View Full Version : Pierburg Valve
Alfa Patch
13-08-12, 21:38
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......
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
13-08-12, 23:14
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?
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.
Boost still drops off...can't be sure of the exact behaviour without driving mine and making a mental note.
wrinx
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They have been largely superseded by a similar type which only has two legs, known by a few names I simply call it 'ball & spring' type.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.
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.
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-CONTROL-BLEED-VALVE-TURBO-SOLENOID-CONTROLLER-/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
14-08-12, 21:58
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/viewitem?itemId=230547141761&index=5&nav=SEARCH&nid=86127786605
Has what I want but is almost certainly Chinese crap. I'm not sure this is an area I should be cutting costs?
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-CONTROL-BLEED-VALVE-TURBO-SOLENOID-CONTROLLER-/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.
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
16-08-12, 11:09
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!!
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
16-08-12, 17:01
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!!!
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
17-08-12, 14:46
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
21-08-12, 20:58
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.
Have you tried winding the controller the other way?
wrinx
Another thought...it is connected the right way around???
wrinx
Alfa Patch
21-08-12, 22:16
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.
What boost controller do you have? Take some photos of the setup.
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
22-08-12, 20:54
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!! :mad:
Alfa Patch
22-08-12, 21:30
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.
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!! :mad:
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.
That looks to be the same as I have. I think you wind it in for more boost (compressing the ball and spring.
That restrictor is a Q4 part which has was connected with the original pier-burg.
Where in Surrey are you?
Alfa Patch
23-08-12, 14:38
That looks to be the same as I have. I think you wind it in for more boost (compressing the ball and spring.
That restrictor is a Q4 part which has was connected with the original pier-burg.
Where in Surrey are you?
I am based in Ham near Richmond and work in Esher.
The instructions say that the more i wind the screw in the more the boost will rise. I suppose its worth a go without the ball and spring before i just chuck it in the bin.
I have tried it with and without the restrictor and it honestly makes no difference.
Getting gradually more frustrated with burning myself making adjustments!!
Damn...a bugger of a journey away to have a look :(
I would wind it in and see how you go.
At least the car works well otherwise...I assume :)
Alfa Patch
24-08-12, 19:51
The car is running pretty well. I have an air / fuel gauge which i am waiting to fit the sensor on so i can double check fuelling is reasonable.
I have now removed the 'controller' again as i need to use the car and am much happier with a consistently safe (albeit slightly slower) car rather than a ticking time bomb that i can't relax whilst driving.
Does EVERYONE see their boost dropping off at higher rpm? Is this simply a case of the turbo being too small to maintain the pressure?
I guess that a manual bleed style controller will always suffer with drop off as the ammount of air to be bled at different rpm's would change? Is this something that electronic controllers eliminate using solenoids?
I have zero experience of turbo cars so am probably asking a lot of schoolboy questions :)
Patch
I do find that the boost on mine will hit about 1.2 and then trail off to about 0.9.
So damn hard to test around here as you end up going pretty quick once you keep your foot down!
Steve Webb
25-08-12, 07:26
Yep thats about the same as mine, the overboost function (Pierburg valve) is only designed and programmed to allow over the 0.7 base boost for a short time before closing.
However with an MBC that Patch and I have it should maintain a contant pressure.
Alfa Patch
25-08-12, 10:05
Constant boost pressure makes such a difference to the way the car drives. Even with lower boost the more linear power makes it much more confidence inspiring and easier to push to the limit.
Can actuators be changed for ones which allow higher boost? I'm not convinced by these bleed controllers, they do seem to adversely affect high rpm performance.
Does anyone get constant boost? If so how? Unless the turbo is not able to pump enough air at high engine rpm to maintain the boost level surely its possible.
Alfa Patch
25-08-12, 10:11
With regards to testing I certainly know what you mean. My boost gauge is where the stereo was so I have to drive with my foot flat to the floor whilst staring at the passenger footwell!! It's incredibly unnerving.
I have found that 5th motorway driving is the best way to get an accurate idea of what boost levels are but needs to be done at night as speeds are so high. My drivers windscreen wiper decided it couldn't deal with the wind speed at 135 mph last night and left me blind for the drive home. I'm not sure if the police will accept "trying to get an accurate boost pressure reading" as a valid reason for such speeds but it would be the truth.
Steve Webb
25-08-12, 10:53
I have found that 5th motorway driving is the best way to get an accurate idea of what boost levels are but needs to be done at night as speeds are so high. My drivers windscreen wiper decided it couldn't deal with the wind speed at 135 mph last night and left me blind for the drive home. I'm not sure if the police will accept "trying to get an accurate boost pressure reading" as a valid reason for such speeds but it would be the truth.
