Some more tuning questions
Thread Starter
Le Mans Master
Joined: Dec 2003
Posts: 7,457
Likes: 144
From: NC
Some more tuning questions
I have plenty of questions so if you happen to be one that knows what you are doing and don't mind answering, here goes (all relative to what I have learned or want to learn in my 96 LT1 Corvette:
1.) Can someone give me a definition on the term Hysteresis.
From what I can tell (relative to cooling fans), it dictates the amount of degrees in celsius that the car needs to have cooled off from the time the fan starts before it will shut off the fan. Is there a better way to define this in more user-friendly terms? I see it used in a few other places too.
2.) Under what conditions does the AIR pump run.
I see a threshold for when it is allowed to come on but what are the other conditions that dictate when it will be active. For example, if I go to WOT, is there something that says to never turn on the AIR pump under these conditions? How about in general cruise?
3.) When I go to WOT, I know that you will typically not be in OL. However, AutoTap shows that I am in fact still in CL but the LTFT's are at 0 during this time. So do you in fact go to OL during WOT or is it a different mode of CL?
4.) Assuming that you do in fact go to OL during WOT, is the table called AFR Vs. Coolant Temp Vs. Map what is used along with VE and MAF Calibration to determine how much fuel the injectors will push?
5.) If the answer to number 4 is yes, why can't I just go into that table and put in 12.5 for my WOT cells and be done. This vs. adjustments to the VE table.
6.) Why would anyone make changes to the MAF calibration table. Seems to me that the MAF calibration is a matter of fact. Making changes to that seems like a bad thing. Assuming the MAF sensor itself is good, why in the world would you ever change the calibration of it. Changing it defeats the purpose of the MAF does it not? I mean, if properly calibrated, it will tell you exactly how much air you have coming in for the computer to make its AFR calculations. Take that exactness out of the equation and now you have lost a major variable that the computer needs to make correct calculations.
7.) IAC tables seem to be relevant to the term Steps. I am guessing that I don't quite understand how the IAC works. How are Steps relevant to the IAC?
8.) There are two tables relative to WOT in my case. One is AFR vs Coolant temp. The other is AFR Vs. RPM. So which one is actually applied or is it both? For example, if the AFR vs Coolant is 15% and the RPM is 8% is the final calculation The standard value based on the VE table + The AFR vs Coolant % value + the correct value from the AFT vs RPM for a total of VE value * 1.23?
9.) Under what conditions would my car go in to SD mode?
I am sure I will have more and as I do, I will add to this thread.
Thanks to all that can answer any of these!
1.) Can someone give me a definition on the term Hysteresis.
From what I can tell (relative to cooling fans), it dictates the amount of degrees in celsius that the car needs to have cooled off from the time the fan starts before it will shut off the fan. Is there a better way to define this in more user-friendly terms? I see it used in a few other places too.
2.) Under what conditions does the AIR pump run.
I see a threshold for when it is allowed to come on but what are the other conditions that dictate when it will be active. For example, if I go to WOT, is there something that says to never turn on the AIR pump under these conditions? How about in general cruise?
3.) When I go to WOT, I know that you will typically not be in OL. However, AutoTap shows that I am in fact still in CL but the LTFT's are at 0 during this time. So do you in fact go to OL during WOT or is it a different mode of CL?
4.) Assuming that you do in fact go to OL during WOT, is the table called AFR Vs. Coolant Temp Vs. Map what is used along with VE and MAF Calibration to determine how much fuel the injectors will push?
5.) If the answer to number 4 is yes, why can't I just go into that table and put in 12.5 for my WOT cells and be done. This vs. adjustments to the VE table.
6.) Why would anyone make changes to the MAF calibration table. Seems to me that the MAF calibration is a matter of fact. Making changes to that seems like a bad thing. Assuming the MAF sensor itself is good, why in the world would you ever change the calibration of it. Changing it defeats the purpose of the MAF does it not? I mean, if properly calibrated, it will tell you exactly how much air you have coming in for the computer to make its AFR calculations. Take that exactness out of the equation and now you have lost a major variable that the computer needs to make correct calculations.
7.) IAC tables seem to be relevant to the term Steps. I am guessing that I don't quite understand how the IAC works. How are Steps relevant to the IAC?
8.) There are two tables relative to WOT in my case. One is AFR vs Coolant temp. The other is AFR Vs. RPM. So which one is actually applied or is it both? For example, if the AFR vs Coolant is 15% and the RPM is 8% is the final calculation The standard value based on the VE table + The AFR vs Coolant % value + the correct value from the AFT vs RPM for a total of VE value * 1.23?
9.) Under what conditions would my car go in to SD mode?
I am sure I will have more and as I do, I will add to this thread.
Thanks to all that can answer any of these!
Last edited by cerino2000; Feb 24, 2007 at 02:02 AM.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
1) You seem to understand it with what youve said, you could look here: http://www.webster-dictionary.org/definition/Hysteresis and see what that does for you.
6) If you were to modify the MAF (i.e. remove the front screen or bore the housing out bigger to flow more air) it will no longer be accurate.
7) The steps of the IAC indicate how far open or closed it is, more steps is further open, further open is more air flow
9) If the MAF fails or if you set it to SD mode in the ECM variables
6) If you were to modify the MAF (i.e. remove the front screen or bore the housing out bigger to flow more air) it will no longer be accurate.
