Generally adding more sealant makes a knock sensor less sensitive, not more. Also usually when looking at knock I look at a scatterplot; it's what Trimalyzer does really well, for example.
Generally adding more sealant makes a knock sensor less sensitive, not more. Also usually when looking at knock I look at a scatterplot; it's what Trimalyzer does really well, for example.
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
dave just curious but what datalog cable are you using?. i read an old post on thirdgen that may be something to consider.... https://www.thirdgen.org/forums/diy-...when-aldl.htmlOriginally Posted by NomakeWan
Basically it's saying to use 10K resistor to connect then turn it off once connected. i know mine was always on 10k...
Considering the 10k resistor thing only applies to the earlier ECMs that used Pin E for 160 Baud ALDL, I'm gonna go ahead and say that won't be it. The '7427 is a '93 PCM, so it'll be using Pin M 8192 ALDL without the resistor.
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
Regarding the sealant, I'm wondering if that could be the cause of my intermittent Code 43? Body of sensor not getting good ground to block at times? Regarding the scatterplot, I've never used Trimalyzer - is it free? I'm decent with Excel, possible to just plot data in Excel with TP output?
I'm using the Moates ALDL cable, the one with the regular USB-A on the computer end. Same cable I was using with the '7060 and I didn't mess with the 10K resistor when I switched. I also have a Moates AutoPROM with a ethernet-type plug on the computer end. I haven't used the AutoProm at all since I switched to the '7427. I had a lot of challenges with it when I used it with the 7060 so I gave up. I think I'll try again, just to see if it helps and it may help with my tuning by allowing me to try things on the fly.
It's possible you aren't getting a good ground, sure. But as I believe I've said before in this very thread, the code isn't really important; the code doesn't mean anything about the signal from the sensor. It's looking for a voltage difference due to a resistor inside the knock sensor that isn't actually related to the function of the sensor itself. So if you're getting proper signal from the sensor, Code 43 is irrelevant. Again, on my '95 Corvette I just disabled the code rather than bothering to replace the sensors, because the sensors were still providing good output.
Trimalyzer is absolutely free. You just need to tell it how your CSV logs are formatted so it can plot the data for you. http://fbodytech.com/trimalyzer
It is absolutely possible to do a scatterplot with Excel as well (since that's all Trimalyzer is actually doing).
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
Thanks - Downloaded Trimalyzer. Really easy to use, had a scatter plot of my knock counts in a few minutes. (attached) but not sure what it's telling me. Most points are in the middle RPM range, not surprising. Looks like there are some anomalies in the low RPM/low load area?
OK, I'll start learning to not worry about the code 43 and will probably eventually disable it in the code. But I am still concerned about my very high knock counts. knock_count_scatter.jpg
Holy crap. Either you have a ton of knock, or your knock filter is shot, or...I dunno, you just magically have an engine with a sound profile that, over its entire range, just happens to fall within your filter parameters?
I've never seen a knock plot that busy before. That's insane. Even the one time I definitely pushed timing too far (and disabled knock retard), all that happened was I developed a blob in one specific spot. Not a ton of tiny dots all over the entire plot.
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
Yeah, that's what I'm saying, an insane amount of knock. I really don't think it's truly knocking. It seems I'd hear it and the motor sounds pretty good throughout the range, with the possible exception of WOT at high load. I've asked a couple times in this thread - can it be the L31 roller cam and valve train? Did the vortec trucks use a different KS and/or filter parameters? I also have roller tip rockers but I don't think they'd be causing much noise?
I started playing with my autoprom last night. It's always been finicky with connections both to PC and ALDL. I had to fiddle with COM port settings to get it to connect to PC at all. It eventually connected, but then wouldn't connect again after that. I'm really hoping it's a faulty USB cable, it seems that the connection was sensitive to touching the cable. It uses an old school USB-A to USB-B; I'll have to hunt around in some boxes to see if I can find another one of those.
Every GM vehicle had a unique knock filter, because GM understood that every operating environment was different, so to improve their ability to detect knock across a wide operating range, they tuned each one according to the platform in question. If your knock filter does not match your platform, then it's not doing its job correctly. Either find a knock filter that matches your setup (chassis, engine configuration, etc), make your own knock filter if such a filter does not exist, or as I think I also mentioned before, just disable knock feedback entirely since it's not working correctly anyway.
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
Well finding an exact match is out - no such thing as a square body suburban with vortec, roller-cam 383 running a '7427 PCM. Closer match, I'm not sure. I do have a vortec black box PCM but I have no idea if there's any compatibility there. And making my own filter is probably out, too, since I wouldn't even know where to start. So unless I figure out some other magic solution I may have to just disable knock feedback but definitely not an ideal solution since I'd really like to get closer to perfection on ignition timing.
Generally any tuning place worth their salt is going to have a knock box. It's an external knock processor with its own knock sensor. Mount it to the motor you're tuning, put on headphones, actually listen for knock and tune that way. You don't rely on the ECU to do it for you, you do it yourself.
It sounds like that's the route you need to go.
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
Weird because the 7427 swap I did wouldn't connect to Turnerpro RT unless I had my cable set to 10K. i do not have the vehicle here to confirm is turning 10K off will stop my knock counts climbing.
I would also try another PCM/memcal just as a sanity check before getting too carried away here
That would be very strange indeed. I confirmed from the Blazer forums that they are indeed using native 8192 baud comms out of Pin M (or Pin 9 on '95 vehicles), without any resistor.
1990 Corvette (Manual)
1994 Corvette (Automatic)
1995 Corvette (Manual)
I will try again the next time the truck is here, could have been something else and switching to 10k was just a coincidence
Truck was by today, would connect with switch in Open or 10K. Also having 10K position had no affect on the increasing knock counts. Most of the counts were on start up and switching between R and D ranges. Also, when counts went up I never saw the knock retard actually pull any timing FWIW. I still think the issues with this truck are worn valve train and timing set, will know early next year when I do cam swap.
PS; I really need to log this thing and build a better VE, BLMs were 113. I guess better rich and pulling fuel than lean........
Last edited by tayto; 10-04-2021 at 05:51 AM.
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