On a private test track of course. :thumbsup:
Alfa Patch
25-08-12, 11:20
On a private test track of course. :thumbsup:
Of course ;) The A3 is private right? I don't actually advocate such speeds generally but sometimes a mans gotta do what a mans gotta do.
This is interesting:
http://miataturbo.wikidot.com/boost-control
Any thoughts? Probably worth trying.
I'm going to try it too....unless anyone can suggest a reason not to?
the wombat
27-08-12, 17:35
Interested to hear the result. Makes a lot of sense. Very interesting thread.
Mine is running the standard pieburg valve with a hybrid turbo and I am seeing the same tail off in boost.
The evitable question - for what reason is it not like this from factory? Probably safer for longevity of the engine.
Alfa Patch
27-08-12, 21:02
Couple of updates.
Firstly i got bored of standard boost and thought i'd have a go with the 'controller' again.
I decided that it must be boosting too much due to too higher pressure on the ball from the spring but i couldn't release any of this pressure as it was wound out as far as it could go.
I considered shortening the spring but didn't want the edge getting trapped on anything so i destroyed a load of perfectly good ballpoint pens instead....
In the picture you can see the controllers spring on the left and 3 others from the pens moving towards the right. I opted for the one on the far right as it was the shortest and had a sort of trumpet to sit the ball bearing in. This particular spring is from a parker ballpoint if anyone else ever has similar problems.
With the new spring in the controller and the controller itself back in i went for a cautious drive. Hurrah i was seeing about 0.7 bar of boost!!!!
I am slowly winding the boost up but am experiencing boost drop off at rpm as everyone else seems to as well.....
Alfa Patch
27-08-12, 21:16
Secondly i thought I'd have a go at copying the MX5 thread i posted on here.
I removed the hose going to the idle control valve and connected in a barbed connector from a kart fuel tank. (Pic 1 + 2)
Then i blanked the original turbine 'actuator outlet' and spun the boost controller round so i could connect it to its new feed. (Pic 3)
I went for another run and somewhat disappointingly still experienced boost drop as rpm rose.
Now i appreciate that this is hardly a fair test, i know my car has various small boost leaks and the way that i connected the new 'actuator outlet' was probably leaking a bit too but i had still expected better results.
Really someone needs to take the plunge and do it properly, preferably someone who has a solid base car. Mine still has too many unknowns to prove or disprove this.
Whats still bothering me is that we have people on here with monster engines (300+bhp), surely they aren't running around with boost drop? How are they getting around it? It's such a simple principle that the answer can't be too complicated......can it?
There are many cars with the boost reference taken after the intercooler as standard. T
This is only really necessary when the intercooler is a restriction. Most intercoolers are designed not be restrictive over their intended use. However when we operate them outside their intended use (more boost/RPM) it may create a larger pressure drop which will cause boost to drop. The question then is should I really be upgradng the intercooler rather than boosting higher to overcome the restriction.
This problem is nothing new, people with 300hp do experence boost drop off. You can spend a lot of money of electronic boost controllers, manifolds and wastegates to get this right. I know it is bloody anoying but that is how it is.
The problem is the mechanical limitations of the wastegate and the efficiency of the turbo. If you get that sorted you wont have a problem. It is very difficult for the internal wastegate to accurately control the boost if the turbo is operated in an inefficient zone. An external wastegate will usually solve the problem.
Likewise, a larger or more efficient turbo for your application will be easier to control with a basic internal wastegate.
JimN's car was running an eBay Chinese turbo with a new IC and he could maintain about 1.45 boost on the track all day long. Was very impressive.
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.
I know about the myths, I read the internet and your posts - like the one where you thought that a Coupe runs 12psi of boost (it's 15) and that you'd gained power by replacing the 15psi chip with another 15psi chip.
Not all B & S valves have holes in them, if they do you can block it off and it doesn't make any difference to the boost pressure, I know because I've done it.
They definitely do not bleed off boost.
A full explanation here: http://autospeed.com/cms/title_Thirty-Dollar-Boost-Control/A_2687/article.html
That article clearly states it needs a small hole in the valve body they call an "excess pressure valve". Call it what you like, that hole is bleeding off air (the excess pressure) as soon as the ball moves off the seat. Can you not see that?
