Tuning Question
09-23-2015, 02:07 PM
#1
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Join Date: Aug 2014
Posts: 30
Tuning Question
I wanted to ask you self tuning guys out there a question about my car. It's a 94 z28 lt1 a4 with 3600 stall and built 4l60e 3.73 and few other small bolt on under hood like CAI air foil...
I have an issue with knock at WOT but I also notice my o2 readings go up around 800 and like to stick there. Is it normal for a car to see o2 readings in 800 range and not fluctuate at WOT? I don't see knock at normal driving conditions until I make a WOT pull. Then it will have small amount of knock for a few moments after.
To me this would indicate I may actually have some spark knock, or I am running rich? What's your opinion, thanks. I have been working on self tuning but I have not adjusted my fuel map or spark maps yet, only Trans tuning thus far although I have done some tuning to other cars but with aftermarket ECU like Haltech.
I have an issue with knock at WOT but I also notice my o2 readings go up around 800 and like to stick there. Is it normal for a car to see o2 readings in 800 range and not fluctuate at WOT? I don't see knock at normal driving conditions until I make a WOT pull. Then it will have small amount of knock for a few moments after.
To me this would indicate I may actually have some spark knock, or I am running rich? What's your opinion, thanks. I have been working on self tuning but I have not adjusted my fuel map or spark maps yet, only Trans tuning thus far although I have done some tuning to other cars but with aftermarket ECU like Haltech.
09-23-2015, 02:32 PM
#2
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Location: Hell was full so they sent me to NJ
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Re: Tuning Question
At WOT, the PCM operates in "power enrichment" (PE) mode. It ignores feedback from the O2 sensors, and richens the A/F ratio to produce best torque and HP. While closed loop operation cycles the A/F ratio back and forth, above and below the stoichiometric ratio of 14.7:1, in PE mode you want an A/F ratio closer to 12.8 - 13.2:1 (most engines). The stock tuning sets a target A/F ratio of 11.7:1, which is actually a bit too rich.
While the stock, narrow-band O2 sensors are not very accurate at anything other than 14.7:1, stock tuning will usually produce readings around 900 milliVolts in PE mode. A tuned setup, leaned out slightly in PE mode, might produce readings in the 850 - 900 mV range.
So... your O2 readings at WOT may not be a problem, if they are above 850mV. If they are closer to 800mV, might be on the lean side, and a lean mixture will produce spark knock (detonation). Rich mixtures do not produce knock. When you say you have a problem with knock, is that based on observing knock retard with a scanner, or on actually hearing knock?
Do you have full roller rockers? If so, do you have an LT4 knock module? Has your PCM been tuned?
While the stock, narrow-band O2 sensors are not very accurate at anything other than 14.7:1, stock tuning will usually produce readings around 900 milliVolts in PE mode. A tuned setup, leaned out slightly in PE mode, might produce readings in the 850 - 900 mV range.
So... your O2 readings at WOT may not be a problem, if they are above 850mV. If they are closer to 800mV, might be on the lean side, and a lean mixture will produce spark knock (detonation). Rich mixtures do not produce knock. When you say you have a problem with knock, is that based on observing knock retard with a scanner, or on actually hearing knock?
Do you have full roller rockers? If so, do you have an LT4 knock module? Has your PCM been tuned?
09-23-2015, 03:20 PM
#3
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Thread Starter
Join Date: Aug 2014
Posts: 30
Re: Tuning Question
At WOT, the PCM operates in "power enrichment" (PE) mode. It ignores feedback from the O2 sensors, and richens the A/F ratio to produce best torque and HP. While closed loop operation cycles the A/F ratio back and forth, above and below the stoichiometric ratio of 14.7:1, in PE mode you want an A/F ratio closer to 12.8 - 13.2:1 (most engines). The stock tuning sets a target A/F ratio of 11.7:1, which is actually a bit too rich.
While the stock, narrow-band O2 sensors are not very accurate at anything other than 14.7:1, stock tuning will usually produce readings around 900 milliVolts in PE mode. A tuned setup, leaned out slightly in PE mode, might produce readings in the 850 - 900 mV range.
So... your O2 readings at WOT may not be a problem, if they are above 850mV. If they are closer to 800mV, might be on the lean side, and a lean mixture will produce spark knock (detonation). Rich mixtures do not produce knock. When you say you have a problem with knock, is that based on observing knock retard with a scanner, or on actually hearing knock?
Do you have full roller rockers? If so, do you have an LT4 knock module? Has your PCM been tuned?
While the stock, narrow-band O2 sensors are not very accurate at anything other than 14.7:1, stock tuning will usually produce readings around 900 milliVolts in PE mode. A tuned setup, leaned out slightly in PE mode, might produce readings in the 850 - 900 mV range.
So... your O2 readings at WOT may not be a problem, if they are above 850mV. If they are closer to 800mV, might be on the lean side, and a lean mixture will produce spark knock (detonation). Rich mixtures do not produce knock. When you say you have a problem with knock, is that based on observing knock retard with a scanner, or on actually hearing knock?
