Performance Issues? Troubleshooting Guide.

Hi.
I have a Golf III TD (engine code AAZ), 1.9L. I replaced the turbocharger because the old one was only producing a maximum pressure of 0.5 bar. To my question: the new turbocharger produces a pressure of 1.5 bar under full load! That's already good. But unfortunately, my top speed has decreased from 185 km/h (according to the speedometer) to only 160 km/h? What could be the problem?
The car runs really well overall, with a fuel consumption of 5 liters per 100 kilometers, good starting performance, and good acceleration.

I only replaced the turbocharger and didn't adjust anything. The old turbocharger was a KKK, and the new one is a Garrett.

Thank you for your help.


Best regards, Mark from Kiel!

Hello,

I assume that the 0.5 bar was a relative pressure compared to normal atmospheric pressure.
Having a pressure of 1.5 bar, which is also considered a relative pressure, will cause your turbocharger and engine to fail much faster than you can count to three.
Assuming that 1.5 bar refers to absolute pressure, which would be approximately 0.5 bar relative pressure, I suspect that replacing the turbocharger was unnecessary.

So, how did you measure the pressure?

Since I'm not very familiar with the AAZ's turbocharger pressure control system, I'll leave that to the experts here.

Best regards, Rainer.

Hi.
Thank you for your reply.
I measured the boost pressure using a boost gauge from VDO. And I stopped by Bosch today, and the mechanic said it wouldn't be so bad if I have a pressure of 1.5 bar. Because if you want to tune your car, the turbocharger's pressure would also be increased.

'And the boost pressure on the old turbocharger was only 0.5 bar; it couldn't produce any more, according to Bosch. The old turbocharger also consumed oil!'

The oil consumption is gone. Unfortunately, as I mentioned, the top speed is also gone.

Best, Mark.

Hi,

The AAZ engine has a turbocharger with a maximum boost pressure of 0.6 bar. If you increase the boost pressure to 1.5 bar, you will likely destroy your engine very quickly.
The wastegate on older turbochargers is adjustable, but I doubt it can reach pressures up to 1.5 bar.

Take a look inside: http://www.golf3td.tk/

Okay, I'll take a look.

My question is: If I want to tune my Golf TD, do I also have to increase the turbo boost? Or what? And the more boost I have, the more power I get, right? But what I still don't understand is why, if I have more power (according to the VDO instrument, 1.3 bar), my car is actually slower, and by as much as 20 km/h? Can anyone give me an answer?

'I've also noticed something since I installed the new turbo: the car seems to accelerate a bit slower when it's cold.'


Thank you for your help, and best regards, Mark.

Hello Mark,

Yes, you can tune a turbodiesel by increasing the turbocharger's boost pressure. However, you should also have an appropriately sized intercooler, otherwise the engine's thermal balance will be disrupted. You only get more power when you also increase the diesel injection amount (no fuel, no power).

If your turbo is actually producing 1.5 bar of boost pressure, it's likely due to a wastegate that's stuck closed. The wastegate is a bypass valve on the turbine that diverts exhaust gases around the turbine when the boost pressure is too high. If it's stuck closed, the back pressure in front of the turbine will increase, which would explain why your power has decreased: the engine can't properly expel the exhaust gases.

Hello.
Wolfgang.

Hi Wolfgang,
Thank you for your reply. So, I will probably have to reduce the boost pressure. Because I don't want to install the LLK (intercooler) until spring. I hope everything will be okay then. The turbocharger is new, and my engine is also new. The engine has only 3000 km, and the turbocharger has about 400 km. I don't want anything to break before that!


Best, Mark.

Hi.
Okay, I've already reduced the turbo boost pressure back to 1.3 bar. Today, I'll try to reduce it further by another 0.3 bar if possible. I'll also go back to the track and check if it's reached its top speed of 185 km/h again (according to the speedometer). I'll let you know what I find.

One more question: Where would you reduce the pressure here?
I still have a screw on the boost enrichment device! I wonder if I can adjust anything there? If so, should I turn it clockwise or counterclockwise?


Thank you, and best regards, Mark.