Disconnect knock sensor question....
Melting Slicks
Joined: Aug 2003
Posts: 3,420
Likes: 408
From: Lakeville MI
I'm surprised no one is concerned about real knock. I'm not convinced.
The 89 bins run quite a bit of spark advance to begin with (around 36 degrees total advance at WOT and even more through the midrange depending upon the load).
Nitrous significantly increases the likelyhood of knock for several reasons as it reduces the burn time of the fuel, increases load and cylinder pressure as well as combustion temperatures.
With the base timing only retarded by 2 degrees, I would say that you have a recipe for knock with this combination.
Has Alvin's tune been tailored for nitrous, with reduced spark advance in the tables? I hope so.
The 89 bins run quite a bit of spark advance to begin with (around 36 degrees total advance at WOT and even more through the midrange depending upon the load).
Nitrous significantly increases the likelyhood of knock for several reasons as it reduces the burn time of the fuel, increases load and cylinder pressure as well as combustion temperatures.
With the base timing only retarded by 2 degrees, I would say that you have a recipe for knock with this combination.
Has Alvin's tune been tailored for nitrous, with reduced spark advance in the tables? I hope so.
Thread Starter
Burning Brakes
Joined: Dec 2006
Posts: 936
Likes: 2
From: Tyrone PA
I'm surprised no one is concerned about real knock. I'm not convinced.
The 89 bins run quite a bit of spark advance to begin with (around 36 degrees total advance at WOT and even more through the midrange depending upon the load).
Nitrous significantly increases the likelyhood of knock for several reasons as it reduces the burn time of the fuel, increases load and cylinder pressure as well as combustion temperatures.
With the base timing only retarded by 2 degrees, I would say that you have a recipe for knock with this combination.
Has Alvin's tune been tailored for nitrous, with reduced spark advance in the tables? I hope so.
The 89 bins run quite a bit of spark advance to begin with (around 36 degrees total advance at WOT and even more through the midrange depending upon the load).
Nitrous significantly increases the likelyhood of knock for several reasons as it reduces the burn time of the fuel, increases load and cylinder pressure as well as combustion temperatures.
With the base timing only retarded by 2 degrees, I would say that you have a recipe for knock with this combination.
Has Alvin's tune been tailored for nitrous, with reduced spark advance in the tables? I hope so.
Melting Slicks
Joined: Aug 2003
Posts: 3,420
Likes: 408
From: Lakeville MI
I've tightened up a bit on my max knock retard settings, both for PE and out of PE to a maximum of 4 degrees.
With standard attack and return rates, I'm still only seeing about 2.3 degrees of knock retard when I do have knock counts present. Perhaps the max setting is a factor in determining the amount of retard beyond serving as a simple limit. I'll have to look into this.
I wonder how much knock retard you're really experiencing that you can feel it.
With standard attack and return rates, I'm still only seeing about 2.3 degrees of knock retard when I do have knock counts present. Perhaps the max setting is a factor in determining the amount of retard beyond serving as a simple limit. I'll have to look into this.
I wonder how much knock retard you're really experiencing that you can feel it.
Tech Contributor
Joined: Jun 2004
Posts: 20,951
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I got a pm last night from a forum member, who I will leave anonymous unless they want me to say who it was, with something to try. I picked up another knock sensor, unplugged the one that is in my block, plugged in the new one, wrapped it in a rag and duct tape, and wire tied it to the top of the starter. This effectively made the knock sensor deaf. Electrically, I don't see the need for the sensor, which just sits electrically isolated in the rag and duct tape. Grounding the signal wire would accomplish the same thing, and also eliminate any RFI being picked up on the wire. But that still doesn't resolve the software diagnostic issue. It worked. I may have some electrical and software disagreements here, but I can't argue with your success in this test.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
I have a tech tip somewhere that shows how to desensitize the knock sensor so it doesn't throw a code.
Has a resistor inline on the sensor wire and one to earth.
The early/ late sensors have different values that the ECM needs to see.
Does not distract from the above mentioned that you need to know whether or not you have a "true " knock situation.
Has a resistor inline on the sensor wire and one to earth.
The early/ late sensors have different values that the ECM needs to see.
Does not distract from the above mentioned that you need to know whether or not you have a "true " knock situation.
Last edited by rodj; Aug 3, 2007 at 08:28 AM.
Burning Brakes
Joined: Mar 1999
Posts: 858
Likes: 5
From: Fl,USA
I have installed a toggle switch in series at the connector of the ESC module on pin "D". The manual says it is circuit #486 and is a brn wire. Mine appears to be black. It is the second wire in starting from the front of the car moving towards the rear on the connector.
Turning off the switch opens the ESC ground circuit and allows the ESC signal to remain high(no retard is given) because there is no ground path to short the voltage to 0. Therefore tricking the ECM to think all is good.
Leaving the switch on closes/shorts the circuit and normal retard operation is allowed(like the switch wasn't there).
My module number is 16052401 9021. There is also a 882401 decal on it.
I have run many diacom and EASE diagnostics to see if this worked because I was seeing false knock from a header leak and exhaust resonance. The retard & knock counts are 0 every time with the switch open. The service engine soon light remains off with no trouble codes like I said earlier unless you toggle the switch when the car is running.
