dynamic tuning concept for ideal AFR's
10-12-2002, 02:15 AM
#1
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Join Date: Jul 2002
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we spend a lot of time talking about tuning. an idea i have thought about a lot for a fair amount of time is the automatic tuning fuel injector controller. first, lets assume that we have a decent aftermarket computer controlling everything as usually setup in a single conversion. it controls the fans, water injection, timing, etc...
now, we disconnect the fuel injector leads. we get a small homebuilt computer and a high quality wideband lambda and heated wideband o2 sensor and hook up the output from the wideband to the home made computer. (assume that the computer has a very very fast clock and is very quick at processing instructions.) the computer has outputs that are connected to the fuel injectors and other oputputs that are connected to the water injection system. further, it has inputs for rpm and oil and water temps.
now, the simplest version of the concept implementation. we write a very simple program that reads the input from the wideband and compares it to a value that we have set for the air fuel ratio. say its 11.5:1. if the wideband reading is 12:1, then the computer program will try to increase the richness by increasing the duty cycles of the injectors. it increases the duty cycle a bit and checks the wideband AF reading again. (the time involved would have to be played wioth a bit as to how often and by how much the duty cycle adjustments are made, since the injectors are mechanical and there will be a lag between the increase in duty cycles and the change in AF due to the increase.)
now, assuming that we can accomplish this basic, automatic adjustment of AF's, there is more that can be done. we assumed that we had one AF value set. in fact, we know that at the lowest rpm, well below the torque peak, we can have a higher AFR. we know that we should have the lowest AFR as we get to and go jhust over the torque peak and can then bring the AFR's up again as we go to redline. now, doing this with a standard map based ecu can be done, but its very hard and very time-consuming.
further, these ecu's have static maps in the first place. they don't adequately adjust for changes in barometric pressure or temperature at all well. rather, they have a map of duty cycle to boost by rpm. the duty cycles are set to result in a certain AFR result under the speciufic conditions they were tested in. if temps and baro change or anything else changes, the AFR's will not be they same for the same maps.
the solution i am suggestiong is nbot all that difficult. i suspect that we have guys on the forum who could program it and build the box. ideally, we would combine the wideband and the fuel control computer into one box. this is an idea worth pursuing,. because the result lets us play with targeted AFR mapos and not have to worry about tuning.
gordon
now, we disconnect the fuel injector leads. we get a small homebuilt computer and a high quality wideband lambda and heated wideband o2 sensor and hook up the output from the wideband to the home made computer. (assume that the computer has a very very fast clock and is very quick at processing instructions.) the computer has outputs that are connected to the fuel injectors and other oputputs that are connected to the water injection system. further, it has inputs for rpm and oil and water temps.
now, the simplest version of the concept implementation. we write a very simple program that reads the input from the wideband and compares it to a value that we have set for the air fuel ratio. say its 11.5:1. if the wideband reading is 12:1, then the computer program will try to increase the richness by increasing the duty cycles of the injectors. it increases the duty cycle a bit and checks the wideband AF reading again. (the time involved would have to be played wioth a bit as to how often and by how much the duty cycle adjustments are made, since the injectors are mechanical and there will be a lag between the increase in duty cycles and the change in AF due to the increase.)
now, assuming that we can accomplish this basic, automatic adjustment of AF's, there is more that can be done. we assumed that we had one AF value set. in fact, we know that at the lowest rpm, well below the torque peak, we can have a higher AFR. we know that we should have the lowest AFR as we get to and go jhust over the torque peak and can then bring the AFR's up again as we go to redline. now, doing this with a standard map based ecu can be done, but its very hard and very time-consuming.
further, these ecu's have static maps in the first place. they don't adequately adjust for changes in barometric pressure or temperature at all well. rather, they have a map of duty cycle to boost by rpm. the duty cycles are set to result in a certain AFR result under the speciufic conditions they were tested in. if temps and baro change or anything else changes, the AFR's will not be they same for the same maps.
the solution i am suggestiong is nbot all that difficult. i suspect that we have guys on the forum who could program it and build the box. ideally, we would combine the wideband and the fuel control computer into one box. this is an idea worth pursuing,. because the result lets us play with targeted AFR mapos and not have to worry about tuning.
gordon
10-12-2002, 12:56 PM
#4
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Location: Bay Area, CA
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Originally Posted by vosko' date='Oct 12 2002, 07:40 AM
i thought i read the AEM can do this ? i bought my own wideband so still trying to figure what cool tricks it can do hooked up to the haltech 
10-12-2002, 02:32 PM
#5
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i think that the TECII had a feature for adjusting AFRs to maintain emmissions at 0-3000 rpm? i didn't know the AEM had such a thing. i looked at their software a while ago, but it wasn't there at that time. can somebody point me to the info on the AEM that does this? if i can find a computer that already does it, i won't need to build it and NO MAPS EVER AGAIN!!! -gordon
10-12-2002, 02:51 PM
#6
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Originally Posted by gmonsen' date='Oct 12 2002, 11:32 AM
i think that the TECII had a feature for adjusting AFRs to maintain emmissions at 0-3000 rpm? i didn't know the AEM had such a thing. i looked at their software a while ago, but it wasn't there at that time. can somebody point me to the info on the AEM that does this? if i can find a computer that already does it, i won't need to build it and NO MAPS EVER AGAIN!!! -gordon
EGO Air/Fuel Ratio Table
The Air Fuel Ratio feedback system uses an 8 x 8 table where the RPM and MAP/kPa breakpoints are defined in the Advance table. The desired air to fuel ratio can be typed in any one of the 64 cells. The TEC will straight line linearize between the points and extrapolate beyond the defined RPM or MAP/kPa values. The computed desired air to fuel ratio appears on the engine monitor screen “DESIRED AFR” next to the actual air fuel ratio “ACTUAL AFR”. The TEC modifies fuel flow to get the actual to equal the desired. Each EGO table Cell can be edited by using the arrow keys to select the cell you want to edit or you can use F3 to edit a complete Row of data or F4 to edit a complete Column of data or you can type “S” and enter a Constant for the entire table. ONFLY can only update the Air/Fuel Ratio data fields. RPM and MAP/kPa must be updated in the Advance Table in Edit mode and Downloaded using Program TEC from the Main Menu.
