Diode Trick: Does it work with AAT and AEL?

Hi there,
The search function did not provide any helpful results.
AAT = 2,5l 5-Zyl. TDI with 115 horsepower.
AEL = 2,5l 5-Zyl. TDI with 140 horsepower.

Thank you and best regards.
Jens.

Hi,
If you're talking about tuning a faulty mass airflow sensor (MAF), then it's not because these engines have a mass airflow meter with a bypass valve.

Hi Christian,
Yes, I mean replacing the mass airflow sensor (MAF) with a diode.
Does the Audi 5-cylinder TDI have a bypass valve? That's interesting; what's its purpose? I always thought those were only found on gasoline engines.
Well, never mind, if that's the case, I'll look for other engines instead.

Regards,
Jens.

Hi,

The throttle valve is designed to do the same thing as the hot-film mass airflow sensor (MAF) in newer TDI engines. It's a valve with a spring attached that sits in the airstream. The stronger the airflow, the more it's pushed back, and this can be measured using a potentiometer -> air MASS.

The HLMM, on the other hand, provides the air MASS – there have already been several posts about its function.

Best regards,

January.

Hi,

To the best of my knowledge, AAT/AEL units manufactured after xx/1994 no longer use volume flow meters but instead use mass flow meters.
Up until 1994, that statement about the check valve is correct - and it also doesn't break .

Okay, sure.
Thank you for the information.
From sometime in 1994 onwards, we used mass instead of quantity .
Did early ATs (Automatic Transmissions) before 1994 actually have exhaust gas recirculation?
Do the earliest AAT models have an oxygen catalytic converter? They were released before the major tax increases came into effect.
Thank you.
Jens.

Hello!

All AAT and AEL models definitely have the older type of air flow meter with a pressure valve (regardless of year of manufacture)!
All AATs (turbocharged engines) also have exhaust gas recirculation (EGR), but the 'early' type called ABP probably doesn't have an air mass meter and therefore no EGR. I don't know if they all have a catalytic converter, but I think most of them do.

However, in 94 vehicles, the emissions standard classification was changed due to the use of different software and injection nozzles (a different pump was also used, although the only difference was the HDK sensor in the flow control unit).

Greetings,
Andi.

Let's forget about AAT and AEL for a moment and turn our attention to the good old 1T.
The 1T engine is the ancestor of all VAG TDI engines and was used until the model year 1990.
Does the 1T have an exhaust gas recirculation system?
Does it have a check valve?
I suspect no, but who can confirm that?
How is the turbocharger (which is definitely a wastegate turbo) on the 1T engine controlled? Is it controlled using the same type of valve and pulse-width modulation as in the 1Z engine?

It would be great if someone knew the answer, thank you.

Regards,
Jens.

1T:

No EGR valve and no pressure control valve (the pressure control valve is only used for measurement, so there's no mass airflow sensor and no pressure control valve).

I don't know much about the wastegate system specifically, but it's highly likely that it works the same way as it does on engines like the 1Z, ABP, AAT, and AEL.

Best regards,
Andi.