If your ESC module has 4 wires on it then it should work the same.
It's worth a try.
Hope it works for you.
John
Turning off the switch opens the ESC ground circuit and allows the ESC signal to remain high(no retard is given) because there is no ground path to short the voltage to 0. Therefore tricking the ECM to think all is good.
Leaving the switch on closes/shorts the circuit and normal retard operation is allowed(like the switch wasn't there).
My module number is 16052401 9021. There is also a 882401 decal on it.
I have run many diacom and EASE diagnostics to see if this worked because I was seeing false knock from a header leak and exhaust resonance. The retard & knock counts are 0 every time with the switch open. The service engine soon light remains off with no trouble codes like I said earlier unless you toggle the switch when the car is running.
If your ESC module has 4 wires on it then it should work the same.
It's worth a try.
Hope it works for you.
John
Burning Brakes
Joined: Mar 1999
Posts: 858
Likes: 5
From: Fl,USA
I failed to mention this previously so in case its not obvious, pin "D" is the ground circuit for the ESC module.
Leave the dark blue wire connected to the knock sensor. It will through a SES code if disconnected once in closed loop.
John
Leave the dark blue wire connected to the knock sensor. It will through a SES code if disconnected once in closed loop.
John
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Melting Slicks
Joined: Aug 2003
Posts: 3,420
Likes: 408
From: Lakeville MI
I used to think I was getting false knock too. I have all the excuses: headers, roller rockers, pulleys, centerfoce clutch. All these noisy parts must be causing my knock counts, right.
After a little work with my spark table: Now I have nearly 0 knock counts. I get a few on start-up and after that hardly any at all unless a hard shift was involved. Occasionally, I get 0 for my entire drive.
On the same roads at the same speeds where I used to pick up 40-50 knocks on uphills, the knocks are now gone.
What has changed?
A few degrees here and there in main spark table in specific rpm and load conditions that were previously causing knock, and also reduced spark in highway mode. Highway mode spark was a big contributor of knock for me.
After this excersise, I have a fair amount of confidence in the knock sensor now.
After a little work with my spark table: Now I have nearly 0 knock counts. I get a few on start-up and after that hardly any at all unless a hard shift was involved. Occasionally, I get 0 for my entire drive.
On the same roads at the same speeds where I used to pick up 40-50 knocks on uphills, the knocks are now gone.
What has changed?
A few degrees here and there in main spark table in specific rpm and load conditions that were previously causing knock, and also reduced spark in highway mode. Highway mode spark was a big contributor of knock for me.
After this excersise, I have a fair amount of confidence in the knock sensor now.
Melting Slicks
Joined: Aug 2003
Posts: 3,420
Likes: 408
From: Lakeville MI
I was just looking at some knock data from another car with standard knock retard tuning.
This car in question is pulling up to 20 degrees of knock retard out of PE.
The fact that my car only pulls about 2.3 degrees suggests that it is the result of reducing the maximum knock retard parameters down to 4 degrees.
20 degrees should be noticeable.
This car in question is pulling up to 20 degrees of knock retard out of PE.
The fact that my car only pulls about 2.3 degrees suggests that it is the result of reducing the maximum knock retard parameters down to 4 degrees.
20 degrees should be noticeable.
Thread Starter
Burning Brakes
Joined: Dec 2006
Posts: 936
Likes: 2
From: Tyrone PA
Thanks for the advice, I'm going to try this. I do believe I have another problem as well. When I got my bottle filled and can run 1050 psi, the hesitation came back, tho not as bad as before. I'm pretty sure my stock fuel pump isn't keeping up. The false knock was 1/2 of the problem, but I think I am "running out of fuel" at the same time the computer is (was) pulling timing. With the zex kit, enrichment fuel is lessened as the bottle pressure comes down. I think the stock fuel pump keeps up until the bottle pressure is over 850, as that is where the stumble starts happening. As I said before, running N/A or with 75 jets there is no problem at all. I think it has to be a fuel thing at this point. I want a high volume pump anyway so I ordered one and will try it before I go any farther. My tune is already set for the nitrous by Alvin so I think the tune is good. I'm trying the new pump (Edelbrock 67 gph) and I'll keep you updated!! Any other suggestions or advice, I'm all ears. Thanks for the info so far!!!
I have installed a toggle switch in series at the connector of the ESC module on pin "D". The manual says it is circuit #486 and is a brn wire. Mine appears to be black. It is the second wire in starting from the front of the car moving towards the rear on the connector.
Turning off the switch opens the ESC ground circuit and allows the ESC signal to remain high(no retard is given) because there is no ground path to short the voltage to 0. Therefore tricking the ECM to think all is good.
Leaving the switch on closes/shorts the circuit and normal retard operation is allowed(like the switch wasn't there).
My module number is 16052401 9021. There is also a 882401 decal on it.
I have run many diacom and EASE diagnostics to see if this worked because I was seeing false knock from a header leak and exhaust resonance. The retard & knock counts are 0 every time with the switch open. The service engine soon light remains off with no trouble codes like I said earlier unless you toggle the switch when the car is running.
