Pierburg Valve

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.

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Originally Posted by SteveNZ

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.

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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_Thirt...7/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:

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Originally Posted by SteveNZ

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?

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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:

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Originally Posted by Evodelta

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?

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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.

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

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Originally Posted by Alfa 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

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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.

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Originally Posted by AlfaJack

Crude but easy.

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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

Sometimes I worry that the forum is just too highbrow. Or maybe its just that I'm too childish!

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Originally Posted by wrinx

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.

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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/soleno...lenoid_new.jpg

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-W12...9a5341&vxp=mtr

http://www.ebay.com/itm/Mercedes-Ben...898c5d&vxp=mtr

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

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.

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Originally Posted by AlfaJack

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.

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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 :)

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Originally Posted by Alfa Patch

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 :)

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: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.

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.

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Originally Posted by SteveNZ

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.

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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.