Sure, without that bleed the boost will still increase untill the ball moves off the seat, opening the WG at that point. However in that state, the chamber will eventually fill with boosted air until the pressure has equilised on both sides of the ball and seat. That "excess pressure vale" needs to start removing that pressure or the wastegate will continue to open further. Without that bleed the valve is not controling anything.
Afterall the only way to accurately hold the WG in a desired position (i.e. to control boost) is to REGULATE the pressure to it. A ball and spring only can't do that, it can only turn it on or off.
I agree this is different to a "gated" boost controller that uses the ball and spring just as a gate. i.e. its is not adjustable. These need an adjustable bleed hole to set the desired boost pressure. The principle is still the same.
Ok, lets talk about one thing at a time, forget the rest:
That article clearly states it needs a small hole in the valve body they call an "excess pressure valve". Call it what you like, that hole is bleeding off air (the excess pressure) as soon as the ball moves off the seat. Can you not see that?
No it isn't. It clearly states:
A small hole in the valve body (called an "excess pressure valve") allows pressurised air to escape from between the controller and wastegate actuator following a boost event. This pressurised air would otherwise be trapped against the wastegate actuator and cause poor boost response.
It is NOT using that hole to control the boost.
I'll type it out again because you must think I'm lying or something:
I put plasticine over this little hole and went for a drive, it did not effect the boost pressure.
There wasn't enough pressure to even blow the plasticine out of the hole or off the valve yet the car is running at 1.5 bar.
If it was using this hole to control the boost how did that happen?
Isn't boost drop off perfectly normal...caused by the exhaust output dropping off as the engine's speed plateaus and can't maintain the required output...or am I simplifying things too much?
wrinx
Edit: just read the Miata article so the above is redundant :roll:
Ok, lets talk about one thing at a time, forget the rest:
No it isn't. It clearly states:
A small hole in the valve body (called an "excess pressure valve") allows pressurised air to escape from between the controller and wastegate actuator following a boost event. This pressurised air would otherwise be trapped against the wastegate actuator and cause poor boost response.
It is NOT using that hole to control the boost.
I'll type it out again because you must think I'm lying or something:
I put plasticine over this little hole and went for a drive, it did not effect the boost pressure.
There wasn't enough pressure to even blow the plasticine out of the hole or off the valve yet the car is running at 1.5 bar.
If it was using this hole to control the boost how did that happen?
I don’t know mate, a leak? Or maybe the same reason why you didn't also suffer "poor boost response" which they say will happen if you don't have the hole. And there leys the whole point IMO, poor boost response.
Evodelta, I'm not here to argue, if you want to believe what's written in that article as gospel, go ahead. For anyone else that is willing to look at it from first principles, rather than an autospeed salesman, it's obvious how it really works. This is what I know; take what you want from it.
These so called boost controllers are not an innovative new technology or anything. They are nothing more than very crude air pressure regulators. A pressure regulator in its most simple form is just a variable restrictor that is controlled by a set load (spring).
http://en.wikipedia.org/wiki/Pressure_regulator
As I have said earlier if you add a restrictor in front of a bleed valve, less air will need to be bled off. Make the restrictor very restrictive and the air bled from the system can be so low, it is negligible. It is also possible to adjust the boost pressure by adjusting the restrictor, not the bleed. These boost controllers work exactly like this with only one difference, as the restrictor is variable (it's a pressure regulator), it has the ability to be totally closed too.
You can use a pressure regulator (without a bleed) as a boost controller if you like. I have used commercial types (Festo) and they work well in some situations, e.g. to regulate the pressure to the top chamber on an external wastegate.
Pressure regulators on their own are not however very suitable as traditional boost controllers as they are intended to be used where air is continuously flowing through them. They "add" only enough air to match any loads (actuators etc) that use the air. As soon as the air flow stops (full chamber), they shut and then cannot regulate the pressure anymore. Whatever pressure remains will be there forever. Now that’s fine at that point where you reach desired boost but the valve then closes and becomes irrelevant and is doing nothing. That’s not really ideal. This is why they should incorporate a small bleed also. The small bleed (load) will enable air to flow through the system and let the pressure regulator work as intended, maintaining the pressure in the chamber. And under this regime, they are working like a traditional restrictor and bleed, only the restrictor is variable.
Using a pressure regulator as a boost controller may seem like a good idea but I don't believe it is. All engines have different dynamics so the effect will different but a set pressure to the wastegate may not necessarily give better boost control. A system that allows for variable pressure is of course going to be best.
