coasting in gear or in neutral

[Xist]

In order to cite me for coasting in neutral, the officer would need to ask me. What are the chances of that happening?

Also, members talk about their cars with automatic transmissions shifting to neutral when they release the gas pedal. Before you considered killing the engine in an automatic, you would need to address transmission lubrication, but would it be lawful to modify your car with an automatic transmission to shift to neutral and kill the engine when you release the gas pedal, but shift back in gear if you brake or accelerate?

It is only legal for us to be in charge, right?

[niky]

Originally Posted by Old Mechanic

Anyone here read about a single citation being written much less a conviction being handed down for coasting, engine of or off?

I've coasted, engine off, beside an official chase vehicle during an eco-run.

They didn't notice at all.

They changed the rules soon thereafter to specifically ban EOC.

Non-hybrids can be built to EOC. Some micro-hybrids are getting there.
All you really need to include is electric power steering and an electric vacuum booster for the brakes.

[user removed]

Any repetitious human activity can be automated. Electrify the power steering and auto transmission using a common lubrication source and you can go neutral-engine off in an auto equipped car. Use the same lubrication. Toothed belt alternator starter and a higher capacity battery for extended engine off up to say 10 minutes. How stupid can you be burning 13% of your fuel expense not moving (USA stats).

Personally I think the manufacturers don't want to see any progress other than glacially slow evolutionary steps. One of the reasons I went to a 23 year old car. They aren't building anything that justifies the exponentially higher cost to just have that $30k plus cage sitting in the drive way.

regards
mech

[cptsideways]

There is a trade off between using no fuel in gear & losing momentum by pumping a huge compressor thats lurking on the hood (eg an engine) disconnect the compressor (neutral or de-clutch) & you can coast for miles on the kinetic energy using just a tiny amount of fuel.

Getting the trade off correct is the skillful part

[COcyclist]

Originally Posted by Eddie25

so was going to ask which is more efficient but did some homework and found that it is more FE to coast in gear rather than neutral in a manual car. I will be changing my driving style accordingly. I can understand if it is a slight downhill the engine braking might cause you to get on the gas a bit sooner. but I live in hilly terrain so a steep downhill is 90% of the time followed by an incline so I need to get on the gas sooner anyway.

Eddie, I do not believe there is a one-size-fits-all answer to your question. In my diesel Golf with a manual transmission and a turbo I frequently coast in neutral with the engine on unless I need to slow down. In the VW coasting in gear results in fuel cutoff, using no fuel, proven by the ScanGuage and by ear with the windows down. In my diesel Jeep Grand Cherokee automatic the fuel does not shut off when engine braking and the computer controlled automatic transmission really does not like coasting in neutral. Gasoline or "Petrol" engines have much better engine braking than diesels and will lose momentum quicker than a diesel. The diesel has lower pumping losses than a gas engine and my car injects only 0.13 gph in neutral netting 350-400+ mpg while coasting in neutral. I drive for mpg and for car longevity so I choose to leave the engine on coasting to save wear and tear on my car. Also, I have a 7 mile downhill where I have to shift into 3rd to keep from speeding and in summer I will even put the A/C on high to put some additional drag on the engine without a mpg penalty. So I think it all depends on the situation.

[bikeprof]

HA! Some of the laws written that are on the books could be re-arranged now that there is new technology, some of them either contradict or cancels the fe performance of:
ie, HYBRIDS. One AND all types of HYBRIDS...

[serialk11r]

Originally Posted by Old Mechanic

Personally I think the manufacturers don't want to see any progress other than glacially slow evolutionary steps. One of the reasons I went to a 23 year old car. They aren't building anything that justifies the exponentially higher cost to just have that $30k plus cage sitting in the drive way.

Well to be fair, a lot of the new German cars are coming with these nice features now (electric water pump or other kind of variable output water pump, variable displacement oil pump, auto start-stop, coasting features) but they are expensive cars that will likely damage the wallet in ways other than fuel usage.

For economy cars, minimum cost of production is still the golden rule. I think most cars are still using low fill ratio round conductor alternators and start-stop has yet to make it to the US for most models. I think some companies are still building 4 speed automatics? I think belt driven power steering is still pretty common on cheap cars. You definitely have to shell out a good amount of money for cars without these dinosaur features.

[bikeprof]

I've thought about going 'lectric on the major HP draws on my vehicles...
May not be a lot individually but should compile enough fe to make it all worth, me thinks...

[Isaac Zackary]

This question has a variety of correct answers depending on various factors.

Many new vehicles shut off the fuel when the engines is being turned at an RPM higher than idle with your foot off the accelerator pedal. I've seen systems that do this since the 1970's! So on long down hill slopes the only difference between shutting off the engine and coasting in neutral and coasting in gear is the former causes more brake wear.

On older cars, especially carbureted ones, I've seen guys rig up solenoid valves and such that shut off fuel by means of a switch. Of course the hard part with a carburetor is draining the bowl. If you're going over a mountain pass and you shut it off too soon you can burn too lean on the incline and blow a piston! But if you do it too late coasting uses such little fuel that your engine will just be finishing up the bowl of fuel by the time you reach the bottom of the pass.

On small slopes it's most efficient to put it in neutral and turn off the engine a ways before the downhill slope. That way your car is going slow enough you won't need any braking by the time you've hit the bottom of the hill. Then you just keep coasting until you slow back down to your normal speed.

As far as automatic transmissions are concerned I knew a guy who ruined a few transmissions coasting them in neutral with the engine off.