dfco settings

[Fast4.7]

I'm confused as to what point you are constructing your counterpoint against lol. Nobody ever said to drive around two footing the pedals so you can have your mind blown by the fact that not doing that conserves fuel. You're right, coasting to a stop (ideally with a calibration that minimizes engine braking) is better on the fuel mileage than smashing on the brakes immediately after letting off the throttle. That said...I can calibrate an engine to plant your face into the steering wheel with engine braking by choking the engine with a throttle snapped completely shut. The effect is the same as mashing on the brakes. It is momentum lost and therefore wasted energy. To address your curiosity in post #5...this is precisely why GM and any other manufacturer of ICE engine passenger vehicles aims to reduce engine braking. They don't decel hard enough to choke you on the seat belt for a reason. The net effect is the same as hitting the brake pedal. So again, to your original point in this thread in the comment below...engine braking does NOT recover ANY energy. The ideal situation would be none at all, but a balanced set of requirements must be met. So every vehicle will have some amount of natural engine braking. It's not doing your gas gauge any favors though. Less is more here...that's just classical mechanics.

Actually most modern vehicles need more engine braking actually far more than they deliver. There is zero reason to have the fuel flowing when you are coasting with Zero TPS. Engine braking DOES recover fuel economy provided DFCO is active and the engine is being motored by the powertrain, bleeding vehicle inertia with the intent of slowing down. Basic physics 101. Having to use the service brake to do what the powertrain should naturally do is absolutely dumb! Drive a stock 60s carbureted vehicle sometime with the idle speed set correctly and you will understand how a vehicle should behave off-throttle. You can control the vehicle speed with your accelerator pedal position alone rather than coasting along at X speed and having to throw the brakes on when the vehicle should have been noticeably slowing down already from engine braking.

[SolarSupremacy]

What the hell did I just read?

[Fast4.7]

What the hell did I just read?

Just my annoyance with almost all modern vehicles that will not slow down when you lift your foot off the accelerator because apparently idiots calibrate them to act like the cruise control is on. Back to the regularly scheduled program.

These OEM calibrators really need to make two simple coast down checks on their programming. At 35 mph, completely lift off the throttle, on level road the vehicle should slow down to 10-15 mph in no more than 1/8 mile from engine braking. In city driving that is a realistic distance to slow for a traffic light or stop sign without having to slam on the brakes because the vehicle wants to continue coasting at nearly the same speed. Second drive to Texas and get out on a 2-lane rural highway. These roads have a sign about 1/4 mile or so ahead of a speed limit reduction going into the next small town. If one is driving the speed limit of say 70 mph and lets off the throttle when they see the reduced speed limit ahead sign, the vehicle should slow down to the speed limit which is usually 55 mph or under it without having to jam on the brakes. Plain and simple real world sanity checks. If your calibration will not do these two simple actions, it is garbage and needs to be revised. EVERYTHING I have owned in the past 10 years that is newer I have had to fix these beyond simple calibration errors. At the end of the day, when you lift off the gas pedal the vehicle does not need to cruise control, it needs to slow down. I sometimes wonder if these calibrators ever even drive the garbage, they are pushing out on to the dealership lots.

The 4L60E factory 2-1 shift table is another fine example of HORRIBLE OE calibration. Coasting up to a red light on an uphill grade about to climb a continued uphill grade on the other side of the light, I am at 10-15 mph, the light turns green, I push on the pedal still going uphill, I am in 2nd gear at 10-15 mph and it will not downshift to first unless I give the thing nearly 90% throttle. You can either chug up the hill in 2nd gear with the engine most likely spark knocking like crazy, floor it and probably break the tires loose, or manually pull the shifter back into first. GM did this on every truck they built with the 4L60E. The old 700r4s were great in comparison, give them a little increase in throttle and they would make a nice part throttle 2-1 downshift and get you rolling with ease. In the 4L60Es case if I were at a stop or under 8 mph which puts it in 1st and accelerating up the same grade, it would hold 1st gear at 50% throttle until 25 mph and at 62% throttle it would hold 1st gear until 30 mph and at 80% throttle it shifts practically at redline. Never will understand why someone felt it would be a good idea to force someone to make a near WOT kickdown to be able to climb a moderate grade accelerating from slow speeds. To add insult to injury GM did not fix this in Tow/Haul mode either. Guess they never slowed to ~ 15 mph on an uphill grade and tried to accelerate normally with 6,000 lbs of trailer behind them and it gets even more stupid in the rain where a high throttle angle kickdown like that would simply haze the tires.

