Boost controller - Bleed Valve

[roz85]

I was told to make a bleed valve u could do this. Just get a $5-10 adjustable valve and a t piece from a plumbing store and conect it in between the line going from the compressor wheel to the wastegate actuator. Stoktg seems to know what hes talking about though could someone go into a little more detail of what to buy, how to make it and how to fit it?

[Stoktg]

Dude. Its fucking easy. Seriously. Will take 3 minutes if that.

Turbos 101:
Ok, trying to make this as simple as possible - See that small black hose at the very front of the turbo? The one that goes to the gold coloured thing with a metal bar coming out of it that connects to a bit on the back of the turbo? Ok, thats the wastegate actuator.

Basically there is a little spring inside that needs about 6.66 pounds to push it open. When the turbo is coming on to boost, the pressure that is being pushed into the engine is also traveling through that hose which pushes against the spring forcing it open. This moves that metal bar and in turn opens the wastegate on the turbo. The wastegate lets some of the exhaust gasses bypass the exhaust wheel in the turbo and go straight into the exhaust. End result of this means less gas traveling through the turbo so it doesnt spin as fast and creates less boost. This is a good thing because a) without it, the turbo will spin faster and faster, creating too much boost and doing bad things to your motor and b) turbos have efficiency ratings. A piazza turbo is efficient to around about 14psi (someone correct me if i am wrong) after this the compressed air gets to hot and can lead to detonation as well as creating undue stress on the turbo. An intercooler will help bring down these air temperatures so if your running one like a stock piazza does then you might be able to squeeze a little more out of it. I can safely crank 14psi from mine with no intercooler 8:1 compression and a re-curved distributor.

Ok, like i said 6.66 pounds of pressure is needed to open the wastegate and once open the boost will stay at this level. If some of the pressure that is going through that tube to the actuator is leaking out into the atmosphere then it means you will need even more pressure to compensate for the loss. This extra pressure the turbo must create that's needed to open the wastegate, will also be forced into the motor. Thats how you can easily run more psi. The more pressure going to the actuator that you 'bleed off', the more pressure the turbo will create.

So to do this, once again you need a metal T-piece. $3 from any PLUMBING store. Look at the size of the tube going to the actuator and get a t-piece that is the right size for the tube. Cut the tube in half and insert the t-piece so one side is coming out of the turbo and the other side is going to the actuator. This leaves one spare place for a tube to be connected. At the plumbing store get a valve that can be easily adjustable all the way from completely off ie. no air can get through it, let a little bit of air through it, all the way through to let as much air as possible through it. Just about any valve will do, doesn't matter if its anodized pink with purple spots or shaped like a leper - you just dont want one that will move easily if its knocked.

The finer the thread on it, the easier it will be to adjust. If its one full turn to change the valve from completely open to completely closed, you will be needing to adjust it by turning it .5mm at at time. Probably far too sensitive to be practical. If the valve needs 10 turns to go from closed to open then you can adjust it in 1/2turn steps. Much easier.
Get another bit of hose, doesnt matter what, fuel hose etc, as long as its the right size to go from the T-piece to the valve. Have a secure way to mount the valve so its not going to fall off anywhere while driving (cable ties can be kinda dodgy but they will work). With a boost gauge, open the valve very slightly and take it for a drive, check what the boost is reaching. Keep opening the valve slowly until you get to the desired boost level. Listen for ANY sign of pinging from the motor. In technical terms, this will fuck it quick smart. To make sure its not pinging boot it up a steep hill in a high gear so the engine is under a lot of load. If you can hear it pinging then back the boost off a little.
That's it. Done. Finished. Adjustable boost for $10.

[Racegem]

Correct me if I'm wrong, I don't own a turbo'd car, but I'd start by taking it for a drive with the valve fully open, allowing factory standard boost, then slowly closing it to restrict the flow allowing more boost before the wastegate opens. Doing it the other way, starting with it shut, would not allow any boost to open the wastegate, causing the turbo to overboost.
Neat idea from a plumbers though, but don't knock autObarn!!

Yonnee.

[martin]

"doesn't matter if its anodized pink with purple spots or shaped like a leper"

HAHAHAHA

that made me laugh good explanation tho!

go read a book

[martin]

"doesn't matter if its anodized pink with purple spots or shaped like a leper"

HAHAHAHA

that made me laugh good explanation tho!

go read a book

[Stoktg]

Nah, i wasnt talking about having the valve plumbed in so it restricts the boost directly, The boost still has a clear path through the t-piece, the valve just vents off extra pressure in the line. When the valve is completely closed, you will have stock boost as no pressure can escape. Completely open will pretty much vent all the pressure that is in the line into the atmosphere and the wastegate probably wont open.
You can hook it up without the t-piece and just have a valve running in series in which case yes, when the valve is totally open then full pressure can get through, totaly closed no pressure will get through and the wastegate wont open but the benefit you receive with the first method is that it at lower rpm the pressure is easily vented so it takes much longer before the wastegate starts to be pushed open eliminating a lot of 'wastegate creep' ie. 3psi of pressure on a 6pound spring is still going to be pushing it open slightly. End result is boost coming in earlier and harder.
Make sense?

