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The upper cylinder still needs lubrication.
fuel is a lube.
Some needs to be injected when coasting.
If no fuel was injected you would quickly come to a stop.
Give it a try drive down you road and let off the throttle.
How far do you go?
Now do it again and this time turn off the ignition.(but don't lock the wheel)
I bet you come to a stop rather quickly compared to coasting.
Fuel is not a lubricant. Oil is not injected via fuel injectors. This post doesn't make sense.
Automatic transmission vehicles are never disconnected from the rear wheels when in drive. This test is invalid.
Then they must be alternating cylinders.
If you stop fueling you stop moving.
Wrong. Vehicle momentum carried through the drive wheels keeps the drivetrain moving and keeps the engine turning. This is why it's done on deacelleration.
Engines certainly depend on lubricity in the fuel; this is especially important with diesels. For instance, ethanol in high concentrations is problematic for engines not intended for its use. Ethanol is an excellent solvent and can "dry" off the cylinder walls to a point where they will be damaged. Or how changing sulfur content of diesel alters it's lubricity, this has become a problem for a variety of injection systems designed prior to ULSD mandate and has urged many others to use fuel additives to balance everything out.
What does the transmission have to do with it and in both scenarios nether are disconnected so what is your point>?
Quote:
Originally Posted by SK360
Fuel is not a lubricant. Oil is not injected via fuel injectors. This post doesn't make sense.
Automatic transmission vehicles are never disconnected from the rear wheels when in drive. This test is invalid.
Not so, the resistance to rotational force as the air in the chambers is still compressed by the pistons this takes energy.
no fuel and the engine becomes a brake.
Unless you found some way to keep the valves open?
gee just turn if off as your going 5mph and see.
Quote:
Originally Posted by SK360
Wrong. Vehicle momentum carried through the drive wheels keeps the drivetrain moving and keeps the engine turning. This is why it's done on deacelleration.
I'm not say'en they don't cut way back on the injection cycles or spray less but to run with out fuel be it gas or diesel is hard on the upper cylinder that already sees so little engine oil as it is. (if the rings didn't bring it there there would be no oil.) so the fuel is also used as a lube.
Last edited by snofarmer; 10-17-2012 at 10:31 PM..
snofarmer, I think you are stuck back in the 1970's. Deceleration fuel cutoff is a FACT in modern engines and has been for many years--at least back as far as 1998--I know that because I had a 1998 vehicle that absolutely had it--and several since then. Buy a ScanGauge and hook it up to your vehicle. Let off the accelerator going downhill and watch fuel consumption drop to zero, then pop back up when the vehicle nears a stop. That's deceleration fuel cutoff working. By the way, the ScanGauge will measure fuel usage down to 0.01 gallons per hour accuracy, so when it shows no fuel usage, it means no fuel usage.
I haven't hooked up my ScanGauge to the 2012 Ford Super Duty 6.7 diesel that I drive some for work, but I would bet that it will show full fuel-cutoff on deceleration, too. Oh, and as far a lack of fuel as a lubricant, how do you explain the Dodge 5.7 Hemi with fuel cutoff that actually cuts fuel delivery altogether to up to 4 cylinders of the V8 engine when the engine is not under heavy load?
Absolutely true that an engine with no fuel being injected into it will eventually stop from resistance. That's called "deceleration" and that is exactly what most people want to happen when they let off of the accelerator. When I'm traveling down miles of 6% grades on a mountain pass, I want that engine to have "resistance" and there is no reason for fuel to be injected into it. Once the engine has decelerated to an RPM level where the engine would die without some fuel injection (usually around 1,000-1,200 rpm), the EFI begins to inject fuel again.
I find the "fuel-lubrication" argument unconvincing. Deceleration fuel cutoff has been used for many years now, and--if anything--engines last more miles by far today than they did, say, 30 years ago. In fact, many of today's engines will likley last 200K miles or more with just routine maintenance--probably outliving the vehicles in which they are installed. You almost never hear about an engine being "carboned-up" the way old carbureted engines would get if they weren't driven frequently on the open highway. There are a lot of things that I miss about the "old days," but carbureted engines are not one of them.
Fuel is a lubricant for the upper cylinder be it gas, diesel or a 2cycel.
Don't tell Lucas oils that it is not.
""Hi-Performance Lucas Upper Cylinder Lubricant with Injector Cleaners and Fuel Conditioners"
Deceleration.
you lift your foot,
fueling falls to low idle.
your vehicle has momentum and pushes agents the transmission and engine.
As your rpms fall to (lets use 1k rpm) 1k and your toque converter unlocks.
and you rpms fall to low idle and you coast along until you reach low idle speed.
With a manual you just slow to low idle speed or it boggs out and dies.
You don't have to give it throttle for it to run or move.
Not say'en some few flanged system actually sacrifices longevity for mpg.
Remember the role lead in gas played old timer?
They now use a additive for this.
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