For that matter the whole D1 Urban calibration is also dumb. Nothing like using 1st gear engine braking on a long, steep downhill descent with a heavy trailer, to suddenly have the truck upshift to 2nd way below the engines redline and start a runaway acceleration that requires heavy braking to counter. Would you rather hear some engine noise or my front bumper crashing through your living room because the 6,000 lbs trailer with working trailer brakes that is under the trucks GCVW overheated my brakes when the engine braking holding my speed down ceased?

[smokeshow]

These OEM calibrators

I was an OEM calibrator. What is it you are confused by? Maybe I can help.

[Fast4.7]

I was an OEM calibrator. What is it you are confused by? Maybe I can help.

I am not confused by anything at all. I was merely pointing out how overly dumb it is to have a vehicle that does not engine brake to bleed off inertia when you are completely off the accelerator pedal. If I wanted cruise control effect I would set the cruise. If I am off the throttle it is to slow down, not keep on coasting with the engine still motoring the vehicle along. Some of us barely want to use the service brake in normal driving conditions. I do not need the PCM to make the vehicle coast as far as possible with my foot off the throttle, I need it to slow down as it should. Many people do not pulse on the throttle and know how to maintain speed and or following distance by modulating the pedal position.

I was absolutely confirming what Kingtalon said previously. On my personal vehicles, I fix the garbage that the OEM calibrators are doing with off-throttle coasting, make the powertrain slow the vehicle in an appropriate manner as it should when you lift the throttle. City mileage increase 2-3 MPG and the brake pad life more than doubles. I also complained about GMs almost non-existent part throttle 2-1 kickdown at slow speeds as well as the 1-2 Urban Mode upshift with the shifter in 1st gear going down a steep grade. I get over a full MPG around town better in a 6,500 lbs brick of a V8 van, using 1st, 2nd, Lockup, 3rd, then 4th for a shift pattern instead of 1, 2, 3, 4, Lockup GM uses factory.

I have been tuning GM vehicles for 20 years now. I know a thing or two about how to make them behave correctly. My biggest efficiency gains when I tune are transmission shift points, torque converter lockup strategy, throttle kicker or follower reduction and DFCO changes to actually slow the vehicle down appropriately when I am off throttle.

[smokeshow]

I am not confused by anything at all. I was merely pointing out how overly dumb it is to have a vehicle that does not engine brake to bleed off inertia when you are completely off the accelerator pedal. If I wanted cruise control effect I would set the cruise. If I am off the throttle it is to slow down, not keep on coasting with the engine still motoring the vehicle along. Some of us barely want to use the service brake in normal driving conditions. I do not need the PCM to make the vehicle coast as far as possible with my foot off the throttle, I need it to slow down as it should. Many people do not pulse on the throttle and know how to maintain speed and or following distance by modulating the pedal position.

I was absolutely confirming what Kingtalon said previously. On my personal vehicles, I fix the garbage that the OEM calibrators are doing with off-throttle coasting, make the powertrain slow the vehicle in an appropriate manner as it should when you lift the throttle. City mileage increase 2-3 MPG and the brake pad life more than doubles. I also complained about GMs almost non-existent part throttle 2-1 kickdown at slow speeds as well as the 1-2 Urban Mode upshift with the shifter in 1st gear going down a steep grade. I get over a full MPG around town better in a 6,500 lbs brick of a V8 van, using 1st, 2nd, Lockup, 3rd, then 4th for a shift pattern instead of 1, 2, 3, 4, Lockup GM uses factory.

