1997 2.5 D boost pressure?

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Nick - 05 Dec 2007 18:09 GMT

I have a 1997 2.5TDi direct injection turbo diesel V70, and I
suspect that the turbo
is not producing the boost it should be.

Can anyone confirm what the boost should be at what revs ?

Thanks,

Nick

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Tim.. - 05 Dec 2007 19:35 GMT

>I have a 1997 2.5TDi direct injection turbo diesel V70, and I suspect that
>the turbo
[quoted text clipped - 3 lines]
>
> Thanks,

From memory 0.9bar at anything over ~2700rpm.

I would be hooking up a gauge and not only checking peak boost is attained
and held through the rev range, but also how it builds.

If it is slow to build as well as down, then either tighten or preferably
replace the wastegate. Heat weakens the spring in time.

Tim..

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Nick - 05 Dec 2007 19:45 GMT

> From memory 0.9bar at anything over ~2700rpm.
>
[quoted text clipped - 5 lines]
>
> Tim..

Hi Tim,

Thanks for the quick reply - I will see if I can do this at the
weekend...

As an aside, if all is well, is it possible to tweak the boost
pressure a little ?
I know that without fuelling adjustments which I guess I can't
adjust, there will be no
power gain, but if there is fuel not being burnt then I guess adding
a little more air
will give a bit more power and reduce pollution - or will too much
air have an
adverse effect ?

Thanks,
Nick

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Tim.. - 06 Dec 2007 10:07 GMT

>> From memory 0.9bar at anything over ~2700rpm.
>>
[quoted text clipped - 19 lines]
> have an
> adverse effect ?

It will self compensate for a mild increase in boost- upto a point.

The only way to increase boost is with a boost controller, or more
elementary a bleed valve type. This wont help a tired actuator, which should
be replaced first.

I would try for 1.0, perhaps 1.1 bar, and see how it goes. Any more, and you
will need a chip to help with the fuelling too.

I assume your MAF and injectors and engine innards are now in rude health??

Tim..

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Nick - 06 Dec 2007 11:04 GMT

> It will self compensate for a mild increase in boost- upto a
> point.
[quoted text clipped - 10 lines]
>
> Tim..

Well, I am at the moment just collecting parts and info as it is
slightly possible that I
will be changing the car for a later model, or even going down to
one car as wife
doesn't drive anymore.... but I need a work car as well as a "nice"
car, so may
still happen yet..

However, I like "fiddling" and I like this car, so not sure...

I found a brand spanking new MAF unit, the injectors are still about
to be done
( now definitely do need doing as I am sure seals have gone on
one/some as I get
a bit of diesel smoke on start up after rest so I assume they are
leaking fuel into
the cylinders when stopped) new brake discs and pads all round just
fitted,
and generally the car is good ....

Years ago I bought an adjustable turbo boost controller for another
car and
never fitted it, but essentially it is an adjustable pressure valve
which goes between
the inlet manifold and the waste gate - at the allotted pressure (
say 1.1 bar)
the valve opens and activates the waste gate, so both controlling
the max boost
but also preventing partial opening as you near the pressure - not
sure if the
waste gate on these is directly operated by manifold pressure or via
a pressure
sensor / switch and a solenoid, but I guess it could still be used.

So, over the break I might get to do these things

Thanks again,

Nick

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