13 replies to this topic

[Ghost-One]

boost controller
take alook at this

[CRXdan]

It says I need to buy it.

But anyways, heres some information Ive figured out with internal wastegates. Maybe this will be useful to some.

Shortening the wastegate to increase boost. Big no no, this puts tension on the wastegate arm. What youl get is called boost spike, the boost will raise to say 10 psi, then settle back to 7. This is because the shorter wastegate arm means the wastegate actuator is trying to open it at say 7 psi boost, but since its under tension, it stays closed and you get a spike.
Lengthening the wastegate to lower boost, this is ok, but youll lose your low end spool. Since the wastegate is now slightly open it takes longer for the turbo to spool. I dont even think it decreases your overall boost, just increases spool time (from my experience).
To increase boost on a internall WG turbo you can buy a brass shutoff valve from princess auto for $5. Run it inline with you wastegate hose and tighten the shutoff valve until you get desired boost level. Even turning the valve a small amount will drastically increase boost. Use with caution.
As far as lowering boost, you have 3 options:
1. More restrictive exhaust system
2. Port the wastegate opening
3. External Wastegate

If you try to lower boost any other way, youll get longer spool up time and the car will suck ass.
Now another option is to remove the Wg actuator all together and run a carb return spring from the flapper to some moutn on the turbo. I have found this also creates spikes, in fact i had spikes of to about 14 psi before it settled down to 5 psi. This is because the wastegate is allowed to open fully, whereas a WG actautor woudl let it open only so far.
So the lesson here, if you plan to run low boost and you find a turbo internally gates to say 8 psi, you may have problems. Raising the boost isnt a problem, but it takes alot of fine tuning to set it where you want. I woudl only use a shutoffvalve or restrictor to raise boost.
Another common problem is boost creep. This is when the boost raises with the RPMS. I had this problem with my turbo, it was creeping to 9 psi and I wanted to run 5. I ported out the wastegate a bit and it lowered it down to 7. Even a bit helps. Now ive raised the boost back up to 9 using the shutoff valve now that I have proper fuel managment.

Thats teh shutoff valev I used. I coudlnt find any small plastic valve so a big brass one for me
it looks purdy in the engine bay
It basically an on off valve but my finding a position somewhere in between you can lower the amount of air flowing through the WG hose, so the WG actuator actually thinks it sees less boost, therefore opengine the WG less.
A boost guage is a must, and never shut the valve off completley.

Edited by CRXdan, 26 October 2004 - 02:14 PM.

[Ghost-One]

what do you mean it says you need to buy it ... i like thi s thing

If you want an even higher initial peak boost value, simply T into the wastegate line a small sealed volume, such as a small aerosol can or the pictured camping water container. This will allow boost to flare a bit, as the can needs to fill with pressurised air before the wastegate starts to move. This can be a surprisingly effective modification - on one Charade Turbo, fitting just the over-boost can was enough to give wheelspin on every full throttle first-second gear change!

[DarkHand]

what do you mean it says you need to buy it

After the first three paragraphs I get:

"Click here for online access to the rest of this article"

And it takes me to a page trying to get me to subscribe

Edited by DarkHand, 26 October 2004 - 04:16 PM.

[Ghost-One]

This is the second of two turbo boost controls covered by AutoSpeed. The first is suitable for cars that use ECU-controlled boost. That control system gives very good throttle control, with boost rising with factory-style gentleness. But if you want boost to come on as hard as possible, or your car doesn't use ECU-controlled boost, this boost control is the one for you.

Over more than seven years and five different turbo cars the control has performed faultlessly. It's cheap, easy to install and costs less than A$75.
Factory Boost Control
Click for larger image

Cars without ECU-controlled boost use a very simple system. A hose from close to the turbo compressor's outlet feeds boost to a wastegate diaphragm. The diaphragm is connected by a rod to the wastegate, a valve that when open allows exhaust gas to bypass the turbine. On the other side of the diaphragm is a factory-set spring. Boost pressure travels down the short connecting hose, deflecting the diaphragm against the spring. If the factory wastegate canister is set up for 7 psi boost (which is typical of many Japanese cars), the diaphragm will be deflected so that the wastegate valve will bypass enough exhaust gas to hold boost at close to 7 psi. On the turbo shown here you can clearly see the hose connecting the turbo compressor outlet to the wastegate actuator.