I have been tuning GM vehicles for 20 years now. I know a thing or two about how to make them behave correctly. My biggest efficiency gains when I tune are transmission shift points, torque converter lockup strategy, throttle kicker or follower reduction and DFCO changes to actually slow the vehicle down appropriately when I am off throttle.

Those are requirements specific to you. The OEMs have to deal with legal flowdown from the EPA...sometimes that comes in the form of compromises to meet emissions/fuel economy requirements and keep your business afloat and producing vehicles. Not to mention, your production vehicle performs to the expectations of the customer base, on average...it was not built to your personal specifications, even if you hand-picked things at the dealer. If you don't know the context for a feature's existence or absence, objectively, you really don't know if its dumb or not lol. Almost always...there are just more requirements to meet than you realize. The lack of engine braking / excess sail-on is there for a very specific reason.

[99k2500]

My brain hurts. I have tried this as my big block suburban eats fuel like how a fish lives in water.... I have normal driving through rural area. DFCO enabled cut coasting down by almost half, meaning.... I had to be on the throttle longer. I tried it this way for 6 months. Same driving everyday. Same roads, same stops, same time for traffic reason. I used an average of 2 gallons more a week using dfco. I may have talked to the wrong people to help me set it up..... regardless, I turned it off and went back to the normal conservative driving I do and saved my 2 gallons per week. It was not in my favor to keep it on. It isn't a professional drawn out conclusion, but that is what I got. It isn't graphs or numbers, it was real life experience. Take it for what its worth, I really don't give a crap. I'm sure some vehicles it can be useful.... But not mine, sorry.

[smokeshow]

My brain hurts. I have tried this as my big block suburban eats fuel like how a fish lives in water.... I have normal driving through rural area. DFCO enabled cut coasting down by almost half, meaning.... I had to be on the throttle longer. I tried it this way for 6 months. Same driving everyday. Same roads, same stops, same time for traffic reason. I used an average of 2 gallons more a week using dfco. I may have talked to the wrong people to help me set it up..... regardless, I turned it off and went back to the normal conservative driving I do and saved my 2 gallons per week. It was not in my favor to keep it on. It isn't a professional drawn out conclusion, but that is what I got. It isn't graphs or numbers, it was real life experience. Take it for what its worth, I really don't give a crap. I'm sure some vehicles it can be useful.... But not mine, sorry.

Lol that'll happen. It isn't meant to save fuel. There's a balance between 'active just often enough to improve emissions' and 'active so often that emissions suffer because of the parasitic loss on your forward momentum and resulting increased fuel consumption'. Always a compromise.

[Tunercharged]

Lol that'll happen. It isn't meant to save fuel. There's a balance between 'active just often enough to improve emissions' and 'active so often that emissions suffer because of the parasitic loss on your forward momentum and resulting increased fuel consumption'. Always a compromise.

I turned dfco off about a week ago, fuel consumption actually went down 2 tenths and the engine braking it not as abrupt. It still engine brakes of course and I think I will try to investigate how to modify the amount of engine braking I can have with it off. Overall I notice that my truck is easier to drive hard around corners off and into the throttle… it’s smoother. Though not really important for me in my heavy truck, it does lend to pushing limits nicely in a turn. I would definitely recommend trying this to any drivers of Corvettes or Camaros who like to dip throttle hard into a corner, suspension doesn’t jump as much, more control I would think. There are definitely benefits, not sure of the drawbacks, I’ll see if I can tune in a little less fuel but not as much starvation as dfco would provide.

[kingtal0n]

It isn't meant to save fuel.

If you drive with DFCO in mind you can definitely pick up some MPGs.

https://www.camaro5.com/forums/showp...69&postcount=3

The point of DFCO is to increase fuel economy.

https://www.corvetteforum.com/forums...post1588374882

Your not injecting fuel and saving money

Why bother measuring it?
I do not believe it would show up on EPA testing, so the car manufacture has little to no reason to add it. -

https://mirageforum.com/forum/showth...ll=1#post58925

Decel Fuel Cut Off: No effect on performance,,, slight increase in fuel economy.