If your ESC module has 4 wires on it then it should work the same.
It's worth a try.
Hope it works for you.
John
Turning off the switch opens the ESC ground circuit and allows the ESC signal to remain high(no retard is given) because there is no ground path to short the voltage to 0. Therefore tricking the ECM to think all is good.
Leaving the switch on closes/shorts the circuit and normal retard operation is allowed(like the switch wasn't there).
My module number is 16052401 9021. There is also a 882401 decal on it.
I have run many diacom and EASE diagnostics to see if this worked because I was seeing false knock from a header leak and exhaust resonance. The retard & knock counts are 0 every time with the switch open. The service engine soon light remains off with no trouble codes like I said earlier unless you toggle the switch when the car is running.
If your ESC module has 4 wires on it then it should work the same.
It's worth a try.
Hope it works for you.
John
Tech Contributor
Joined: Jun 2004
Posts: 20,951
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
JOHN89,
I misread/misinterpreted your first note. I thought you were opening up the sensor line, instead of the module ground line. My mistake. IIRC, the module has a pullup resistor to the supply voltage. Opening the ground would still allow the pullup to work, but prevent the ESC circuitry from pulling this line low. Makes sense. A friend of mine did a slightly different thing for his tests. He wired in a switch and resistor between the supply voltage and the retard request line going to the ECM. He could then disconnect the ESC retard request line from the ECM, and with the resistive pull-up he could force a high signal to the ECM (signifying no knock occuring).
I still don't understand why the spark/diagnostics test didn't cause a check engine light. Does the test happen so rarely (like every 50 ignition cycles) or do you have that test disabled?
I misread/misinterpreted your first note. I thought you were opening up the sensor line, instead of the module ground line. My mistake. IIRC, the module has a pullup resistor to the supply voltage. Opening the ground would still allow the pullup to work, but prevent the ESC circuitry from pulling this line low. Makes sense. A friend of mine did a slightly different thing for his tests. He wired in a switch and resistor between the supply voltage and the retard request line going to the ECM. He could then disconnect the ESC retard request line from the ECM, and with the resistive pull-up he could force a high signal to the ECM (signifying no knock occuring).
I still don't understand why the spark/diagnostics test didn't cause a check engine light. Does the test happen so rarely (like every 50 ignition cycles) or do you have that test disabled?
Thread Starter
Burning Brakes
Joined: Dec 2006
Posts: 936
Likes: 2
From: Tyrone PA
JOHN89,
I misread/misinterpreted your first note. I thought you were opening up the sensor line, instead of the module ground line. My mistake. IIRC, the module has a pullup resistor to the supply voltage. Opening the ground would still allow the pullup to work, but prevent the ESC circuitry from pulling this line low. Makes sense. A friend of mine did a slightly different thing for his tests. He wired in a switch and resistor between the supply voltage and the retard request line going to the ECM. He could then disconnect the ESC retard request line from the ECM, and with the resistive pull-up he could force a high signal to the ECM (signifying no knock occuring).
I still don't understand why the spark/diagnostics test didn't cause a check engine light. Does the test happen so rarely (like every 50 ignition cycles) or do you have that test disabled?
I misread/misinterpreted your first note. I thought you were opening up the sensor line, instead of the module ground line. My mistake. IIRC, the module has a pullup resistor to the supply voltage. Opening the ground would still allow the pullup to work, but prevent the ESC circuitry from pulling this line low. Makes sense. A friend of mine did a slightly different thing for his tests. He wired in a switch and resistor between the supply voltage and the retard request line going to the ECM. He could then disconnect the ESC retard request line from the ECM, and with the resistive pull-up he could force a high signal to the ECM (signifying no knock occuring).
I still don't understand why the spark/diagnostics test didn't cause a check engine light. Does the test happen so rarely (like every 50 ignition cycles) or do you have that test disabled?
Melting Slicks
Joined: Aug 2003
Posts: 3,420
Likes: 408
From: Lakeville MI
It appears that load (LV8) must be > 170 and coolant temp > 90 C (194 F) to enable the code 43 test.
It should be possible to run the test each start, but the load and temp conditions may not always be fulfilled, due to the high load and high temperatures required.
10 degrees of advance is added during the test.
It should be possible to run the test each start, but the load and temp conditions may not always be fulfilled, due to the high load and high temperatures required.
10 degrees of advance is added during the test.
Burning Brakes
Joined: Mar 1999
Posts: 858
Likes: 5
From: Fl,USA
I don't know why it didn't throw a code either. Was it still in open loop or did you drive it for a while so it went into closed loop?
Any way ...on a side note, I agree 100% with tequilaboy for the concern with real vs false knock. My intentions were never to completely eliminate the knock sensor. I realize its value.
I too have reduced my knock counts down to only a few when I initially stomp it. I hardly run with it off.
John
Any way ...on a side note, I agree 100% with tequilaboy for the concern with real vs false knock. My intentions were never to completely eliminate the knock sensor. I realize its value.
I too have reduced my knock counts down to only a few when I initially stomp it. I hardly run with it off.
John
