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[conalnugent]

http://www.endmemo.com/sconvert/psiinhg.php

[martin42]

Your fitting a boost gauge totally different to what webby is on about.

[Shackeng]

Where is the right place to connect the boost gauge into my 2.5td??? Currently I plumbex it into the small pipe thst comes off the bottom of the inlet manifold.  Is this alright? The gauge is in bar. Reads 0 on idleand just below 2000rpm boost kicks in and goes swiftly up to 15psi / 1 bar of boost then at the top of the rev range drops off.

Must upload a video before the day is out.

As long as you use a tee-piece, as the other end of this goes to somewhere important

[Webby the Bear]

I can not tell you if you can convert the readings from PSI to inHG.

However, you mentioned you got 15psi... looking at your link to conversion that would be 30inHG..... which is far too much. so i'd say it was the wrong test.

although might be worth waiting for one of the experienced guys to confirm

[Andy H]

Where is the right place to connect the boost gauge into my 2.5td??? Currently I plumbex it into the small pipe thst comes off the bottom of the inlet manifold.  Is this alright? The gauge is in bar. Reads 0 on idleand just below 2000rpm boost kicks in and goes swiftly up to 15psi / 1 bar of boost then at the top of the rev range drops off.

Must upload a video before the day is out.

Sounds about right for a turbo boost gauge.

There will be very little boost until the turbo is spinning fast enough.

As you approach the red line the ECU will start to reduce fuel input which will also reduce the volume of exhaust gas. I don't know if your ECU can control the wastegate to reduce turbo output directly

[Andy H]

I can not tell you if you can convert the readings from PSI to inHG.

However, you mentioned you got 15psi... looking at your link to conversion that would be 30inHG..... which is far too much. so i'd say it was the wrong test.

although might be worth waiting for one of the experienced guys to confirm

A petrol engine uses a throttle to restrict the amount of air drawn into the engine which is why you get a vacuum at idle. The primary control of engine output is the throttle position - the ECU adds fuel to maintain the necessary conditions for combustion.

A diesel generally* doesn't have a throttle, it needs a full charge of air in each cylinder to compress & generate the conditions so that ignition occurs when the diesel is injected (hence 'compression ignition' being another name for a diesel engine). The primary control of engine output is the quantity of fuel injected into the cylinder.

* some old diesels used to have a throttle flap that could close to generate a vacuum for the brake servo. Some of the newest diesels have throttles to control the air intake to modify emissions.

[TheBoy]

Where is the right place to connect the boost gauge into my 2.5td??? Currently I plumbex it into the small pipe thst comes off the bottom of the inlet manifold.  Is this alright? The gauge is in bar. Reads 0 on idleand just below 2000rpm boost kicks in and goes swiftly up to 15psi / 1 bar of boost then at the top of the rev range drops off.

Must upload a video before the day is out.

Sounds about right for a turbo boost gauge.

There will be very little boost until the turbo is spinning fast enough.

As you approach the red line the ECU will start to reduce fuel input which will also reduce the volume of exhaust gas. I don't know if your ECU can control the wastegate to reduce turbo output directly

TD has a mechanical wastegate. Its not exactly a complicated engine setup, being BMW  , but is quite a likeable lump, apart from being dirty, noisy and fragile.