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Ok, so of course there's an apparent side effect to the benefits of my increased ignition timing. Lol...
I'm noticing knock counts and up to 10-12 deg of retard at times.
I was doing some datalogging and happened to notice it. However, I don't hear any knocking/pinging, my spark plugs don't show any obvious evidence of that "pepper" like appearance, etc.
Years ago when I was trying to get away with 10.2:1 compression and a small cam in my old ZZ4 350, I could hear the knocking/pinging very prominently even with the windows down. Had to reduce the compression down to 9.8 to get rid of it. I now run about 9.6 to 9.7 on my 383 with about a proportionally small cam for the engine size. Running the same cylinder heads as I had on the ZZ4.
Here's the complicating factors that's not making it obvious whether its false or real...
- The knock sensor I was running on my ZZ4 got transferred to the 383 about two years ago. However about mid-June this year, I was under the car and noticed the electrical plug on the sensor was dangling (the plastic connector on the sensor actually broke off) so I replaced it with another one I had. I verified it was the 3.9kOhm type since I have a 7730. Installed with some teflon tape since it goes into the water jacket and torqued to 13 ftlb.
- The knock retard isn't consistently happening each time I get into those map/rpm areas... generally about 1800-2200 and 60-80 kPa. I would think if it was real knock, I'd get it consistently in the same areas to roughly the same degree.
- I went back to look at some old datalogs and it looks like I actually started getting this kind of knock retard happening about the time I changed the sensor. However, since the old one was broken, I can't say that having no knock retard previously means there was no knocking. So I also can't say that the current sensor is too sensitive. Yet, I can't say that I noticed anything unusual, or power loss or anything that would have hinted at detonation.
- My recently increased ignition timing isn't in the areas where this significant knock retard is occurring. So I'm getting knock retard kicking in for the same amount of spark timing as before. The timing increase was mainly in the low to mid-map (like 50 kPa and blow) areas. That's basically light cruising maps. Even at 10.2:1 on my old ZZ4, I wouldn't get knock retard and audible knocking kicking in until I was at least into the 70 and above kPa regions.
- That said I actually occasionally get some knock counts and retard (roughtly about 1-2 deg max) also kicking in at very low maps and even before the engine gets up to temperature. How would you ever get real knocking/pinging at 30-40-ish kPa on a cold engine? One time I was cruising on the freeway at light load and all of a sudden the knock retard started going crazy for about 10 seconds and then went back to 0.
- The engine runs pretty consistently at the 180F temperature of the thermostat.
- Spark plugs are standard AC Delco 5's, gapped at about .045-.050.
- I experimentally pulled about 5-6 deg out where the knocking is occurring and didn't make any difference.
If my old knock sensor was was broken, then if the engine itself was prone to such severe detonation and the ECM had no way to counteract it, I'm sure I would have heard it audibly and the spark plugs would show evidence of it, no? They've been in the car since I installed the 383 two years ago.
I do know that my roller rockers generate some noise. Wondering if the new sensor is too sensitive and there's something going on with rocker noise getting picked up by the sensor?
I guess one thing I may try is to put in some octane booster and see if the knock retard goes away. Either that or get a new Delco knock sensor. I actually don't know what brand or p/n my current one is and I've had it in my stash for probably the last 15-20 years.
Ok, so of course there's an apparent side effect to the benefits of my increased ignition timing. Lol...
I'm noticing knock counts and up to 10-12 deg of retard at times.
I was doing some datalogging and happened to notice it. However, I don't hear any knocking/pinging, my spark plugs don't show any obvious evidence of that "pepper" like appearance, etc.
Years ago when I was trying to get away with 10.2:1 compression and a small cam in my old ZZ4 350, I could hear the knocking/pinging very prominently even with the windows down. Had to reduce the compression down to 9.8 to get rid of it. I now run about 9.6 to 9.7 on my 383 with about a proportionally small cam for the engine size. Running the same cylinder heads as I had on the ZZ4.
Here's the complicating factors that's not making it obvious whether its false or real...
- The knock sensor I was running on my ZZ4 got transferred to the 383 about two years ago. However about mid-June this year, I was under the car and noticed the electrical plug on the sensor was dangling (the plastic connector on the sensor actually broke off) so I replaced it with another one I had. I verified it was the 3.9kOhm type since I have a 7730. Installed with some teflon tape since it goes into the water jacket and torqued to 13 ftlb.
- The knock retard isn't consistently happening each time I get into those map/rpm areas... generally about 1800-2200 and 60-80 kPa. I would think if it was real knock, I'd get it consistently in the same areas to roughly the same degree.
- I went back to look at some old datalogs and it looks like I actually started getting this kind of knock retard happening about the time I changed the sensor. However, since the old one was broken, I can't say that having no knock retard previously means there was no knocking. So I also can't say that the current sensor is too sensitive. Yet, I can't say that I noticed anything unusual, or power loss or anything that would have hinted at detonation.
- My recently increased ignition timing isn't in the areas where this significant knock retard is occurring. So I'm getting knock retard kicking in for the same amount of spark timing as before. The timing increase was mainly in the low to mid-map (like 50 kPa and blow) areas. That's basically light cruising maps. Even at 10.2:1 on my old ZZ4, I wouldn't get knock retard and audible knocking kicking in until I was at least into the 70 and above kPa regions.