The above explaination is correct, under decel, the fuel injectors are not pulsed.

https://ls1tech.com/forums/pcm-diagn...ml#post5941716


Patent doc published DFCO

based on estimating that choosing period of time ground initiation DFCO event can make fuel be cut off quickly, and can provide the fuel consumption saving.

DFCO signal 260 into active state based on estimation choosing period of time ground fuel is cut off quickly, and the fuel consumption saving can be provided.

https://patents.google.com/patent/CN103016178A/en

This means you are experiencing forward movement with no fuel cost.

https://www.clubxb.com/threads/dfco.15997/post-261348

Chevrolet Cruze decel fuel cutoff (DFCO) boosts fuel economy by 2%

https://www.autoblog.com/2011/06/30/...el-economy-by/

Though simplistic, this technology increases the Cruze's fuel economy by up to two percent, depending on driving conditions. This means that on a each tank of fuel, DFCO adds up to 17 miles of the overall range on the Cruze Eco and 11 miles to the non-Eco models

DFCO should be configured to come in when you want to slow the car down.

https://forum.efilive.com/showthread...l=1#post164713

How can I use DFCO to increase my MPG?

Let me count the ways...

- When traveling down a grade get into DFCO mode instead of racing from corner to corner or riding your friction brakes, etc.

- As soon as you hit an exit ramp off of the highway go into DFCO all the way to the end of the ramp.

- When approaching a stop or turn use DFCO to decelerate down to just a few MPH before applying the friction brakes.

- When you're stuck in heavy traffic use the well-known technique of finding the right speed to keep a few car lengths of distance ahead of you and maintain forward momentum, then use DFCO to decelerate when needed instead of your friction brakes.

- Use DFCO to maintain controlled forward movement while you're trying to stay moving while approaching a traffic light that you're waiting to turn green.

https://www.yarisworld.com/forums/showthread.php?t=4248

There are many values that have to be met for dfco to enable/disable,when you figure out where to put them dfco works great
I have done alot of things with my tahoe and others that is giving them an additional 3.5-4MPG increases.it works very very well
Avgerage they were doin about 14.5-15MPG,now they are getting 18.5-19MPG and this is with hardly any highway driving

https://www.performancetrucks.net/fo...2/#post3977385

I think I will never purchase another car without DFCO.

https://www.cleanmpg.com/community/i...e-2#post-76181

I personally like tuning with DFCO on because it gives pretty much all positives and no negatives. Cleaner running engines, better mileage, smoother, more consistent decel, cleaner plugs,

https://www.ctsvowners.com/threads/d...72/post-373281


It is clear the purpose of cutting fuel to any engine during deceleration is to avoid wasting fuel during situations which would waste fuel.

Those are requirements specific to you. The OEMs have to deal with legal flowdown from the EPA...

In other words, you don't know why or what is happening, so you blame the EPA without evidence


Facts
The purpose of a tuning forum is to learn how to tune an engine for requirements specific to our driving desires and account for non-OEM modifications.
whether that improves or reduces emissions is NOT important to most of us.

That is literally why people modify their engine away from OEM because the OEM was not suitable for them, and we make mods which increase emissions such as camshaft profiles that bleed fuel during overlap.
We run an engine with a long overlap at low rpms coasting or idle then the emissions is far greater than it was when stock, regardless of economy, apples to apples still applies


$.02
Fuel cutoff for deceleration is going to save fuel if the intent is to slow the vehicle down (decelerating) to avoid using the brakes when coming to a stop. If the intention is to coast then coasting can maintain vehicle kinetic energy which will prevent unnecessary power enrichment coming out of a coast (high manifold pressure accelerating from a lower speed) In other words, if the intention is to "engine brake" then you are deliberately slowing down a vehicle to save the brakes and save fuel as evinced by so many details regarding DFCO (all of them can't be wrong including the DFCO patent which explicitly implies DFCO is for saving fuel). On the other hand if the intention is to 'keep the vehicle moving via coasting' then you would not want to cut fuel OR use the brakes (fuel cut = braking) because why would you want to slow down the vehicle if you wanted to coast along without losing much kinetic energy and momentum.

