Boost Pressure Measurement for 038 TDI Engines

Hi,

On older 028 TDI engines (1Z, AHU, AFN, ALE), it's easy to tap into the pressure line leading to the engine control unit (ECU) using a T-piece to obtain the boost pressure for a boost pressure gauge (BPG).

For 038 TDI engines starting with the Golf 4, this is no longer possible because these engines have the sensor mounted externally on the intercooler. However, these engines also have a bypass valve (except for the very first 90 hp AGR models). The housing of the bypass valve is not universal for transverse and longitudinal engines, meaning it can be either left- or right-hand intake. Therefore, the threads for the vacuum actuator of the bypass valve are present on both sides (but logically only one side is used).
A standard hose connector can be easily screwed into this thread.

Now, you just need to drill through the face of the threaded hole with a smaller drill bit so that pressure is also applied to the connector.

If you ever want to stop using a particular type of lighting (LDA), you can simply turn a screw into the thread.

Since I don't have a Leon with a 038 TDI engine (that one is being transported), I haven't tested it thoroughly, but a test using a 50 ml syringe showed only minimal leaks (completely irrelevant compared to the engine's flow rate). If you glue the connector in place, it will be completely leak-proof.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Why make it so complicated? Festo offers a connector designed for sensors in pneumatic systems. It's an adapter from M5 to a 3mm hose (a 3.2mm ID hose also fits) and costs only a few cents.

If you like, I can also send you one; it fits in an envelope.

Simply drill a hole in the intake manifold, tap it with an M5 thread, screw in the fitting (a suitable Teflon gasket is also available), and connect the hose.
If the connector is no longer needed, simply screw in an M5 screw.

HI,

You mean something like in the attachment?

Well, the connectors I mentioned are something that any average person can find at a hardware store, but Festo is naturally a more high-end brand .

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Nebelwerfer_TDI wrote:

Simply drill the intake manifold and tap an M5 thread.

The trick when using the unused M5 threaded holes on the EGR unit is that you don't need to cut any threads.

@martin
I wouldn't vouch for the quality of that push-fit connector.

When a warm engine is briefly turned off, heat creeps into the EGR unit, causing the connector to soften – and it can then be shaken or blown out of the threads during the next engine start or LD (Load Dump) test.
-> Screw nipple rules .

You mean something like this:


Yes, something like that. The connector you showed has an additional locking nut, which unfortunately makes it less suitable for rubber hoses, such as those used for oil lines.

The fittings I was referring to look the same in terms of the thread and the hexagonal shape, but they have a longer, open hose nipple on the back.
A coolant hose should be secured with a small hose clamp (there are even self-tightening ones available in automotive accessories, for example, for the windshield washer system), ensuring it's done properly.

That's the trick when using the unused M5 threaded holes on the EGR unit: you don't need to cut any threads.


Ah- so, you would just need to 'finish drilling' them? That would be ideal .

Quote:

Ah - so, you would just need to "finish drilling" them? That would be ideal.

That was my plan, I probably just didn't express myself clearly .

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Now, you only need to drill through the front surface of the threaded hole with a thinner drill bit so that pressure is also applied to the connector.


My mistake - I apparently didn't read carefully enough.

However, I would strongly recommend using a high-quality Festo connector instead, as the hose connector is likely not very durable.

@ fogthrower

My Euro 4 BLT doesn't have those large holes in the EGR unit. Could I drill directly into the intake manifold and tap an M5 thread there, or would that cause problems due to the aluminum casting?

Where can I get the nipple you mentioned?

greetings

'On my turbocharger, I tap into the boost pressure at the EGR unit. The EGR unit is divided into two sections, and I drilled a hole through the flange in the middle and tapped it with an M5 thread. A hose fitting is then screwed in there, and a hose is attached to it leading to the boost gauge.'

'For the hose connection on the back of the boost gauge, I purchased an M12x1.5 threaded adapter with a matching hose barb. It fits perfectly and is available at a very low price from companies that offer hydraulic services or specialize in pressing hoses.'

greetings

Hello,

also ich hab damals beim Leon das Hartplastiksaugrohr nach LLK aber noch vor AGR bzw Abstellklappe aufgebohrt. With 4 mm.
I simply cut the T-piece that came with the LDA. Then, I pushed the remaining piece (towards the LDA), which was 4.5mm thick, into the opening and secured it with resin. Later, I applied a few drops of resin to the seam all around to ensure it sealed properly. Soap solution pressure tests revealed no leaks.

Advantage: The LDA is then nicely balanced; the narrowing in the T-piece and the hose connector fit perfectly with the hose.

Disadvantage: If I hadn't wanted the LDA (Lambda Direct Injection) anymore, I would have had to get a new, unused plastic intake manifold from a junkyard or a friendly source.

This measure can also be cleverly hidden underneath.

Best regards,

Please provide the text you would like me to translate from German to English. I will then give you only the translation.