GoremanX
Veteran Member
Finally got my TDI-converted Audi A4 on the road this week, been nice to get it out of the garage after all this time!
Now I'm having issues with getting the actuator setup properly on the GTB1756VK. This is a push-type actuator sitting on top of the turbo. It supposedly came pre-set by the seller, but I've since clocked and modified the actuator setup so many times, everything's out-of-whack and nothing works as expected.
Keeping in mind that this is a slightly bored-out 2.0 litre BHW mounted longitudinally...
From the info I've been able to find, I should have the set screw adjusted so that running Basic Setting 011 shows a difference of about 80 to 120 mbar while the N75 is cycled from 9% to 90% duty cycle. That's not too difficult, I achieved that easily (0.987 to 1.09x mbar).
Then I guess I need to make sure the actuator rod starts moving around 3 to 5 in-hg and bottoms out on the set screw around 17 in-hg. I was able to manage 6 to 17 in-hg, but that's about it. This does mean the actuator is still pulling up on the VNT lever when no vacuum is applied (ie, the lever is locked fully open and preventing the rod from moving all the way back into the vacuum canister). I haven't checked recently what the rod's range of motion is, but I believe it's about 10mm in this setup.
So with the engine idling in neutral, if I goose the go-pedal, the engine revs up to about 3000rpm, the exhaust pressure spikes (15+ psi), there's barely any boost (like less than 5psi), and the engine stumbles and misfires until I let it idle for a few seconds. When I release the accelerator, the actuator suddenly goes back to wide open and there's a loud whoosh of escaping exhaust that sounds almost like a BOV.
The only way I've been able to make the engine drivable is to adjust the set screw until the difference during Basic Setting 011 is only about 30 mbar. Even then, I never see more than 5-10 psi of boost while driving, and the exhaust pressure is always 2 to 3 times more than the boost (no, I'm not exaggerating). Increasing the engine load too much causes the same exhaust pressure spike followed by a WHOOSH of the N75 suddenly dumping the backed up exhaust. So I'm essentially feathering the accelerator all the time and keeping my revs up to reduce the need for boost.
I know the turbo is spinning, I took the inlet pipe off while the engine is idling and there's some serious sucking going on in there... the good kind of sucking. I can practically spin the compressor wheel just by blowing on it with my lungs, it spins super freely and smooth. As long as I keep the engine load down, the engine runs nice and smooth. But exhaust pressure is ALWAYS high and boost is ALWAYS low. I also know my gauges for boost and exhaust pressure are accurate because I tested them with a MightyVac.
So what am I doing wrong?
Now I'm having issues with getting the actuator setup properly on the GTB1756VK. This is a push-type actuator sitting on top of the turbo. It supposedly came pre-set by the seller, but I've since clocked and modified the actuator setup so many times, everything's out-of-whack and nothing works as expected.
Keeping in mind that this is a slightly bored-out 2.0 litre BHW mounted longitudinally...
From the info I've been able to find, I should have the set screw adjusted so that running Basic Setting 011 shows a difference of about 80 to 120 mbar while the N75 is cycled from 9% to 90% duty cycle. That's not too difficult, I achieved that easily (0.987 to 1.09x mbar).
Then I guess I need to make sure the actuator rod starts moving around 3 to 5 in-hg and bottoms out on the set screw around 17 in-hg. I was able to manage 6 to 17 in-hg, but that's about it. This does mean the actuator is still pulling up on the VNT lever when no vacuum is applied (ie, the lever is locked fully open and preventing the rod from moving all the way back into the vacuum canister). I haven't checked recently what the rod's range of motion is, but I believe it's about 10mm in this setup.
So with the engine idling in neutral, if I goose the go-pedal, the engine revs up to about 3000rpm, the exhaust pressure spikes (15+ psi), there's barely any boost (like less than 5psi), and the engine stumbles and misfires until I let it idle for a few seconds. When I release the accelerator, the actuator suddenly goes back to wide open and there's a loud whoosh of escaping exhaust that sounds almost like a BOV.
The only way I've been able to make the engine drivable is to adjust the set screw until the difference during Basic Setting 011 is only about 30 mbar. Even then, I never see more than 5-10 psi of boost while driving, and the exhaust pressure is always 2 to 3 times more than the boost (no, I'm not exaggerating). Increasing the engine load too much causes the same exhaust pressure spike followed by a WHOOSH of the N75 suddenly dumping the backed up exhaust. So I'm essentially feathering the accelerator all the time and keeping my revs up to reduce the need for boost.
I know the turbo is spinning, I took the inlet pipe off while the engine is idling and there's some serious sucking going on in there... the good kind of sucking. I can practically spin the compressor wheel just by blowing on it with my lungs, it spins super freely and smooth. As long as I keep the engine load down, the engine runs nice and smooth. But exhaust pressure is ALWAYS high and boost is ALWAYS low. I also know my gauges for boost and exhaust pressure are accurate because I tested them with a MightyVac.
So what am I doing wrong?
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