S6 AAN turbo gauge question

[Giacomo]

Hi

My S6 is total stock, except for Ultimot stage 1 chiptuning 280 hp.

I have just red 2.6 bar on my gauge: is it possible? I know the gauge cannot go over 2.5 and even if you get 300 Kpa sensor inside the motronic you have to keep in mind that top real pressure 3.0 bar will be marked 2.5 on the gauge.

Is my gauge mad?

[UrS4boy]

Is my gauge mad?

What gauge are you talking about? The stock in-dash digital gauge or an aftermarket analogue gauge?

The digital gauge reads absolute pressure, relative to a perfect background, i.e. no boost = atmospheric pressure = about 1.01 Bar. A Stage 1 boost of about 21 psig boost will be about 1.45 Bar on an analogue gauge and about 2.45 Bar absolute on a digital gauge. Complicating things is the fact that the OE absolute pressure digital gauge was calibrated with the expectation that the Manifold Absolute Pressure (MAP) sensor in the ECU is a 250 kPa (2.5 Bar) unit, not a 3.0 Bar unit. Once you go to the 3.0 Bar MAP sensor the OE digital gauge readings are off from reality by some (variable) factor.

[Giacomo]

Yes, I'm talking about the OEM digital gauge inside dash. No aftermarket. No 300 kpa sensor.

An S6 owner friend told me that the OEM gauge range is 0 - 2.5 bar. So I should never read 2.6 or more because every value higher than 2.5 should be shown by the instrument at 2.5 bar.

No boost = 1,0 bar on the gauge
0,5 bar of boost = 1,5 bar
1,0 bar of boost = 2,0 bar
1,3 ...... 2,3
1,5 ...... 2,5
1,6 ....... 2,5
1,8 ...... 2,5
2,1 bar of boost ..... always 2,5 on the OEM gauge

[Giacomo]

Maybe I understand: at 2,5 absolute bar the Motronic makes cut-off (in fact, while I was reading 2,6 I feel the cut off), if I install the 300 Kpa sensor, the cut off appears at 3.0 bar absolute, but "for some reason" the gauge range remains 0 to 2,5 bar absolute.

Is it so?

[Giacomo]

Also, there is no way at all to make OEM gauge mark up to 3,0 bar with 300 Kpa sensor?

[UrS4boy]

Also, there is no way at all to make OEM gauge mark up to 3,0 bar with 300 Kpa sensor?

As far as I know, nobody has figured out a way to do that. I think you have found the limitation of the OE digital absolute pressure manifold pressure gauge.

Here is one alterative (there are others out there that read in Bar, i.e. up to 2 Bar)

[GazzaG60]

get a quality gauge if you want to read boost.

I use defi.

[Giacomo]

What if I turn the key one step, turning the dash on but not the engine, and I push air under pressure in the intake manifold someway?
The boost gauge is on and should give the atmosphere pressure (1 bar) plus the pressure I push in, and if it gets over 1,5 bar then we could know if OEM gauge marks abs pressure over 2,5 bar.

[UrS4boy]

Moisture Trap Info

What if I turn the key one step, turning the dash on but not the engine, and I push air under pressure in the intake manifold someway?

Never heard of anybody trying that but it might work.

Another way would be to disconnect the boost line at the moisture trap (down by the ECU) and feed in a known pressure (with the ignition "ON" (run)). Just don't exceed 2.5 Bar absolute (1.5 Bar extra).

Moisture Trap Info: http://forums.quattroworld.com/s4s6/msgs/20401.phtml