Does a car consume fuel under engine braking?

[letdown427]

This is still going? Wow.

No, a modern fuel injected doesn't use fuel under engine braking.

 

[DivideBYZero]

I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

 

[exdeath]

Pretty sure the injectors cut out as engine RPM drops to idle while coasting, then resumes at idle RPM to intercept the stall condition, since the rest of the engine system is still running (ignition, etc).

If you want to know for sure, quit reading this thread and go out and stick a test light on the injector harness and put it where you can see it.

I predict it would light up brightly when accelerating to high RPM then go out completely when you let off the gas, then come back on once RPM hits around 900-1000. (Note the light is pulsing with the injector PWM strobes, but even at idle RPM this should appear to be solid and constant on)

Or you could always learn some motorola assembly and reverse engineer your ECU and look at the injector pulse calculations.

Don't know why people argue about things that can be tested IRL.

But then again it may depend entirely on the car. I know the '06 Avalon seems to coast forever when you let off the throttle at highway speeds, so there is probably a cruise mode or something in the ECU that tries to maintain current speed even when coasting? It's a high compression (like 11.5:1) 91 octane V6 making 280 HP NA, and there aren't any new frictionless rings and rod bearings out that I'm aware of, and finally the fact that its brand new and still nice and tight inside... yet it takes a year and a half for the RPM to drop while coasting...and no, no cruise control. I really doubt the injectors are being cut off in this particular car. Yet it still gets 32 mpg with 280HP... gotta love technology.

 

[BD2003]

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

Please tell me you are not serious.

 

[DivideBYZero]

Originally posted by: BD2003

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

Please tell me you are not serious.

Read the whole thread...

 

[Don Vito Corleone]

Originally posted by: BD2003

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

Please tell me you are not serious.

He's just jerking you around to keep this thread alive, by regurgitating the nonsense others have posted here. It's still fun . . .

 

[ZickZJ]

It really depends on the vehicle, because not ever vehicle uses the same system or programming. I know for a fact that on my 03' Silverado my fuel injector do not shut off fuel while coasting down hill because I can clearly watch them run via HP Tuners. There is a system in my programming that allows me to enable DFCO which basically shuts down the injectors to about 99% to use less fuel but then the truck feels like a semi with the jack brake on. I don't like it so I keep it turned off.
Maybe other vehicle can shut off fuel completly while coasting or whatever so this question can not be answered with a simple yes or no.

 

[dug777]

Originally posted by: BD2003

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

Please tell me you are not serious.

:laugh:

Indeed. I've had my engine die at speed a few times (spark problems, and run out of fuel), so it's left me coasting, in gear, with no fuel entering the engine, and no spark. I've still coasted an extremely long way in gear before coming to a halt So what you say is a (nonsensical and parodical(? parodic?) joke.

 

[DivideBYZero]

Originally posted by: dug777

Originally posted by: BD2003

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

Please tell me you are not serious.

:laugh:

Indeed. I've had my engine die at speed a few times (spark problems, and run out of fuel), so it's left me coasting, in gear, with no fuel entering the engine, and no spark. I've still coasted an extremely long way in gear before coming to a halt So what you say is a (nonsensical and parodical(? parodic?) joke.

You STOPPED because there was NO FUEL!! You, sir, are OWNED!

 

[dug777]

Originally posted by: DivideBYZero

Originally posted by: dug777

Originally posted by: BD2003

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

Please tell me you are not serious.

:laugh:

Indeed. I've had my engine die at speed a few times (spark problems, and run out of fuel), so it's left me coasting, in gear, with no fuel entering the engine, and no spark. I've still coasted an extremely long way in gear before coming to a halt So what you say is a (nonsensical and parodical(? parodic?) joke.

You STOPPED because there was NO FULE!! You, sir, are PWNED!

Fixed. You've got to stop making basic mistakes DBZ

 

[BD2003]

Originally posted by: DivideBYZero

Originally posted by: BD2003

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

Please tell me you are not serious.

Read the whole thread...

I did. Just because there are other idiots that agree with you don't make you any less wrong.

Your car will NOT stall and come to a dead stop on a hill when you run out of gas.

I'd forgive your ignorance if there wasnt a weeks worth of ignorance built up in this thread already.

 

[Zenmervolt]

Originally posted by: Tom

Originally posted by: Zenmervolt

Originally posted by: Tom
Yes, I know. My point is, assuming some cars use something like this, then it isn't true that all cars with EFI cut off fuel delivery entirely during engine braking, which a great deal of posts in this thread insists is the case.

Unless you're buying cars made in a third-world country, all modern FI vehicles have a fuel cut-off under engine braking. It's a "free" way for the auto maker to increase fuel mileage for a vehicle.

There are differing methods for resuming fuel injection when the threshold RPM has been breached, but any modern FI car will cut off fuel under deceleration.

The pattent only addresses the brief (less than one second) transition period from normal fuel flow to fuel cut-off. It actually proves that any car using your patent does have a 100% cut-off mode since the pattent covers only the transition to and from complete fuel cut-off.