7) The steps of the IAC indicate how far open or closed it is, more steps is further open, further open is more air flow
9) If the MAF fails or if you set it to SD mode in the ECM variables
Last edited by Casethecorvetteman; Feb 24, 2007 at 09:25 AM.
Melting Slicks
Joined: Aug 2003
Posts: 3,404
Likes: 398
From: Lakeville MI
1.) Can someone give me a definition on the term Hysteresis.
In control terms, hysteresis typically means a dead band. The output will not change while the input is within the dead band.
The temperature range between the fan on and fan off temps is a good example of hysteresis.
It can also apply to physical systems, brakes have hysteresis, tires have hysteresis etc.
2.) Under what conditions does the AIR pump run.
Typically during warm up, calibration specific. I don't have the details for your engine.
3.) When I go to WOT, I know that you will typically not be in OL. However, AutoTap shows that I am in fact still in CL but the LTFT's are at 0 during this time. So do you in fact go to OL during WOT or is it a different mode of CL?
WOT fueling is primarily controlled by PE or power enrichment. It can occur either in open loop or closed loop mode, this only influences the normal a/f target. The PE control however is actually an open loop control, since it is not subject to feedback.
The normal a/f target (14.73:1 if in closed loop) is inverted to get to fuel/air. Store this value.
This fuel/air is then multiplied by the coolant temp table value to determine the coolant temp correction. Store this value.
The fuel/air is then multiplied by the rpm table to determine the rpm correction. Store this value.
Add all three values considering the sign and invert again. This gives the target A/F ratio in PE.
I'll have to get back to you when I have some more time......
4.) Assuming that you do in fact go to OL during WOT, is the table called AFR Vs. Coolant Temp Vs. Map what is used along with VE and MAF Calibration to determine how much fuel the injectors will push?
5.) If the answer to number 4 is yes, why can't I just go into that table and put in 12.5 for my WOT cells and be done. This vs. adjustments to the VE table.
6.) Why would anyone make changes to the MAF calibration table. Seems to me that the MAF calibration is a matter of fact. Making changes to that seems like a bad thing. Assuming the MAF sensor itself is good, why in the world would you ever change the calibration of it. Changing it defeats the purpose of the MAF does it not? I mean, if properly calibrated, it will tell you exactly how much air you have coming in for the computer to make its AFR calculations. Take that exactness out of the equation and now you have lost a major variable that the computer needs to make correct calculations.
7.) IAC tables seem to be relevant to the term Steps. I am guessing that I don't quite understand how the IAC works. How are Steps relevant to the IAC?
8.) There are two tables relative to WOT in my case. One is AFR vs Coolant temp. The other is AFR Vs. RPM. So which one is actually applied or is it both? For example, if the AFR vs Coolant is 15% and the RPM is 8% is the final calculation The standard value based on the VE table + The AFR vs Coolant % value + the correct value from the AFT vs RPM for a total of VE value * 1.23?
9.) Under what conditions would my car go in to SD mode?
In control terms, hysteresis typically means a dead band. The output will not change while the input is within the dead band.
The temperature range between the fan on and fan off temps is a good example of hysteresis.
It can also apply to physical systems, brakes have hysteresis, tires have hysteresis etc.
2.) Under what conditions does the AIR pump run.
Typically during warm up, calibration specific. I don't have the details for your engine.
3.) When I go to WOT, I know that you will typically not be in OL. However, AutoTap shows that I am in fact still in CL but the LTFT's are at 0 during this time. So do you in fact go to OL during WOT or is it a different mode of CL?
WOT fueling is primarily controlled by PE or power enrichment. It can occur either in open loop or closed loop mode, this only influences the normal a/f target. The PE control however is actually an open loop control, since it is not subject to feedback.
The normal a/f target (14.73:1 if in closed loop) is inverted to get to fuel/air. Store this value.
This fuel/air is then multiplied by the coolant temp table value to determine the coolant temp correction. Store this value.
The fuel/air is then multiplied by the rpm table to determine the rpm correction. Store this value.
Add all three values considering the sign and invert again. This gives the target A/F ratio in PE.
I'll have to get back to you when I have some more time......
4.) Assuming that you do in fact go to OL during WOT, is the table called AFR Vs. Coolant Temp Vs. Map what is used along with VE and MAF Calibration to determine how much fuel the injectors will push?
5.) If the answer to number 4 is yes, why can't I just go into that table and put in 12.5 for my WOT cells and be done. This vs. adjustments to the VE table.
6.) Why would anyone make changes to the MAF calibration table. Seems to me that the MAF calibration is a matter of fact. Making changes to that seems like a bad thing. Assuming the MAF sensor itself is good, why in the world would you ever change the calibration of it. Changing it defeats the purpose of the MAF does it not? I mean, if properly calibrated, it will tell you exactly how much air you have coming in for the computer to make its AFR calculations. Take that exactness out of the equation and now you have lost a major variable that the computer needs to make correct calculations.
7.) IAC tables seem to be relevant to the term Steps. I am guessing that I don't quite understand how the IAC works. How are Steps relevant to the IAC?
8.) There are two tables relative to WOT in my case. One is AFR vs Coolant temp. The other is AFR Vs. RPM. So which one is actually applied or is it both? For example, if the AFR vs Coolant is 15% and the RPM is 8% is the final calculation The standard value based on the VE table + The AFR vs Coolant % value + the correct value from the AFT vs RPM for a total of VE value * 1.23?
9.) Under what conditions would my car go in to SD mode?
