WRONG?

LOL, do tell me how I am wrong. It is you who is a bit confused, so I will jump in and correct you.

Do you understand how a wastegate actuator works? It will eventually open mechanically, when the backpressure in the exhaust housing(pre turbine wheel) sees more pressure than the wastegate spring, but trust me you don't want to wait that long. So, you feed manifold pressure(or boost pressure) TO the actuator. This will mechanically open the actuator as when it equalizes the manifold pressure to the spring pressure it will reach its cracking point(doesn't work out exactly, but it's close). How to raise boost then? Well you bleed off the manifold pressure signal to the wastegate to "trick it" into seeing less pressure thereby INCREASING boost. You can keep this solenoid open until the last possible second, then begin the regulation by diverting the bled off pressure to the actuator, which is how you can control "spool" if you will. You have effectively raised the "cracking point" of the actuator. The only way this work the way you are describing is if the static point of the actuator were keeping the wastegate OPEN at rest, and not closed.

An EXTERNAL WASTEGATE works close to the way you are describing. In that case it uses manifold pressure plus spring on the lower port to open the gate, and pressure on the upper port to close the gate and to help with regulation and RAISE boost pressure.

If the Porsche system works differently from almost all of the other actuated systems, please correct me with proof, not talk.

Now, there are some actuators that can regulate both spring side and top side, but the porsche doesn't use them.

Justin

 

Justinn is spot-on

 

This is correct. The ECU can only increase boost IF the wastegate wastegate spring holds....

The stock wastegate spring has trouble holding past 1.1 bar steady and will show up as weak boost build up, lower torque and a generally muddy feel.

I like Markski's idea of a 12 PSI (.8 BAR) spring

 

I had 1 bar actuators and upsolute flash for 1.2 bar but I flashed the car back with oem flash and at full throttle boost was indeed 1 bar.

 

Why is this so hard to understand? both external and internal W/G do the same damned thing! The spring is the boost that it will run with no intervention. YES some springs are weak and backpressure can push them open but that's not a design feature - it's a mistake! When the W/G diaphragm sees pressure from the intake it tries to open - when the pressure is high enough it DOES open and it bypasses exhaust around the turbo or in an external vents to atmo etc.

So how does it ever go higher than spring pressure? EASY! You put a bleed in the line that feeds the W/G diaphragm! You can use a fishtank bleeder, you can use a solenoid, you can do ALL sorts of things! Hell disconnect that line and it will gladly blow your motor as you free boost to the Moon!

Now Justin also mentioned another thing about some external W/G (dual port gates) and I guess some other may do it. Some good W/G will feed pressure from the intake to BOTH the top and bottom of the W/G. This keeps the gate closed even when the exhaust pressure is high - it won't just push open as easily. Then the solenoid bleeds from both top and bottom and allows the gate to open....

So duh Justinn is right, Ard you need to maybe listen to him here and perhaps tune one of these and you'll understand better.

 

kinda what we use... is is the way to go...

 

I understand fine. Thanks for your rambling about dual port wastegates and fishtank bleeders...all of which are not on topic.

 

NO actually it's RIGHT on topic. You seem to think that the W/G works exactly OPPOSITE of the way it does! When you bleed pressure from the line leading to the W/G from the intake - with a solenoid or bleeder valve like those used on FISH TANKS to control bubbler airflow - then boost goes UP not down as you seem to think. That's not topical?

Oh look, here's a company that makes mechanical W/G valve controls that even mentions fish tank valves while talking about why their valve is better at controlling boost. I could explain to you why a simple bleeder valve is a bad idea, I could even explain to you how other valves with springs and check valves work but I'm betting you're still not going to listen. <sigh>

Boost from the intake manifold opens the W/G by pressurizing a spring loaded can on the gate, bleeding that pressure off delays the opening so that you get higher than the standard W/G pressure. Lots and lots of ways of changing that pressure signal, OEM porsche (and GM among many many others) use solenoid valves. Multi port solenoids (GM uses them) can be used with dual port W/G so that pressure is applied to hold the gate closed until set boost and then switched to push it open when that pressure is reached. YES that's topical - that kind of gate is less prone to having the gate pushed open by volume of exhaust gas - you get much better control over pressure.