Injector Scaling and 14.7 AFR
#16
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I had the same reservations before looking into this in detail, but looking over Aaron's (English Racing) shoulder while he road tuned my car this way got me curious, and learning more about it convinced me otherwise. The graph above is a generic to illustrate the point, this one (below) is specific to the O2 sensor in the Evo and in the region of interest:
Yes we "all" used narrowband to tune at one point in time, however now that widebands are so cheap, if you are at all into learning and tuning your own car, I would urge people to buy a wideband.
-Bryan
Last edited by GST Motorsports; Apr 28, 2009 at 09:53 PM.
#17
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The only thing this proves, is that you can get the o2 reading to be the same throughout a pull, it doesn't say a lot, really, about the actual AFR, other than that there are no extreme peaks or dips.
If things are set up right, your fuel map and actual AFR should be reasonably close, but without using a wideband at some point in the tuning process ... the best you can do is get your trims right on, and hope it's "close enough".
If things are set up right, your fuel map and actual AFR should be reasonably close, but without using a wideband at some point in the tuning process ... the best you can do is get your trims right on, and hope it's "close enough".
Last edited by jrohner; Apr 28, 2009 at 11:22 PM.
#19
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You answered the question yourself. I believe it needs to meet both conditions of throttle and load to work correctly.
The secondary tables are probably for some switchover point similar to the switchover point for gear dependent boost control... maybe even the same one. If you want to be on the sure that your setting takes set them both to the same thing.
Any particular reason you want to change the switchover?
#21
I noticed that "Open Loop Load #1" and "Open Loop Load #2" had different values in my ROM, and was trying to understand why. Also trying to learn what the "14.7" in the AFRMAP is good for - if the ECU never reads that cell could it be any value (like zero?) without it making any difference?
The "Open Loop Throttle Table" has RPM in the left column but ranges 0-3 in the right column, so I didn't understand what they represent. For TPS I would expect different values ... I've attached the tables so you can see what I mean.
The "Open Loop Throttle Table" has RPM in the left column but ranges 0-3 in the right column, so I didn't understand what they represent. For TPS I would expect different values ... I've attached the tables so you can see what I mean.
#22
The 14.7 is there kind of for a holding place to keep the stoich plateau open. Since the car operates in closed loop with the stock open loop load tables...it won't even be looking at the fuel map, it will be calculating everything from the o2 sensor.
Not sure if anything would change if you put 0s in the plateau.
Not sure if anything would change if you put 0s in the plateau.
#23
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I'm guessing the TPS tables are voltage, have you checked what scaling is set to them? You can change that to percentage if that is the case.
I thought that the 14.7 (rather the area in the closed loop curve) was used as a check-back for the closed loop fuel control, but that may have been defunct.
I thought that the 14.7 (rather the area in the closed loop curve) was used as a check-back for the closed loop fuel control, but that may have been defunct.
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Once you run the car in open loop via those tables and fuel map, you will understand more how the narrowband sensor loses resolution and accuracy the further away from Stoich it goes.
- Bryan
- Bryan
#26
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I think you may have just lost any reliable tuner input with the hillbilly O2 logic you posted. And dont get me started with using EGT as a tuning tool... you will have better luck using astrology to tune than a narrow band sensor and an EGT meter! Maybe some magets will also help.
#27
Common "EvoM wisdom" is that this region does not need changing, but you know me ... I question everything . This could explain some of the cold start problems people are having with larger injectors (myself included). I'll do some experimenting when I get the chance and let you know what happens.
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I think that may be the right answer, it makes sense that the ECU runs open loop until the car is warmed up and needs something to target even while in the closed-loop region of the map. However, if that's true that tells me I need to change the 14.7 region just like any other part of the map after changing injectors - otherwise the AFR will be off while warming up (before going into closed-loop)?
- Bryan
Last edited by GST Motorsports; Apr 29, 2009 at 11:46 PM.
#29
We have finally dialed our fuel trims. Are we done done now? Not yet.
Now you MUST go back and adjust your AFR fuel map to fit the new injector scaling. You are basically going to have to re-tune your fuel map to fit the new injectors. Just follow the section about AFR adjustment in this write-up.
Now you MUST go back and adjust your AFR fuel map to fit the new injector scaling. You are basically going to have to re-tune your fuel map to fit the new injectors. Just follow the section about AFR adjustment in this write-up.
At this point I'm convinced that if the map needs changing, then all of it needs to be changed (including the closed loop 14.7 block); however, if having near zero LTFTs is what you mean as "correct" scaling/latency changes, then none of the map should need changing at all. So which one is it