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Discussion Starter #1
Hello all, I just wonder if I can have a comparison with other 2.4 diesels.

I've noticed recently that the turbo pressure boost gauge drops to zero when my engine is idling. I seem to recall that unless it was running a DPF regeneration, that when idling it always registered some boost albeit not much.

If anybody can confirm mine is "misbehaving" I would appreciate it. There don't seem to be any running issues.

Thanks.
 

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No turbo car has boost when its idling, there isnt enough volume of exhaust gas to run the turbo.
The turbo gauge will drop like a stone to 0 on the overun if its doing a regen where as normaly it will drop slowly to just above 0
 

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your car runs a negative boost ie. a vacume at tick over

normal! the guage is poor in alfa as it should be showing a vacume at tick over and also it should show negative boost but it doesnt!

Mark C
 

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Discussion Starter #4
Thanks for the clarification. I could have sworn that .........

It just goes to show........my brain is definately not what it was:eek:
 

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I remember never seeing it rest at zero before but now it does. Wonder whether its now been run in properly?
 

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normal! the guage is poor in alfa as it should be showing a vacume at tick over and also it should show negative boost but it doesnt!

Mark C
Diesels never really have a negative pressure in the inlet since they do not have a butterfly like a petrol motor.
Hence the vacuum pump sitting on the rear of the head.:thumbs:
 

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Not accurate at all unless you drive a 1750 TBI
 

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Negative boost?

Hmmm, not sure this is very accurate ...
Do you actually know what a negative boost is ??

And an Internal cumbustion engine be it deisel or petrol sucks at the inlet which should create or at least try and create a vacuum.

Try this, on tick over if a pipe was removed from the plenumn chamber (inlet manifold ) at tickover I believe there would be a "suck" from the hole Not a "blow".

So I would conclude that since the guage fitted in Alfa 159 can not go negative then it is inacurate. (or maybe I am dumb!)

Over the weekend I will connect an after market boost guage and see what it reads just to see if it does go negative on tick over and see if alfa does infact have negative boost at times.

I am new to "VGT" cars and was more familiar with vacuum controlled waste gates / dump valves so I will check and post what I find, so I accept that I may be wrong!

Mark Flintshire.
 
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