Why does injector scaling affect SD MAP Sensor VE?
Jun 9, 2012, 05:38 PM
#16
Thanks for the clarification on that, greatly appreciated!
-Jamie
-Jamie
MAPVE and RPMVE calculate load and they both have an equal part in the equation. Upping MAPVE 10% is the same as upping RPMVE 10%...more or less.
Load and injector scaling are then used to calculate IPW.
If you drop the VE table 50%, and then reduce the size of the injector scaling by 50%, yes, it will keep IPW (mostly) the same while having a huge change on load.
Your method of matching SD Load to MAF Load is a good plan. If you greatly change the loads seen, it will move you around in the fuel and ignition tables. Also, below a load of about 90, there are lots of little calcs going on and if the load is out side of an expected window, it can have erratic results.
To answer your question though, changing injector scaling does not change the MAPVE scaling, persay. It simple changes the fuel delivered at a given load, which then means you have to go change the VE table to correct for it. SD in this case is kind of superficial as the ECU is not calculating a fuel requirement table based on true engine VE. You are simple adjusting the VE tables to get the AFR you want.
The stock ECU has several tables in it though that could be used to make the setup very VE based though. Like an injector linearity table for pulse width requests under 2ms.
Load and injector scaling are then used to calculate IPW.
If you drop the VE table 50%, and then reduce the size of the injector scaling by 50%, yes, it will keep IPW (mostly) the same while having a huge change on load.
Your method of matching SD Load to MAF Load is a good plan. If you greatly change the loads seen, it will move you around in the fuel and ignition tables. Also, below a load of about 90, there are lots of little calcs going on and if the load is out side of an expected window, it can have erratic results.
To answer your question though, changing injector scaling does not change the MAPVE scaling, persay. It simple changes the fuel delivered at a given load, which then means you have to go change the VE table to correct for it. SD in this case is kind of superficial as the ECU is not calculating a fuel requirement table based on true engine VE. You are simple adjusting the VE tables to get the AFR you want.
The stock ECU has several tables in it though that could be used to make the setup very VE based though. Like an injector linearity table for pulse width requests under 2ms.
May 27, 2013, 12:12 PM
#17
I have a question for you Jamie,can you please confirm my thinking:
Main goal is to keep load in check with the MAF tune to avoid messing all existings load based corrections in the ECU.
So
-I logged kpa (on MAF tune)
-I applied that to MapVE to get basically the same curve
-This lead to a very lean car, and raising RPM VE would mess back the load calculation.
So if I understand correctly, I will have to drop injector scaling to adjust base fuel, and then make only minor corrections to RPM VE make load behavior the same as with the MAF tune.
In other words, injector scaling and fuel maps would be the key to play with fuel at a certain load, without affecting load calculations. And to keep trims in check, only injector scaling and latency can be adjusted. Fuel map could be used for open loop situations.
edit: From progress tonight, I can say that I'll end up having a very different fuel map if I continue working to keep load behavior the same as with MAF tune. This need a different fuel map shape
edit2: I answered myself: my understanding of it was right.
Main goal is to keep load in check with the MAF tune to avoid messing all existings load based corrections in the ECU.
So
-I logged kpa (on MAF tune)
-I applied that to MapVE to get basically the same curve
-This lead to a very lean car, and raising RPM VE would mess back the load calculation.
So if I understand correctly, I will have to drop injector scaling to adjust base fuel, and then make only minor corrections to RPM VE make load behavior the same as with the MAF tune.
In other words, injector scaling and fuel maps would be the key to play with fuel at a certain load, without affecting load calculations. And to keep trims in check, only injector scaling and latency can be adjusted. Fuel map could be used for open loop situations.
edit: From progress tonight, I can say that I'll end up having a very different fuel map if I continue working to keep load behavior the same as with MAF tune. This need a different fuel map shape
edit2: I answered myself: my understanding of it was right.
Last edited by domyz; May 30, 2013 at 04:06 AM.
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