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Re: WGFV testing procedure.
> I have a hard time with that statement.......
> If you remove the WGFV, you are REMOVING the back presure from the WG
> diaph. meaning, the only thing that is preventing your WG from opening
> is the spring in the WG?...........
> How can it possibly go to overboost?........
> Your thoughts............
That's right as far as I understand. But it would indicate that the
FV is faulty or not. As far as I understand, the ECU will provide
overboost features only when nailing it hard. However, mine at the
moment easily indicates 1.5 bar boost whereas it never showed any
sign or interest in exceeding 1.1 boost up at altitude where the
atmospheric pressure is about 0.8 bar. About 2 weeks ago at the
coast I put the pedal to the floor and only saw 1.3 bar come up at
about 140km/h. Now I can see 1.5 doing something like 80-120km/h
and I'm up at altitude.
What does puzzle me is why the boost should even go to 1.4 bar with
the FV disconnected. I mean, at altitude the boost available (if the
turbo is working as at the coast) should really be 0.2 bar below
(depending on the height), right? Or am I grossly mistaken? How does the
spring and atmospheric pressure work? Does atmospheric pressure play a
part in holding the WG down? If that is the case then moving up to a
higher altitude, with the same spring which provides 1.4 bar boost
release at the coast (1 bar atmospheric), should release the pressure at
1.1 to 1.2 bar. If that is the case then the car was working correctly
before I ventured down to the coast at the start of this year. Last
year up here at altitude I never had the boost go beyond 1.1 bar, which
would be correct if my assumptions about atmospheric pressure assistance
to the WG release is correct.
Another thought, if the FV is jammed open for some reason then intake
pressure is always being applied to the WG independent of whether the
ECU has requested it or not. This means boost will not release at the
specified value set by the spring. I confirmed this by disconnecting
the connector on the FV that runs to the ECU (I think that's the
one that controls when the valve operates, isn't it? It is a 2-prong
plug on the unit with the 3 vacuum/pressure lines on it. I assume I'm
not mistaken and that connector is the one that connects to the ECU
and the one the ECU uses to open the valve for overboost). The boost
merrily went on to 1.5 bar and it shouldn't have done that at
altitude and with the connector off. Well, that's what the pressure
reading indicated on the electronic readout. I've checked codes and
the ECU reckons 4444 (no problems) and I don't know how to test the
pressure switch in the ECU housing, perhaps idle the car and connect
a cycle pump to the connector and have an inline pressure gauge and
then pump up the gauge and watch the correspondence on the electronic
readout. I believe this was suggested, but not at idle, maybe at
I think I need to determine whether the ECU is offering overboost
instead of it all going funny in the turbo and it is spinning over.
The method for this is those LED hookups people have spoken of on this
list that connect to the connector on the FV and will indicate whether
boost assistance is being applied. But this can also be confirmed
by disconnecting the FV electrical connector and leaving all the
vacuum lines in place, can't it? If that is the case then I've
already done it and no overboost assistance is needed to get the
car up to 1.5 bar boost at altitude.
Well, those are my thoughts. I need to get to the bank as someone has
taken $20 from and given me nothing in return, so I guess if I get
that back then I'll do the test on the vacuum/pressure hoses and
replace what I can. My T-piece crank breather connector is torn and
might even be the cause of this problem (too much air getting sucked in)
and other problems (whistling sounds), and I will need to make a
make-shift T-piece. (At the moment, about $3 left in the bank, quit
my job and 2 weeks to pay-day!)
"a thousand miles from here, there is another person smiling"
1990 Turbo (200T)
name : gerard van vught
tel : +27-57-912 2658 (w) / 082 923 9609 (cell)
url : http://www.acenet.co.za/homepages/gerard/
e-mail : firstname.lastname@example.org / email@example.com
firstname.lastname@example.org / email@example.com