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knock system questions...



wow dan, that's the clearest explanation i've heard of that.  so, the reason 
that setting idle advance at greater than stock doesn't increase power is 
that the most you're going to advance under load is to the map value.  ok. 
i've tested the rpm advance ad nauseum. to test vacuum advance, how about 
just connect/disconnect the hose at ~3k rpm? presumably the timing should 
advance with the hose connected, and retard when disconnected, right? i've 
tested switches, at least wot; i'll recheck idle (though i think that's 
working).  thanks again. btw, i've found at least one difference b/t the 
4k/16v boxes: the 4k has a 6800 rpm rev limiter, which is enough to get me 
to switch back to the old box...



-Michael Abatzis
Hotlanta! GA-->Soon to be New Orleans!
1988 Scirocco 2L 16v RIP-->parting, finally taking orders: 
www.learnlink.emory.edu/~mabatzi/mikes_page1.html
1987 Scirocco 2L 16v...




>From: "Dan Bubb" <jdbubb@ix.netcom.com>
>To: "Michael Abatzis" <abatzis2@hotmail.com>,<scirocco-l@scirocco.org>
>Subject: Re: knock system questions...
>Date: Mon, 28 Apr 2003 17:57:01 -0300
>
>The knock box is a map based system. In other words it uses two basic 
>inputs
>to determine ignition advance. On top of the two basic inputs are 3
>additional inputs that are used to modify the amount of igniton advance.
>The two basic inputs are RPM, to determine the, uh...RPM! and intake
>manifold vacuum to determine engine load. The vacuum port musted be
>connected to manifold vacuum, not ported vacuum. Don't connect it to the
>vacuum port on the TB. Connect it to a port on the big assed vacuum hose
>that goes to the brake booster.
>Typically, as RPM increases the ignition advance increases until you get to
>a certain RPM (~3500-4000) after which it will stay constant.
>Easy to test. Just disconnect the vacuum line from the unit and watch for
>igniton advance as the engine is revved.
>Also, as vacuum increases the ignition will advance. This is more difficult
>to test because the amount of vacuum/load based advance depends on RPM. I'd
>test it by holding the engine at 3000 RPM with the vacuum hose disconnected
>then check advance while sucking/pulling a vacuum on the hose.
>The 3 additional inputs are; idle switch, full throttle switch, and knock
>sensor.
>The idle switch tells the knock box to not to adjust advance due to engine
>vacuum while idling. This gives a nice stable idle and allows consistent
>timing to set the advance. If this switch isn't working the advance will be
>more than it should at idle and the total advance under load will be less
>(way less) than is optimum for power. (provided your vacuum hose is hooked
>up to manifold vacuum)
>The knock sensor, of course, alerts the knock box of knock. The box will
>retard timing until knock goes away, then try to readvance timing to the
>base number unless knock reappears. The knock box does not try to keep
>advancing from the base map value until it senses knock. The base map value
>is, presumeably, optimum for power and the until only retards from that
>value if knock is sensed.
>I'm not sure what the full throttle switch does, but I suspect it again
>tells the knock box not to look at manifold vacuum and just use the base 
>WOT
>settings.
>I'd check that the unit is advancing based on the RPM test and vacuum test
>above, and check for correct operation of the full throttle and idle
>switches.
>Hope all that was clear.
>Dan
>
>
>----- Original Message -----
>From: Michael Abatzis <abatzis2@hotmail.com>
>To: <scirocco-l@scirocco.org>
>Sent: Monday, April 28, 2003 6:27 PM
>Subject: knock system questions...
>
>
> > still can't figure out why the car is slow.  went to the yard, pulled 
>the
> > knock/fuel boxes from an audi 4k. it ran a little strange, so i checked
> > timing and for some reason it was way advanced. i thought i found my
> > problem, retimed, but still slow. questions:
> >
> > 1. is the knock box and fuel ecu the same on the 4k? look the same, have
> > different part #'s. i was wondering if the ignition map might be a bit
> > different (hence the screwed up timing).
> > 2. a basic knock sensor question: how the hell does it work? does it
>advance
> > it a certain amount (the 13' that bentley says?) and retard based on 
>knock
> > sensor input, or does it keep advancing till it senses knock, then 
>retard
>a
> > certain amount? some combo of the 2?
> > 3.  what is the vacuum hose input for?
> >
> > still pretty ticked at this car...
> >
> > -Michael Abatzis
> > Hotlanta! GA-->Soon to be New Orleans!
> > 1988 Scirocco 2L 16v RIP-->parting, finally taking orders:
> > www.learnlink.emory.edu/~mabatzi/mikes_page1.html
> > 1987 Scirocco 2L 16v...
> >
> >
> >
> >
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>


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