[Racegem]

Fully makes sense. )

I've only started researching turbos recently because at work we've only started stocking Turbosmart equipment, so to sell it, I've got to know a bit about it. Makes the salesman/person look stupid if he knows less than the customer.
Anyway, from my current, limited understanding, the only drawback from this set-up, as ingenious as it is, would be the restriction of the flow of the valve. Put simply, the physics of the pressure build-up in the line are still going to build-up enough to open the wastegate if the valve and lines don't flow enough.
I'll put it into context.
Let's say you've got a garden hose (the wastegate feed line). Your hose nozzle is the valve you've put in. A small split in the hose is the t-off to the wastegate. Now with your tap on half, and your nozzle fully open, you'll still get a leak or squirt at the split. Turning your tap up to 3/4 will increase the pressure relief at the nozzle but also increase the pressure at the split/leak. Now if 3/4 is the maximum the nozzle will flow, turning the tap on further will only increase the leak (pressure to the wastegate) Therefore, in theory, you wouldn't get as much maximum boost because if the valve was enough of a restriction at say 20 p.s.i., enough might get through to open the wastegate, never allowing more than the 20 p.s.i. of boost. Now while this is good in theory, in practice, the restriction might not actually be an issue, meaning that it might take 60 p.s.i. to have the restriction open the wastegate but without testing both setups on a dyno, who knows. I can see the benefits of both, with your set-up being good on the street, while the other (with, in theory, infinite boost), would be ideal for a race car where lower rpm is not so much an issue.
Any thoughts?

Yonnee.

[turbs]

The wastegate opening is a good thing!! When you have a turbo ie T3 that can pump out 35+psi you definetly want the waste gate to open so its not pumping that many pounds into your motor. There are not many gemi engines that will take that sort of boost and to build one that will is going to cost some serious dollars. When the turbo spins too fast (just like an engine on red line) bad things can start to happen. When you compress air it heats up. When the turbos trying to compress more air than its been designed to, then the air is going to get very hot. When your feeding your motor on hot compressed air, add some fuel then compess the air making it even hotter, it will be quite likely that its going to go diesel style and not wait around for a spark to ignite it. As you know, this is bad.

You want some of the pressure to be vented out so the wastegate takes longer to open, but definetly not all of it.
Keep it real.
keep your motor.

[Racegem]

Yes I realise this, but my querie was if the system that's being talked about only will boost to say 15 p.s.i. before opening the wastegate anyway, this would not be desireable in a motor that is built for more. About 10 years ago a guy I knew, by the name of Sam McKinnon, had, at the time, Australia's quickest 4 cyl. Gemini. A TC coupe with TE front, running a highly modified 1600 block with Sierra Cosworth pistons, water/methanol injection that ran 23 pound adjustable boost. In his case this system may not have produced the potential that it had if the wastegate opened too soon.

Clear as mud?

[roz85]

Now STOCKTG - seeing u know this so well, on to my next question. HOW DO U MAKE A BOV?????? I will go buy the parts tonight to make the bleed valve. Is there any way to make a BOV???

[Stoktg]

Why do you want a BOV? is it for the sound? They are gay. In my opinion the only worth while bov is silent plumb back style. Yes you can make them but sorry i cant be fucked telling you how although there not that hard and you can make them fairly cheeply, Do a search on the net for one. You can also buy them pretty cheep for about $70-80.

[Stoktg]

My valve is heaps bigger than the what the actuator has to work with so i dont think it would be too much of a problem and can always run a bigger line to it. Does what i need it to do and im happy, can send you a pic of it if you really want/care but if i was starting to run more serious boost then would probably be getting a modified actuator and have it done properly rather than a $10 backyard job on an expensive motor.

[roz85]

Come on man, let me know how to make a BOV! and yes i do want it for the sound though i dont want one too loud. The one on the piazza atm is a pop-off valve and u cant hear it, so can u tell me how to make one!

[roz85]

I DONT MEAN TO MAKE A FUK OF MYSELF, but i went and tried to get that t-pipe but i couldnt find it. I looked at bunnings and they didnt have any of that discription, so which hardware should i go to?

[Stoktg]

Go to a PLUMBING store. The word of the day is PLUMBING. Tell them you want a brass t-piece connector to connect 3 pieces of rubber hose together, im sure they will know what your talking about.
If its this hard to get adjustable boost sorted theres no point even getting started on the bovs. Like i said, do a search on the internet and find out how to make them. Im sure you will be able to find a site with pictures etc. Heres a start, took all of 4 seconds http://www.udnet.net/~pauls/bov.htm
Personally i wouldnt bother and would just buy one. Actually, i probably wouldnt even bother buying one.
Btw, pop off valve/blow off valve - same shit different name.