KR when pulling 2000-6200 rpm in 2nd gear, only
10-15-2004, 01:44 PM
#1
KR when pulling 2000-6200 rpm in 2nd gear, only I have noticed a strange situation from my C5 that I can repeat 100% of the time...
If I am out tuning and do a WOT run from 2000 to 6200 rpm in 2nd gear I will get bad KR (approx. 4000 rpm)...
BUT...
If I row through 1st gear at WOT (approx. 6000 rpm) and then shift to 2nd and then 3rd, etc.. I get absolutely no KR...
What gives
If I am out tuning and do a WOT run from 2000 to 6200 rpm in 2nd gear I will get bad KR (approx. 4000 rpm)...
BUT...
If I row through 1st gear at WOT (approx. 6000 rpm) and then shift to 2nd and then 3rd, etc.. I get absolutely no KR...
What gives
10-15-2004, 02:12 PM
#2
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This sounds like the behavior of false KR to me. As a
diagnostic I would back off timing by (say) 2 degrees
about the RPM point where it typically comes on. Get
the same amount of KR, then it's likely false.
As a cover-up you might want to go into the KR vs RPM
table and just "blank" the one RPM "slot" that corresponds
to the trouble (also foregoing any KR protection there
but, oh, well).
Hopefully we will soon see some knock sensor filtering
"*****" to try and squash it at the front end, where it
needs it.
diagnostic I would back off timing by (say) 2 degrees
about the RPM point where it typically comes on. Get
the same amount of KR, then it's likely false.
As a cover-up you might want to go into the KR vs RPM
table and just "blank" the one RPM "slot" that corresponds
to the trouble (also foregoing any KR protection there
but, oh, well).
Hopefully we will soon see some knock sensor filtering
"*****" to try and squash it at the front end, where it
needs it.
10-15-2004, 02:38 PM
#3
THANKS!!! Some how I knew you would be 1st to answer.... 
The KR (8 degrees) happens at 4000 rpms and .76 g/cyl load (24 degrees timing). The timing starts recovering (KR goes away) immediately as rpms go up...
The KR (8 degrees) happens at 4000 rpms and .76 g/cyl load (24 degrees timing). The timing starts recovering (KR goes away) immediately as rpms go up...
Last edited by SideStep; 10-15-2004 at 02:52 PM.
10-15-2004, 02:59 PM
#4
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Going down the "not false" fork in the road, I would
check the spark table and see that 4000RPM (or
whatever) is not a place where you have any sudden
increment in spark advance or sudden drop in PE table
value (I know I've seen some funny things, where folks
have dips and bumps rather than nice smooth surfaces).
I have had to go and push out the spark rise from 25 to
26, 76 g/cyl, from 4400 to 4800 for example to hold off
some pinging. That works, that means it wasn't false.
If it's slamming you bad try decreasing the attack to 0.100
and bring the recovery up to 0.200, then KR will be less of a
performance hit when it does come on. You'll see it jump by
a fraction of a degree rather than 2-4 degrees on the first
blip and it will be gone in a second instead of 2, etc.
check the spark table and see that 4000RPM (or
whatever) is not a place where you have any sudden
increment in spark advance or sudden drop in PE table
value (I know I've seen some funny things, where folks
have dips and bumps rather than nice smooth surfaces).
I have had to go and push out the spark rise from 25 to
26, 76 g/cyl, from 4400 to 4800 for example to hold off
some pinging. That works, that means it wasn't false.
If it's slamming you bad try decreasing the attack to 0.100
and bring the recovery up to 0.200, then KR will be less of a
performance hit when it does come on. You'll see it jump by
a fraction of a degree rather than 2-4 degrees on the first
blip and it will be gone in a second instead of 2, etc.
10-15-2004, 08:05 PM
#5
Bad news...
I pulled 3 degree out of that particular cell (.76 g/cyl - 4000 rpm) and I am still getting KR but not as much... Now I am showing 2.5 to 3 degrees KR and it is still happening at 4000 rpm. I repeated the WOT run 3 times. I take it this means no false knock.