It is two completely different situations and they need to be dealt with separately and DFCO/Throttle cracker needs to be tuned on a per-vehicle basis to maximize these two different situations for their benefits. For example heavy trucks would prefer to coast because accelerating a heavy load could dip into Power Enrichment which interferes with fuel savings whereas coasting along without enrichment can maintain kinetic energy to avoid stopping/slowing... but this will only work if there is no need to use the brakes (hence, the lack of dramatic engine braking). The point of DFCO is to avoid using brakes which saves fuel and brake wear. If there is some reason to use brakes then coasting will not work because you can't coast at the same speed and brake at the same time, they are mutually exclusive conditions. Thus it is unreasonable to say that engine on coasting is superior to DFCO because one of them requires braking and one does not, as there will never be a time when both situations apply equally. It would be like pressing the gas and brake at the same time.

[kingtal0n]

I turned dfco off about a week ago, fuel consumption actually went down 2 tenths and the engine braking it not as abrupt. It still engine brakes of course and I think I will try to investigate how to modify the amount of engine braking I can have with it off. Overall I notice that my truck is easier to drive hard around corners off and into the throttle… it’s smoother. Though not really important for me in my heavy truck, it does lend to pushing limits nicely in a turn. I would definitely recommend trying this to any drivers of Corvettes or Camaros who like to dip throttle hard into a corner, suspension doesn’t jump as much, more control I would think. There are definitely benefits, not sure of the drawbacks, I’ll see if I can tune in a little less fuel but not as much starvation as dfco would provide.

To get DFCO saving fuel on automatric transmission I need to enable locked deceleration so it functions like a manual transmission fuel cut
https://www.youtube.com/watch?v=_4xc-avcVtk

All manual trans cars to my knowledge cut fuel while decelerating in gear above some set RPM point near 0% tps. I noticed this in the 1980's. All of them do this to enable engine braking which saves fuel by extracting kinetic energy from the drivetrain to keep the engine turning instead of using the brakes, brakes are what wastes 100% of the kinetic energy that dissipates to heat.

Automatic transmissions are different because fluid coupling multiplies torque, which I believe works both ways. Engine brake with an unlocked converter extracts excess energy from the engine, the RPM drops rapidly causing the ECU to exit DFCO and rebound, rpms rising again and falling, extremely inefficient and possibly why the OEM tuned seemingly weird DFCO conditions for auto trans vehicles, as coming in and out of DFCO does weird things to the timing and thus energy extraction from fuel.

Furthermore, the RPM and gear ratio where DFCO is entered as well as the parasitic internal loss of the engine is part of the fuel saving equation.
In other words, it isn't simply whether DFCO is "ON" or "OFF". For example If I upshift to 4th gear (low rpm) and 'coast' in DFCO (fuel is turned OFF while vehicle decelerates) the energy extracted from the drivetrain is fed into the engine at low RPM which is low parasitic losses at low rpm. On the other hand, if I downshift to 3rd (high engine RPM) and Enter DFCO, the vehicle decelerates much more rapidly as the higher engine RPM has a higher parasitic loss and shorter time in DFCO, resulting with a faster deceleration but more energy being wasted to run the engine at higher RPM where parasitic is higher due to friction of higher RPM.

