Turbocharger Response: Ibiza 6K, AFN Engine

Hello,

I used to have a Golf III with an AAZ engine and intercooler, among other things. The performance was perfectly fine, and the engine ran very well on gas (LPG).
Now I've bought an Ibiza 6K with the AFN engine and I'm disappointed.
At 1800 RPM, it immediately delivers a significant amount of torque, but when I'm cruising in third gear at 3000 RPM and suddenly accelerate, there's a noticeable delay. It feels like the turbo boost is building very hesitantly.

I took my car to a mechanic I trust, and he inspected the turbocharger and said it's a wastegate turbo. Could that be the case for an AFN engine? The turbo is mounted much lower compared to an AAZ engine. The linkage from the pressure sensor (VTG or wastegate?) goes vertically upwards from the center, and the pressure sensor is on top of it. Now, you probably already know what kind of turbocharger this is... I think it's a VTG.

How about the performance that's been slow to materialize?
'When I'm at 4000 RPM, shifting quickly and trying to accelerate further, I always seem to fall into a 'dip' first. This can't be normal, right? Both the VW master technician and my trusted mechanic consider it normal.'


I've traced the hose from this pressure sensor multiple times. Each time, I end up at a T-fitting that leads to two electro-pneumatic valves. It seems like it's stuck on both the EGR valve and the VTG valve. On my 6K model, both valves are mounted on the injection nozzle.


Thank you very much.
Greetings,
Martin.

The AFN engine has a VTG turbocharger. Unfortunately, the VTG adjustment mechanism on this type of turbocharger tends to get stuck. It might be worth checking its "smoothness" or ease of movement. My 1Z engine with a "fixed" (non-adjustable) turbocharger doesn't have any problems building boost at 3000 rpm because there is already a certain base pressure at that speed.

I can pull the rod located below the pressure chamber upwards about 5 mm with two fingers against a spring force. This is just a rough estimate. Therefore, the VTG (Valve Timing Gear) shouldn't be stuck, right?

I have traced the hose from this pressure sensor multiple times. Each time, I ended up frustrated at a T-piece that led to two electro-pneumatic valves. It seems to be connected to both the EGR (Exhaust Gas Recirculation) and the VTG (Variable Turbine Geometry) valve. In my 6K model, both valves are mounted on the injection nozzle.




Yes, what now?

From the hose on the turbocharger, the tube should go directly to one of the two valves, without any T-pieces or other connectors.

Are you looking here?
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Also, feel free to check this out sometime:
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CU Gremlin.

... Thank you very much!
I will check the cable routing again in daylight.

Furthermore, the question remains whether the pressure build-up is slowed down at higher speeds. In my experience with the AAZ engine, the turbo boost increased in sync with the pedal position even at high RPMs. There was no noticeable delay.

Hello,

I'm bringing this thread back up because I have the exact same vehicle (for about 20,000 km) and am experiencing the exact same 'problem.' At around 3200 RPM, my boost pressure drops to 0.6 bar and then increases again to 1 bar by 3900 RPM. This has been happening since the beginning; I tested the VTG adjustment back then, and it was without any defects. I also swapped the control valve with the one from the AGR system, but there was no change. After that, I performed the ULF boost test several times and logged the results. I consistently achieved the target values, usually about 0.5 seconds faster. Because of this, I haven't paid much attention to the 'problem.' Could it be normal? Or should it perform even better?
My heavier Ibiza TDI is as fast in a straight line with its standard engine (perhaps just very slightly slower) than a Polo 6N GTI with 120 horsepower.



Best regards, Dr. B.