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Old 06-06-2009, 02:48 PM   #1
sam o nela
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Default Fuel Economy 101

Originally Posted by Danny


Many members have written about bad fuel economy and I am one of them I would like to target this issue and resolve it once and for all. I have gathered bits and pieces from other posts and the net to compose this thread. I would like to attempt to compile a check list with the help of all of you that everyone can contribute to, and use to help resolve each of our particular fuel economy related issues. I am looking forward to participation from everyone who has some insight. Also, maybe we can all post our gas mileage to compare.
Thank You

Introduction:

The fuel system provides fuel storage in the vehicle, filters out particulates, delivers fuel to the intake air system, and mixes the air and gasoline in the correct ratio to provide the most efficient combustion (i.e., the highest fuel efficiency) in the engine.

Making sure your flow of gas is not blocked is vital to getting the most mileage for your money. Optimal use of your gasoline is helped by fighting the accumulation of performance robbing deposits in the fuel system. Today's modern engines are more susceptible to deposit build-up than ever before. Deposits have been found to start forming in as few as 1,500 miles. Studies have shown that deposits can decrease your fuel efficiency by as much as 11 percent.

The list:

1. One main factor for decreasing fuel economy is a partially blocked exhaust . As catalytic converter undergoes wear and tear, they may collapse internally, leading to restricted exhaust from the engines.

2. Dirty air filters can also cause your engine to run at less than peak efficiency.

3. Malfunctioning brakes can significantly increase fuel consumption because the vehicle must work harder to overcome the resistance.

4. Check for misaligned tires , which will drag instead of rolling freely, leading to increased fuel consumption and causing problems with the car's handling.

5. New spark plugs alone can increase fuel economy by 3%.

6. The Positive Crankcase Ventilation or PCV valve regulates the flow of unburned gases from the crankcase back into the combustion chamber, to be re-burned. The valve helps maintain correct fuel economy and idling, and prevents oil and gases from accumulating in the air filter housing.

7. Fuel injectors are manufactured to operate and last for 150,000-plus miles. Because of their significance on emissions, some vehicle manufacturers warranty injectors for five years or 50,000 miles. However, over a period of time, harmful deposits can build up around an injector nozzle. Deposits can also build up inside the injector or clog the injector filter basket and reduce the amount of fuel being delivered. When the fuel delivery decreases, the injector pulse width will increase, creating additional heat in the injector. A leading cause of this is short-drive cycles. Short-drive cycles with repeated temperature change create fuel diffusion. The lighter gases evaporate and the heavier particles of the fuel settle at the tip of the injector. Engine heat then bakes the heavier particles, making them hard deposits. The deposits can clog an injector, reducing the volume of fuel delivered or distort the spray pattern. When the fuel delivery is out of spec, driveability problems exist because the powertrain control module (PCM) is unable to maintain the proper overall air/fuel ratio. Some injectors may be commanded by the PCM to go richer or leaner depending on if the problem injectors are clogged or leaking.

8. The thermostat plays an important part in obtaining good fuel economy. Temperature sensors on the engine tell the fuel injection computer to inject more fuel when the engine is cold. A faulty thermostat will prevent the engine from reaching normal operating temperature so extra fuel is always being injected. If the temperature gauge is reading low or the car heater is not putting out hot air, have the thermostat checked immediately. Your fuel economy will increase.

9. Change Your Fuel Filter . Your fuel filter removes contaminants including rust and corrosion from the fuel before it enters the fuel injectors or carburetor.

10. Oxygen sensors "may" need to be replaced. The codes are 41 and 42.You can check your Oxygen sensors with a (DVOM) Digital Volt Ohm Meter.
Common symptoms of a worn out sensor include excessive fuel consumption, high emissions, engine surging or hesitation, or premature failure of the catalytic converter. When examining the sensor, a shiny deposit on the sensor's heat shield or any gummy deposits indicate it's time to replace the sensor and determine the root cause of those deposits.