ZV

Your own reply corroborates my statement. And disproves the opposite claim. Even if the duration is brief, which is information you supply, not me, then the fact is a car with such a system would consume fuel, perhaps a very small amount, during engine braking.

And before you interject that the amount is trivial, by the same token this entire discussion is about a trivial difference in fuel consumption, except for those lucky few who only ever drive downhill.

No, the patent you cite covers a transition to FULL CUT-OFF. That's 100% fuel stoppage. Under engine braking, instead of just shutting everything off at once, it shuts down "gradually" (in this case, "gradually" being over perhaps one second rather than instantly), but it still completely shuts down fuel flow. The patent does NOT indicate that fuel is never cut-off, only that the transition between normal flow and complete shut-off is gradual and not instantaneous in order to smooth out that transition.

ZV

 

[Tom]

Originally posted by: Zenmervolt

Originally posted by: Tom

Originally posted by: Zenmervolt

Originally posted by: Tom
Yes, I know. My point is, assuming some cars use something like this, then it isn't true that all cars with EFI cut off fuel delivery entirely during engine braking, which a great deal of posts in this thread insists is the case.

Unless you're buying cars made in a third-world country, all modern FI vehicles have a fuel cut-off under engine braking. It's a "free" way for the auto maker to increase fuel mileage for a vehicle.

There are differing methods for resuming fuel injection when the threshold RPM has been breached, but any modern FI car will cut off fuel under deceleration.

The pattent only addresses the brief (less than one second) transition period from normal fuel flow to fuel cut-off. It actually proves that any car using your patent does have a 100% cut-off mode since the pattent covers only the transition to and from complete fuel cut-off.

ZV

Your own reply corroborates my statement. And disproves the opposite claim. Even if the duration is brief, which is information you supply, not me, then the fact is a car with such a system would consume fuel, perhaps a very small amount, during engine braking.

And before you interject that the amount is trivial, by the same token this entire discussion is about a trivial difference in fuel consumption, except for those lucky few who only ever drive downhill.

No, the patent you cite covers a transition to FULL CUT-OFF. That's 100% fuel stoppage. Under engine braking, instead of just shutting everything off at once, it shuts down "gradually" (in this case, "gradually" being over perhaps one second rather than instantly), but it still completely shuts down fuel flow. The patent does NOT indicate that fuel is never cut-off, only that the transition between normal flow and complete shut-off is gradual and not instantaneous in order to smooth out that transition.

ZV

What you are saying doesn't contradict what I said. I agree that according to the patent, the fuel could be shut off completely, at some point. My point is that during the "gradual" transition, some fuel would be consumed, and the engine would be slowing down, causing engine braking to occur, during the transition.


I came across something else I hadn't thought of. Has this thread addressed cars with automatic transmissions ? I have a feeling that there aren't very many cars with conventional automatics where the fuel is completely shut off during engine braking ?

I also came across a website for a Saturn Hybrid, where one of the "features" was exactly what this thread is about, shutting fuel off during engine braking. Which seems kind of curious that they claim it as a "feature" of this particular model, since according to this thread ALL cars with EFI work that way.

http://www.gm.com/company/gmability/adv_tech/100_news/hybridvue2_10906.html

 

[Don Vito Corleone]

Originally posted by: BD2003

Originally posted by: DivideBYZero

Originally posted by: BD2003

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

Please tell me you are not serious.

Read the whole thread...

I did. Just because there are other idiots that agree with you don't make you any less wrong.

Your car will NOT stall and come to a dead stop on a hill when you run out of gas.

I'd forgive your ignorance if there wasnt a weeks worth of ignorance built up in this thread already.

Dude, he's joking. Just relax.

 

[Nyati13]

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

The tachometer only measures the rotation of the crankshaft, it does not directly measure fuel usage and does not indicate fuel usage.
Idle on most cars is 800-1000 RPM. And your "Fact" is dead wrong, and purely uninformed opinion. FACT! If the engines fuel supply is cut off while moving and in gear, the drivetrain rotation will drive the engine, and all accessories, alternator, and power options will remain powered. FACT! The lack of fuel while in gear will cause the vehicle to de-accelerate at a certain rate determined by the weight of the vehicle/the angle of the surface being traversed/and the gear ratio involved. This does not equal immediate "DEAD STOP" in the real world.
It is a fact beyond dispute that many (most even) cars do completely shut off fuel delivery when off throttle and in gear. Other cars mostly shut off fuel supply (to levels below what is needed to idle), and some other much older cars return throttle to idle.

 

[randay]

I vote DivideBYZero for either BAN or title change to "Supreme Necro Overlord".

