Re: question: ignition advance and CIS-E

[Brett Van Sprewenburg <brett@netacc.net>]

>The way I understand it , CIS-E runs a knock box which serves to
>retard timing if the knock sensor detects knock.  So basically, the
>engine management system runs full advance until knock is detected,
>and then timing is retarded until no more knocking.  Correct?

Sorta...there's more then 'full advance' and static advance stages.

> With
>the stock 6 degrees of advance, the system would run a MAX 6 degrees
>of advance until/if knock is detected, correct?

No.

16v timing is not controlled via centrifugal or vacuum assisted advance,
like the 8v's.  All advance beyond static (6 degrees in your case) is
controlled by the computer...and there's plenty of it.  The electronics
will retard timing back to static (in stages), which is 6 degrees,
if knock is detected.

>
>If I set the ignition timing to 6+3 degrees advance, for a total of 9
>degrees advance (from top dead center on flywheel), or, in other
>words, 3 degrees advance more than stock, the CIS-E system would try
>to run at 6+3 until/if knock is sensed and then it would retard timing
>until no more knock.  Correct?

Not exactly.  Yes, static timing would be 9 degrees advance, but there
are RPMs / engine loads which ping at 9 degrees static + CIS-E map
timing, so yes, the electronics would retard timing and performance would
suffer.  Say, normally you'd get 6 + 14 = 20 degrees advance at a certain
RPM, but you've added just enough for ping to set in (9 + 14 = 23), so
the knock sensor / electronics step in and retard the timing back some
amount > 3 degrees...say 10...now you're running a 'safe' 13 degrees
instead of 20 ... performance suffers.  This is why advancing the timing
on a 16v generally results in lower performance.

>
>Anyone running 6+3 degrees on their 16vs?

Don't bother, as numerous testing by people like Techtonics have
determined that 16v performance suffers beyond 6 degrees static advance.

> Is there any advantage?

Doubtful.

> I
>was running a lot of advance on my old 8v with the Euro distributor
>and I like what it did for the down low power.  The great thing about
>the Euro distributor was that it didn't kill my top end.

Totally different beast, the 8v likes more timing, and if it doesn't
ping, can tolerate it and create a bit more power.  In fact, there
used to be a 'free' 4-5hp mod by advancing the timing to 12 degrees
on the 8v.

>
>what is the verdict on 16vs?  I have a 2.0L bottom end, euro intake,
>performance exhaust and will be slapping a 50mm intake on.  I was
>thinking about advancing the timing a little bit to accomodate the
>small loss of low end torque due to the 50mm intake.

Let us all know how the 50mm affects performance.

>
>Since I have a timing gun I can do this fairly easily.  Too bad I
>don't have a G-Tech, or I would be able to post some #rs to the list.

Put the timing light on the cam gear for instance, watch the 0 degree
TDC notch...rap on the throttle and see the notch 'lean' into the
engine rotation under computer controlled advance.  I'd say you could
use the flywheel, but the timing hole is so small and difficult to
see, it's easier demonstrated with the cam gear.

>
>Thanks,
>
>Victor

==Brett

 \/  '84 Scirocco (ITB racer 2B) | "Hot VW's, take two home. They're small"
\/\/ '88 Scirocco 16v (Show), '92 Passat 16v (Winter+) | - brett@netacc.net

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