Knock Sensor, Knock Filter, ESC and swaps!

[JeepsAndGuns]

One thing that puzzles me, is there has to be more to a knock filter than simply matching it to the engines bore size. If it was as simple at that, then should it not be the same knock filter on the tpi 350's and the tbi 350's, and even yet, since the 4.3 v6 has the same bore and stroke as a 350, then in theory should it not use the same one too? Be we know it does not.
But I knida agree with 1project, I think I would probably try and mpfi mod a 350 tbi memcal before I used a jumpered v6 memcal, I would think a tbi 350 knock filter would be a lot closer than a v6 one.
Has no one really tried that, or has it been tried and failed, and we just dont know about it? I could use the mpfi modded tbi memcal from my Jeep and put it in a 7730 on my test harness and run it to see if I get any error codes, if anyone cares?

[RobertISaar]

Knock sensor has to match knock filter whether it's in memcal or ESC... and the sensor has to be for engine. So your point of V6 knock sensor matching V8 because of bore and stroke is valid. We started to collect info on this but there were so many GM numbers I don't think we ever came to a conclusion. But that needs to go in another thread...

there is SOME leeway here... the same knock sensor (KS8) is used on 2.0, 2.3, 2.8, 3.1, 3100, 3300, 4.0, 4.6.... that's a range of 86 - 94mm bores from 4, 6 and 8 cylinder engines. and quite a few engines that have a bore inside of that range that don't use it... it's really a combination of rough bore size and rough sensitivity... the knock filter is more or less tailored to each specific application to further tune the signal.

[RobertISaar]

doing some digging since i have a few MEMCALs floating around...

trying to make sense of the "P4 Style ESC" image (http://i.imgur.com/mDg0Lzk.jpg)

i've made sense of the "cal code" and "ID Res Kohms", but not much else...



the red line, hook up your multimeter and do an ohm-check, your reading is the "ID RES Kohms" value.
red circle is the letter or number that represents the "cal code".

trying to figure out the rest of it will be interesting....

i also have a little bit of info to add, the 94-95 3.4DOHC is different than the 91-93 3.4DOHC. 147K resistor ID, 36 Cal Code. other than that, no idea.

[JeepsAndGuns]

I do not think it is the actual knock sensor that is (always) engine specific. Its more like there is a specific list of engines it can be used on, like Robert is pointing out. Example:
Look up the knock sensor for a 95 C1500 truck, 5.7, auto trans.
Now look up the same for a 95 C3500 7.4, auto trans.
Now look up the same for a 91 camaro 5.7.

Notice anything? They all list the same part number knock sensors.
ACdelco 21392
Airtex/wells 5S2167
Delphi AS10016

So if a 95 5.7 truck, and a 91 5.7 camaro use the same knock sensor, and both engines are the same displacement, what is different about the knock filters? Could they interchange successfully? I do not seem to have too very much trouble finding V8 TBI 7427's. I'm not just falling over them, but they are far from hard to find. Unlike the V8 TPI memcals that are made of unobtainum. So could you simply jumper the TBI memcal for MPFI, replace the chip with a EEPROM and have a useable V8 TPI memcal?

[JeepsAndGuns]

I was typing when you posted that. I went a got a BJYL memcal (95 5.7 TBI $0D) and measured it. Now bear with me as I am using a cheap craftsman multimeter. With it on the 20k setting, it reads 0.86, on the 2000 setting, it reads 865. The number in the red circle is 26.

Next I tested a BNKM memcal (95 P30 5.7 TBI $31) On the 20K setting it measures 2.26, on the 200k it measure 2.6, on the 200 setting it reads nothing. The number in the circle is 34.

Tested a BJYM, it tested the same as the BJYL, same number too on the board.

Last I have is BJKW (95 7.4 TBI $0E) it measured the same as the BNKM memcal and has the same number on the board.

Now that is really strange, seeing as how BNKM is a 5.7 memcal, bcc find puts it as 5.7/4L80E, and I specificly remember pulling it from the van and it definately had a 350. Yet it appears to use the exact same knock filter as a 7.4.
Humm (scratches head)

[RobertISaar]

So could you simply jumper the TBI memcal for MPFI, replace the chip with a EEPROM and have a useable V8 TPI memcal?

hell of a lot better than what some people are doing.

I was typing when you posted that. I went a got a BJYL memcal (95 5.7 TBI $0D) and measured it. Now bear with me as I am using a cheap craftsman multimeter. With it on the 20k setting, it reads 0.86, on the 2000 setting, it reads 865. The number in the red circle is 26.

Next I tested a BNKM memcal (95 P30 5.7 TBI $31) On the 20K setting it measures 2.26, on the 200k it measure 2.6, on the 200 setting it reads nothing. The number in the circle is 34.

Tested a BJYM, it tested the same as the BJYL, same number too on the board.

Last I have is BJKW (95 7.4 TBI $0E) it measured the same as the BNKM memcal and has the same number on the board.

Now that is really strange, seeing as how BNKM is a 5.7 memcal, bcc find puts it as 5.7/4L80E, and I specificly remember pulling it from the van and it definately had a 350. Yet it appears to use the exact same knock filter as a 7.4.
Humm (scratches head)

gah, i hate non-autoranging multimeters...

so:
BJYL = 26 / 865ohms
BNKM = 34 / somewhere between 2260 and 2600 ohms(probably closed to 2260)
BJYM = 26 / 865ohms
BJKW = 34 / somewhere between 2260 and 2600 ohms(probably closed to 2260)

and the first 3 are 5.7, last is 7.4... 5.7 = 4" bore, 7.4 = 4.25" bore (or 101.6mm and 107.8mm)

yet both use not only the same sensor, but the same filter as well? 5.7 has a knock frequency of 5642Hz, 7.4 is 5310Hz... they're actually not very far off.

based off of the knock filter document, they both PROBABLY used a filter based around 5KHz, as does at least two 4.3(4" bore) applications(3 others are centered on 7KHz).....



so either GM cheaped out and didn't make new filters when they should have(and false knock could be detected or worse, real knock ignored) or it's not as clear-cut as it seems?

[RobertISaar]

put the knock filters together for a little comparison... i probably should have grabbed the 3.1 MEMCAL, but i can do that later if necessary....

http://i.imgur.com/AJKnl5J.jpg

the MEMCAL with the 27SF512 in it is the 91-93 version, the one with the factory PROM is the 94-95. note that the size of a few components changed, but otherwise they all seem to be in the same location. some portions of the traces stayed the same, but that changed quite a bit too.... notice that the blue layer can have both traces above and below it on both. i have to wonder what the little component is in the center.... seems like it would be an IC, definitely something custom made for Delco. lots of laser-cut resistors too.

have to wonder how difficult making a DIY knock filter would be..... doing the bandpass calculation(for a given bore size) isn't too bad, but then just have to figure out a way to ground the circuit that signals knock to the processor.... and then having a method to allow for sensitivity adjustment...

[EagleMark]

One thing that puzzles me, is there has to be more to a knock filter than simply matching it to the engines bore size. If it was as simple at that, then should it not be the same knock filter on the tpi 350's and the tbi 350's, and even yet, since the 4.3 v6 has the same bore and stroke as a 350, then in theory should it not use the same one too? Be we know it does not.

Knock sensor has to match knock filter whether it's in memcal or ESC... and the sensor has to be for engine. So your point of V6 knock sensor matching V8 because of bore and stroke is valid. We started to collect info on this but there were so many GM numbers I don't think we ever came to a conclusion.