Mitzelj

iTrader: (1)

I've got a 99 Vette that I'm having throttle transtion or tip in KR with. When I
look at the raw excel file, it seems that one 02 is always low(double digit)
at that onset of the throttle opening. So I have a couple questions.

Would this be a lean hole in the VE table and would I tweak the primary or
secondary?

99 Vettes appear to have the burst knock table set to a delta of 16 and
then other burst knock table is zeroed out,is this normal?

I pulled a bin from Horist's site and the 99 Vette there is the same as
mine but 99 F-body's have the burst knock info populated as do later model
Vettes.

Any thoughts would be appreciated. Thanx, Jeff

jimmyblue

iTrader: (11)

I saw deltas of 0.010 being too low (on a '99 truck)
and triggering BK just from the changes in airflow on
RPM run-up. Moving up to 0.020 made things better
(no mystery spark pullout during WOT). To see the
(approximate) delta CylAir, take your Excel table of
Cylair and make a column of =max((N3-N2)/8,0) and
copy/past all the way down. The /8 is for the scaling
of 100mS frame rate vs 12.5mS calc rate. Plot this
and look at what your peak deltas are during WOT
run-up vs opening-throttle, and pick a burst knock
threshold that leaves WOT alone but (if you want)
suppresses tip-in ping.

However you probably want to fix it by VE enrichment
at the points where you see ping-hits. Primary table is
what you need, Secondary is what you get if the MAF
faults. Both should be fixed up. The secondary is just
every other line of the Primary, you can make an Excel
sheet that builds a Secondary off the Primary that way,
for convenience.

Mitzelj

iTrader: (1)

I saw deltas of 0.010 being too low (on a '99 truck)
and triggering BK just from the changes in airflow on
RPM run-up. Moving up to 0.020 made things better
(no mystery spark pullout during WOT). To see the
(approximate) delta CylAir, take your Excel table of
Cylair and make a column of =max((N3-N2)/8,0) and
copy/past all the way down. The /8 is for the scaling
of 100mS frame rate vs 12.5mS calc rate. Plot this
and look at what your peak deltas are during WOT
run-up vs opening-throttle, and pick a burst knock
threshold that leaves WOT alone but (if you want)
suppresses tip-in ping.


My CylAir Burst knock delta's are currently 16.0
which will prevent burst knock from ever engaging,
what I am logging is actual KR up to 8 degree on large
TPS deltas. If I understand it correctly Burst Knock
pulls timing in a preemptive strike to prevent KR from
ever occuring, correct? Would there be any downside
to enabling the burst knock table in my tune as it
appears the factory did in later years?

However you probably want to fix it by VE enrichment
at the points where you see ping-hits. Primary table is
what you need, Secondary is what you get if the MAF
faults. Both should be fixed up. The secondary is just
every other line of the Primary, you can make an Excel
sheet that builds a Secondary off the Primary that way,
for convenience.

I have scaled the VE table in the past and it really
didn't seem to help, but I'll play with it. Thanx, Jeff.

luv2spd

iTrader: (1)

Why don't you try doing a sd tune? If you get your trims negative in sd mode, you should take care of any lean spots. If you still get kr then mess w/ burst knock.

Mitzelj

iTrader: (1)

Why don't you try doing a sd tune? If you get your trims negative in sd mode, you should take care of any lean spots. If you still get kr then mess w/ burst knock.

That will be my next step, my trims run around 4 degrees negative and zero out when I go WOT. Thanx, Jeff

Mitzelj

iTrader: (1)

Here's what my research has revealed. My knock
occurs at low RPM to high RPM transtions.
It begins as a single event and the ramps down to
either 0 or stops when the throttle is lifted.

It's onset is unafftected by raising VE values or
reducing spark. I used burst knock and spark
reduction to pull the spark timing at the event to as
low as 10 degrees which resulted in a KR pull to
2.5 degrees total advance.

It's onset is not affected by fuel octane as I have
run the car with 100/104 CAM2 unleaded and still
observed the same KR events.

I have elminated all audible rattles in the engine/exhaust
system.

So, I believe this has to be an engine, valve train or exhaust
related harmonic that is causing the sensors to hear knock when
there is none. This coupled with my understanding that knock
events occur from low octane, excessive advance, lean fueling or
high engine loadings, leads me to believe the knock is false, as it is
most present when the motor spins up prior to a downshift or
against the converter during launch. The event always occurs
prior to the engine actually being loaded and then bleeds off
if the throttle is kept open.

So what I've done is descrease the knock sensors sensitivity
below 2800 RPM in the Knock Sensor Level vs
RPM vs CYL table. This has eliminated all of the KR.

So given that long explanation does anyone agree or disagree?

Thanx, Jeff

luv2spd

iTrader: (1)

Sounds like you did a good job of eliminating other possibilities. Good job!

Dragman

What did u put that figure on??

Mitzelj

iTrader: (1)

Quote:
Originally Posted by Mitzelj


So what I've done is descrease the knock sensors sensitivity
below 2800 RPM in the Knock Sensor Level vs
RPM vs CYL table. This has eliminated all of the KR.

So given that long explanation does anyone agree or disagree?

Thanx, Jeff



What did u put that figure on??

The stock table was 8,9,10 in places, a 2001 Cal I have has 11's and I raised it 15 then to 17 between 0 and 2800. I may lower it down above 1600 with futher testing. I am almost thinking the sensors are hearing the driveline or maybe the converter when the revs are ramping up quickly. The car has run it's best ET's by launching from idle, a 15 value fixed everything but the launch and a 17 cleared it completely. I still wonder if it is actual knock but no amount of octane or spark reduction seems to effect the incidence of the KR. Good luck your mileage may vary. Jeff

Dragman

can u post table?

Mitzelj

iTrader: (1)

Here are the tables I hope.

Dragman

Thanks I will look at my table and see what gives. Did u mess with gobal gain?

Mitzelj

iTrader: (1)

Nope, no changes. Jeff

Dragman

tried it but didnt help looks like false knock!

BLK02WS6

iTrader: (2)

When you were seeing this on launch, was it logging as actual KR, or just reduced timing?

I am seeing my timing drop down on launch to as low as 11 degrees and then not get back up to full 28* until 5,000 rpm. It is not showing as KR though - just reduced timing. At the tree, stalled up to 2,000 rpm, I have 28*, but as soon as it goes to 100% TPS, it drops down to 11 or 12 degrees and slowly climbs back up. No KR whatsoever. Subtracting the values in the burst knock or tip-in tables (not both, but don't know which it might be) from the high octane table seems to correspond pretty close to the values I am seeing.

So far, I zero'ed out the burst knock table completely below 5,000, but that didn't fix it, so I am suspecting the tip-in. I wanted to zero the tip-in table as well last night, but couldn't get another pass. I will try it next time I go to the track.

Anyone else experience this?