- That said I actually occasionally get some knock counts and retard (roughtly about 1-2 deg max) also kicking in at very low maps and even before the engine gets up to temperature. How would you ever get real knocking/pinging at 30-40-ish kPa on a cold engine? One time I was cruising on the freeway at light load and all of a sudden the knock retard started going crazy for about 10 seconds and then went back to 0.
- The engine runs pretty consistently at the 180F temperature of the thermostat.
- Spark plugs are standard AC Delco 5's, gapped at about .045-.050.
- I experimentally pulled about 5-6 deg out where the knocking is occurring and didn't make any difference.
If my old knock sensor was was broken, then if the engine itself was prone to such severe detonation and the ECM had no way to counteract it, I'm sure I would have heard it audibly and the spark plugs would show evidence of it, no? They've been in the car since I installed the 383 two years ago.
I do know that my roller rockers generate some noise. Wondering if the new sensor is too sensitive and there's something going on with rocker noise getting picked up by the sensor?
I guess one thing I may try is to put in some octane booster and see if the knock retard goes away. Either that or get a new Delco knock sensor. I actually don't know what brand or p/n my current one is and I've had it in my stash for probably the last 15-20 years.
Anyone else have any thoughts?
I tuned the knock sensor out of my 383. Too much mechanical noise for it to be much use.
Until my car is warm, occasionally I get random high knock counts on the EBL. When it's warmed up, even under load and high rpm, nothing. I have no symptoms, on the plugs or any detectable noise. The only thing I can think of is a v band clamp on the down pipe close to the frame rail so I've chosen to ignore it.If you've pulled 5 or 6 degrees in the RPM range where you get knock and no change, I'd lean towards false knock.
Waiting for the tank to get near empty so I can refill with the octane boost. I retorqued the sensor (this time at 11-12 ftlb) and ran another datalog.
The below is the maximum knock retard the ECM applied during the run. This has to be bogus.... 10 deg at idle speeds? 10 deg at 20 kPa map? Even at >10:1 compression a few year ago with audible knock I never got knocking at those areas.
I'll run the octane boost test just for completeness, but at this point I think I have a bum sensor. Probably going to order a new Delco sensor.
Ok, pretty sure I had a bum knock sensor. I ended up swapping to a new Delco one and torqued to 11 ftlb. Didn't try the octane boost and probably won't at this point.
But the new sensor pretty much cleared it up. I still get a few random counts and a degree or two of retard here and there, but to me that seems to be WAY more realistic.
Where I was getting knock counts and retard before (idle speeds, less than 40 kPa during light cruise, even before the engine fully warmed up, etc) was absolutely absurd for a 9.8:1 engine with aluminum heads and very efficient combustion chambers.
Any rate, the thing absolutely rips with no retard kicking in... I remember when I was getting audible knock several years ago at 10.1:1, you could feel the power loss even before the knocking became audible, and much more so after it became audible. So I'm pretty convinced now it was either a bad sensor, torqued too high, or some combination of the those factors. Plugs are also clean as well, so there's pretty much zero physical/empirical evidence of knock going on.
Ok, pretty sure I had a bum knock sensor. I ended up swapping to a new Delco one and torqued to 11 ftlb. Didn't try the octane boost and probably won't at this point.
But the new sensor pretty much cleared it up. I still get a few random counts and a degree or two of retard here and there, but to me that seems to be WAY more realistic.
Where I was getting knock counts and retard before (idle speeds, less than 40 kPa during light cruise, even before the engine fully warmed up, etc) was absolutely absurd for a 9.8:1 engine with aluminum heads and very efficient combustion chambers.
Any rate, the thing absolutely rips with no retard kicking in... I remember when I was getting audible knock several years ago at 10.1:1, you could feel the power loss even before the knocking became audible, and much more so after it became audible. So I'm pretty convinced now it was either a bad sensor, torqued too high, or some combination of the those factors. Plugs are also clean as well, so there's pretty much zero physical/empirical evidence of knock going on.
I am actually on the hunt for a NOS GM sensor for mine.. AC Delco knock sensors are not the same as they once were. Noticed mine has a P0327 pending in the PCM from time to time, but never sets the DTC.
I am actually on the hunt for a NOS GM sensor for mine.. AC Delco knock sensors are not the same as they once were. Noticed mine has a P0327 pending in the PCM from time to time, but never sets the DTC.
I was going to be investing in a GM Genuine knock sensor to throw in mine. I would imagine the one listed on RockAuto is a new Delco sensor and not NOS...hopefully I don't see any issues.
I was going to be investing in a GM Genuine knock sensor to throw in mine. I would imagine the one listed on RockAuto is a new Delco sensor and not NOS...hopefully I don't see any issues.
I got my delco from Rock Auto. Seems to be doing the job
My latest max knock history after a few runs with the Delco knock sensor, torqued at 11 ftlb. Much more believable. Though even the couple degrees I'm seeing is probably bogus. But, I can't tell the difference now, seat of the pants. So this is good enough at this point.
I went thru the same issue as u have for a while. I flip flopped between “yeah real” to “ no false”.
And it seemed to occur with small incremental increase or decrease in MAP kPa. And it was usually .7-1.5d KR and maybe .35 at times. Playing w AE helped that. Also dropped SA by .7-1d, especially in cruising zones and decel. That also helped to where I didn’t record any knock as of my latest log.
09-28-2023, 08:32 PM
