Improving Fuel Mileage

[LTC8K6]

That thing is junk. What you want is a Scangauge. But even then, the instant mpg readout only tells you the same thing common sense does. Accelerate slow = less gas. Cruise slow = less gas

I have a scangauge2. I just used it to pull a code about 1/2 hour ago.

 

[Howard]

Not really. If you look at an efficiency curve of a gasoline engine, you'll notice right away that open throttle is more efficient than throttled

For some reason I doubt that WOT is most efficient in terms of HP/gas flow.

 

[ShawnD1]

For some reason I doubt that WOT is most efficient in terms of HP/gas flow.

http://en.wikipedia.org/wiki/Engine_efficiency

At slow speed (i.e. low power output) the efficiency is much lower than average, due to a larger percentage of the available heat being absorbed by the metal parts of the engine, instead of being used to perform useful work. Gasoline engines also suffer efficiency losses at low speeds from the high turbulence and head loss when the incoming air must fight its way around the nearly-closed throttle; diesel engines do not suffer this loss because the incoming air is not throttled. Engine efficiency improves considerably at open road speeds; it peaks in most applications at around 75% of rated engine power, which is also the range of greatest engine torque

When you're at 75% of rated power, that's a wide open throttle condition. Cars have fairly flat torque curves, so the power is mostly linear with RPM. My car's max power is at 6200 rpm I think, so 75% power would mean pedal to the floor at roughly 4650 rpm. Simply put, max efficiency is when you're flooring it and running at max torque.

If you need to pick between a wide open throttle condition and a throttled condition, the wide open condition will usually (not always) have better efficiency. An example of this would be hauling a trailer up a hill with the pedal all the way down while driving in top gear. Efficiency goes down considerably when dropping gears so that the engine has a lot more power available than what is required; this causes a throttled condition.

Another comparison would be between the I4 and V6 models of the same car like a Toyota Camry. Both cars have the same weight within 5%, so why does the V6 burn way more gas to get the same amount of work done? Again, because the V6 has more power, it needs to be throttled all the time.

 

[Howard]

http://en.wikipedia.org/wiki/Engine_efficiency

no citations = lose. You can't seriously be quoting wikipedia without citations?

 

[PlasmaBomb]

no citations = lose. You can't seriously be quoting wikipedia without citations?

Look up brake specific fuel consumption (BSFC).

Wikipedia even has a page on it.

Sorry it's late and I'm knackered. ZV can probably fill you in, or if you do a search for BSFC, it has come up on the forums before.

Night

 

[BUTCH1]

That thing is junk. What you want is a Scangauge. But even then, the instant mpg readout only tells you the same thing common sense does. Accelerate slow = less gas. Cruise slow = less gas

My display on the dash gives me a constant MPG, I thought most modern cars do this..

 

[ShawnD1]

Look up brake specific fuel consumption (BSFC).

Wikipedia even has a page on it.

This page has the same problem as the efficiency page where it doesn't reference a lot of things.

http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption

Any engine will have different BSFC values at different speeds and loads. For example, a reciprocating engine achieves maximum efficiency when the intake air is unthrottled and the engine is running near its torque peak. However, the numbers often reported for a particular engine are a fuel economy cycle average statistic. For example, the cycle average value of BSFC for a gasoline engine is 322 g/(kW·h), translating to an efficiency of 25%. However, efficiency for that engine can be lower or higher than this average statistic depending on the operating condition. In the case of a production gasoline engine, the most efficient BSFC is approximately 225 g/(kW·h), which is equivalent to a thermodynamic efficiency of 37%.

One of the linked pages really bugs me.
http://en.wikipedia.org/wiki/Fuel_economy-maximizing_behaviors

Hypermilers are drivers who exceed the United States Environmental Protection Agency (EPA) estimated fuel efficiency on their vehicles by modifying their driving habits.

So apparently I'm a hypermiler because I'm not a retard. EPA's official mileage for my car is 26mpg, but real world mileage I'm getting is about 30-31mpg. My corolla is a 4 speed automatic but it's usually still in second gear when I reach the 40mph speed limit; hopefully that gives you some idea of how quickly I accelerate.


Here's another blood boiling article
http://en.wikipedia.org/wiki/Hypermiling

Hypermiling as a sport
In some places, hypermiling contests have been held to see who can get the highest mpg on a selected course.

The recent Maximum Fuel Economy contest was held in Elkhart, Indiana, where "world records" for the Honda Insight (213 miles per US gallon (1.10 L/100 km; 256 mpg-imp) round trip), Toyota Prius (136 miles per US gallon (1.73 L/100 km; 163 mpg-imp) round trip) and the Ford Escape Hybrid (76 miles per US gallon (3.1 L/100 km; 91 mpg-imp) mpg round trip) were achieved, albeit having been achieved while rolling through all stop signs and having the vehicle tires inflated well beyond recommended specifications.[6]

Fleabag :hmm:

 

[alkemyst]

hypermilers need to get off the fucking major roads and stick to side streets. I am waiting for one of these fucks to cause a major accident attempting to merge onto a 70mph expressway while 'coasting' up to speed at 30-40mph by the time they merge.

 

[TraumaRN]

hypermilers need to get off the fucking major roads and stick to side streets. I am waiting for one of these fucks to cause a major accident attempting to merge onto a 70mph expressway while 'coasting' up to speed at 30-40mph by the time they merge.

Sure I try to maximize my fuel economy but I try to do in it in such a manner that is safe for me and everyone else on the road. I far too often see people who just plain aren't paying attention while merging onto the freeway at 30mph. I would know because I tend to say in the right lane on the freeway and see people who merge at 30mph while talking on a cell phone or some other BS. It's not just 'hypermilers' plenty of people don't merge at a safe speed. Personally when I merge I give my car the spurs until I reach my desired speed. Thanks for pigeon holing though.