KR Only at Shift
04-13-2006, 05:18 PM
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KR Only at Shift Need some help figuring out which direction to go to get rid of logged KR. Not seeing any during daily driving, only under WOT at the track and then only at the shift. I had some tip in KR but have been able to fix that by tweaking RPM/TPS that PE kicks in.
Here's the particulars on the run, by the way it is a 98 in a 3rd Gen, Custom CAI and no CAT exhaust, other wise stock.
KR logged 2.5
Shifted 1/2 at 5641 (I'm working on that, commanded at 6K)
Speed at shift 42
IAT was a little high, 108, ECT 198
Dyn CylAir .62, MAF 9008Hz
MAP 97
O2s 933/924mV (PE enrichment multipliers tables still stock)
Advance 26.5 immediately prior to shift and before KR. Spark table shows I should have been at 28/29, I think it was pulling some timing because of the IAT temp.
KR kicked in as soon as shift was commanded and RPMs had just started to drop (5325) At the point KR was logged no of the other parameters had changed hardly any from those described above.
No KR logged on 2/3 shift.
Considering tweaking the knock sensor global gain up a little from stock setting of 1 but don't want to loose the protection.
Any suggestions appreciated.
Here's the particulars on the run, by the way it is a 98 in a 3rd Gen, Custom CAI and no CAT exhaust, other wise stock.
KR logged 2.5
Shifted 1/2 at 5641 (I'm working on that, commanded at 6K)
Speed at shift 42
IAT was a little high, 108, ECT 198
Dyn CylAir .62, MAF 9008Hz
MAP 97
O2s 933/924mV (PE enrichment multipliers tables still stock)
Advance 26.5 immediately prior to shift and before KR. Spark table shows I should have been at 28/29, I think it was pulling some timing because of the IAT temp.
KR kicked in as soon as shift was commanded and RPMs had just started to drop (5325) At the point KR was logged no of the other parameters had changed hardly any from those described above.
No KR logged on 2/3 shift.
Considering tweaking the knock sensor global gain up a little from stock setting of 1 but don't want to loose the protection.
Any suggestions appreciated.
Last edited by crewchef; 04-13-2006 at 05:24 PM.
04-13-2006, 05:35 PM
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Do you still have the 1998 knock sensors in the car or did you upgrade to the newer style sensors w/ harness?
Also, is the knock consistent or does it occur only sometimes?
Also, is the knock consistent or does it occur only sometimes?
04-13-2006, 05:49 PM
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Purchased what is supposed to be a stock 98 pull out. I didn't check the part numbers on the knock sensors while we had it apart but assume they're stock.
I see no KR at all in normal driving around town but I hardly ever do WOT passes on the road either. Only KR I've logged has been at WOT at the track.
I was only able to get two passes in, we had a short private test time but we were working on an Outlaw car at the time and it got priority. First pass had the tip in problem and KR was still present from that at the 1/2 shift. Tweaked that out and made the second pass and saw the KR at shift. Short answer, only got one good log that shows the KR.
Hoping to get out to regulart T&T night tomorrow and log a few more runs. I was hoping to have a potential fix ready to try out if I see it on the first pass.
I see no KR at all in normal driving around town but I hardly ever do WOT passes on the road either. Only KR I've logged has been at WOT at the track.
I was only able to get two passes in, we had a short private test time but we were working on an Outlaw car at the time and it got priority. First pass had the tip in problem and KR was still present from that at the 1/2 shift. Tweaked that out and made the second pass and saw the KR at shift. Short answer, only got one good log that shows the KR.
Hoping to get out to regulart T&T night tomorrow and log a few more runs. I was hoping to have a potential fix ready to try out if I see it on the first pass.
04-13-2006, 09:08 PM
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The 1998 knock sensors are notorious for picking up false knock. I actually have a set of the '99+ sensors and wiring harness sitting on my workbench waiting to go in my car. I have logged tons of sporadic and inconsistent knock over a variety of conditions. There was also a TSB on the '98 sensors about building a dam of RTV around them to prevent water from engine washing from corroding the sensors.
Many people desensitize or completely eliminate knock retard with tuning, but I don't like this idea. Some use Teflon tape (pipe thread sealant) on the sensor threads to desensitize them. Last but not least is the swap to newer style sensors and wiring harness to eliminate the problem. This solution was just under a $100 from GMpartsdirect.com, I'm hoping it works well.
Many people desensitize or completely eliminate knock retard with tuning, but I don't like this idea. Some use Teflon tape (pipe thread sealant) on the sensor threads to desensitize them. Last but not least is the swap to newer style sensors and wiring harness to eliminate the problem. This solution was just under a $100 from GMpartsdirect.com, I'm hoping it works well.
04-14-2006, 12:15 AM
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Perhaps you want to play with the attack and decay
rates so that persistent knock is suppressed but any
single detect brings on less retard and goes away
quicker. Not to the point of audible ping, but some.