Do you have full roller rockers? If so, do you have an LT4 knock module? Has your PCM been tuned?
I have been looking for a LT4 knock module but haven't had luck in finding one in the local junkyards. Although I get knock readings at WOT I do not hear a spark knock or notice any performance issues but the scanner reading knock worries me.
I have no tuning done to the fuel or spark maps I haven't been past the transmission options on this tune. I did flash from the EEC to EE tune hence Tuber PRO didn't have good supporting data files. It was a factory 94 tune and I modified from there the Trans and left it be for now.
There isn't anyone local who does lt1 tuning and I'm kinda iffy about mail orders; I think I'll be able to figure this out just gonna have to buy a wide band and get it installed.
09-23-2015, 04:48 PM
#4
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
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Re: Tuning Question
PE is enabled by a table of values showing RPM vs. throttle percent. Doesn't have to be at WOT (TPP = 100%). You can enter PE at fairly low RPM depending on the throttle position.
The "knock retard" value indicates the knock sensor has picked up what it believes to be the noise signature of knock, and the PCM has pulled timing to eliminate the knock, in order to prevent damage. It responds so fast, you won't hear any knock. Stock programming can pull up to 15 degrees of timing. If you hear knock, you have a problem. If you get knock retard and don't hear knock, you are losing HP.
Hopefully, you are not confusing "knock retard" with "knock count".
If the O2 sensors appear to be reading lean in PE (closer to 800mV) and you have knock retard, check the fuel pressure with the engine under max load (WOT/over 5,000RPM). Fuel pressure should not drop below 40 psi.
The "knock retard" value indicates the knock sensor has picked up what it believes to be the noise signature of knock, and the PCM has pulled timing to eliminate the knock, in order to prevent damage. It responds so fast, you won't hear any knock. Stock programming can pull up to 15 degrees of timing. If you hear knock, you have a problem. If you get knock retard and don't hear knock, you are losing HP.
Hopefully, you are not confusing "knock retard" with "knock count".
If the O2 sensors appear to be reading lean in PE (closer to 800mV) and you have knock retard, check the fuel pressure with the engine under max load (WOT/over 5,000RPM). Fuel pressure should not drop below 40 psi.
09-24-2015, 12:50 PM
#5
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Thread Starter
Join Date: Aug 2014
Posts: 30
Re: Tuning Question
PE is enabled by a table of values showing RPM vs. throttle percent. Doesn't have to be at WOT (TPP = 100%). You can enter PE at fairly low RPM depending on the throttle position.
The "knock retard" value indicates the knock sensor has picked up what it believes to be the noise signature of knock, and the PCM has pulled timing to eliminate the knock, in order to prevent damage. It responds so fast, you won't hear any knock. Stock programming can pull up to 15 degrees of timing. If you hear knock, you have a problem. If you get knock retard and don't hear knock, you are losing HP.
Hopefully, you are not confusing "knock retard" with "knock count".
If the O2 sensors appear to be reading lean in PE (closer to 800mV) and you have knock retard, check the fuel pressure with the engine under max load (WOT/over 5,000RPM). Fuel pressure should not drop below 40 psi.
The "knock retard" value indicates the knock sensor has picked up what it believes to be the noise signature of knock, and the PCM has pulled timing to eliminate the knock, in order to prevent damage. It responds so fast, you won't hear any knock. Stock programming can pull up to 15 degrees of timing. If you hear knock, you have a problem. If you get knock retard and don't hear knock, you are losing HP.
Hopefully, you are not confusing "knock retard" with "knock count".
If the O2 sensors appear to be reading lean in PE (closer to 800mV) and you have knock retard, check the fuel pressure with the engine under max load (WOT/over 5,000RPM). Fuel pressure should not drop below 40 psi.
I made a WOT pull last night in cooler weather (low 60s) and had o2 mV reading of 870-890. Started with low knock retard maybe 3 deg then in between shifts went up to 10 and fluctuated between 7-10 for remainder of pull. Low counts of .3-1.0 for 5 mins of the drive after the WOT pull. I start my car up to drive to work and no knock at all during normal driving conditions.
09-24-2015, 04:39 PM
#6
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,648
Re: Tuning Question
What I would review is a Scan9495 data log. Knock can be the result of:
-low octane fuel
-too much ignition advance *
-excessive inlet air temp *
-excessive coolant temp *
-lean A/F ratio *
-oil in intake charge
-excessive compression ratio (e.g. carbon buildup)
-incorrect spark plug heat range
I've seen the problem result from a piece of solids in the coolant that lodged in the opening in the knock sensor.
You need to watch as many as possible of those ( * ) at once, and that's what Scan9495 is very useful for.
-low octane fuel
-too much ignition advance *
-excessive inlet air temp *
-excessive coolant temp *
-lean A/F ratio *
-oil in intake charge
-excessive compression ratio (e.g. carbon buildup)
-incorrect spark plug heat range
I've seen the problem result from a piece of solids in the coolant that lodged in the opening in the knock sensor.
You need to watch as many as possible of those ( * ) at once, and that's what Scan9495 is very useful for.
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