 

[Vic]

Originally posted by: Nyati13

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

The tachometer only measures the rotation of the crankshaft, it does not directly measure fuel usage and does not indicate fuel usage.
Idle on most cars is 800-1000 RPM. And your "Fact" is dead wrong, and purely uninformed opinion. FACT! If the engines fuel supply is cut off while moving and in gear, the drivetrain rotation will drive the engine, and all accessories, alternator, and power options will remain powered. FACT! The lack of fuel while in gear will cause the vehicle to de-accelerate at a certain rate determined by the weight of the vehicle/the angle of the surface being traversed/and the gear ratio involved. This does not equal immediate "DEAD STOP" in the real world.
It is a fact beyond dispute that many (most even) cars do completely shut off fuel delivery when off throttle and in gear. Other cars mostly shut off fuel supply (to levels below what is needed to idle), and some other much older cars return throttle to idle.

Skoorb lives again! :laugh:

 

[DivideBYZero]

Originally posted by: randay
I vote DivideBYZero for either BAN or title change to "Supreme Necro Overlord".

Even thought I don't understand it, I prefer the second option.

 

[UNCjigga]

DIRECT INJECTION FTW!!!!

(2.0T FSI Turbo driver here)

 

[DivideBYZero]

Originally posted by: Vic

Originally posted by: Nyati13

Originally posted by: DivideBYZero
I find it hard to beleive that no gas is used, the tachometer is reading 1000 rpms not 0.

Down hill in neutral would even cause your car to accelerate, while only using gas to keep the engine at idle, which is being used anyway, to keep the motor running, head out on the highway, looking for adventure, or whatever comes my way.

Fact. If your car was ever cut off from fuel it would stall. Idle is on most cars at 1200-1600 RPM. If kept in gear and it shuts the fuel off then the car would chug rally bad for not having that equal momentum or pressure on the pistons. IE: Coast down hill and turn your car off and see what happends. That would be like shutting off the gas and see how fast no real matter the grade your car slows down to a stop.

A DEAD STOP.

The tachometer only measures the rotation of the crankshaft, it does not directly measure fuel usage and does not indicate fuel usage.
Idle on most cars is 800-1000 RPM. And your "Fact" is dead wrong, and purely uninformed opinion. FACT! If the engines fuel supply is cut off while moving and in gear, the drivetrain rotation will drive the engine, and all accessories, alternator, and power options will remain powered. FACT! The lack of fuel while in gear will cause the vehicle to de-accelerate at a certain rate determined by the weight of the vehicle/the angle of the surface being traversed/and the gear ratio involved. This does not equal immediate "DEAD STOP" in the real world.
It is a fact beyond dispute that many (most even) cars do completely shut off fuel delivery when off throttle and in gear. Other cars mostly shut off fuel supply (to levels below what is needed to idle), and some other much older cars return throttle to idle.

Skoorb lives again! :laugh:

How in the fvck does someone get such a 'red mist' they miss that?

 

[RichUK]

Apart from the funny nonsense in here. I'm wondering does the same apply to CI engines. Not that i care just wondering. Hmm i'm assuming it does.

By the way peeps a petrol car doesn't consume fuel under engine braking. It's even been proven previously in this thread.

 

[bwatson283]

Originally posted by: Baked
Does the pistons move when your car's moving?

The pistons are always moving, that is what an internal compustion engine is. Pistions move to create combustion and those explosions are what keep the engine on.

 

[DivideBYZero]

Originally posted by: bwatson283

Originally posted by: Baked
Does the pistons move when your car's moving?

The pistons are always moving, that is what an internal compustion engine is. Pistions move to create combustion and those explosions are what keep the engine on.

See? This guy knows what he's on about. Pistons move and they need fuel to keep them on. /Thread.

 

[letdown427]

Originally posted by: DivideBYZero

Originally posted by: bwatson283

Originally posted by: Baked
Does the pistons move when your car's moving?

The pistons are always moving, that is what an internal compustion engine is. Pistions move to create combustion and those explosions are what keep the engine on.

See? This guy knows what he's on about. Pistons move and they need fuel to keep them on. /Thread.

Tell you what, next time you fill up, get 5litres spare in a jerry can.

Run your car out of fuel. Leave it in gear. Notice the rpms are still up there? And they slowly go down as the car coasts to a halt? Yeah exactly.
/Thread.

 

[DivideBYZero]

Originally posted by: letdown427

Originally posted by: DivideBYZero

Originally posted by: bwatson283

Originally posted by: Baked
Does the pistons move when your car's moving?

The pistons are always moving, that is what an internal compustion engine is. Pistions move to create combustion and those explosions are what keep the engine on.

See? This guy knows what he's on about. Pistons move and they need fuel to keep them on. /Thread.

Tell you what, next time you fill up, get 5litres in a jerry can.

Run your car out of fuel. Leave it in gear. Notice the rpms are still up there? And they slowly go down as the car coasts to a halt? Yeah exactly.
/Thread.

Yeah, but the fuel has been shut off and the car stopped. Owned.

On a side note, what would happen, if say you had a six pot motor, if one of the pistons stopped? Would the car go slower or faster because there is less friction with only five pots firing and one stopped?