Driving style doesn't change mpg?

[jigen]

Originally Posted By: Quattro Pete
Originally Posted By: jigen
It's always more noticeable in a vehicle that makes you work for decent MPG. High powered turbo vehicles, or V8's.

Yeah, even my I6 makes you work for decent MPG. When you see that instant MPG needle sink to the bottom of the scale, it takes all the fun away from driving it.

A little piece of electrical tape over that gauge should do the trick. Out of sight out of mind. Lol.

 

[Nick1994]

Have gone through 3 tanks since the last post. I've been driving it a lot harder again, maybe some less idling too and my mpg has gone up to 25.

I won't be driving it nicely anymore, doesn't change mpg for this car. Maybe better mpg driving it harder.

 

[Jetronic]

has the weather gone colder?

 

[Nick1994]

Originally Posted By: Jetronic
has the weather gone colder?
Maybe 5-10 degrees

 

[Jetronic]

that'll do it with a reduced load on the AC, and possibly more advanced timing

 

[Nick1994]

Originally Posted By: Jetronic
that'll do it with a reduced load on the AC, and possibly more advanced timing
The A/C compressor has more drag when it's hotter outside? I still have it on 100% of the time when driving.

 

[Hokiefyd]

Originally Posted By: Nick1994
Originally Posted By: Jetronic
that'll do it with a reduced load on the AC, and possibly more advanced timing
The A/C compressor has more drag when it's hotter outside? I still have it on 100% of the time when driving.


The compressor cycles on and off to condition the air to what you've set inside. If the air is cooler and drier outside, the compressor's actual "on" time is less than it is when it's hotter and more humid.

Just like your house air conditioning (unless you have a swamp cooler). If you have the thermostat set to 60 degrees, and it's actually 60 degrees outside and inside, the air conditioning won't run very often, if at all. But if it's 100 degrees outside, it's going to be running non-stop to try to keep it 60 degrees inside.

 

[Nick1994]

Originally Posted By: Hokiefyd
Originally Posted By: Nick1994
Originally Posted By: Jetronic
that'll do it with a reduced load on the AC, and possibly more advanced timing
The A/C compressor has more drag when it's hotter outside? I still have it on 100% of the time when driving.


The compressor cycles on and off to condition the air to what you've set inside. If the air is cooler and drier outside, the compressor's actual "on" time is less than it is when it's hotter and more humid.

Just like your house air conditioning (unless you have a swamp cooler). If you have the thermostat set to 60 degrees, and it's actually 60 degrees outside and inside, the air conditioning won't run very often, if at all. But if it's 100 degrees outside, it's going to be running non-stop to try to keep it 60 degrees inside.
Interesting. I didn't think my car would be that smart. I figured if it was on, it was on.

 

[DriveHard]

In my Miata I average 25 mpg per tank no matter how I drive it. In my truck, how I drive it can change mileage by 50% or more. In the truck there is a HUGE difference on how hard I accelerate and its effect on mileage. I can average 18-19 in my daily commute if I drive like a grandma...or 10-11 if I drive it like my Miata.

 

[Jetronic]

Originally Posted By: Nick1994
Originally Posted By: Hokiefyd
Originally Posted By: Nick1994
Originally Posted By: Jetronic
that'll do it with a reduced load on the AC, and possibly more advanced timing
The A/C compressor has more drag when it's hotter outside? I still have it on 100% of the time when driving.


The compressor cycles on and off to condition the air to what you've set inside. If the air is cooler and drier outside, the compressor's actual "on" time is less than it is when it's hotter and more humid.

Just like your house air conditioning (unless you have a swamp cooler). If you have the thermostat set to 60 degrees, and it's actually 60 degrees outside and inside, the air conditioning won't run very often, if at all. But if it's 100 degrees outside, it's going to be running non-stop to try to keep it 60 degrees inside.
Interesting. I didn't think my car would be that smart. I figured if it was on, it was on.


They don't need to be smart for this. the evaporator gets heated by the intake air much slower when it gets colder, and this has an impact on the pressures in the system.

 

[Hokiefyd]

Originally Posted By: Nick1994
Interesting. I didn't think my car would be that smart. I figured if it was on, it was on.


It's not really "brains" as much as "physics". A/C systems have operated the same way* for decades. Physical pressure switches used to cycle the compressor on and off, and I'm sure that hasn't changed much, except for those signals likely running through computers these days.

* Footnote: the main exception I can think of is the variable displacement compressor which is engaged all the time and uses its own internal mechanism to maintain the correct pressure in the system rather than a binary clutch that clutches in and out as pressures fall and rise. I'm also not sure how prevalent these are -- seems most vehicles still use a clutched compressor.

 

[javacontour]

Originally Posted By: Nick1994
I don't really care what mpg it gets as long as it's decent. It's rated for 20 city and 28 highway, I at least get that. It also idles for probably 30-35 minutes a day with the A/C on.


Now we are getting somewhere. What percentage of engine on time is your idle time? You are getting zero MPG at idle.

Try to eliminate that idle time, and use some of the tips such as looking well ahead, trying to conserve momentum, and nothing more than 75% throttle acceleration and let us know how you do.

 

[Jetronic]

Originally Posted By: Hokiefyd

* Footnote: the main exception I can think of is the variable displacement compressor which is engaged all the time and uses its own internal mechanism to maintain the correct pressure in the system rather than a binary clutch that clutches in and out as pressures fall and rise. I'm also not sure how prevalent these are -- seems most vehicles still use a clutched compressor.


The variable displacement compressors are becoming very prevalent, but they're usually also equipped with a clutch these days. the idea of the variable displacement is to not undercool the incoming air when it needs heated again afterwards, and saving fuel that way.