No you are getting minus 0.7 bar... because the engine at idle is a vaccum (negative pressure) when you drive your car, it will go between negative whatever and positive whatever, depending on whether the turbo is forcing induction. Eg you put your foot down the turbo will start to spin up, and force induction.

 

Installing a B5 TIP and open cone filter will not change the boost pressure, it may even drop a bit as there'll be better air flow. To change your boost you need to update the map.

 

-0.7 bar = -20.7 in hg which is about right for a engine without any vacuum leaks 8)

 

.... I fitted a mechanical gauge today and I'm getting around 25 Hg on idle and showing 11 psi on WOT in second and third. The gauge was second hand and doesn't look to be of the greatest quality so I'm dubious about the readings. I'm planning to replace it with something of higher quality. I like Prosport gauges!

 

No you are getting minus 0.7 bar... because the engine at idle is a vaccum (negative pressure) when you drive your car, it will go between negative whatever and positive whatever, depending on whether the turbo is forcing induction. Eg you put your foot down the turbo will start to spin up, and force induction.

Sorry my bad I meant -0.7 (just edited my original post) I was trying trying understand if the negative reading was what I should expect when idle.

 

Installing a B5 TIP and open cone filter will not change the boost pressure, it may even drop a bit as there'll be better air flow. To change your boost you need to update the map.

My main aim was to fit the boost gauge so that I could make sure that I had no vacuum leaks before moving to the tip and filter install, then at least this way I know where to troubleshoot if needed. Cheers

 

-0.7 bar = -20.7 in hg which is about right for a engine without any vacuum leaks 8)

Thanks for the reply, that's exactly what I wanted to hear!

Shortly after posting the original questions I took it for a spin to test the gauge out and was getting a reading of +0.7 bar what's the verdict on that? Cheers

 

10 PSI is low for a 225, should be around peak of 14/15 psi on a WOT run. A bad N75 or boost leak can cause this.
Or does it peak then settle down at higher RPM?

 

.... I fitted a mechanical gauge today and I'm getting around 25 Hg on idle and showing 11 psi on WOT in second and third. The gauge was second hand and doesn't look to be of the greatest quality so I'm dubious about the readings. I'm planning to replace it with something of higher quality. I like Prosport gauges!

This was my first attempt on installing any kind of gauge, took me a lot longer than I thought it would, Getting the vacuum hose to the engine was the easiest part, the wiring was a bit more challenging, but got there in the end! I bought the 52mm EVO LCD Peak / Warn Series https://prosportgauges.co.uk/gauges-52mm-evo-lcd-peak-warn-series-c-3_166/ and used the Cloude9 Customs 3D printed vent gauge adapter https://cloude9customs.com/product/audi-tt-mk1-vent-gauge-adaptors/. I'm really happy with the result looks factory fitted especially with the red LCD.

 

10 PSI is low for a 225, should be around peak of 14/15 psi on a WOT run. A bad N75 or boost leak can cause this.
Or does it peak then settle down at higher RPM?

Thanks davebowk, yeah thought that was going to be the case! What steps would you take to diagnose, should I just replace the N75 straight off the bat? It hasn't been replaced as I know the history or the car.

I'm going out for a longer spin tomorrow so I will take another look at the reading then.

 

Gauge could be reading low. Have you got torque app to compare the PSI numbers

 

a stock 225 isn't 15psi it is like 12.8psi

(157.67 * 10) + 300 = 1,880 - 1bar ambient = 880mbar

880 mbar in psi = 12.76

 

a stock 225 isn't 15psi it is like 12.8psi

(157.67 * 10) + 300 = 1,880 - 1bar ambient = 880mbar

880 mbar in psi = 12.76

Thats why i asked about peak and settled.