Alfa Patch
31-08-12, 12:49
It seems odd to me that boost drop off is accepted as 'just one of those things'. Surely bhp figures would be seriously improved by maintaining maximum boost up until redline? This has gotta be one of the first things you would sort on a turbo engine? Why bother even raising the boost if you don't already have what you should be getting at all rpm, are you not just stressing the engine at parts of its rev range where its never going to make max bhp anyway due to rpm being a big factor in the equation for bhp (i forget the exact equation)?
Is basically the only way around this to get a proper electronic controller? I am assuming that as they work with an electric solenoid they change the ammount of air they are bleeding off to maintain steady boost pressure at the inlet manifold regardless of rpm. If they work in the same way as an MBC and just bleed off a constant ammount of pressure they seem like a horrendous waste of money.
Steve - What you say regarding wastegates is interesting, i have read another post of yours where you describe the benefits of external ones and i am intrigued by it. Is the problem with internal that they are generally weaker? I guess that they are really only there to stop the turbo overboosting rather than maintain good boost levels. With this in mind I will seriously consider an external 'gate when it comes time to replace the manifold.
Patch
It seems odd to me that boost drop off is accepted as 'just one of those things'. Surely bhp figures would be seriously improved by maintaining maximum boost up until redline? This has gotta be one of the first things you would sort on a turbo engine? Why bother even raising the boost if you don't already have what you should be getting at all rpm, are you not just stressing the engine at parts of its rev range where its never going to make max bhp anyway due to rpm being a big factor in the equation for bhp (i forget the exact equation)?
Is basically the only way around this to get a proper electronic controller? I am assuming that as they work with an electric solenoid they change the ammount of air they are bleeding off to maintain steady boost pressure at the inlet manifold regardless of rpm. If they work in the same way as an MBC and just bleed off a constant ammount of pressure they seem like a horrendous waste of money.
Steve - What you say regarding wastegates is interesting, i have read another post of yours where you describe the benefits of external ones and i am intrigued by it. Is the problem with internal that they are generally weaker? I guess that they are really only there to stop the turbo overboosting rather than maintain good boost levels. With this in mind I will seriously consider an external 'gate when it comes time to replace the manifold.
Patch
I agree with your first paragraph, stopping boost dropping off is very important if you are looking for maximum performance.
To give the engineers some credit most cars from the factory hold relatively stable boost. And where they don't, if you didn't have a boost gauge you probably would not notice. Maximum boost at redline for max power is not usually the most important factor for a road car. They are usually tuned with smaller than optimum turbos for obvious reasons.
Usually it's only when we modify, operate them outside of their intended window where we usually see this problem at its worst. And that there is most of the problem. Fit a larger turbo suitable for boost and flow at higher rpm and a basic internal wastegate will probably do the job fine. Likewise fit a really good wastegate and problems are usually solved. Internal wastegates really only have limited effect. They are OK at working over a small window. External wastegates are far more precise and are able to work over a much larger window.
All my European cars have tended to drop boost at higher RPM but it is also common for the boost to rise unwanted. Japanese cars were bad for this, Subarus and Mazdas I recall would hit the boost cut with some minor modifications.
I have tried electronic boost controllers on cars where boost is falling off and they can’t always solve this problem. Some more expensive, highly tuneable controllers possibly could. But the run of the mill ones can’t. Even though they work on a closed loop, the trimming available is not fine tuned for your engine. The trim given may not be enough. They will be conservatively programmed this way to avoid wild fluctuations on other cars that don’t need so much trimming. I know on my car, as the boost dropped off the controller would have a go and bringing it back up, but it was too slow to be effective before I needed to change gear and boost control was “wavy”. Some controllers say they can self tune. I’m yet to see that work effectively. Fitting an aftermarket wastegate however usually has a dramatic effect. Any reduction in boost will move the wastegate and as these wastegates are designed well, should change the flow through the wastegate. The problem with an internal wastegate is a small movement in the gate may have little effect.
Internal wastegates are pretty crude. They don’t flow well. They operate like a swing door, not like a valve. Their flow rate vs opening is not going to be a nice shape so accurately controlling flow with that sort of valve is difficult to start with. And to control the valve, we usually get a small diaphragm with a week spring, mounted on a flimsy bracket. An external wastegate attends to all these problems. Flow well, large powerful diaphragm etc. Also if you want to use a boost controller with one, you don’t need to significantly change the pressure to the diaphragm. The underside just gets a boost line to open the valve, like a normal actuator. The valve will not creep so it does not need to be interrupted with ball and spring valves or manipulated with bleed valves to raise the boost. To raise the boost, you need only add a few psi of pressure to the other side of the diaphragm, effectively increasing the spring pressure. More boost is then required to open the valve.
