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Rev Limiters (was RE: Knock Sensor Q)



Thank you to all, after reading allot of the tech answers on the subject  I
finally get it.

==========================================
ATS - Patrick Bureau
1985 8v **Planning 3A/JH  Upgrade**
1988 16v ** FOR SALE : 1500.00$ **
Web Site : http://longcoeur.com/scirocco


=>-----Original Message-----
=>From: drew [mailto:drew@dyermaker.cs.uoguelph.ca]
=>Sent: Friday, May 24, 2002 7:26 AM
=>To: ATS - Patrick Bureau
=>Cc: Brian Honnold; scirocco list
=>Subject: RE: Rev Limiters (was RE: Knock Sensor Q)
=>
=>
=>
=>Patrick, I'm running a similar setup in my 87 Jetta winter beater.  I
=>slapped some RD pistons in a JH block, threw on the JH head with a G
=>grind, and grafted a knock sensor ignition in from an A2 GLI.  I kept the
=>stock CIS, and the cat-free from factory 87 makes for some fun exhaust
=>options without having to worry about emissions woes (not that I do
=>anyways.)
=>
=>The kock box I used came from an 86 8V GLI, and the fuel pump relay was
=>the stock 87 Jetta CIS relay.
=>
=>I didn't think about rev limiters too much when assembling the system.
=>As a matter of fact, I didn't think about it too much when I installed the
=>16V instrument cluster with its 8K tach and 260km/h speedo, either.  For
=>some reason I developped a tendency to bounce of the 8V's top end when the
=>tach needle told me I had another 1000rpm to go before hitting the red...
=>:)
=>
=>I generally shift when the power starts to drop off, which is just about
=>6K anyways (limitation of the G grind?) however one morning I was in a
=>tight spot and kept into 3rd gear at WOT, and it kept pulling hard until
=>about 6200, when the engine started to buck like mad.  I dropped into 4th
=>and it started pulling again - my guess is I hit a rev limiter function
=>that was cutting fuel to the motor.
=>
=>My fuel pump relay is straight CIS (GX/MZ engines: 321 906 059H - compare
=>with CIS-E relays for RD/PL: 191 906 383 C)  Your 85 Scirocco should have
=>come with the "059 F" part - heaven knows what subtle engineering change
=>prompted the shift from F to H.
=>
=>My expectation, as I believe others have confirmed, is that the knock box
=>cuts the coil pulse to the relay, which then in turn cuts power to the
=>pump.  This "protection" mechanism, which keeps the pump from pumping an
=>accident scene full of fuel, has been present in CIS fuel systems for a
=>long time - I'd have to go back to the wiring diagrams to check, but I'm
=>pretty sure it was there in 81+ german-built cars.  Definitely there in
=>84+ cars.  Running either a 16V or 8V knock box (I'd go with the 8V box if
=>you're running an 8V engine, personally) with your stock fuel pump relay
=>should result in a rev limiter - it's just where it is that's the
=>question.
=>
=>HTH,
=>
=>Drew
=>
=>
=>
=>
=>On Thu, 23 May 2002, ATS - Patrick Bureau wrote:
=>
=>> but I have a MKII 85, running cis, not converting, just hybrid
=>3a/jg engine,
=>> I need a knock box because of 10.5:1 compression.
=>> does what you just stated (keep my current relay) simply
=>install a knock box
=>> (which ever no matter 8v or 16v) and it will never have a rev limitator?
=>>
=>> ==========================================
=>> ATS - Patrick Bureau
=>> 1985 8v **Planning 3A/JH  Upgrade**
=>> 1988 16v ** FOR SALE : 1500.00$ **
=>> Web Site : http://longcoeur.com/scirocco
=>>
=>>
=>> =>-----Original Message-----
=>> =>From: scirocco-l-admin@scirocco.org
=>> =>[mailto:scirocco-l-admin@scirocco.org]On Behalf Of Brian Honnold
=>> =>Sent: Thursday, May 23, 2002 2:18 PM
=>> =>To: scirocco list
=>> =>Subject: RE: Rev Limiters (was RE: Knock Sensor Q)
=>> =>
=>> =>
=>> =>Here's what I did when swapping cis-e into my MkI.
=>> =>
=>> =>Keep the stock fuel pump relay and wiretap the ground wire from
=>> =>the cis-e brain to the correct wire on the fuel pump relay.
=>> =>
=>> =>This give you a complete circuit with no rev limiter.
=>> =>
=>> =>Brian H
=>> =>
=>> =>-----Original Message-----
=>> =>From: scirocco-l-admin@scirocco.org
=>> =>[mailto:scirocco-l-admin@scirocco.org]On Behalf Of Ken Bates
=>> =>Sent: Thursday, May 23, 2002 10:25 AM
=>> =>To: Jonas K.; Cory Langford; scirocco list
=>> =>Subject: Re: Rev Limiters (was RE: Knock Sensor Q)
=>> =>
=>> =>
=>> =>This is exactly MY problem and why I started this thread the
=>other day.  I
=>> =>am not getting a ground on the switching side of my fuel pump
=>realy and
=>> =>suspect my Knock Box is not "completing" this circuit.
=>> =>I am about to do just exactly what Jonas is saying and jumpering
=>> =>a seperate
=>> =>ground to the FPR.
=>> =>I ma followingthis closely.  I appreciate all the input.
=>> =>Ken
=>> =>'79 Scirocco 16v project "McFly"
=>> =>'86 16v (parts car)
=>> =>VORTEX:  "Indiana Red"
=>> =>
=>> =>----- Original Message -----
=>> =>From: "Jonas K." <jkarlsso@metabolex.com>
=>> =>To: "Cory Langford" <cory.langford@icbc.com>; "scirocco list"
=>> =><scirocco-l@scirocco.org>
=>> =>Sent: Thursday, May 23, 2002 11:59 AM
=>> =>Subject: Re: Rev Limiters (was RE: Knock Sensor Q)
=>> =>
=>> =>
=>> =>> On 5/23/02 10:36 AM, "Cory Langford" <cory.langford@icbc.com> wrote:
=>> =>>
=>> =>> > 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?
=>> =>>
=>> =>> From my stydy of the system a couple of years back, (i.e. hazy
=>> =>memory) the
=>> =>> Knock box actually provides the ground that keeps the relay
=>going. When
=>> =>the
=>> =>> rev limit is exceeded the ground is removed and fuel pump shuts off.
=>> =>>
=>> =>> Cutting the wire would render the FPR permanently off. The
=>worst kind of
=>> =>rev
=>> =>> limiter there is. :-)
=>> =>>
=>> =>> You might be able to short the wire to ground permanently,
=>for a crude
=>> =>> "fix", or with some creativity one could probably retrofit an
=>> =>earlier FPR
=>> =>> without too much difficulty. The rev limiter should be de-activated.
=>> =>>
=>> =>> Let me know if it works.
=>> =>>
=>> =>> Jonas
=>> =>>
=>> =>>
=>> =>> _______________________________________________
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=>> =>>
=>> =>
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=>>
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=>
=>Drew MacPherson - '84 Wolfsburg Edition Scirocco TurboDiesel
=>
=>