Boost pressure increase for a 1999 Passat TDI with AJM engine, 115 hp

Hello.

After installing a powerbox that increases the fuel injection, I would like to increase the boost pressure on my engine by a maximum of 0.25 bar. I have already read the article about increasing boost pressure on the AFN engine, but I am not sure if I can apply it directly to my engine and my engine control unit. Does the increase in boost pressure in the engine control unit require replacing a resistor, or can an adjustment be made to the boost pressure sensor that will increase the boost pressure by the specified factor? As far as I know, the turbocharger is originally operated with a boost pressure of 1.1 bar, which I can read on my analog boost pressure gauge. I want to increase the boost pressure to a maximum of 1.3 bar in order to first utilize the additional fuel injection and second, to minimize soot production. I would appreciate it if one of you could provide me with specific information on this matter.

Regards,

hb2000

Some TDIs have the turbocharger pressure sensor integrated into the engine control unit. Then, logically, you can only solder the resistor in at that specific location.
If your boost pressure sensor is located in the intake manifold, you can certainly install a resistor there as well.

hb2000 wrote:

Does the increase in boost pressure in the control unit need to be achieved by replacing a resistor, or can an adjustment also be made at the boost pressure sensor

The AJM should, in my opinion, have the combination sensor (pressure + temperature) directly in the intake manifold or at the outlet of the intercooler: a single unit with a 4-pin connector.
Pin/Cable 3 is likely the pressure signal (no guarantee!).

The simplest way to increase the voltage would likely be to cut the cable and insert a diode in the forward direction (e.g., 1N4148, with the anode connected to the engine control unit).
If the result is not sufficient, connect additional diodes in series.

hello ulf

I also believe that the AJM has a combination sensor in the intake manifold, and that this is the right point for increasing boost pressure. I can't estimate how much of an increase a diode will provide, but I really don't want to subject my turbocharger to more than 1.3 bar of boost, especially if there's a risk of overboost towards 1.5 bar. I can easily check the whole experiment using the boost gauge, and I hope to get a reasonable result. Are you absolutely sure about the installation direction, 'ring facing the engine control unit,' or should I perhaps try an experiment with a resistor instead? What resistor value would lead to the desired result, or is a resistor not the right approach? The right way to trick the engine control unit (ECU) is to simulate a false boost pressure. You can do this by inserting a resistor into the cable or connecting it in parallel to ground. There are many questions, but I'm sure you have the knowledge to answer them competently.

greetings

hb2000

hb2000 wrote:

are you absolutely sure about the installation direction, "ring facing the engine control unit"

Okay.

Quote:

or should I perhaps try using a resistor instead. What resistor value would lead to the desired result, or is a resistor not the right way to trick the engine control unit into thinking there's a different boost pressure.

Resistance can also be used, but its value must be adjusted to match the input impedance of the measurement signal generator (MSG). -> When the sensor is disconnected, use an ohmmeter to measure the resistance between wire 3(?) and ground. Make sure the ignition is off, otherwise error messages will be recorded.

As a starting point for the tuning resistor, I would suggest beginning with approximately 10% of the measured value. If increasing the printer's pressure is not enough, use a larger resistor.

Or use a potentiometer for initial testing, adjust it to the correct value, and then replace it with a fixed resistor.

A diode is easier to handle due to its characteristic curve and can be used practically without any prior measurement.

Quote:

insert the resistor into the cable

Okay.

An LDA (Liability Disclosure Agreement) is practically mandatory for actions like these!
In any case, initially, only apply a little bit of pressure on the accelerator pedal, so that you can immediately lift your foot if the pressure becomes too high.

hello ulf

I already have the diode right here on the table, and I'm waiting for the end of the workday so I can install it in my device. I'm curious to see if a single diode will achieve the desired result, or if I'll need to connect a few of them in series. Thank you very much for your detailed explanations.

greetings

hb2000

hello ulf

Okay, one more quick question - I only have '1N 4003' rectifier diodes on hand, but they should work for the experiment, right? Or won't it work with these diodes?

greetings

hb2000

hb2000 wrote:

just a quick question - I only have "rectifier diodes" 1N 4003, but they should also work for the experiment - or won't it work with these diodes?

However - unless they are broken .

hello ulf

Let's hope it's not the case that these things are already junk.

Furthermore, I have a whole collection of that stuff here.

greetings

hb2000

I believe that the diode is not suitable for increasing the charging pressure because a temperature difference of 20 Kelvin at room temperature already has a significant impact on the voltage drop across the diode, and the difference between winter and summer temperatures makes this effect possible.
-> Higher temperature = lower voltage.
-> Low temperature = higher pressure => can be dangerous => boost pressure may be too high!!!!

Marfan wrote:

Winter and summer make it possible. -> Higher temperature = lower voltage. -> Low temperature = higher voltage => can be dangerous => boost pressure may be too high!!!!

Basically, you're right.

The question is, however, how much "the small mV difference" between warm and cold actually affects the charging pressure.

Given a measurement voltage range of around 5 volts, I would estimate that it doesn't reach truly dangerous levels.

But as I said: LDA is, in my opinion, a must-have .