Sorry if I repeat something discussed before.
I think you miss some of the advantages of the Pierburg valve. Lancia was just the first car to use the concept, now all new turbo cars does. As a turbo's waste gate has the turbo pressure working against a spring there are always an amount of leakage through the waste gate, even from very low rpm. Now the waste gate is kept closed by the spring pressure, the boost from the manifold will work against the spring and open the waste gate at the adjusted boost. The Pierburg is a 3 way solenoid one of the first 2 legs can be open to the 3rd. Pressure tapped from the turbo outlet goes through the open channel of the Pierburg and help the spring of the wastegate to keep it closed. Now there are no leakage and have a little boost pressure, way lower than before. When the planned boost is reached the ECU switch the Pierburg's solenoid, the channels change and now the boost from the manifold work against the spring to open the waste gate, keeping the boost pressure at the planned level. This gives a much more linear power supply without the huge shove in the back at 3500 rpm and it is much more usable on a track. The waste gate actuator used with the Pierburg, then will have a tube on either side of the actuator's diaphragm. I am not the electronic expert but the ECU do not just open and close the Pierburg but rather pulse it to open or close the channels a little. This stops the solenoid from chattering, due to open an closing on the boost limit.
An external waste gate have a larger diaphragm and the spring is then stronger to counter the larger force the pressure now supply. The larger spring allow less leakage and the control of a boost controller will be more accurate.
The only possible advantage to go without the Pierburg is to have less power below 3000 rpm, saving fuel in town.
The bleed valve is the crudest form of boost control and are only work satisfactory in some cases where the waste gate is set to a lower everyday setting and by opening the bleed valve the pressure will go to a higher boost pressure before the waste gate are opened.
Thanks, very interesting.
Trouble is, I think a lot of the Peirburg valves are faulty and it's cheaper to remove and install a MBC....plus finding them in the UK was/is hard.
I know one ex-owner had to buy one from the States but the car was reported not to run well with it and a subsequent owner took it off.
wrinx
Interesting. Thanks, and welcome to the forum. I remember contacing you a couple of years ago on AO.
I like the MBC as it is the simple way to get a higher initial boost pressure. Crude but easy.
Steve Webb
16-09-12, 08:22
Crude but easy.
Just how I like my women.
I'll get my coat, I've nothing more to add here.
Well...that was a thread stopper :lol:
wrinx
Steve Webb
16-09-12, 20:31
Sometimes I worry that the forum is just too highbrow. Or maybe its just that I'm too childish!
Trouble is, I think a lot of the Peirburg valves are faulty and it's cheaper to remove and install a MBC....plus finding them in the UK was/is hard.
The Pierburg is not the only solenoid that can perform this function. You could use the equivalent part used by VW/Audi or by Focus ST. According to the tuner I use, the VW part is popular and freely available.
Interesting...do you have a link?
wrinx
Unfortunately not at this stage
Found this:
http://www.jbubu.com/index.php?id=36700
My Pierburg seems to work fine but I have a MAC valve to use inplace as suggested by Xavier. This is a common solenoid used with many electronic boost controllers, mine is from a Gizzmo IBC. Once installed I have the option to control it like a Pierburg valve or off the Gizzmo IBC too.
http://www.lanciahf.eu/
http://www.lanciahf.eu/images/solenoid%20mac/solenoid_new.jpg
Alfa Patch
18-09-12, 13:32
There are two Q4 Pierburgs on German Ebay. I was tempted to get one but there seem to be mixed opinions on how effective they are. Having never had one on my car i can't comment but if they work well i can't see why you'd waste cash on EBCs.
The difference is controllability; with an EBC you can change the boost characteristics whereas you're stuck with the factory settings with a PV...unless you go for a remap of course. but even then, the settings are static.
The argument about whether the controllability is good for the engine is another matter...
wrinx
http://www.ebay.com/itm/MERCEDES-W123-VACUUM-VALVE-DEPRESSION-SWITCH-/270542721857?pt=Motors_Car_Truck_Parts_Accessories&hash=item3efd9a5341&vxp=mtr
http://www.ebay.com/itm/Mercedes-Benz-W116-W114-280-450-300-Fuel-pump-valve-Pierburg-M115-M110-M117-New-/221115944029?pt=Vintage_Car_Truck_Parts_Accessorie s&hash=item337b898c5d&vxp=mtr
Steve Webb
18-09-12, 20:26
Can't see the number of the one in the first link, but the one in the second link is a different part number to the one fitted to the Q4.