Inoperative or faulty sensor signals can result in the ECU causing engine backfire (due to a rich mixture), rough idle quality and lean condition misfire. Also, bear in mind that a “faulty” oxygen sensor data signal may actually be caused by malfunctioning component(s) of other systems such as the EGR (Exhaust Gas Recirculation) system. Also included are plugged fuel filters, vacuum leaks, inadequate (too high or too low) fuel pressure, fuel injectors leaking gas or air, leakage on the exhaust system or other related parts. Do not automatically assume that the oxygen sensor itself is the root cause of the sensor code. Remember also, a degraded oxygen sensor does not always set a code. If the sensor is replaced, a future sensor code or engine damage may be triggered again if the root cause is not corrected.

11. Exhaust Gas Recirculating (EGR) system .
Here is a good link: http://www.autoshop101.com/forms/h61.pdf

12. Throttle Body inspection and cleaning.

http://www.southgatemotors.com/item_1.htm

http://www.mm-inet.com/535594.shtml

Some of the members have recommended getting some
BG 44K Fuel System Cleaner.

http://www.bgprod.com/bgprofessional.../autofuel.html

http://shop.store.yahoo.com/wyattarp...bgautprod.html

I already bought some Liqui Moly Jectron, Liqui Moly Ventil Sauber and Liqui Moly Pro-Line Fuel System Cleaner, because it is available locally and the BG44k is not.
If the Liqui Moly doesn't work, then I will try the BG 44K.

The liqui-moly site is :
http://www.liquimoly.de/web/lmhomeen...es/index_flash
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Old 06-10-2009, 07:41 PM   #2
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13. Fuel type: 100% gasoline will provide better mileage than gasoline containing ethanol.
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Old 01-06-2010, 11:49 PM   #3
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Here is a pretty useful fuel economy calculator, it is Canadian government but it shows MPG and KPG.

http://oee.nrcan.gc.ca/transportatio...ator-input.cfm

I'm only getting around 10 MPG, I guess due to the cold weather, lame.
I need to try to change some things to correct this.
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Old 01-07-2010, 07:32 AM   #4
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Quote:
Originally Posted by derpderp View Post
Here is a pretty useful fuel economy calculator, it is Canadian government but it shows MPG and KPG.

http://oee.nrcan.gc.ca/transportatio...ator-input.cfm

I'm only getting around 10 MPG, I guess due to the cold weather, lame.
I need to try to change some things to correct this.
Definitely. I've never heard of a G1 getting such bad mileage. Does it appear to run okay otherwise??
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Old 01-07-2010, 07:56 AM   #5
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Quote:
Originally Posted by derpderp View Post
Here is a pretty useful fuel economy calculator, it is Canadian government but it shows MPG and KPG.

http://oee.nrcan.gc.ca/transportatio...ator-input.cfm

I'm only getting around 10 MPG, I guess due to the cold weather, lame.
I need to try to change some things to correct this.
I might be able to see that if you drive only short distances while the engine is cold. I've gotten 13 MPG once only with cold city driving and with my driving now I get 20-24 average MPG depending on my mix of highway/city.

If I were you I'd get the car up to a warm temperature and drive it on the freeway and check the MPG for that trip; and if it isn't in the 20's then you've got some issues to take care of before you end up burning more of your money.
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Old 01-07-2010, 05:56 PM   #6
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DrDave addressed this problem in a G2 post:

"I had a similar problem many years ago. A locking gas cap fixed the problem.

Dave "
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Old 01-15-2010, 05:05 AM   #7
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A locking gas cap? WAT

Ok ok ok, so let me elaborate here. I was at first letting it warm up but since I was buring so much gasonline I discontinued this, I never end up having to go far since I live in a town and drive to work or really anything is only a couple minutes away, I know I shouldn't, but letting it run for 15 minutes every day for a 5 minute trip seems a bit much, so I let it run for about 2 - 5 minutes then go.

I do have a small bhg in the back, it isn't major and hardly causes buring of the coolant but it is there, it also causes a lifter tick for the first few minutes from a cold start which I figure is just because of the gasket.