My High Octane table (factory) shows 21 degrees advance for that cell. BUT, when I log I see 24 degrees for that cell on the scanner , on the few times KR has not shown up and mashed the timing down......
I know I have good AF ratios.... see below (DunoJet WBC)
TIME RPM AFR
11.617 2448 13.2
11.737 2568 13.3
11.857 2657 13.6
11.988 2776 13.4
12.108 2864 13.4
12.238 2977 13.3
12.358 3064 13.3
12.478 3174 13.3
12.598 3218 13.4
12.659 3314 13.2
12.779 3417 13.3
12.909 3518 13.3
13.029 3565 13.3
13.079 3661 13.3
13.199 3726 13.3
13.279 3836 13.3
13.400 3890 13.3
13.480 3975 13.2
13.580 4083 13.3
13.700 4194 13.2
13.830 4301 13.1
13.950 4391 13.1
14.071 4403 13.1
14.091 4497 13.0
14.211 4596 13.0
14.331 4686 13.0
14.451 4744 13.0
14.501 4844 13.1
14.621 4916 12.8
14.742 5023 12.8
14.862 5075 12.8
14.942 5178 12.8
15.062 5221 12.7
15.142 5313 12.8
15.262 5404 12.8
15.383 5434 12.7
15.443 5499 12.7
15.563 5556 12.8
15.643 5647 12.7
15.773 5727 12.7
15.903 5755 12.7
15.943 5828 12.7
16.063 5923 12.7
16.194 5948 12.7
16.244 6010 12.7
16.364 6053 12.7
16.444 6139 12.7
16.564 6199 12.6
Where NEXT
I pulled 3 degree out of that particular cell (.76 g/cyl - 4000 rpm) and I am still getting KR but not as much... Now I am showing 2.5 to 3 degrees KR and it is still happening at 4000 rpm. I repeated the WOT run 3 times. I take it this means no false knock.
My High Octane table (factory) shows 21 degrees advance for that cell. BUT, when I log I see 24 degrees for that cell on the scanner
, on the few times KR has not shown up and mashed the timing down......I know I have good AF ratios.... see below (DunoJet WBC)
TIME RPM AFR
11.617 2448 13.2
11.737 2568 13.3
11.857 2657 13.6
11.988 2776 13.4
12.108 2864 13.4
12.238 2977 13.3
12.358 3064 13.3
12.478 3174 13.3
12.598 3218 13.4
12.659 3314 13.2
12.779 3417 13.3
12.909 3518 13.3
13.029 3565 13.3
13.079 3661 13.3
13.199 3726 13.3
13.279 3836 13.3
13.400 3890 13.3
13.480 3975 13.2
13.580 4083 13.3
13.700 4194 13.2
13.830 4301 13.1
13.950 4391 13.1
14.071 4403 13.1
14.091 4497 13.0
14.211 4596 13.0
14.331 4686 13.0
14.451 4744 13.0
14.501 4844 13.1
14.621 4916 12.8
14.742 5023 12.8
14.862 5075 12.8
14.942 5178 12.8
15.062 5221 12.7
15.142 5313 12.8
15.262 5404 12.8
15.383 5434 12.7
15.443 5499 12.7
15.563 5556 12.8
15.643 5647 12.7
15.773 5727 12.7
15.903 5755 12.7
15.943 5828 12.7
16.063 5923 12.7
16.194 5948 12.7
16.244 6010 12.7
16.364 6053 12.7
16.444 6139 12.7
16.564 6199 12.6
Where NEXT
Last edited by SideStep; 10-15-2004 at 10:21 PM.
10-15-2004, 10:17 PM
#6
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Some people like 13.0 AFR for power on these motors
but I think you should push on the PE vs RPM table,
5000RPM and below, and get the AFR consistently
below 13:1. Maybe 13.3:1 is just a little too light &
snappy to stay quiet.
In fact I say put it all to 12.8:1 and see if that shuts
it up.
but I think you should push on the PE vs RPM table,
5000RPM and below, and get the AFR consistently
below 13:1. Maybe 13.3:1 is just a little too light &
snappy to stay quiet.
In fact I say put it all to 12.8:1 and see if that shuts
it up.