Worth a try though for that price.
I moved the inlet pipe for the boost controller today and put in a t-piece at the small bore plastic pipe which runs up the side of the battery and round the back to the inlet manifold.
As a result I seems to have a lot more stable boost pressure - I put my foot down from 50 to 90 and 1 bar all the way. I will need to do more testing on the airfield but so far I am impressed at the lack of drop off.
I won't go too nuts until I have an EGR gauge installed as I remember a problem a while ago of the engine feeling like it was hesitating when at prolonged full pelt.
Got many other issues to address though - this cars just loves to weep oil from everywhere!
Where was it spliced in before?
Mine is the same area as yours now, but I'm not sure which run it cuts into.
wrinx
Alfa Patch
07-10-12, 12:17
I fitted an old HKS electronic controller bought from ebay to my car on thursday, haven't had chance to configure it properly yet but it holds boost much better in it's 'manual mode' than the MBC i had did. It remains to be seen how ggod it is once it has 'learnt' the turbos characteristics but it seems like it was money well spent.
I moved the inlet pipe for the boost controller today and put in a t-piece at the small bore plastic pipe which runs up the side of the battery and round the back to the inlet manifold.
Thats the feed for the BOV isn't it? Will that create a problem for the turbo 'overspinning' when you close the throttle as the MBC will be seeing a vacuum? It probably won't as i assume there will be minimal exhast gas going to the compressor (so it won't spin that fast) but if i'm right the wastegate will remain firmly shut. Reading this back again god knows!! Sundays aren't my most switched on of days :)
Thats the feed for the BOV isn't it? Will that create a problem for the turbo 'overspinning' when you close the throttle as the MBC will be seeing a vacuum? It probably won't as i assume there will be minimal exhast gas going to the compressor (so it won't spin that fast) but if i'm right the wastegate will remain firmly shut. Reading this back again god knows!! Sundays aren't my most switched on of days :)
:wacko: Nope, i'm not sure either. Seems OK though. That pipe is connected to the inlet directly so it simply sees the boost pressure from the last point possible - i.e way after the IC.
Wrinx, before the feed in to the MBC was straight off the connection on the turbo housing. That has now been blocked off.
Alfa Patch
07-10-12, 23:18
Sounds like a very neat fix if it works though. The ebc I bought has 4 ports.
1. To wastegate actuator
2. To turbo boost feed as original
3. To inlet manifold
4. To nothing. I think this is where the solenoid vents the pressure.
It seems to work by reading the boost at the inlet through .3 and then trying to match it by adjusting the flow of boost from .2 to .1 using an electronic solenoid.
You have to wonder why the pressure feed isn't usually taken from inlet since that's the pressure we are trying to maintain and are reading from. It might be something to do with closed throttle behavior but i can't think what.
Fit a larger turbo suitable for boost and flow at higher rpm and a basic internal wastegate will probably do the job fine.
Internal wastegates are pretty crude. They don’t flow well.
My opinion is the pressure drop at high revs is a function of boost leaks or the turbo is to small and can not deliver more air than the engine takes away. Fiat designed their turbo/engine combinations too get drop off at high rpm t protect the engine. Lancia's T3 should stay closer to the ideal but may not be perfect.
Steven is quite correct about the air flow through an internal wastegate turbo. A T3 with an external wastegate can deliver 25/30% more air than a T3 with an internal wastegate. The reason is with an external waste gate the exhaust gas run through a pipe with no obstructions through the down pipe into the exhaust. With an internal wastegate the gasses that are bled off mix with the gas flowing from the turbine in a non structured space. The turbulance cause much less gas to get out of the turbo and the pressure is higher at the outlet side than in the case of an external waste gate turbo. Then turbine wheel can not speed up more because it is turned by flow of gas and gas only flow from a higher pressure to a lower pressure.
For the same reason the down pipe is important, it must get the gas out of the turbo pronto. On high performance engines this is even more important, because hot gas that can not get out of the turbo, keep more hot gas in the engine. The combustion chamber temperature rise and the potential for detonation increase many times. A good down pipe and exhaust is very important.
On standard engines a turbo with an internal wastegate functions perfectly, the amount of gas coming out of the turbo is not more than the outlet of the turbo can allow.
The hole in the Pierburg do not leak boost it, only leak a little air in the system that open the wastegate against a spring. If it do not, then like an earlier poster said, there can be not wastegate adjustments.
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