Strange, I cannot edit my previous posts, the .PDF I linked disappeared, and I am unable to load the Wayback Machine. Putting Deceleration Fuel Cutoff into Google shows:
1. This thread!
2.
Quote:
DFCO - Wikipedia
https://en.wikipedia.org/wiki/DFCO
DFCO may refer to: Dijon FCO, Dijon Football Côte d'Or; Deceleration fuel cut-off, see Fuel economy-maximizing behaviors (section: Burn and coast) ...
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However, clicking on Wikipedia sends me to
This page, where "Burn and Coast" was fortunately renamed "Pulse and Glide," with the following statement "Most modern petrol vehicles cut off the fuel supply completely when coasting (over-running) in gear, although the moving engine adds considerable frictional drag and speed is lost more quickly than with the engine declutched from the drivetrain," although there is not a reference, and it does not mention Deceleration Fuel Cutoff.
I found two people in forums quoting that, but not any direct source, although this is similar:
Quote:
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While coasting with the engine running and the transmission in gear, most cars' engine control unit with fuel injection will cut off fuel supply, and the engine will continue running, being driven by the wheels. Compared to coasting in neutral, this has an increased drag
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Hypermiler | Project Gutenberg Self-Publishing - eBooks | Read eBooks online
Quote:
According to Paul Williamsen, the product education manager at Toyota, “All contemporary Toyota and Lexus vehicles (and every other car built since the 1990s that I’ve looked at) can detect the condition when engine revs are higher than idle with a fully closed throttle: Under these conditions, all current to the fuel injectors is stopped, and no fuel is injected.” That means if your foot is off the gas while the car’s in gear, you’re not using any fuel.
Tom Read, GM’s powertrain spokesman, agrees: “Shifting into neutral in an automatic will cancel fuel cutoff. Thus, it is better to remain in gear and let the drive wheels pull the engine airflow down to where fuel cutoff can be enabled or where fuel flow is minimized.”
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Gas Pains: Mileage Myths and Misconceptions - Car Comparison - Feature Article - Page 3
By the way, the previous page shared this:
Turn Off Your Air Conditioner
Several people have insisted that using the air conditioning does not increase fuel economy, I tell them to stop watching Mythbusters, and the conversation gets stuck between a rock and a hard place.
This page describes it for the 1990 GM Prizm:
| Repair Guides | Emission Controls | Deceleration Fuel Cut-off System | AutoZone.com
I found this statement I cannot confirm: "According to Mazda, the fuel cut prevents overheating of the catalytic converter due to misfire and improves fuel economy."
DFCO: Deceleration Fuel Cut-off - RX8Club.com
Also, this:
Green Car Congress: GM says deceleration fuel cutoff in Cruze increases fuel economy by up to 2%
United States Code Title 42 - THE PUBLIC HEALTH AND WELFARE, CHAPTER 85 - AIR POLLUTION PREVENTION AND CONTROL, SUBCHAPTER II - EMISSION STANDARDS FOR MOVING SOURCES, Part A - Motor Vehicle Emission and Fuel Standards, Sec. 7521 - Emission standards for new motor vehicles or new motor vehicle engines, (m)(1):
“Within 18 months after November 15, 1990, the Administrator shall promulgate regulations under subsection (a) of this section requiring manufacturers to install on all new light duty vehicles and light duty trucks diagnostics systems capable of—
(A) accurately identifying for the vehicle's useful life as established under this section, emission-related systems deterioration or malfunction, including, at a minimum, the catalytic converter and oxygen sensor, which could cause or result in failure of the vehicles to comply with emission standards established under this section,
(B) alerting the vehicle's owner or operator to the likely need for emission-related components or systems maintenance or repair,
(C) storing and retrieving fault codes specified by the Administrator, and
(D) providing access to stored information in a manner specified by the Administrator.”
https://www.gpo.gov/fdsys/pkg/USCODE...tA-sec7521.htm
Clearly, the EPA established the standard, which was developed and named afterward, and I imagine the same applies to DFCO. I did not find that acronym or “deceleration” in any of the regulations or elsewhere.