The easiest way of getting maximum boost is to simply pull off this wastegate hose! That way, all the exhaust gas from the engine will pass through the turbine - none will be wasted. You can't get any more boost out of the turbo than that - but the peak boost pressure will almost certainly be too high. Too much boost results in detonation and broken pistons.... not what's wanted.

But if you remove just a little pressure from this hose, the wastegate won't open as far, more exhaust gas will pass through the turbine - and boost will be a bit higher.
Wastegate Bleeds

Any device that reduces pressure in the wastegate hose by letting air escape from it is called a bleed. However, it is very important to note that not all wastegate bleed systems work in the same way! This point is often overlooked.
Click for larger image

This diagram shows a typical wastegate bleed. A T-piece is inserted in the wastegate hose and air is bled out. One of the problems with taking this approach is that often a lot of air needs to be bled from the line before the wastegate actually sees a lower pressure. That's because there is an awful lot of air available from the turbo - bleeding off just a bit often makes little difference to the pressure seen by the wastegate actuator.
Click for larger image

The way to overcome this problem is to insert a restriction before the bleed, as has been done here. This way, the bleed needs to flow only a small amount of air to make a large difference to the pressure seen by the wastegate diaphragm. Introducing the restriction is fundamental to the way in which this system works. The insertion of the restrictor also adds a measure of wastegate delay - the wastegate doesn't start to open until all the hosing the other side of the restriction is filled with pressurised air.
Doing It
Click for larger image

That's the theory - what about the practice? You'll need two valves, one or two T-pieces, some quarter inch hose and some hose clamps. The main in-cabin (or under-bonnet) control valve is a quarter inch needle valve, which is the valve on the left in the picture. A needle valve is a multi-turn (often 5 or 8 turns) brass valve that gives fine control over flow. It's like a well-made tap. For the restriction, it's best to use a quarter inch ball valve (on right). A ball valve also allows adjustment of the flow through it, but it's a valve that either shuts off the flow or fully opens it with just a 90 degree turn. Both of those valves are available from companies than specialise in pneumatics and hydraulics - check your phone book. While you are at the valve supplier, pick up a quarter inch T-piece and some hose clamps. The only other part needed is a couple of metres of quarter inch fuel hose - you can easily work out exactly how much you need before you go to buy it.
Click for larger image

The system is organised as shown in the diagram. The location of the ball valve restriction, T-piece and needle valve are important - don't get their positions within the system confused. The ball valve (the restriction) is normally placed under the bonnet close to the turbo. The needle valve (the adjuster) can also be under the bonnet or if you wish, you can mount it inside the cabin.
Setting Up

* With the system connected, fully open the ball valve and fully shut the in-cabin needle valve. Drive the car and check the peak boost. It should be standard.

* Next, fully open the needle valve. Again drive the car - in most cars, boost should be standard or up only a little. However, be careful - boost might be raised at this point.

* With the needle valve fully open, close down the ball valve by a very small amount. Boost should now be lifted a little. Keep closing it down and test-driving until boost reaches your new maximum.

* With the needle valve fully open, the boost level should reach the new maximum. With it closed, boost should fall to standard. An "in between" setting of the needle valve should give an "in between" boost level.

* Put a dob of epoxy glue on the ball valve handle so that it can't be inadvertently knocked open or closed.

