AFN 81kW Turbo Problem: Troubleshooting Guide

Hello everyone,

SEAT IBIZA, year 2000, 117,000 km (70 highway miles), has the following problem: a general and significant loss of power. Around 2000 RPM, there's an additional 'fluttering' sound without any noticeable increase in power. Recently, I could only manage 90 km/h (56 mph) uphill, whereas normally I can easily reach 180 km/h (112 mph) without any problems! The mass airflow sensor, turbo control valve, and hoses have already been checked – everything is okay! However, the turbo is not building any pressure. The car is making a lot of noise (which has never happened before). The engine has been chipped to approximately 109 kW (359 Nm). My question to you is whether it could be something other than the turbo, and if not, would it be beneficial to install a larger turbo?

Thank you for your responses!

best regards
thirsty

Have you checked if, at idle, the VTG (Variable Turbine Geometry) actuator fully retracts into the turbocharger?

Air leaks in the intake system? The 'puffing' sound could be an indication of this.

joergs wrote:

Are there any leaks in the charge air duct? The "whooshing" sound could be an indication of this.

Yeah, I agree.
And in the case of unusual smoke development, depending on the size of the leak, there is a high risk of life for the operator, because the loader may partially dig into empty space and, in doing so, over-rev .

Hello,

Don't worry. If the pressure line is leaking and the boost pressure drops, the driving force for the turbine is also lost on the other side – this type of over-revving of the turbocharger cannot occur. Worse are the excessively high exhaust temperatures that occur when the amount of air suddenly decreases while the injection amount remains the same. Not to mention the excessive soot formation. A leak on the boost pressure side has the same effect as venting the exhaust flow before the turbine, for example, in a turbocharger with a wastegate. It serves to regulate or limit the boost pressure. In principle, there is no difference between VTG and wastegate turbochargers on the compressor or boost pressure side.
@durts
For a 'quick' check of the turbocharger while it's still installed, you can remove the intake pipe on the compressor side to access the impeller (compressor wheel and shaft). If the impeller can be easily turned by hand without the impeller blades rubbing against each other under slight radial pressure, and you can't detect any noticeable axial play, then the bearings are likely still okay. Otherwise, you should also perform a visual inspection (possibly with a mirror). This would allow you to identify any wear marks on the compressor housing or missing impeller blades, and potentially prevent further damage. The same applies to the turbine side, but access is much more difficult there. If the damage is that advanced, the only solution is to replace the turbocharger – so don't continue driving. I don't want to be negative, but it's better to check it out.
Please keep us updated.

Best regards.

Sepp.

It sounds like a torn ACL to me...

Or maybe not all the hoses and pipes were thoroughly checked...

Sure, here is the translation of the text from German to English:

'Cu Gremlin'

Sepp wrote:

If the pressure line is leaking and the boost pressure drops, then the driving energy for the turbine is also missing on the other side - in this way, over-revving of the turbo cannot occur.

Hm, are you absolutely sure about that in all possible cases?

The fact is that the regulation aims to achieve the target pressure.
And if the turbocharger not only has to supply air to the engine, but also compensate for a leak, the mass airflow and, consequently, its speed will increase, according to the characteristic curve.

If the leak is not too large, the engine can still provide enough power to cause the turbocharger to spin excessively if the control system aggressively activates the variable turbine geometry (VTG).

If the car is only running like an SDI engine, you might be right - but as I said, there are other possible states between that condition and a fully functioning engine...

ulf wrote:

If the pressure line is leaking and the boost pressure drops, then the driving energy for the turbine is also missing on the other side - in this way, over-revving of the turbo cannot occur. Sepp wrote: Hm, are you absolutely sure about that in all possible cases? The fact is that the regulation aims to achieve the target pressure. And if the turbocharger not only has to supply air to the engine, but also has to compensate for a leak, the mass airflow and, consequently, its speed will increase, according to the characteristic curve. If the leak is not too large, the engine can still provide enough power to cause the turbocharger to spin excessively if the control system aggressively commands the variable turbine geometry (VTG). If the car is only running like an SDI engine, you might be right - but as I said, there are other possible states between that condition and a fully functioning engine. I agree with Ulf's opinion.

@Durst:
Let's just leave the problem as it is for now, if the turbo can last another half year.
The statement made by Sepp is correct.

One could precisely determine it by comparing the turbine's speed with the speed in a fully operational state.

Hey guys!

