Idle screw on NG engine (actually more CIS/ISV now)

[rob hod]

    Interesting. I didn't think my ISV was open at rest but I'm prolly
wrong. Even with a partially-open-at-rest ISV ,  if the basic throttle
setting is too high your ISV can't do zippety about bringing the idle speed
down.

 On my RT (like an NG but no ECU) it certainly dips when disconnected, I may
have to do a bit of experimenting with settings and report back. Not too
keen on trying to keep an idle going on an auto tranny car if the IS system
ever fails.

However the actual point I was trying to make but didn't say outright, is
that it seems like good practice to have your throttle stop at a nice place
approximating a warm idle, I mean otherwise aren't you just making more work
for your ISV ?



rob
----- Original Message -----
From: Huw Powell <human747 at attbi.com>
To: rob hod <rob3 at hod3.fsnet.co.uk>
Cc: <quattro at audifans.com>
Sent: Thursday, April 11, 2002 7:25 PM
Subject: Re: Idle screw on NG engine (actually more CIS/ISV now)


>
>
> >     I think you've still got to adjust the idle screw properly as far as
> > getting a correct basic setting is concerned, - i.e. one which
approximates
> > on its own to a normal idle on a warm engine. Although I'm only familiar
> > with ISV systems rather than full blown ECU control, it seems that any
> > auxiliary air device that is 'shut at rest' could do little about a
> > situation where the basic idle setting is too high and flows *more* air
than
> > needed.  On the other hand a basic setting that was too low would mean
that
> > if your stabilization system took a dive for whatever reason you would
be
> > faced with a non-idling car.
>
> The NG ISV is about 1/4 open at rest.
>
> >      On a well tuned ISV car you should be able to disconnect the ISV
plug
> > at idle and have the engine dip in revs but keep running.
>
> and an unplugged ISV (or idle switch) results in a higher idle.
>
> There are, however, I believe, some ISV systems where it is closed at
> rest.  On those an idle air screw could be a useful way to provide a
> "limp idle" mode.  Not that it matters much, you can always use your
> right foot to get the car home, right?
>
> --
> Huw Powell
>
> http://www.humanspeakers.com/
>
> http://www.humanthoughts.org/
>