The Guinea Pig


We fitted this boost control to AutoSpeed's Project EXA. Before the system could be installed, the EXA's safety pressure relief valve on the plenum chamber was removed and a normal hardware store water pipe plug screwed in to replace it. The ball valve restriction was then mounted on the inner guard close to the turbo and the needle valve was placed at a convenient location on the dash.
Click for larger image

A comparison of the new and old boost curves is shown here. Note that the new boost curve falls in level as revs climb. This characteristic of the boost control system causes concern to some, but it has a major benefit. The control system has a built-in "scramble" or "over-boost" capability that allows the engine to pull a higher peak boost pressure for a short time. Most cars can tolerate a peak boost level higher in the mid-range than can be sustained at high revs. If desired, adjustment of the two valves can be used to dial out much of this drop-off, which also varies from car to car.


If you want an even higher initial peak boost value, simply T into the wastegate line a small sealed volume, such as a small aerosol can or the pictured camping water container. This will allow boost to flare a bit, as the can needs to fill with pressurised air before the wastegate starts to move. This can be a surprisingly effective modification - on one Charade Turbo, fitting just the over-boost can was enough to give wheelspin on every full throttle first-second gear change!

[eastsiderider]

Hey ghost, great article. Is there a way you could post the pictures from it as well?

[Ghost-One]

well apparently any quirk which allowed me to see the full article is no more i wonder why that is

[CRXdan]

Good article, but this higher initial peak value is called boost spike. Id much rather have peak boost at higher rpms, as when my ecu sees anything over 10 psi, it cuts. Also, spikes make driving the car very weird. It will pull hard for a certain amoutn of time, then when the boost falls of itll feel like a bucket.

[eastsiderider]

So one could suppose that this system would work well for an external wastegate as well?

[CRXdan]

Extenral wastegates use diferent springs i belive, but u could use this setup as well

[Grant Bailey]

I have been a long time subscriber to Autospeed. I think buying the article is worth it, they really don't cost very much. If you email me and beg, I might send you a pdf, but it had better be some pretty good begging since I paid to get it. Autospeed's articles are a little hit and miss, however. If I were a potential subscriber I would just look through the back articles and pick and choose. One thing I like about them is that they don't care who anybody is. If they think a car sucks they'll tell you straight up, some of their reviews are just brutal.

I had a buddy that built the more sophisticated controller they have instructions for on there, the one for cars with ECU boost control. It uses a regulator to determine overall boost pressure and a relief valve to determine boost rise. Really it's will work whether or not you have ecu boost control, and it's a neat system. Since what ultimately determines your boost pressure is what pressure the wastegate sees, the idea here is that the lower the regulator is turned, the higher boost will go in the engine. For an example, if the wastegate spring triggers at 4psi, set the regulator to 6psi. You could have 20psi coming in to the regulator and all the wastegate will ever see is 6psi. Obviously this takes some tuning to get right. The beauty part is the relief valve. If you set it to 10psi, the wastegate won't see anything until 10psi is reached and the valve pops. Then, the regulator takes over control of wastegate behavior. Read this article if you're curious.

The Audi's DIY Boost Control

Pretty standard off the shelf parts, it cost my friend less than $40 to make it. It was a great boost controller, gave a lot of flexibility. The only real problem with it was that you needed to be underhood to adjust it, which wasn't the best. What do you want though, it's made of pneumatic engineering parts. Sooner or later I will build one of these.

Grant

[eastsiderider]

Great find, very informative. I have been contemplating how I will be controlling my boost. I think I am going to end up going electronic, w/ a Greddy Profec Type-S. I will incorperate it in w/ the electronic wastegate acctuator. I will most likely end up doing a write up on it for thos that will be interested.

Here is a link so you can get the idea of the controller im speaking of....

eBay link

[xenocron]

I like my DIY 'Gus Mahon' style boost controller. I think it cost me roughly ~$10 in parts and works well. No creep, no spikes and consistant level every time.

http://www.gusmahon....oostcontrol.htm

Defies the 'you get what you pay for' saying this time around.

[Grant Bailey]

Cool, looks really simple. Maybe I'll try that one instead. I like the idea of two stage boost.

Grant