EGO Air/Fuel Ratio Table Interactive 3D Graph With the EGO interactive 3D graph, the user can move the blue oval cursor to any position on the graph by using the arrow keys (see * 3D Graph Arrow Keys above) on the keyboard. Once you get to the point you want to change, as defined in the fields in the upper left hand corner, just press the + key or the - key to move the values up and down at that point. When you have reached the desired value, you can return to the EGO Air/Fuel Ratio Table and you will see that the value at that point has been changed and is now the same as the 3D Graph. This will help the user to visualize the EGO Air/Fuel Ratio Table values and how they relate. This 3D Graph is not available while ONFLY is active.
The Air Fuel Ratio feedback system uses an 8 x 8 table where the RPM and MAP/kPa breakpoints are defined in the Advance table. The desired air to fuel ratio can be typed in any one of the 64 cells. The TEC will straight line linearize between the points and extrapolate beyond the defined RPM or MAP/kPa values. The computed desired air to fuel ratio appears on the engine monitor screen “DESIRED AFR” next to the actual air fuel ratio “ACTUAL AFR”. The TEC modifies fuel flow to get the actual to equal the desired. Each EGO table Cell can be edited by using the arrow keys to select the cell you want to edit or you can use F3 to edit a complete Row of data or F4 to edit a complete Column of data or you can type “S” and enter a Constant for the entire table. ONFLY can only update the Air/Fuel Ratio data fields. RPM and MAP/kPa must be updated in the Advance Table in Edit mode and Downloaded using Program TEC from the Main Menu.
EGO Air/Fuel Ratio Table Interactive 3D Graph With the EGO interactive 3D graph, the user can move the blue oval cursor to any position on the graph by using the arrow keys (see * 3D Graph Arrow Keys above) on the keyboard. Once you get to the point you want to change, as defined in the fields in the upper left hand corner, just press the + key or the - key to move the values up and down at that point. When you have reached the desired value, you can return to the EGO Air/Fuel Ratio Table and you will see that the value at that point has been changed and is now the same as the 3D Graph. This will help the user to visualize the EGO Air/Fuel Ratio Table values and how they relate. This 3D Graph is not available while ONFLY is active.
10-12-2002, 04:19 PM
#7
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Location: Peoria, AZ
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Originally Posted by gmonsen' date='Oct 12 2002, 02:32 PM
i think that the TECII had a feature for adjusting AFRs to maintain emmissions at 0-3000 rpm? i didn't know the AEM had such a thing. i looked at their software a while ago, but it wasn't there at that time. can somebody point me to the info on the AEM that does this? if i can find a computer that already does it, i won't need to build it and NO MAPS EVER AGAIN!!! -gordon
10-12-2002, 05:18 PM
#8
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Join Date: May 2002
Location: California
Posts: 22,465
that would be really cool. a friend of mine (www.16paws.com) has been looking at cracking the stock ecus. he is just doing it for fun, but even a stock 86na ecu has more features than any of the aftermarket ones, and it will start the car hot and cold.
on the other hand if we take gordons idea we will have one table for fuel, it would be afr vs load vs rpms and a table for timing, maybe using knock sensors? or the factory uses pressure sensors to detect knock, maybe one in each rotor housing? that way you have 2 tables, the fuel and the timing. for the timing you set the max cumbustion pressure.
hmmmmm
mike
on the other hand if we take gordons idea we will have one table for fuel, it would be afr vs load vs rpms and a table for timing, maybe using knock sensors? or the factory uses pressure sensors to detect knock, maybe one in each rotor housing? that way you have 2 tables, the fuel and the timing. for the timing you set the max cumbustion pressure.
hmmmmm
mike
10-14-2002, 11:24 AM
#10
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Join Date: Jan 2002
Location: Birmingham, AL
Posts: 844
Here is the way the AEM works from my understanding. You have to tune it one time so that it has a starting point. Then from that point on i THINK you can just tell it what a/f you want and it makes adjustments to get that.
I believe its based on the Speed Pro system which also auto tunes, AEM bought Speed Pro and couple years or so ago. We never hear about Speed Pro cause it didnt work with rotary but the AEM of course does.
STEPHEN
I believe its based on the Speed Pro system which also auto tunes, AEM bought Speed Pro and couple years or so ago. We never hear about Speed Pro cause it didnt work with rotary but the AEM of course does.
STEPHEN