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Spark Plugs - pre ignition issue
Ben's pinging is quite a bit more than that... It will ping not only under
throttle transitions (which can tend to happen on moving-part air meter
systems), but also under constant load. Whether the KS is actually working
in his case is really unimportant in terms of finding the problem with
detonation... Obviously it would potentially correct it, but as they say,
that's putting a Band-Aid over a bullet wound. The question here is, more
than anything else, why the car is pinging like this.
Ben, some questions:
1. How is it on cool evenings and mornings? If it still does it,
something changed, because it didn't do it this spring when it was cool out.
2. Have you done a compression check to see what your effective
compression really is? (Mine puts 195-205psi, and can take only about 9'
before I start hearing pinging on 93).
3. Perhaps the Schrick 260/276 cams are resulting in hotter exhaust
manifold temperatures, which is resulting in the pinging... and causing you
to not be able to advance to stock timing.
4. Since the advance on the 16V is vacuum-actuated, perhaps the additional
air you're flowing is causing more of an advance at higher loads than would
normally be the case. Check your total advance with and without the vacuum
line connected and compare it to that of a stock 16V at 2000, 3000, and
4000rpm. (I'll do mine if you need me to).
5. IIRC, isn't it the KS Box that controls RPM and Load-Dependent ignition
advance? Since we already know that something is kooky with your KS Brain
(i.e. it doesn't do shit), perhaps you should swap it out with another and
see what happens.
6. Since it's so difficult to get a true reading of ignition advance at
idle with your cams, who's to say that just averaging the timing mark is
actually where the timing is set to? It could be that your timing is, in
fact, advanced further than the reading shows, but the KS Brain is
interpreting the lumpy idle as knocking, and continually messing with
timing? Disconnect the KS brain and see if the timing is less jumpy at
idle. If not, measure timing at 1500rpm (or as low as you can get a smooth
idle) and use that to interpolate base 1000rpm timing compared with another
16V.
7. Another possible crutch would be to use a ridiculously low temperature
thermostat. Your car runs fantastically cool oil temperatures, but IIRC
you'll see "normal" (i.e. needle on the LED) water temps. Reduce the water
temp and you'll cool the head some more.
8. Did any of the plugs you remove indicate that perhaps only one cylinder
was experiencing the detonation? Check it out -- if so, it might be a
partially-clogged injector that is causing one cylinder to lean out.
9. Where is your O2 sensor? Stock location, right?
10. Could it be that the wiring in your A/F gauge is causing an O2 sensor
reading that is too high, resulting in your Fuel box leaning out the
mixture more than it should? The gauge shows you running just lean of
stoich, but hey, you never know...
11. Do you have a pyrometer (or whatever those non-contact high-temp
thermometers are called)? If so, check the temp of each runner on the
exhaust manifold and see if one is running much hotter than the
others. That would indicate a potential source for the problem...
12. It does also ping under full-throttle, right? If so, we can ignore
the O2-sensor arguments. ;)
Jason
At 06:32 AM 7/24/2003, Allyn wrote:
>after the 2.0 swap (standard compression) on the rieger, i can hear some
>onset to detonation during shifts (as i accelerate into the next gear). this
>is with standard timing, and only happens on really hot days. the only
>electrical part i changed during the swap was the knock sensor that came
>with the 2.0 block. my guess is that all it takes is a bad knock sensor.
>i'll know soon enough, once i dig up the old sensor and throw it back on.
>Al
>
>----- Original Message -----
>From: "Benjamin Harder" <vwtype53@yahoo.com>
>To: <scirocco-l@scirocco.org>
>Sent: Wednesday, July 23, 2003 11:36 PM
>Subject: Spark Plugs - pre ignition issue
>
>
> > I've been having an issue lately with pre-ignition (pinging) on my mk1's
> > 2.0 16v engine. Engine is freshly rebuilt with approximately 11:1
>compression,
> > running CIS-E, stock ignition, always on 93 octane, etc.
> >
> > If I set the ignition timing to stock settings (6-8 degrees) the engine
> > will ping (my knock sensor is obviously not functioning). I will then
>retard
> > the timing to around 4-6 degrees and everything seems fine... just the
>fact
> > that I'm losing some performance. :(
> >
> > So, I checked my spark plugs to see that I was running the stock 3
>electrode
> > Bosch plugs for the 2.0 16v, which have a heat rating of 6.
> > Due to my higher compression, I sourced a different Bosch plug with heat
>rating
> > of 5 (colder plug). Thinking that this would dissipate heat faster
> > and help solve my pre ignition issue... nope.
> > The new plugs don't seem to have helped.
> >
> > Anyone have experience in the high-compression world with this pinging
> > issue. Sure I could run octance booster or race gas, but I know that
> > there must be a way to run 93 pump gas... right? :/
> >
> > If I go to a colder plug (like a 4 rating), would this possibly help?
> >
> > TIA!
> >
> >
> > =====
> > Benjamin Harder
> > 86 Scirocco 16v
> > 80 Scirocco 16v
> > 93 Passat GLX
> >
> > http://www.geocities.com/vwtype53/
> >
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>
>
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