Perth-WRX.com - What Boost Controller To Go For?

I think this may well change your mind....
One of the most interesting threads on boost control in quite a while...

[url]http://www.mrtrally.com.au/forums/topic.asp?TOPIC_ID=19839[/url]

I'll add my 2c worth in here, (it's not worth much as I really have no idea what I'm talking about!).

2 port versus a 3 port.

You know the differences in how they acheive boost control I assume, and I will make that assumption.

In my opinion the difference between the two will be seen in a couple of areas depending on a few variables.

Variables
i) Turbo size
ii) Boost threshold
iii) Boost targets
iv) Overall engine gas flow (intake, header / exhaust manifold, turbo and exhaust)
v) Pre turbo exhaust gas pressure
vi) Wastegate acutator tension
vii) Restrictor sizing (if any is used)

That's a pretty simplistic list mind you.

Now given a smaller turbo with a low boost threshold and low boost targets (ie where they are actuall acheviable by the turbo and flow characteristics of the engine and support modifications) either a 2 port or a 3 port will do pretty much the same job.

Take the above with higher boost targets where the smaller turbo can't really achieve those high boost targets in the higher rev range. The 2 port will suffer as it will not be able to 'bleed' away enough pressure from the actuator as the 3 port. But in saying that in reality the turbo is working way too hard to try and achieve those boost targets and may well be outside of efficiency ranges.

Lets move to a larger turbo, higher boost threshold, good flow. Depending on the actuator tension, the 2 port may not be able to bring boost on as quickly as it really has no way of completely taking all pressure away from the wastegate actuator, yes it will take most of it but not all. The 3 port can effectively be made to present zero pressure to the wastegate actuator. So the 3 port may well be able to bring on boost a little quicker. Depending on what is controlling it however the 3 port may induce a larger boost spike than the 2 port and potentially the onset of boost target oscillation.

Once we get up to the higher boost targets that larger turbos are efficient at, the difference in the two solenoids really won't come into it that much. The turbo is not having to be worked hard to keep boost targets. But if you start pushing the turbo again, or you have some flow problems the 3 port will be better suited to controlling the boost with it's on or off technique.

Pre-turbine pressure will come into play as it can effectively blow the wastegate off of it's seat and then you'll have big problems with boost control regardless of the solenoid you are using...

Restrictor sizing will help the way initial control of the boost is done, it can restrict the initial amount of air coming through to allow the solenoids to better control the onset of boost.

Now the difference in solenoid control, as in reality if you've chosen your modifications and turbo sizing and boost targets correctly the solenoid shouldn't hamper you that much in the grand scheme of things.

As you know boost control requires, a target, a pressure reference, a starting reference, and a sensitivity or feedback speed setting. It then comes down to two main things;

i) How good a job the programmer did at taking those variables and giving a feedback to the solenoid
ii) How well the person tuning it understands how the programmer set things up.

For the layman a fuzzy-logic controller is relied upon to do the job with minimal input and understanding from the layman, ie you set you targets, you pick a feedback / sensitivity and initial setting and go, the controller will then through a set of procedures determine the best base settings to achieve consistant boost control.

For a expert (term used loosly), they can take a controller that does not have all those fancy self calibrating / changing functions and do the same thing over a period of time.

So what am I saying with all this waffle?

i) A 3 port or 2 port solenoid will work equally well when combined with a correct state of modification.
ii) A 3 port will be able to do a better job when you are trying to make your combination of modifications work outside of it's optimum.
iii) A fuzzy-logic controller is better for quick settings but the same can be attained from a more rudimentary control system with time and experience.

I know this is not really ECUTek versus a fuzzy-logic argument, but you can take it that way if you understand where I am coming from.

Cheers
Brett (Not B Middleton)

=================

So after all that, use a decent aftermarket ECU only and get this 3-Port Mac Solenoid cheaply and get your tuner to do it properly the first time using the ECU for boost control.

MAC DDBA-1BA
0.17 Cv 1/8" 35 D CT

Plus 3 nipples
01027-02
[url]http://www.pneumatics.com.au/contact.htm[/url]
about $75 in GST.
J