Quote:
Originally Posted by KarTek
There's just a light weight return spring in the wastegate that actually tried to open it. The Vacuum is what holds it closed and keeps boost up. You have to maintain the ECU controlled boost because when the car reaches highway speed and levels out, the ECU will release pressure on the wastegate to lower boost and back pressure for best economy.
If the ECU doesn't see the corresponding drop in boost pressure, you will get a code.
So, in short, you can't run a traditional bleed off type boost controller on this car.
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Ah I see, so the turbo is actually controlled via vacuum only rather than boost?
Seems quite an interesting way to control the turbo - would this setup work on a VNT/VGT turbo though as I always thought that the solenoid would be simply modulating the boost to the wastegate - might look into swapping out the actuator to be default closed rather than default open.
Is this the same setup as all of the other cars that use the K14 turbo or is it a Mercedes only actuator being used?
What would the code mean to the running of the rest of the engine? Would it need to see a drop in boost at the MAP sensor or would it simply be happy that the boost solenoid is still plugged in?
Edit:
Just reading up on this a bit more, I thought that all turbo actuators ran off boost rather than vacuum - lean something new everyday!
I guess it also means that its a bit easier to run a VNG/VGT turbo by simply plugging the stock vacuum line in as before.
With regards to the bleed manual boost controller, I can see how that now wouldn't work on this setup - might be able to use it on another part of the vacuum system though maybe on the MAP sensor or the vac line to the transducer.