Knock sensors:
- Thread starter racprops
- Start date
Id suggest running the knock sensor designed to match the PCM your using in a similar engine application.
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NewbVetteGuy
Well-Known Member
Many / Most knock sensors have built-in filters that filter out the frequencies that are NOT associated with knock on a given engine's bore. (The frequency that knock makes varies by engine bore.) -You need a sensor designed for your rough engine bore because of this. (A 350 / 383, an SBC 400, and a BBC should all have different knock sensors.)
If you search the Holley EFI forums, you'll find some recommended knock sensors for an SBC with a 4.000" - 4.030" bore with links from Danny Cabral.
I had to rebuild my PC and I can't find some of my OneNotes, including the one that lists the specific knock sensor that I used in my 350 SBC... I'm using Holley EFI, though and it can work with almost any knock sensor.
The Holley ECUs require you to "tune" the knock sensor to get good results; I'm not sure how this works with a GM ECM...
With the modern Holley ECUs: you put crappy gas in the tank and then lug the engine up a steep hill in high gear to get some definite knocks to show up in the logs. -Then you look at the intensity of those knock events in the log and you set a % Knock Threshold in the knock configuration. (When you look at the knock log as a chart, you'll see the intensity of the TRUE knock event(s) that you generated by lugging it up a hill, then you can look back in the log for other events that created sounds at the knock frequencies but at lower noise levels (piston slap after engine startup when the engine is cold, lifter noise, etc..). -Your goal is to set the knock threshold HIGHER than those other non-knock events, but LOWER than the ACTUAL knock events with the Threshold settings. Then you can setup how many degrees of timing you want pulled when knock exceeds that threshold and how quickly you want to put timing back in after it's been pulled.
Adam
If you search the Holley EFI forums, you'll find some recommended knock sensors for an SBC with a 4.000" - 4.030" bore with links from Danny Cabral.
I had to rebuild my PC and I can't find some of my OneNotes, including the one that lists the specific knock sensor that I used in my 350 SBC... I'm using Holley EFI, though and it can work with almost any knock sensor.
The Holley ECUs require you to "tune" the knock sensor to get good results; I'm not sure how this works with a GM ECM...
With the modern Holley ECUs: you put crappy gas in the tank and then lug the engine up a steep hill in high gear to get some definite knocks to show up in the logs. -Then you look at the intensity of those knock events in the log and you set a % Knock Threshold in the knock configuration. (When you look at the knock log as a chart, you'll see the intensity of the TRUE knock event(s) that you generated by lugging it up a hill, then you can look back in the log for other events that created sounds at the knock frequencies but at lower noise levels (piston slap after engine startup when the engine is cold, lifter noise, etc..). -Your goal is to set the knock threshold HIGHER than those other non-knock events, but LOWER than the ACTUAL knock events with the Threshold settings. Then you can setup how many degrees of timing you want pulled when knock exceeds that threshold and how quickly you want to put timing back in after it's been pulled.
Adam
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NewbVetteGuy
Well-Known Member
I have a lot on my plate but I HOPE to get my OneNotes all restored this Friday and if I find the KnockSensor that I ordered I'll post it here. I think it cost $50 -something. I ended up screwing it into one of the coolant drain plugs on the bottom of the block -it ALMOST gets in the way of one of the oil pan bolts, but it works.
The one I selected was a 2 wire sensor (I think there are also 3 wire sensors from memory). I DID have to modify my EFI harness to work with the connector that it required AND I think it was highlight likely that the wire could touch my header and melt so I had to buy some heat insulation and wrap it around the wires and partially plastic connector and secure it with a stainless clamp to protect it from my headers.
Not the greatest photos, but one picture showing the knock sensor (it's really FAT in the middle, which creates the challenges with the oil pan).
The picture showing the insulation was taken before I secured it with a large stainless hose clamp.
The one I selected was a 2 wire sensor (I think there are also 3 wire sensors from memory). I DID have to modify my EFI harness to work with the connector that it required AND I think it was highlight likely that the wire could touch my header and melt so I had to buy some heat insulation and wrap it around the wires and partially plastic connector and secure it with a stainless clamp to protect it from my headers.
Not the greatest photos, but one picture showing the knock sensor (it's really FAT in the middle, which creates the challenges with the oil pan).
The picture showing the insulation was taken before I secured it with a large stainless hose clamp.
NewbVetteGuy
Well-Known Member
Ok, this motivated me to go get my OneNotes back and working.
The knock sensor I used is ACDelco 10456288 ADO-213-324 $37
If your EFI harness doesn't have the weird round plastic 2 wire connector, you'll need to get one of those, too.
www.summitracing.com
Adam
The knock sensor I used is ACDelco 10456288 ADO-213-324 $37
If your EFI harness doesn't have the weird round plastic 2 wire connector, you'll need to get one of those, too.
ACDelco 10456288 ACDelco GM Genuine Parts Knock Sensors | Summit Racing
Free Shipping - ACDelco GM Genuine Parts Knock Sensors with qualifying orders of $109. Shop Knock Sensors at Summit Racing.
Adam
NewbVetteGuy
Well-Known Member
IMHO, TPI engines pushing the DCR, like yours (and mine) Rich, can be super knock prone AND have fairly sizeable cylinder-to-cylinder distribution issues and they're the ultimate engine that can benefit from a knock sensor, ESPECIALLY if you're going to tow (you are) AND you want to push the ignition timing and run lean AFRs at cruise to drive for the best fuel economy (I KNOW you are).
Lots of EFI tuner people will steer you away from knock sensors and say that if you have a "good tune" that you don't need them, but for your engine and what you're doing with it the knock-sensor is a NO BRAINER $37 "insurance policy" if you push the eco tuning too far.
Good TPI engines chasing fuel economy and knock sensors are a "perfect pairing", IMO.
Lots of EFI tuner people will steer you away from knock sensors and say that if you have a "good tune" that you don't need them, but for your engine and what you're doing with it the knock-sensor is a NO BRAINER $37 "insurance policy" if you push the eco tuning too far.
Good TPI engines chasing fuel economy and knock sensors are a "perfect pairing", IMO.