Turbo Gauge

[exmee46]

Having looked a bit more at the turbo gauge I've noticed that it never goes down into the green section i.e into the vacuum section, is this normal for a diesel as whenever I have had one fitted to a petrol engine it always went full over to the left on deceleration.

With a petrol engine, when the throttle butterfly closes the pistons create a partial vacuum in the inlet manifold. A diesel engine always takes a full charge of air into the engine (no butterfly) - power is regulated simply by the amount of fuel (which is why they run away so alarmingly if you get any other source of oil into the cylinder). Hence no vacuum (which is why of course there is a separate vacuum pump to power the brake servo).

Kev

[paulh]

1 bar = 1 x std atmospheric pressure at sea level (15psi).

so 0.6 bar is about 9psi which is right according to the book.

Kev

Actually since I posted that quote I changed the tubing to the gauge as the soft plastic tube that I originally used was being affected by the heat under the bonnet and now I have fitted some stiffer tube the gauge shows 0.8 bar but the only time it goes into the green is when I switch off the engine, then it dips about half way down the green for a second.

[paulh]

With a petrol engine, when the throttle butterfly closes the pistons create a partial vacuum in the inlet manifold. A diesel engine always takes a full charge of air into the engine (no butterfly) - power is regulated simply by the amount of fuel (which is why they run away so alarmingly if you get any other source of oil into the cylinder). Hence no vacuum (which is why of course there is a separate vacuum pump to power the brake servo).

Kev

Good point, never thought of that, might get one that goes full circle in boost only.

[exmee46]

Actually since I posted that quote I changed the tubing to the gauge as the soft plastic tube that I originally used was being affected by the heat under the bonnet and now I have fitted some stiffer tube the gauge shows 0.8 bar but the only time it goes into the green is when I switch off the engine, then it dips about half way down the green for a second.

Book actually says 9 - 11 so you are still OK

Kev

[dirtydog]

Actually since I posted that quote I changed the tubing to the gauge as the soft plastic tube that I originally used was being affected by the heat under the bonnet and now I have fitted some stiffer tube the gauge shows 0.8 bar but the only time it goes into the green is when I switch off the engine, then it dips about half way down the green for a second.

yep mine whizzes down when i turn it off - Ive only got a 1 bar guage so it goes far enough, around 0.6-just under 0.7bar is the most it will show which sounds spot on.
Mine came with some tubing which I thought had cracked as it is hard and gone brown and stopped working - nothing wrong with except I jammed it somewhere behind the dash . sorted now by accident!

[Bikenuts]

With a petrol engine, when the throttle butterfly closes the pistons create a partial vacuum in the inlet manifold. A diesel engine always takes a full charge of air into the engine (no butterfly) - power is regulated simply by the amount of fuel (which is why they run away so alarmingly if you get any other source of oil into the cylinder). Hence no vacuum (which is why of course there is a separate vacuum pump to power the brake servo).

Kev

The 1KZ-TE has not one but two throttle butterflys, one big one small. The large one is conected directly to the throttle pedal and has A throttle position sensor at the other end. The small butterfly is operated by a vacume unit, it is normaly open but closes after a few seconds on overrun and when the engine is switched off so you should see vacume (if you conect your gauge to the MAP sensor pipe) when using engine braking and on shut down.