POC vs. Out of gear coasting - Fuel Economy, Hypermiling, EcoModding News and Forum

ac7ss · 09-26-2008, 05:28 PM

I have recently added a MPGuino to my vehicle and have noticed that the mileage when taking the car out of gear is around 130 or so but the gauge tops out if I leave it in gear with the accelerator off or just slightly on.

Has anybody else noticed this?

I understand the concept. Fuel is required to keep the engine running if it is not in gear. However, I have not seen this mentioned anywhere. I suppose that you need an Econometer that shows instant MPG to be able to get the sweet spot.

ptsmith24 · 09-26-2008, 06:18 PM

Yea, fuel cut off. I found mine is around 55mph (~1800RPM in that gear). I found it using the MPGuino in my car. Although it isn't calibrated (sorta close, but still too far to do any good), it goes from 31MPG at 55MPH to 38-40MPG after releasing the throttle. I'll try and keep that in mind if I ever P&G eventually.

ac7ss · 09-26-2008, 08:27 PM

There seems to be a sweet spot on the throttle where there is little or no fuel being delivered and you don't loose speed. This is the point I was wondering about.

MetroMPG · 09-26-2008, 09:44 PM

Well, you can't be using no fuel and still maintain speed (unless you're going downhill or being towed!), but you're right in noticing that you can often feather the throttle back to an absolute minimum and maintain your current speed.

I've read a few times when people get instant fuel consumption displays how surprised they are at how relatively minor throttle position changes can have relatively big MPG changes.

MetroMPG · 09-26-2008, 09:45 PM

PS: what's "POC"?

KJSatz · 09-26-2008, 10:52 PM

I think it means "pedal off coast" or coasting in gear with your foot off the pedal.

I think that you are better off coasting in neutral. It is true that in gear with your foot off the gas, you can use zero fuel (if you're above a certain RPM and your vehicle has a fuel injector cutoff feature), whereas coasting out of gear uses a little fuel to keep the engine running. But you lose speed faster in gear, and based on my observations, you end up using more fuel on the other end when you have to speed up again.

Hasbro · 09-27-2008, 04:19 AM

Quote:

Originally Posted by KJSatz

I think it means "pedal off coast" or coasting in gear with your foot off the pedal.

I think that you are better off coasting in neutral. It is true that in gear with your foot off the gas, you can use zero fuel (if you're above a certain RPM and your vehicle has a fuel injector cutoff feature), whereas coasting out of gear uses a little fuel to keep the engine running. But you lose speed faster in gear, and based on my observations, you end up using more fuel on the other end when you have to speed up again.

Especially when your tires are at 70 psi!

ac7ss · 10-02-2008, 05:20 PM

Petal off coast
or
Power off coast (Same thing.) Yes that is what I meant.

Going down hills I can POC and maintain speed. (Handy for my particular commute.) I think that I will keep it in gear and find the 'sweet spot' for maintaining speed. I have been comparing numbers on my MPGuino and at 60mph, it is a tossup (Neutral vs. feathered.)

PaleMelanesian · 10-02-2008, 06:25 PM

DFCO - we've talked about it a lot.

I get the results I do with NO dfco usage. I'm always using neutral instead. Usually the engine is off, but in certain cases I leave it on.

HondaHound · 10-02-2008, 07:48 PM

Quote:

Originally Posted by PaleMelanesian

DFCO - we've talked about it a lot.

I get the results I do with NO dfco usage. I'm always using neutral instead. Usually the engine is off, but in certain cases I leave it on.

How much more MPG would you estimate that gives you?

HHINLA