I have been told that you can fine tune the Tial 46mm Wastegate with various spring rates to regulate the minimum amount of boost?

What advantages would there be to regulating the minimum amount of boost?

 

If you only wanted to run one boost level, you could select springs for that boost level and not need to worry about any sort of external boost control. Much simpler system relying purely on the mechanics, no vacuum input needed.

 

How would regulating the minimum amount of boost be benificial?

If you used a spring that set the minimum boost level at say .9 bar would this equate to instant .9 bar of boost as soon as the turbo spools up?

 

Aside from the reason I just listed, a boost controller's capability to regulate boost pressure is based upon many things including but not limited to:

1) How quickly your solenoid can open and close (or how quickly your bleed valve can vent pressure)
2) How much pressure needs to be vented.

If you think about what you are doing with a boost controller (essentially tricking the wastegate into staying closed in order to build more boost), the less pressure that needs to be vented, the better able the boost controller will be at doing its job - regulating the pressure. It shouldn't have much, if any impact on spool time.
And no, your turbo does not instantly build pressure equal to that of your wastegate spring by relying solely on the spring for boost control. The rate of pressure build up is determined by how fast the turbine is being pushed by the exhaust gases. The wastegate limits the maximum speed of the turbine by venting exhaust gases around it. The wastegate opens when it receives a vacuum input from the intake tract that exceeds the rated pressure of the springs. With age, the springs weaken, which is why older stock wastegates open earlier than they should.

What this also means is that the further spring pressure is away from the pressure you are using the boost controller to obtain, the less effective your boost controller will be at regulating that pressure. A spring that is much weaker than the pressure you are trying to run will naturally want to open, making it difficult to build the pressure you are trying to get. You want to run a spring pressure that isn't too far off from the pressure you intend to run, which is why it is beneficial to pay attention to the spring rating.

 

Paul, great explanation.
Based on me wanting to run between 1.1 and 1.3 bar, what would your recommended spring rate for my 46mm Tial be?
I am one of those people that prefers no external boost control and would rather rely on the mechanical setup. Less chances of human error.
Regards and thanks for your reply in advance.
Raj

 

Raj,
There are plenty of people that prefer the strictly mechanical boost control. It is so much simpler than running a boost controller and all of the associated problems that can bring with it. The trade off is that you will be unable to adjust your boost. Set and Forget. Some like the simplicity, others need adjustability.

Really, for the relatively mild pressures anyone here is running (no one into 2 Bar and beyond territory), the .8 bar spring will suffice just fine. If you want to run just 1.1 Bar, no more and no less, you can get a spring combination from Tial for 1.1 Bar and be done with it. Leave both ports on the wastegate open and plug the banjo bolt hole on your intercooler pipe.

PS - Love your car.

 

Personal preference –
Run the spring pressure at the lowest you will ever what to run your boost and then add a boost controller.

The spring alone will not give as quick an opening rate or as fast a reaction as a good controller.

I have the ability to run any boost pressure (over .8bar) due to the stand alone management system – this is very handy at the track, I can run a warm up pressure, running boost, qualifying boost and more important – wet boost level. Running 15+ boost is asking for it in the rain – not much fun!

As I understand it the Vitesse set ups support varying boost levels too – if you have a system that is not tuned to just one boost level then get a controller and the .8 bar spring.

Chris White

 

Thanks guys.
Paul/Chris, my plan was to pre-set a certain boost level, take the car to Cyntex and get it dynotuned for that boost level and call it a day. That is the way I prefer, much cleaner, no additional lines/hoses and less chances of me screwing things up.
I was thinking of running 1.1 bar as suggested or maybe 1.2 bar. I currently run 1 bar but since I have swapped my cam (Based on Jon Milledge's recommendation and my setup) I am looking at getting custom burnt chips anyway. I figured, I might as well take the opportunity and get a bit higher boost level. Ultimately I plan to go standalone but for now I think stock may have to suffice.
Once again, I greatly appreciate your responses.
Raj

 

Here is my experience with the 38mm Tial with a 1.1 bar (16 psi) spring. Before installing the WG, I bench tested it by applying pressure to the side port and carefully measuring how much pressure it took to open the WG valve. I found it first started to crack open at 17 psi, which is close the spring rating.

Then I installed it in the car and ran a line directly from the stock banjo bolt to the side port of the Tial, with no boost controller inline. This setup regulated the boost to a maximum of 14 psi, which is 2 psi below the spring rating. How can this be? I think the answer is that the pressure sent from the banjo bolt to the WG is higher than the actual intake manifold pressure where boost is measured. The difference is the pressure drop across the intercooler. When there is 14 psi boost in the manifold, there is at least 17 psi at the banjo bolt (before the intercooler), causing the WG to open.

Now I run a Reliaboost controller that regulates the boost to 18 psi max and that works fine (except that the turbo itself won't hold 18 psi to redline).

 

Keep in mind that there is pressure on the wastegate valve as well as the manifold pressure to the actuator. This will act to lower the threshold of the opening pressure.

Chris White