CIS basic idle/mix ballparking advice

[roccit_53 at scirocco.cs.uoguelph.ca (C Boyko)]

On 10:08:26 am 07/31/05 "Dan Bubb" <jdbubb@verizon.net> wrote:
> Uhhh.....
> The distributor should not get vacuum at idle. 


Oh, sorry, I wasn't clear on my post, there was no vaccuum at idle, and
vaccuum when off idle (as per guage...). Sorry. Before there had been none.
At all. I'm gonna stop replying, obviously I don't write real
clearly!..though it may not have been my post to which you are responding.

But, does this indicate that my primary plate is in fact correctly adjusted?



And, with all that big thread about vaccuum diagrams, did anyone ever come
up with a location for them? The old (MkI) Bentley has them, but for the
newer cars (MkII), I don't see them. I'm sure these would be very helpful,
especially if you are doing a swap. If none exist (they surely must)
perhaps one of the more graphically skilled on the list could cook
something up, certainly there are enough cars out there as examples...just
a suggestion..

Cathy



One of the ports on
> the TB is "ported" vacuum. The little pin hole through to the inside
> is on the atmosphere side of the primary plate. It doesn't see vacuum
> until the plate is opened some. That's why it's important that the
> primary throttle plate is adjusted correctly, so the distributor
> doesn't have vacuum at idle and cause incorrect ignition timing.
> Just to run over this whole thing again. Your engine needs a certain
> amount of advance at wide open throttle. This amount starts out
> around 6-10 degrees and increases to 30-34 degrees in the 3000-3500
> rpm range and stays fairly constant from there on up. This advance is
> accomplished by the mechanical advance which is strictly RPM
> dependant. When your engine is in cruise mode, 3000-4000 RPM and
> light throttle, it is not pulling in a great amount of air and fuel.
> As a result the mixture burns more slowly. Due to this the engine
> needs more ignition advance. This is accomplished by the vacuum
> advance. High manifold vacuum more advance, low manifold vacuum (WOT)
> low vacuum advance. The thing is the engine doesn't need the vacuum
> advance at idle or lower engine speeds and both the vacuum and
> mechanical advance are designed to provide the correct advance based
> on zero vacuum advance at idle. The KS ignition emulates this basic
> control strategy with better control. Dan
>
> ----- Original Message -----
> From: "Gordy Stedman" <ydrogs@gmail.com>
> To: "Dan Bubb" <jdbubb@verizon.net>; <Scirocco-l@scirocco.org>
> Sent: Saturday, July 30, 2005 8:28 PM
> Subject: Re: CIS basic idle/mix ballparking advice
>
>
> If you have a vaccum advance distributor make sure the place you
> attach the vaccum line to on the TB, usually before the butterfly
> valve, is not plugged or clogged.  I finally found out the reason my
> car was running so sh*#%y was because my distributor was not geting
> any vaccume. I had 2 outlets on the back of the TB and just switched
> the line to the one that weas sucking.  Just an experience I had that
> someone else might run into.  Also, what Dan said on adjusting the
> throttle isle position is right on, as always:)
>
> On 7/30/05, Dan Bubb <jdbubb@verizon.net> wrote:
> >  I'd start by backing off the primary throttle plate stop screw.
> >  It's right on top with an 8mm locking nut and usually some yellow
> >  paint to hold it. Back that out until the plate is fully shut then
> >  screw it in just enough that you know the plate has been opened
> >  some. The plate will tend to bind if
> >  it's allowed to close all the way and I believe that is the
> >  purpose of the stop screw, to hold it just a tad open. Alot of
> >  times people don't realize there is an idle adjustment screw and
> >  use the primary plate screw to adjust
> >  idle, so maybe that's it..
> >  Also, make sure the secondary plate is closing all the way.
> >  Sometimes they will bind open just a bit.
> >  If those two aren't it, then it's either a vacuum leak, auxilliary
> >  air valve
> >  that's not closing fully or an intake duct not fully seated.
>
> --
> Gordy
> MK1 x 3
> Audi 80 - Slated for parts car
>
>
>
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