This is exactly what I am saying. It's our perspective, vs theirsOriginally Posted by eXo3901
ours (2. optimized efficiency/economy, 1.power, 0.Emissions)
VS the OEM (1. emissions 2. economy 3. power)
The OEM research the impact of DFCO on catalyst performance. There are many published papers in this subject.
https://www.sciencedirect.com/scienc...74667015368142An additional beneficial outcome is that this immediate enrichment helps to reduce NOx emissions by restoring catalyst conversion efficiency.
Another study will clearly show
how different catalyst technologies respond to DFCOsA subsequent section will show that the DFCOs are important
for optimizing HC trap performance in the UF position.A catalyst with a higher level of OSC results in a longer rich regeneration event after the DFCO.Notice the
increase in NOx emissions for catalyst B on the ensuing
acceleration after the DFCO event. We believe this is due to
the longer rich regeneration for catalyst Ahttps://www.jstor.org/stable/26272320Non-DFCO optimized
HC trap solutions, even at a much higher PGM, may net only
10-15% overall conversion on average (10). There is room
for additional calibration optimization, especially during high
flow accelerations. However, employing DFCOs early in the
FTP shows a clear advantage for this type of HC trap system
For us, there are several unknowns. For example DFCO does not seem to fully cut the fuel in GM OEM ecu whereas DFCO in aftermarket stand-alones does fully cut fuel, 0% duty cycle the injectors are off. Many OEM vehicles I've tuned with catalytic converters will completely cut fuel such as Nissan and Toyota, Subaru, Mitsubishi, the GM ecu is the first I've encountered that doesn't, all of the Stand-alone ECU will of course. Perhaps the fuel is not completely cut because of the catalyst performance or requirements, reducing economy and NOx emissions as some published papers seem to suggest. Published instantaneous relationships may not capture the big picture and HC emissions during rapid enrichment event while a cat is too cool as some papers discuss, there is some 'DFCO Request' in many ECU which no stand-alone ECU will use, its usually just a temperature threshold such as Coolant temp, not a request based on emissions equipment. Perhaps a full DFCO will increase emissions for some types of converters or have some influence which requires us to re-tune the DFCO properly- of course anytime we change an engine part there is some re-tuning needed, even if the engine still seems to run fine it may often be improved.
Engine tuning 101: It probably needs to be fine tuned for your application, otherwise of course performance or economy will suffer
I don't use a cat, many people don't use cats, we don't have anyway to know and nobody is sharing this information. Nothing has been offered or provided for us despite months of discussion, we aren't getting any details. That is a big problem with this discussion, somebody that wants to argue a point but provides no evidence or details, I can't accept that. Either they think we are too stupid to understand it or they are withholding it purposefully to prevent us from learning or they simply don't know the answer and want to pretend they know something we don't know and hold it over our heads. I can't guess the answers and since I take my perspective from vehicles using stand-alone ECU without cats anyways that is what I focus on and that is what I care about.
In those stand-alone ECU and generic non-cat fuel cut examples (e.g. a button on the fuel injector power wires you press when decelerating to ensure 100% cut fuel with which to derive data for fuel consumption) I can't think of a way to improve economy while harming emissions or visa versa. There is a kinetic energy term and where the energy is going during a deceleration, bleeding off as heat to the brakes while the engine idles in neutral using fuel or is the energy keeping the engine turning over while no fuel is going in, which one do we want? I don't want to use the brakes when I need to slow down, let the vehicle energy turn over the engine instead while I cut fuel.
I've seen many examples on this forum where the OEM methodology is highlighted as 'proper' whereas the actual tuning theory and using your brain to think outside the box and perform some unorthodox or non-OEM solutions isn't even considered or proffered. For example closed loop tuning using narrowbands is obsolete for performance apps yet people still rely and use fuel trims to tune their modded engines despite having or needing a wideband sensor anyways. A wideband has a narrowband inside, it doesn't make sense for any application to use 14.7:1 as a switching point because that a/f ratio isn't optimal for anything other than emissions and those engines often have removed cats and long duration camshafts. This goes back to perspective and using your brain to not blindly do something just because OEM does it and the guy on the forum is strict to OEM methods. Another example is VE map tuning, the OEM methodology imposes a strict stoich '14.7:1' section separated from power enrichment, and it is considered 'taboo' to evaluate the VE map as one would in a stand-alone system where enrichment outside of Power Enrichment mode can make a smooth transition for situations which demand increasing torque, reduced knock, with slight enrichments without actually entering PE mode, which is perfectly acceptable to Gen3 applications as where VE weight is practically negligible with respect to transmission pressure and engine torque calculations in those regions (55 to 80KPA usually being off by 1.0 or 1.5 a/f value) and it may prevent the constant knocking on 87 octane fuels everyone complains about that is 'acceptable knock' which I think is absolutely ridiculous people would rather have engine knock than tune their engines properly just because the OEM does it a certain way which causes knock on non-PE fuel map transitions- And yet many are told to move their PE conditionals despite the lack of tuning around the new requirement for entering PE- its like they are only using half of the functionality of the ECU just because the OEM does things a certain way that works for them. Another example is scaling a fuel map when it isn't necessary, when I read the countless discussions about tuning timing for forced induction its like people don't even read or understand what options the OEM ecu has to offer, there is a map called AFR advance which allows you to remove or add timing based on enrichment which follows boost (you are richest at max boost and minimum timing) yet this map has been overlooked in countless discussions and even ignored when it is drudged up because nobody is willing to read and understand its usage, they either blank it or keep it OEM. And there are several associated maps which when working together can properly time the engine well beyond 1.2g/cyl limitation for boost without having to scale anything. I think many forums (all forums) core, highly experienced members are in somewhat of a tunnel vision of doing things the same way for decades and due to the age, simplistic nature of routine following and complacent with how things 'have always been' and the fear of change or actually having to think about something is holding everyone back.
I'm not saying I have all the answers but when it comes to simple, basic evaluations, such as: what is my timing, a/f ratio, trans pressure? Does the engine run properly? What is the economy and how do the plugs look? All good? Then who the F@#*&@# cares how I accomplished that goal, whether its 'proper' or not? I weight my VE table outside of PE for enrichment during transitions to help with port wall wetting and accel enrichment, I tuned to 15.5:1 cruise and idle, I used the available tables for my 2.0g/cyl timing increments for 21psi of boost on a 14.5psi 2-bar map sensor, it works, its fine, I have 50,000 miles on the setup for 5 years, the OEM ECU is absolutely capable of these things as incredulous as it sounds, if you actually tuned it instead of just doing what everybody else and the OEM does all the time.
Use your head, not your brakes.
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