Join Gremlin:
As someone who's seen a lot of old AJM turbo hoses and coolant lines fail, I'd say you should look for oil leaks around the hose area. Cracks in hoses are often not immediately visible.

Hello everyone!

Thank you for all the replies. My friend (a mechanic) has now explained everything to me... he tried everything and checked everything! Unfortunately, the problem is with the turbo... it's no longer building any pressure. Well, what can you do? How much does a turbo typically cost?

I could potentially have a larger turbo installed... is it true that a larger turbo would have a longer lifespan (due to lower revolutions)?

Thank you again for your support!

Greetings.
Thirst.

Hi durts,

'Sorry about your charger. Theoretically, you're right; a larger charger would likely be less stressed with the same output. However, you probably wouldn't be happy with that solution, because the response and turbo boost build-up would noticeably worsen, not to mention the installation effort. If you have the designation of your turbo – you'll find it engraved on the compressor housing – you can ask the AFN specialists here in the forum which is the latest Garrett model (for the 81kW transverse installation) and, above all, which version is best suited for tuning. Or, as they say, use the search function first.'

Regards,

Sepp.

I just had a turbocharger failure. I paid 517 euros plus VAT for a Garrett turbocharger. Audi only replaces with the same type. So, you get what was originally installed. A KKK turbocharger costs around 700 euros. However, you can find it for about 100 euros cheaper as an aftermarket part.

Deine Beschreibung hört sich ganz nach Druckverlust im Ladebereich an. Nach meinem Turbotausch ist gleich ein Schlauch geplatzt und hat genau Deine Symptome hervorgerufen. Das Steuergerät erkennt den Defekt nicht und die Luftmasse, die gemessen wird, kommt nicht im Motor an. DIt's smoky over there.

If the turbocharger fails to build up pressure, the engine control unit detects this through pressure and air mass sensors, and adjusts the fuel injection accordingly – preventing soot formation.

With your chip, you also have a significantly higher boost pressure. This could cause something to burst in the intake system, possibly the intercooler, as it's not designed for such high pressures.

They couldn't even see the crack in my hose. It was quite a hassle to find it. The tear was on the inside, running lengthwise at the bend. All that was clear was that air was leaking out somewhere. You couldn't see anything at all when it was installed.

I would double-check to make sure everything is sealed properly. Maybe it's not the charger after all...

Best regards, Uwe.

Your answers are all quite good, but the actual problem hasn't been solved. It's just been discussed what the charger does when there's a leak in the charging air system. If there's a leak, shouldn't the pressure sensor trigger an alarm? I also have a solution to the original problem that hasn't been addressed yet: have you checked the catalytic converter? A friend of mine had the same problem, even with all new parts, including the turbo, and still had the same issue. He cleaned all the gunk out of the catalytic converter, and then it worked perfectly! The turbo wasn't broken. So, you absolutely need to check it! Best regards, Bernd. P.S. Waiting for a response

Well, I guess we'll have to wait until Durts comments on it.

Experienced mechanics often diagnose 'turbo failure' whenever there's a problem with the boost pressure.

I still think there's a leak in the charge air duct.

Sure, here is the translation of the text from German to English:

**Keywords in the original post:**

-'to peacock'
-'makes a lot of noise'

CU Gremlin.

and that was also the basis for the discussion. It became a 'blabla' situation...

Personally, I don't believe it's a faulty turbo or a defective catalytic converter.

I completely agree with my predecessor.

'There's nothing wrong with the turbo. Let's take a look and see what could possibly be broken.'

VTG might be stuck, but you probably aren't.

He might be leaking oil, and you would definitely see it!

He might have a bearing failure, but if that were the case, a shaft spinning at over 100,000 RPM would immediately fail.

The turbo's power output is in the range of 20 horsepower. A reduction in power due to a stiff bearing is therefore unthinkable, because even a 10% power loss would mean that approximately 2 kW of thermal friction would be generated on a shaft of about 10 mm in diameter. It would happen in a matter of milliseconds...

Conclusion: It's everything else, but not the turbine. I should probably check that tip about the catalytic converter. I once had to drive back from France with the catalytic converter removed because the car could barely reach 40 km/h due to the exhaust back pressure.


The test is simple - remove the cat (catalytic converter) from the turbo and drive without it, leaving the turbo outlet open. This works for a short test. If it then works, that's it.

Here's another point: The accuracy of the friendly staff's diagnoses regarding turbos is evident in the fact that E**Y consistently has around 20 used, fully functional turbos available for sale.