Whats an acceptable amount of KR?
07-17-2004, 12:39 PM
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Whats an acceptable amount of KR? Whats an acceptable amount of KR? The shop that is doing my tuning says .5 is what cars will usually see for the most part. I was assuming that if tuned properly and the car not having any false KR that it should always be zero.
07-17-2004, 02:50 PM
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If MBT lies prior to onset of detonation then KR
in the steady state is telling you that you've got
more spark timing than you need, as well as more
than the engine tolerates. I do not have any good
reference as to just -how close- to ping limit the
MBT timing point lies. But definitely before.
There is also the difference between steady-state
knock / retard, and event- or transition-initiated
knock. These really aren't "handled" well by the
MAF, IFR, PE, timing table changes that are the
tuning "norm". Transient KR I believe comes in when
things like throttle tip-in, fast upshift under load,
etc. abruptly change airflow faster than the MAF,
and MAF-based things (like CylAir that controls
the timing) can respond. In these cases of abrupt
RPM/MAP/etc. transitions I believe the PCM has
to "fall back on" the speed-density mode, which
is something very few of us have any kind of
handle on (and I ain't one of 'em). This is where
having a VE table that is accurate, shines through.
At any rate if you see knock that comes in only
on engine changes, you may have to chase it
down a different rabbit-hole.
in the steady state is telling you that you've got
more spark timing than you need, as well as more
than the engine tolerates. I do not have any good
reference as to just -how close- to ping limit the
MBT timing point lies. But definitely before.
There is also the difference between steady-state
knock / retard, and event- or transition-initiated
knock. These really aren't "handled" well by the
MAF, IFR, PE, timing table changes that are the
tuning "norm". Transient KR I believe comes in when
things like throttle tip-in, fast upshift under load,
etc. abruptly change airflow faster than the MAF,
and MAF-based things (like CylAir that controls
the timing) can respond. In these cases of abrupt
RPM/MAP/etc. transitions I believe the PCM has
to "fall back on" the speed-density mode, which
is something very few of us have any kind of
handle on (and I ain't one of 'em). This is where
having a VE table that is accurate, shines through.
At any rate if you see knock that comes in only
on engine changes, you may have to chase it
down a different rabbit-hole.
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07-17-2004, 04:35 PM
#8
Originally Posted by ataylors
have you verified that it is real not false knock?
Bill
07-17-2004, 08:03 PM
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If it's real knock then it should decrease in magnitude
when you enrich the mixture (at that point of operation)
or pull out timing.
False knock often tends to "like" a particular RPM.
Wherever something that buzzes or rattles, happens
to make the right "beat note" with the engine RPM
that the knock sensor blanking circuits use to
filter out the many false knock sources (mostly).
when you enrich the mixture (at that point of operation)
or pull out timing.
False knock often tends to "like" a particular RPM.
Wherever something that buzzes or rattles, happens
to make the right "beat note" with the engine RPM
that the knock sensor blanking circuits use to
filter out the many false knock sources (mostly).
07-18-2004, 10:34 AM
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How do you tell if it is false knock? I do not hear anything and the car does run great. I tuned the timing back a little and did not see any difference. I cleaned the MAF, tried gas booster, even tried a couple different air cleaners.
07-18-2004, 02:13 PM
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Originally Posted by ataylors
Sounds like false, one of the best ways is to go buy some race gas and drive around for a while then re-log it. If it stays the same start looking for knocks or rattles like motor mounts, trans mounts, exhaust, etc.
07-27-2004, 09:09 PM
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I always tune to zero. If you have any on the dyno and most of you own Fbodys then more than likely you will have more on the street. NOT BC OF IT LEANING OUT!!! that is FALSE! The reason is because it loads the motor harder than if you were on the dyno. Another thing is the "amount" in deg is not of any real significance, some cars have an allowable 10 deg retard in some areas where others are 4 deg max. The FREQUENCY is what really matters. I like to have the decay rates up real high and then you can find where within the retard the REAL problem area is.
EG. If the retard is decaying @ 3deg and 4800RPM and the car pulls more timing again before the 5200 cell (and goes right back up to 4 deg)then and there you know exactly how much timing to pull out in that area.
Jeremy Formato
EG. If the retard is decaying @ 3deg and 4800RPM and the car pulls more timing again before the 5200 cell (and goes right back up to 4 deg)then and there you know exactly how much timing to pull out in that area.
Jeremy Formato
07-28-2004, 05:04 PM
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Originally Posted by Richiec77
False knock can also be caused by Your valve springs. They can either be binding or creating harmonics which would cause valve chatter. This will also set the knock sensors off. I know. Just replacing the valve springs got rid of my false knock.
