Will it cause any issues in the LR3 if I coast in neutral gear for a long time?

[jaamrode]

The spark plugs still fire but with no fuel there is no detonation. While coasting in gear think of the engine like an air compressor, air still moves through the engine and is still being compressed, hence the term engine compression braking. So there still is some exhaust noise because the air is being forced out of the engine on the exhaust ******.

On bigger diesel trucks there is what is called an exhaust brake which is a flap that closes off the exhaust pipe and really makes the engine work like a compressor and the more pressure it builds the harder it is for the wheels to turn the engine thus slowing down the truck.

If you would like I can go into how a modern four ****** car engine works.

 

[johnsoax]

I understand how a four ****** engine works, thanks...

 

[paula]

I live in the hills of San Gabriel and the freeway is about 3 miles downhill. So I decided to put the neutral vs coasting to test.

While driving in neutral for 80% of the time for the 3 mike journey, I got 26mpg. While driving in D and coasting with no foot on gas for 80% of time, I for 22mpg.

 

[BearishDriver]

I live in the hills of San Gabriel and the freeway is about 3 miles downhill. So I decided to put the neutral vs coasting to test.

While driving in neutral for 80% of the time for the 3 mike journey, I got 26mpg. While driving in D and coasting with no foot on gas for 80% of time, I for 22mpg.

brilliant! mystery solved then, neutral is more fuel efficient

 

[Houm_WA]

...doesn't make it a smart thing to do!

 

[jwest]

Sorry... Not possible.. You are using fuel for the RPM's. The LR3 uses the engine to brake the speed of the truck going down hills..

To test your theory, go down a hill and then shut off your ignition, I bet you immediately slow down due to loss of power from the engine.

If his theory is correct, you won't slow down.

You have to ask yourself a few questions... How does the car know you are going downhill? Because there is still load on the engine.

You just contradicted yourself in the first 2 sections.

And about your "down a hill" idea, that's ridiculous. If I am going to down a steep enough hill, the vehicle will in fact accelerate due to gravity with engine off or in N. The engine running, and transmission in gear, slows the vehicle to more of a "terminal velocity" than simply coasting without that engine braking and system friction. In N the drive line is not engaged.

There may be multiple "truths" in these seemingly opposing ideas but the specifics of each situation will make the difference in which version uses less fuel.

 

[jwest]

...doesn't make it a smart thing to do!

Nor is it inherently un-smart. Not all situations, vehicles, or drivers are the same!

About using more brakes.... open your mind dude.... ZERO brakes are used if rolling into an uphill.

Even moreso on the coasting, is when the "hill" is too slight to maintain speed if IN gear which then requires FUEL for throttle to stay at speed. I find that in my BMW which seems to roll much more efficiently (due to aero, tires, driveline, etc) shifting the 6 spd manual into N it will coast with ease. Sometimes the LR3 will coast noticeably faster simply due to it's mass of 7000-8000 lbs.

That whole thing about being able to "accelerate quickly for safety" is the biggest BS in this thread when you consider how SLOWLY the LR3 accelerates anyway.

The only evasive driving possible will be done by steering or braking!

 

[jwest]

I live in the hilly regions of LA and my mpg is pretty bad. I was thinking that if I coast downhill in neutral in a safe manner, I can save a lot of gas and make up for the return uphill drive.

Are there any potential issues to the LR3 for such neutral coasting? Thanks

Paula.

See what you started?!

The best test you can do is one fuel tank, NO coasting. Verify mileage on odometer but gallons of fill up. Your dash mpg is interesting as a comparison but in short distances it is not as accurate.

Then a full tank coasting everywhere it makes sense for you, especially those long hills where you can avoid brakes at ll and roll into your flat or uphill speed never using brakes.

Really this is best done like on the exact same route like if you have a commute and can avoid any other driving for the week. The problem is that long stops at lights or like a drive-through bank window can really screw up the results.

The best mpg I've gotten before is when taking my mom on a camping trip where first, the speed limits were 50-60 and second, because we weren't in any sort of hurry in a scenic routes.

The LR3 does much better at 50-60, and mpg really plummets above 70 because it will too often drop/shift itself into 5th gear.

 

[toddjb122]

Here is an article from popular mechanics also stating you use no fuel while coasting

http://www.popularmechanics.com/cars/hybrid-electric/a5977/coasting-in-neutral-fuel-economy/
...

That's an interesting story. Thanks for sharing that. Seems pretty clear and he claims to have hard data to back it up (by monitoring the injectors).

I live in the hills of San Gabriel and the freeway is about 3 miles downhill. So I decided to put the neutral vs coasting to test.

While driving in neutral for 80% of the time for the 3 mike journey, I got 26mpg. While driving in D and coasting with no foot on gas for 80% of time, I for 22mpg.

If anyone actually read the PM article above, you'll see paula's honest mistake mentioned specifically.
Read below...

...I hear this argument as well: My car-mileage-information computer goes wild with increased mileage while coasting.

The algorithm the trip computer uses is not based on how much fuel is actually consumed, but on some calculated value based on airflow past the mass airflow sensor, manifold vacuum and engine rpm. And it's not accurate under these coasting conditions. That's why when we report fuel economy here at PM, we never just print the numbers we read off the trip computer's display: We use the gallons pumped into the tank divided by the mileage on the odometer—which we check against a handheld GPS...

Interesting debate/discussion either way!

 

[Houm_WA]

jwest....from my standpoint you just have less control of the vehicle when it's hurtling down a hill in N. Generic statement. ....for all the trouble of having to shift out of D and then find a suitable time/place to put it back in, you save 4 mpg for an entire ~10 seconds.

Hence my blanket statement of it being not smart. I don't disagree with the independent facts that you state....I just think at the end of the day it's not something I'd do or advise doing just because of the hassle.