Rev Limiters (was RE: Knock Sensor Q)

[green536@hotmail.com (Chris DeLong)]

Why ground the CIS-E brian ground to the same ground as the relay? They both 
go to the same place; ground. Simple. Not a switched ground. And have you 
taken apart a MK1 fuel pump relay? I'm sur eyou have. Well that little 3 
pronged black thingy combined with the biasing resistors and caps basically 
make up an Ne 555 IC. So you are basically incorrect. An Ne 555 has 
resistors etc built in for less space to be taken up the board. Hence the 
smaller size of the MK2 relay. Still operates on the same basic principle as 
a MK1 relay. The little spade connector is fed a pulsed ground trigger from 
the knock brain on a CIS-E car. Jsut as it is fed a ground from the coil on 
a MK1 car. The only difference being that it is a more sophisticated relay 
on a MK2 and the fact that the ground comes fromt he knock brain and not the 
coil. HTH

>
>They ain't got no fancy schmancy 555 chips in the MkI fuel pump relay.  So 
>wire the fuel pump and the relay like a MkI use the MkI relay and ground 
>the cis-e brain into the relay ground.
>
>Simple yet Effective :-)
>
>BcH
>
>-----Original Message-----
>From: scirocco-l-admin@scirocco.org
>[mailto:scirocco-l-admin@scirocco.org]On Behalf Of Marc scirocco Québec
>Sent: Thursday, May 23, 2002 4:00 PM
>To: scirocco-l@scirocco.org
>Subject: Re: Rev Limiters (was RE: Knock Sensor Q)
>
>
>The fuel pump relay is more than just a relay. There
>is a circuit in there that picks up a pulse from the
>coil, blends it with a 555 timer (IC), and that gives
>it a solid signal to drive a transistor, and then to
>drive the actual relay (more or less that way).
>
>This is done for safety reason: as soon as the motor
>stops physically turning (like in an accident), the
>fuel pump stops working, after a second or two.
>
>Of course, since it picks up a signal from the coil,
>it can shut the pump at a desired preset.
>
>Simple, yet brilliant!
>
>Cheers.
>
>Marc
>'83 Scirocco
>'88 Scirocco Slegato
>
>  --- Cory Langford <cory.langford@icbc.com> a écrit :
> >
> >  Just a wild thought here.
> >
> > If the Knock Box tells the Relay when to shut down
> > the fuel pump, I
> > would suspect that would be done via a voltage/no
> > voltage situation to a
> > specific pin from the box to the relay.
> >
> > So if that wire was cut (the connection between the
> > relay and the knock
> > box) would not the rev. limiter be removed?  If
> > there was a need for
> > voltage, I am sure you could connect the correct
> > voltage from another
> > source to keep the fuel pump working.
> >
> > I do realize this brings up other issues, like
> > safety if the engine cuts
> > out and the fuel pump keeps on going, but who needs
> > safety for a engine
> > that can rev till it fly's apart :)
> >
> >
> >
> >
> > -----Original Message-----
> > From: Jonas K. [mailto:jkarlsso@metabolex.com]
> > Sent: Thursday, May 23, 2002 9:57 AM
> > To: ATS - Patrick Bureau; scirocco list; Chris
> > DeLong
> > Subject: Re: Knock Sensor Q
> >
> >
> > On 5/23/02 6:43 AM, "ATS - Patrick Bureau"
> > <pbureau@attbi.com> wrote:
> >
> > > you know I read your replies 3 times... and you
> > make no sense what so ever.
> >
> > Aagh, sorry, guess that's what I get for trying to
> > be thorough. :-)
> >
> > > 1. you are saying that the 8v and 16v knock box
> > are the same (or you don't
> > > know)
> >
> > Yes. :-) Don't know for _sure_, but they should have
> > the same wiring.
> > Best
> > bet would be to use a harness and box from the same
> > (8v or 16v) that way
> > you're safe.
> >
> > > 2. then you say the relay has nothing to do with
> > it, but the cut off is
> > > controlled by the knock box
> >
> > What I meant is that the relays between the RD 8v's
> > and the PL 16v's are
> > the
> > same. The knock box controls at what RPM the relay
> > shuts off the fuel
> > pump.
> >
> > > now if the knock boxes are the same and the relays
> > are not the controlling
> > > device, how does the
> > > knock box know its controlling an 8v (6800Rpm) or
> > 16v engine (7200 rpm) and
> > > adjust itself to the proper engine?
> >
> > Aha, I see the confusion. The 8v and 16v knock boxes
> > have entirely
> > different
> > part numbers, and somewhat different interals. They
> > are clearly not the
> > same. The main diffenerce AFAIK is that the rev
> > limits are set
> > differently
> > between the two. I thought this was understood, and
> > that the question
> > was if
> > a 16v knock box would connect up to an 8v harness
> > and be a plug-n-play
> > bump
> > up in the rev limit.
> >
> > > what I want to know is
> > > what controls the rev limitation (knock box?
> > relay?) if knock box, then
> > > logic dictates that an 8v and 16v knock box would
> > be different JUST because
> > > they rev limitator are set different  (no matter
> > if they are wired the same)
> >
> > The rev limit is strictly set by the knock box. The
> > 8v is different in
> > this
> > respect from the 16v.
> >
> > > and btw.. I am talking about SCIROCCO here not A2.
> >
> > Right, I got that. What I was telling you is that
> > when you put the
> > knocksensing system into your scirocco, you will
> > retain your stock fuel
> > pump
> > relay. This one does not take an input from the
> > knock box, so regardless
> > of
> > which box you use, you will not encounter a rev
> > limiter.
> >
> > I've got the 8v system in my 85 and in my 78, no rev
> > limit other than my
> > right foot, and frailed nerves.
> >
> > Hope that cleared things up, sorry for the
> > confusion.
> >
> > Jonas
> >
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>
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Chris DeLong
ICQ#45030867
Seattle, WA USA
'80 16V 'Rocco ragtop
'91 GLi 2.0 16V
'77 Rabbit 16V
'80 'Vert (parting out!)
'61 17 Window type II
'91 Vanagon
'78 Rabbit
'84 Jetta


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