I'm bored so I thought I'd share this little tidbit of information. This is more for those of us that are anal retentive about having our K being spot on. Some of you may already have thought of it.
I've been doing a lot of reading about dyno tuning ecus because we're getting a dyno soon. Long story short, I've read from a number of people that its common for AFRs to change based on which gear you are using during a run. In other words if you tune for a particular AFR using 3rd gear pulls when you do a pull in 2nd gear it might run leaner or in 4th it might run richer. It's likely this happens for a number of reasons including acceleration enrichments, the way the load and rpm transition through the maps, and lag in the efi system.
So I got to thinking. Most of us are probably tuning our K by logging AFRs and trying to get them to match what's on the fuel map. Obviously it works but could it be better? There has got to be some variation due to gear changes and different driving conditions that are encountered during logging runs.
What I'm wondering is what the afrs would look like in steady state mode on the dyno. If we were able to do steady state it should allow the ecu to stabalize and get rid of any error due to acceleration enrichment, lag, or transitioning affects. We could set the entire fuel map to a constant afr and then pick a couple load/rpm points to steady state in and log the afrs. I think it would be interesting to see how close the ecu could keep the afrs relative to the target fuel map with a good K. How close would a stock ecu with stock injectors and afm get to the target afrs?
It seems to me that this would be the ultimate way of tuning the K constant. The only remaining question would be, does a K tuned in this manner result in accurate AFRs on the road? This is something thats going on my list of things to test when we get the dyno.
Questions, comments, did you fall asleep?
I've been doing a lot of reading about dyno tuning ecus because we're getting a dyno soon. Long story short, I've read from a number of people that its common for AFRs to change based on which gear you are using during a run. In other words if you tune for a particular AFR using 3rd gear pulls when you do a pull in 2nd gear it might run leaner or in 4th it might run richer. It's likely this happens for a number of reasons including acceleration enrichments, the way the load and rpm transition through the maps, and lag in the efi system.
So I got to thinking. Most of us are probably tuning our K by logging AFRs and trying to get them to match what's on the fuel map. Obviously it works but could it be better? There has got to be some variation due to gear changes and different driving conditions that are encountered during logging runs.
What I'm wondering is what the afrs would look like in steady state mode on the dyno. If we were able to do steady state it should allow the ecu to stabalize and get rid of any error due to acceleration enrichment, lag, or transitioning affects. We could set the entire fuel map to a constant afr and then pick a couple load/rpm points to steady state in and log the afrs. I think it would be interesting to see how close the ecu could keep the afrs relative to the target fuel map with a good K. How close would a stock ecu with stock injectors and afm get to the target afrs?
It seems to me that this would be the ultimate way of tuning the K constant. The only remaining question would be, does a K tuned in this manner result in accurate AFRs on the road? This is something thats going on my list of things to test when we get the dyno.
Questions, comments, did you fall asleep?
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