ECU timing map...
04-29-2003, 06:48 PM
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ECU timing map...
I would like discuss something that puzzules me about the Ignition map. (On the DIS on the 3.4L). This system has a knock sensor that tells the ECU to back the timing when ping is detected.
One question : When the ECU detects ping, does it retard the timing at the specific Load/Rpm point, or does it retards the whole timing map; at every Load/Rpm point.
If the second is true, an engine ping below 3000RPM would yeild a bad chance of obtaining maximum power above "the ping RPM point".
Another one : The ECU as the capability to retard the timing to a certain point. Just for example, it may be able to retard a maximum of10*. So it basically mean when a Stock truck pings, it's because the timing is not retarded enougn; the DIS has reached it's maximum retard value.
I have also heard the knock sensors only come online at around 3000 RPM.
Anyone knows about this stuff?
One question : When the ECU detects ping, does it retard the timing at the specific Load/Rpm point, or does it retards the whole timing map; at every Load/Rpm point.
If the second is true, an engine ping below 3000RPM would yeild a bad chance of obtaining maximum power above "the ping RPM point".
Another one : The ECU as the capability to retard the timing to a certain point. Just for example, it may be able to retard a maximum of10*. So it basically mean when a Stock truck pings, it's because the timing is not retarded enougn; the DIS has reached it's maximum retard value.
I have also heard the knock sensors only come online at around 3000 RPM.
Anyone knows about this stuff?
05-02-2003, 07:50 AM
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Hey Chris,
As for the knock sensor(s) in the 5VZ-FE, they are microphones designed to detect certain sounds and frequencies. I've heard it both ways regarding which RPM points they operate above or below. Above 3000 RPM's seems, to me, to be too high for any circuit to accurately detect pings or knock given the fact that there are so many noises occurring in the engine spaced so closely together. Most of the information I've read concering OEM knock sensors states that they do NOT operate above 3K RPM's.
Gadget has mentioned that the 5VZ-FE is too noisy at lower RPM's for the knock sensors to work below 3K. It is rather clanky.
I have never verified whether the sensors in the 5VZ-FE work above or below 3K. However, based on my research with the Stock Timing curves on these engines, Toyota has severely limited Timing Advance under WOT at the higher RPM's, which makes me think that the Knock Sensors are taken out of the equation above a certain RPM. There are at least a few cases of blown engines due to detonation that were TRD S/C Equipped, but did not have any ECU or Fuel Modifications done to them. This seems to support my thinking that the Knock Sensors are rather insensitive and most likely do not function above a certain RPM, rather than the other way around. But, this is just my opinion.
I think that the maximum amount of Timing Retard that the stock ECU can achieve is 12*. I also think that the Timing Retard is a Dynamic function based on input from various sensors and once activated, only occurs as long as the condition which triggered the event is present. It seems counter-productive to safety and performance to design the ECU Timing Maps and Timing Control range differently than that.
For some looks at the stock Timing Curves, check out this thread. You'll see that maximum Timing Advance occurs in the midrange, where the engine reaches maximum Volumetric Efficiency.
I hope this helps with some of your questions.
Dr. Z
As for the knock sensor(s) in the 5VZ-FE, they are microphones designed to detect certain sounds and frequencies. I've heard it both ways regarding which RPM points they operate above or below. Above 3000 RPM's seems, to me, to be too high for any circuit to accurately detect pings or knock given the fact that there are so many noises occurring in the engine spaced so closely together. Most of the information I've read concering OEM knock sensors states that they do NOT operate above 3K RPM's.
Gadget has mentioned that the 5VZ-FE is too noisy at lower RPM's for the knock sensors to work below 3K. It is rather clanky.
I have never verified whether the sensors in the 5VZ-FE work above or below 3K. However, based on my research with the Stock Timing curves on these engines, Toyota has severely limited Timing Advance under WOT at the higher RPM's, which makes me think that the Knock Sensors are taken out of the equation above a certain RPM. There are at least a few cases of blown engines due to detonation that were TRD S/C Equipped, but did not have any ECU or Fuel Modifications done to them. This seems to support my thinking that the Knock Sensors are rather insensitive and most likely do not function above a certain RPM, rather than the other way around. But, this is just my opinion.
I think that the maximum amount of Timing Retard that the stock ECU can achieve is 12*. I also think that the Timing Retard is a Dynamic function based on input from various sensors and once activated, only occurs as long as the condition which triggered the event is present. It seems counter-productive to safety and performance to design the ECU Timing Maps and Timing Control range differently than that.
For some looks at the stock Timing Curves, check out this thread. You'll see that maximum Timing Advance occurs in the midrange, where the engine reaches maximum Volumetric Efficiency.
I hope this helps with some of your questions.
Dr. Z
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