When you shift at WOT you have a moving air column
stuffing down a slowing-down throat. This briefly will
increase MAP and cylinder pressures, perhaps challenge
the spark timing (which may not yet have pulled back,
all sensors lag reality). So too may your fuel shot be
a bit late to the party?
If you see a MAP spike or Dynamic Cylinder Air spike
then inspect the timing table at that end and see if
maybe it's not faded against rising cylinder air charge
enough.
Or just throw more fuel at the shift-to RPM, if you see
a lean dip in the O2s.
rates so that persistent knock is suppressed but any
single detect brings on less retard and goes away
quicker. Not to the point of audible ping, but some.
When you shift at WOT you have a moving air column
stuffing down a slowing-down throat. This briefly will
increase MAP and cylinder pressures, perhaps challenge
the spark timing (which may not yet have pulled back,
all sensors lag reality). So too may your fuel shot be
a bit late to the party?
If you see a MAP spike or Dynamic Cylinder Air spike
then inspect the timing table at that end and see if
maybe it's not faded against rising cylinder air charge
enough.
Or just throw more fuel at the shift-to RPM, if you see
a lean dip in the O2s.
04-14-2006, 07:19 AM
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Thanks for the response, I'll go back over the log and and watch each of these to see what was happening during the shift.
If you're checking back in on this thread could you also add your .02 on why it may be shifting early? WOT shift RPM is set 1/2 @ 6000, 2/3 @ 5900 but it shifted at 5650 and 5750. WOT shift speeds are 34/75/126 in all three tables. Enable TPS is 90, disable at 80 and in this particular run it was WOT/100% at the shifts. Part throttle shift table 100 TPS column matches with WOT shift speeds. Shift speed parameters had been exceeded when it shifted just didn't reach the desired RPM.
If you're checking back in on this thread could you also add your .02 on why it may be shifting early? WOT shift RPM is set 1/2 @ 6000, 2/3 @ 5900 but it shifted at 5650 and 5750. WOT shift speeds are 34/75/126 in all three tables. Enable TPS is 90, disable at 80 and in this particular run it was WOT/100% at the shifts. Part throttle shift table 100 TPS column matches with WOT shift speeds. Shift speed parameters had been exceeded when it shifted just didn't reach the desired RPM.
04-14-2006, 09:20 AM
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Originally Posted by jimmyblue
then inspect the timing table at that end and see if
maybe it's not faded against rising cylinder air charge
enough.
maybe it's not faded against rising cylinder air charge
enough.
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04-14-2006, 12:09 PM
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No, I mean that your timing table should continue to pull
out timing as CylAir increases, just as you see in the
normal range of operation; more cylinder pressure (air)
needs less spark because the burn speed goes up. But I
have seen some tunes where everything above 0.8 or so,
keeps the same spark timing. Like my stock tune from GM.
As if air above 0.8 suddenly disobeys combustion physics.
I made a figure showing what I'm talking about:
out timing as CylAir increases, just as you see in the
normal range of operation; more cylinder pressure (air)
needs less spark because the burn speed goes up. But I
have seen some tunes where everything above 0.8 or so,
keeps the same spark timing. Like my stock tune from GM.
As if air above 0.8 suddenly disobeys combustion physics.
I made a figure showing what I'm talking about:
04-14-2006, 01:07 PM
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Jimmy, if that's what my spark table needs to look like I'm starting in a different ball park. I would like to see the table that goes with the graph just to see what you're numbers look like. Currently mine still has the stock table and it's pretty ugly, especially with that big trough at 4000 to 5600 RPM.
I went back and checked my log file again and it doesn't appear that there were any spikes in the air mass. If you wouldn't mind taking a look I can email you the file. Tried attaching but can't get it small enough in .jpg format and can't attach a .hpl file. One thing I hadn't notice because of my focus on the KR is that it doesn't appear that there's any TQ Mgmt going on during the shift. Wanted to point that out because it is still enabled right now and I did see it on the other pass I logged. It was my son't first pass down the strip and he never got true WOT. Is there no TQ Mgmt at WOT? Based on what I've read I thought there was but maybe I missed something.
Maybe it was just false knock anyway and I need to log some more passes to see if it's consistently there before I try to start fixing a problem that really isn't one.
If you get a chance to respond on the tranny shifting I would appreciate it.
I went back and checked my log file again and it doesn't appear that there were any spikes in the air mass. If you wouldn't mind taking a look I can email you the file. Tried attaching but can't get it small enough in .jpg format and can't attach a .hpl file. One thing I hadn't notice because of my focus on the KR is that it doesn't appear that there's any TQ Mgmt going on during the shift. Wanted to point that out because it is still enabled right now and I did see it on the other pass I logged. It was my son't first pass down the strip and he never got true WOT. Is there no TQ Mgmt at WOT? Based on what I've read I thought there was but maybe I missed something.
Maybe it was just false knock anyway and I need to log some more passes to see if it's consistently there before I try to start fixing a problem that really isn't one.
If you get a chance to respond on the tranny shifting I would appreciate it.