boost will also come in earlier and stronger.. Fingers crossed



Car boosts way too high. Wound it all the way out and still too high. More fiddling to be done tomorrow.

[Alfa Patch]

Even with the boost controller wound all the way out the boost is still too high. Anyone know of why this may be?

My thought is that the fixed bleed hole is too large but it seems odd that it would be raising the boost by so much. I haven't hit the ignition cut but that's because I have been gentle with the throttle. I'm sure it would boost over 1.5 bar if I floored it. I was getting 0.6/.7 bar of boost with nothing in the actuators air feed before so 0.8+ bar raise sounds like a lot when it's the minimum difference the controller can make?

I was making enough boost to blow some vacuum hoses of including the one to the gauge which was worrying.

[wrinx]

Have you tried winding the controller the other way?

wrinx

[wrinx]

Another thought...it is connected the right way around???

wrinx

[Alfa Patch]

I followed the instructions exactly although I will triple check. I haven't wound it all the way in but did quite a lot and try that, I guess I should at least try all the way in. Again though it's the opposite of what the instructions say. Worth a punt.

[SteveNZ]

What boost controller do you have? Take some photos of the setup.

[wrinx]

Again though it's the opposite of what the instructions say. Worth a punt.

It is the opposite...but you never know!

wrinx

[Alfa Patch]

What boost controller do you have? Take some photos of the setup.

Photo 1 shows the boost controller that was fitted on the left and the ball and spring type now fitted on the right.

Photo 2 shows this deliberate restriction / coupler that was also in the hose. Seems to be original as it had those fecking irritating clips holding it in place, i have tried it with and without and makes no difference.

Photo 3 shows the 'controller' fitted in place

Have taken it out, wound it off as far as i dare (before it runs out of thread) and am going to refit. If it boosts to infinity again i will not be held responsible for my actions!!

[Alfa Patch]

Took the car up the road. Boost rose quickly to about 1.4 bar and dropped back down to 0.9/1bar area just as quickly as revs rose. Basically not what I wanted at all.

Fully pissed off with it. I'll remove the "I'm not controlling sod all" controller in the morning and drive the car for a bit with 0.7 bar. Rather get to give the car a good drive rather than worry about blowing it up the whole time.

Very annoying but I will certainly revisit this once I forget what a gargantuan kick in the balls the last couple of days have been.

[SteveNZ]

Photo 1 shows the boost controller that was fitted on the left and the ball and spring type now fitted on the right.

Photo 2 shows this deliberate restriction / coupler that was also in the hose. Seems to be original as it had those fecking irritating clips holding it in place, i have tried it with and without and makes no difference.

Photo 3 shows the 'controller' fitted in place

Have taken it out, wound it off as far as i dare (before it runs out of thread) and am going to refit. If it boosts to infinity again i will not be held responsible for my actions!!

First of all remove the restrictor thing in photo 2. When you fit an aftermarket BC it should be fitted without anything else.

I don't have the instructions but I assume you should wind it in to get less boost? Is that right? You said you wound it out. Since you have a massive spike. Remove the ball and spring and retry, see what happens. You should get much lower boost. You may not be able to increase it as far as you want, thats all. To be honest, Im not surprised you are having trouble with this. I gave up making my own and using these "homemade" type controllers as the commercial types work well and cost bugger all.