These variables (engine RPM for DFCO in terms of gearing, torque converter coupling loss) are part of tuning DFCO properly, it isn't enough to just have it turn 'on' and then subjectivelly say 'well it decreases my fuel mileage'. Its like tuning anything else, for example I can lean out an engine for cruising on the highway and experience a loss in MPG if it is done incorrectly. The same way I can increase timing advance beyond some point and experience a loss in torque and power without detonation on some fuels. Tuning isn't easy or face value, it is understanding and evidence collected a specific way as data. Most people do not understand how to collect data properly to begin with. Many that report fuel economy MPG savings or losses aren't even doing that properly. For example I can't count the number of posts I read with people overestimating fuel savings of DFCO because their little LED screens say 9999mpg when the vehicle is decelerating in DFCO. I hate to be the one scientist on the forum because now its my job to point out that all these guys arguing over the 'data' that their little screens are telling them is actually garbage and useless to give any meaningful information with respect to gains or lossoes in DFCO.

[Tunercharged]

I hate to be the one scientist on the forum because now its my job to point out that all these guys arguing over the 'data' that their little screens are telling them is actually garbage and useless to give any meaningful information with respect to gains or lossoes in DFCO.

You express many intriguing observations.

Fortunately I was only expressing an opinion that there may be good points to not use DFCO. I will see how it “feels” when I combine no DFCO and Closed Throttle Downshift Torque Management disabled on a test run tonight. Maybe that will make things more fun. I’m trying to prepare myself for a cam change and higher stall torque converter. I’ve read the CT Downshift Torque Management is supposedly a good thing to disable to avoid surging when decelerating so I’ll give it a whirl in advance for learning’s sake.

[Tunercharged]

Disabling Closed Throttle Downshift Torque Management and disabling DFCO produced a downshift that actually is a little firm but I think I can get used to it even with the raised shift rpms I have currently set. The fueling while coasting down is less rich than it was with just the DFCO disabled (is now around 5 percent richer than stoic compared to 10 to 15 percent with just DFCO disabled) and the fueling also is much more consistent during idling. I’m liking it.

[kingtal0n]

I've never felt a closed throttle downshift before. They should be seamless. I also don't think you should have any downshifts during DFCO which are automatic. DFCO is only active at higher rpms and auto downshifts with closed throttle should happen at lower RPM below DFCO. It sounds like your transmission could to be tuned so it only downshifts at appropriate speeds, it may be shifting too early, unless you are manually shifting in which case you need higher pressure and more firm downshifts to prevent slippage and this is already programmed into most ECU to some extent for manual downshifting and even the valve body of some transmissions will offer higher pressure for manual downshifts and other fluid channels for activating additional clutch packs. For example 4l80e when you manually downshift from 4 to 3 it will activate additional over-run clutch pack to backup the roller clutch. I also wonder if you ever connected a pressure gauge to the transmission to determine whether the real world downshift pressure is appropriate. There is a whole table(s) for transmission pressure which influences downshift feeling and if the pressure is high it will cause a firm downshift feeling. It shouldn't matter if DFCO is active because all DFCO does is eliminate all torque from the engine which should be the safest possible feeling downshift possible. In other words, the best time to upshift or downshift any transmission is when there is nearly 0 torque being applied to the clutches, and DFCO should be pretty close to zero as to be negative. Although anything close to 0 is fine, -50, 50, 0, is negligible.

Tuning is more than just an *on* or *off* setting to see what happens. When considering how to time and when to control torque, there are many software based pressures and manual valve body fluid circuits with checkballs and clutch clearances/wear and boost valve/PR valve setting and converter characteristics etc... all of which must be 'tuned' to some specific application or desire and function independently of engine torque while also being part of delivering that torque effectively without wasting energy if possible.

