Help me understand EOC (engine off coasting)

[redpoint5]

Originally Posted by Rival879

The headlights turn off with the ignition, yes. Unfortunate, but how Subaru designed the lights. I'm in the same boat where I have to EOC cautiously or with just my parking lights on. The only lights that can stay on when the ignition is off are the parking lights. They have a dedicated hardware switch typically on the top of the steering column. I learned that soon after I bought my first Subie.

You don't want the key off the entire time the car is coasting, only long enough to kill the engine. Turn the ignition back to run once the engine has died. It will stay off until the clutch is let out or the starter is used.

My point is, your headlights probably only need to be off for 2 seconds tops.

Engine kill switch is the correct way to do this if you expect to EOC frequently. That would leave headlights on since the ignition isn't switched off.

[Taylor95]

If you can just turn off the key to do this, why do people install engine cutoff switches? It seems like a lot of work when you can just turn your key.
I recall asking before but this is only possible with manual transmissions right?

[euromodder]

Originally Posted by DeliveryGuy89

Hi!

I have a manual, but I'm not really sure how it works

Try coasting first - with engine on that is.
Put the gear in neutral, and just let it roll
You'll be amazed how far it can roll
Yes, it'll use some fuel, but you get a whole lot further than with engine braking.

Get a hang for how far it'll roll from your usual steady speeds, and use coasting from a lot further out instead of engine braking


Only accelerate up to the speed you need to reach the next turn / stop / lights / crescent of the road / top of a bridge / ... at a normal speed for this conversion point, then coast towards it, accelerate again and coast to the next point.

You're a delivery guy, this works well in town or suburbs


The idle fuel use makes coasting with engine on not really worth it under about 15-10 mph .


Downhill, if not too steep you can coast engine on in neutral, or put it in gear and use engine braking if it starts building too much speed (uses 0 fuel)


A combination of engine on coasting and engine braking when you need to stop, can improve your fuel economy a lot.


Turning the engine off after the acceleration phase, is the next level in coasting.

[mpg_numbers_guy]

Originally Posted by Taylor95

I recall asking before but this is only possible with manual transmissions right?

It is possible to engine off coast in an automatic or CVT, but it is presumably bad for the transmission.

In the Civic I used to have I never did any engine off coasting above 10 MPH for any distance further than 100 feet (i.e., parking lot, driveway).

[Hersbird]

Or just buy an hybrid and let the computer do it all for you.

[racprops]

I had to add my 2 cents worth.

My big bad old 2000 Mercury Grand marques was able to get 28/30 MPG at 65MPH.

This was at about 2 GAL per hour. (Via Scan Gauge II)

At idle it ONLY used .45GAL per hour. IF I could get a car that used that little fuel driving it would be getting 100MPG+.

SO killing your engine is a waste of time and dangerous. Leave it running at idle out of gear; you can then simply put it back in gear when you need it.

This keeps everything working, power brakes, power steering, A/C, all gauges and lights, and there is much less drain on the battery as even an idling engine can be charging the battery, and IF you drain your battery coasting with the motor off you then pay for a heavy charging load recharging it.

The one problem with this is some car and trucks seem to have a odd thing happen, IE my Mercury and 03 Crown Vic will maintain engine RPMS at or higher that the RPMS needed at speed. Yet my 1993 Chevy Van and my 2002 Ford Explorer will drop to idle when shifted out of gear.

So unless someone can figure a way to get these cars that will not drop to idle to drop to idle, this will not work as good as it will on cars and truck that do drop to idle out of gear.

As I have not considered using this I cannot say how many GPH it was using out of gear and still revving to RPMS, could still be much less GPH as the engine is free spinning and NOT under any load out of gear.

Rich

[Piotrsko]

The merc and crown vic could have lock up torque converters which could be unlocked. Been my experiences that Ford likes to downshift some trannies out of overdrive for any excuse hence with a locking tq the engine up rev.

[Ecky]

Originally Posted by racprops

I had to add my 2 cents worth.

My big bad old 2000 Mercury Grand marques was able to get 28/30 MPG at 65MPH.

This was at about 2 GAL per hour. (Via Scan Gauge II)

At idle it ONLY used .45GAL per hour. IF I could get a car that used that little fuel driving it would be getting 100MPG+.

SO killing your engine is a waste of time and dangerous. Leave it running at idle out of gear; you can then simply put it back in gear when you need it.

This keeps everything working, power brakes, power steering, A/C, all gauges and lights, and there is much less drain on the battery as even an idling engine can be charging the battery, and IF you drain your battery coasting with the motor off you then pay for a heavy charging load recharging it.

The one problem with this is some car and trucks seem to have a odd thing happen, IE my Mercury and 03 Crown Vic will maintain engine RPMS at or higher that the RPMS needed at speed. Yet my 1993 Chevy Van and my 2002 Ford Explorer will drop to idle when shifted out of gear.

So unless someone can figure a way to get these cars that will not drop to idle to drop to idle, this will not work as good as it will on cars and truck that do drop to idle out of gear.

As I have not considered using this I cannot say how many GPH it was using out of gear and still revving to RPMS, could still be much less GPH as the engine is free spinning and NOT under any load out of gear.

Rich

In my Insight, idle is ~0.19 gallons per hour. I already get 100mpg cruising at steady speed. EoC helps further, but the better your gearing is, the smaller the gains from EoC. A vehicle geared such that it's at 90-100% load at your cruising speed would probably have almost no gains from EoC, aside from those from running at the RPM of peak BSFC. Might be another 5-10%? Anyway a good, modern CVT would probably see almost no returns from EoC, whereas a sports car with very short manual gearing would have a ton to gain from it. My previous Honda would cruise at ~4300rpm at ~65mph. Steady-state driving it delivered anywhere from 27 to 35mpg. With EoC I was able to break 50mpg on flat terrain a few times.

Dangerous though? Maybe in some cars. My car weighs in at ~1700lbs right now and stops fine even when the vacuum booster is empty for the brakes. It also steers fine without the electric power steering active... but the EPS actually stays active when the engine is off, so it's doubly a non-issue. My car is just about to turn 20 years old, and most new vehicles have electric power steering now.

[racprops]

Originally Posted by Piotrsko

The merc and crown vic could have lock up torque converters which could be unlocked. Been my experiences that Ford likes to downshift some trannies out of overdrive for any excuse hence with a locking tq the engine up rev.

I have seen what I would call a 1/2 downshift, the torque convertor unlocks and the engine spins up about 400/500RPMS, if that is not enough then she drops out of overdrive.

And again T double checked, my 2002 Ford Explorer does not hold RPMS coasting out of gear but drops to idle nicely.

Rich

[Rival879]

Originally Posted by redpoint5

You don't want the key off the entire time the car is coasting, only long enough to kill the engine. Turn the ignition back to run once the engine has died. It will stay off until the clutch is let out or the starter is used.

My point is, your headlights probably only need to be off for 2 seconds tops.

Agreed. I just don't like flashing my lights at oncoming traffic. If I switch over to all LED including headlights, I might change the power source of the headlights. If I feel ambitious.