This is a est~ km I got out of my last two tanks.

First Fill
Prem 91 Octane Est ~ 350KM tell I was a 1/4 full, was letting it run for awhile every morning and it was cold, like -15 to -30 *C cold.

Second Fill
Regular 87 Octane Est ~ 425KM which I got to about 1/8 full. Was driving longer distances.

And I'm on my 3rd tank around 140km with 3/4 full. It is pretty warm right now because of Alberta chinook winds.

Would a small head gasket leak be causing all this? What else could be the issue? I'm not driving faster then the speed limit, so at most I probably did 110KM for about 30 minutes to get to the City of Calgary.
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Old 09-23-2011, 01:41 PM   #8
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Default links in Post #1 need an update

Quote:
Originally Posted by sam o nela View Post
Originally Posted by Danny

11. Exhaust Gas Recirculating (EGR) system .
Here is a good link: http://www.autoshop101.com/forms/h61.pdf

12. Throttle Body inspection and cleaning.

http://www.southgatemotors.com/item_1.htm

http://www.mm-inet.com/535594.shtml

Some of the members have recommended getting some
BG 44K Fuel System Cleaner.

http://www.bgprod.com/bgprofessional.../autofuel.html

http://shop.store.yahoo.com/wyattarp...bgautprod.html

I already bought some Liqui Moly Jectron, Liqui Moly Ventil Sauber and Liqui Moly Pro-Line Fuel System Cleaner, because it is available locally and the BG44k is not.
If the Liqui Moly doesn't work, then I will try the BG 44K.

The liqui-moly site is :
http://www.liquimoly.de/web/lmhomeen...es/index_flash

the links in post #1 of this thread need to be updated. Most of the sites listed appear to be non-existent, or i have serious connection problems O_o
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Old 09-23-2011, 03:36 PM   #9
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Default can't beat stoichiometric by much....

OK... most of the stuff I work on lately is airborne, but assuming your car is "running right", then the air/fuel mixture is hopefully close to "stoichiometric". Therefore for a given amount of air passing thru your engine, you are gonna burn a proportional amount of fuel$$.
You can't beat chemistry....

If your car is running "rich" you are feeding it more Fuel than it needs. "Rich conditions" waste fuel (obviously), but it also wastes combustion energy because un-burned fuel robs some of the heat that would otherwise expand the hot air to generate additional RWHP. SO, you take a double wammy if you are running rich.

I think for a typical internal combustion engine the stoichiometric mass ratio is about 14:1, air to GAS? I believe.... Might be wrong - - it's been a lot of years for that... But regardless - - your engine is basically an air pump.

The amount of Air/Fuel volume per cycle is your displacement. The rate of your cycles (per sec, min, or hour) is proportional to your RPM. For the sake of this discussion let's not argue 2 cycle vs 4 here....

So, if you want to burn less fuel you have to "pump" less VOLUME over time, i.e., in general you have to run less RPM (or pump your air/fuel mixture to smaller displacements like some cars that can cruise on fewer cylinders).

ALso, unless you have a hybrid with regenerative braking, you lose money (energy$$$) everytime you use your brakes.

So, to maximize your MPG for a given car, perform maintenance to ensure it runs as close to "stoichiometric" as possible. Also run RPM's as low as possible (obviously without lugging or excessive pinging), and coast to Red Lights & "Stops" with as little braking as possible.

OK, excuse me now while I drive my 1995 3.2L air-compressor to the corner store....
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Old 09-23-2011, 06:48 PM   #10
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Quote:
Originally Posted by mike_engr View Post
ALso, unless you have a hybrid with regenerative braking, you lose money (energy$$$) everytime you use your brakes.

So, to maximize your MPG for a given car, perform maintenance to ensure it runs as close to "stoichiometric" as possible. Also run RPM's as low as possible (obviously without lugging or excessive pinging), and coast to Red Lights & "Stops" with as little braking as possible.
I need more explanation as to why using your brakes wastes fuel. Help me connect the dots somebody....
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