[Tunercharged]

I've never felt a closed throttle downshift before. They should be seamless. I also don't think you should have any downshifts during DFCO which are automatic. DFCO is only active at higher rpms and auto downshifts with closed throttle should happen at lower RPM below DFCO. It sounds like your transmission could to be tuned so it only downshifts at appropriate speeds, it may be shifting too early, unless you are manually shifting in which case you need higher pressure and more firm downshifts to prevent slippage and this is already programmed into most ECU to some extent for manual downshifting and even the valve body of some transmissions will offer higher pressure for manual downshifts and other fluid channels for activating additional clutch packs. For example 4l80e when you manually downshift from 4 to 3 it will activate additional over-run clutch pack to backup the roller clutch. I also wonder if you ever connected a pressure gauge to the transmission to determine whether the real world downshift pressure is appropriate. There is a whole table(s) for transmission pressure which influences downshift feeling and if the pressure is high it will cause a firm downshift feeling. It shouldn't matter if DFCO is active because all DFCO does is eliminate all torque from the engine which should be the safest possible feeling downshift possible. In other words, the best time to upshift or downshift any transmission is when there is nearly 0 torque being applied to the clutches, and DFCO should be pretty close to zero as to be negative. Although anything close to 0 is fine, -50, 50, 0, is negligible.

Tuning is more than just an *on* or *off* setting to see what happens. When considering how to time and when to control torque, there are many software based pressures and manual valve body fluid circuits with checkballs and clutch clearances/wear and boost valve/PR valve setting and converter characteristics etc... all of which must be 'tuned' to some specific application or desire and function independently of engine torque while also being part of delivering that torque effectively without wasting energy if possible.

Thanks, but I’m just tuning for desire. I love to look at charts and graphs sometimes but the thing that really makes me happy is the feeling of a strong motor that can roast some tires if I want to. To achieve my goals sometimes I press the button on at least an educated guess or when I have been told by someone who I lend trust that it would be okay to try and see what happens. I don’t personally know anyone on this forum any better than I know the authors of various engineering or trade books I have been inclined to read and derive information from over the extent of my life but I am pretty sure that if a person were to turn something off where it was on before and create a situation that is more pleasant to his person that it would be considered an improvement to the tune of that person’s vehicle and thereby, if logic may be allowed to follow, that person has just performed an action of Tuning. Most of my tuning actions are as I result of the trust I have put into the tuners in this forum who sometimes it would seem might try something based on its ability to be turned on or off.

[kingtal0n]

try something based on its ability to be turned on or off.

It's good to be curious and inquisitive, but also dangerous.

For example turn off torque management on a stock transmission often ruins the transmission or severely impact lifespan no matter how good it feels. Some things that don't 'feel' good are there for a reason.

You can't just turn things on and off without consequences, sometimes.

[Fast4.7]

Lol that'll happen. It isn't meant to save fuel. There's a balance between 'active just often enough to improve emissions' and 'active so often that emissions suffer because of the parasitic loss on your forward momentum and resulting increased fuel consumption'. Always a compromise.

As I have previously stated you only lose forward momentum if you are completely off the pedal. If you are 1-2% into the throttle you maintain momentum without out going into DFCO. 1-2% TPS is practically idle.

[kingtal0n]

As I have previously stated you only lose forward momentum if you are completely off the pedal. If you are 1-2% into the throttle you maintain momentum without out going into DFCO. 1-2% TPS is practically idle.

Unfortunately, He doesn't seem to understand momentum or kinetic energy. That was our biggest hurdle to communicate here, there seems to be a lacking in undergraduate engineering mathematics coursework and obstinate attitude.
This entire discussion is based on momentum and energy and he never once uses those terms to describe what we intuitively understand as energy which will be wasted as heat or fed back into the engine during a necessary deceleration.

There is also something wrong with the implied logic. If fuel economy decreased due to some algorithm in the computer then emissions is going up provided the same or worse conversion of fuel to power (see below). How or why can a computer program be used to both simultaneously clean up emissions and decrease fuel economy? It doesn't make sense and there is no clear explanation just a holier than thou attitude of disrespect that he pretends to know something that nobody else knows without any evidence to support claims.


Below
https://x-engineer.org/brake-specifi...sumption-bsfc/
"Similar to the brake specific fuel consumption, the highest fuel conversion efficiency is obtained at mid engine speeds and high load (torque)."

The worst conversion of fuel to power is at low rpm with low load.
Attachment 127814

Conversion of fuel to energy is worst as light load and low rpm (top left of graph). Thus the option of coasting at low load low rpm is unattractive in terms of economy and emissions.

Published research is giving us the same thoughts of how fuel cut is used to raise economy

Fuel consumption was reduced by approximately 4% in both the experimental and simulated results for the West Coast Highway in South Korea.

https://link.springer.com/article/10...239-013-0020-4

Simulation results show that the AFR and fuel cut-off controller able to maintenance AFR at the stoichiometric range during normal operation and able to cut the fuel flow at deceleration time for saving fuel and reducing emissions.

https://mev.lipi.go.id/mev/article/view/374

The increase in fuel costs has called for the development of dedicated equipment to reduce fuel consumption. This paper deals with an electronic system designed to perform the following two functions: (1) Control of the operations related to the engine stop and restart; and (2) Fuel Cut-Off during vehicle deceleration.

https://trid.trb.org/view/218460

As a conclusion, DFCO system is promising to be applied on LPG-fuelled vehicles for saving fuel and reducing emissions.

http://dosen.unimma.ac.id/public/doc...tiyo_et_al.pdf
LPG stands for liquid petroleum gas


Etal; Cutting fuel is for saving fuel and reducing emissions. There is not one paper out of hundreds published resources which seem to indicate otherwise.

[kingtal0n]

It is found that the cut-off of vehicle deceleration fuel, automatic transmission gear-shifting curve, and engine idle speed can be optimized to reduce the fuel consumption of the vehicle through calibration optimization.

https://link.springer.com/chapter/10...1-287-978-3_55

Not only are these events the most prevalent deceleration events
encountered during most driving styles, they also offer the
opportunity to recapture braking energy, which allows for
improved fuel economy.

Within the context of these negative tractive force events,
two distinct vehicle behaviors can be observed for
conventional vehicles. Figure 2 shows the fueling rates for
two vehicles during a fairly nominal deceleration event from
the UDDS cycle. The Ford Fusion shown in blue shows
behavior that would be consistent with the estimated
deceleration fuel rate discussed in Equation 1. In contrast, the
VW Jetta TSI shown in red shows no fueling during the
entire deceleration event. This deceleration without engine
fueling is frequently referred to as Decel. Fuel Cut-off
(DFCO)

https://www.jstor.org/stable/26169018

During the ramp gliding, only gliding in gear can be adopt to achieve fuel-saving by DFCO
function. When the road gradient is greater and there is a long distance flat road after downhill, use
the engine braking during downhill, and use the gliding in neutral on flat road, it could make the
fuel economy effect more significant

When the predictable distance is short or
automobile speed is high and transmission is also in high shift, compared with gliding in neutral,
gliding in gear can reduce the velocity through ?engine braking? instead of unnecessary braking and
could make full use of DFCO, so it can benefit from the kinematic energy stored in the vehicle

https://www.researchgate.net/profile...co-driving.pdf

[eXo3901]

FWIW, I am talking or typing? out of my ass.

I am fairly certain cats operate most efficiently within a certain temp range and that temp range also correlates directly with durability. We would not have cat light-off and COT if that was not true, right? Those are the extremes, but the in-the-middle is controlled by what parts of the calibration? I have to assume DFCO is one part? How does DFCO not effect overall cat temp? If wacky (in your opinion) DFCO settings are required to get the best efficiency out of a cat(keep it in the optimal operating range for emissions efficiency) so be it. Why would OEMs not direct their R&D departments to explore that? A 1%(arbitrary number) decrease in emissions(not fuel consumption) multiplied over thousands of vehicles is something. All the personal preference talk about energy and vehicle control is cool and I mostly get it, I hate how a traverse drives, but the thousands of other normal people buying normal cars do not give a shit.

Do most people with jobs have to operate within a specific set of guidelines on certain projects to meet the expectations of their employer? How is it the engineers fault? lol Poopoo them for not thinking of something more cute to reduce emissions.

I don't expect answers to my questions.