[exdtuner]

Bob can you explain to me how a bad o2 sensor affects gas mileage? I know that sounds like a noob question but I honestly don't know the answer.

 

[mtlelantra]

By the way, the numbers that Hyundai, and other companies come up with, are not the absolute most that the car will get. The number is a conservative estimate based on tests in 2 different locations in the USA, each one with a different climate and elevation. When you're outside of those two test areas and scenarios, you can get better or worse mileage.

No, it's lab tested.... so it's not even close to a road test.
http://www.fueleconomy.gov/feg/how_tested.shtml

 

[BobMs_wht2k2]

Bob can you explain to me how a bad o2 sensor affects gas mileage? I know that sounds like a noob question but I honestly don't know the answer.

tHE front O2 is more important as it reads Air/Fuel mixture and adjusts the engine from there. If it's reading "leaner" than what it really is, than the engine will dump more fuel to make it even out to the a/f ratio it wants at that specific load/speed. The rear is only moderately impacting, but if it senses the cat is not working enough, it will enrichen the fuel to get the cat hotter to work more effectively. When the rear O2 doesn;'t shoe enough difference, the engine will try to compensate for it's "polluting ways" from the engine side then. It all comes together.

 

[robs02elantra]

I thought that I read somewhere that the cars are tested in San Diego and somewhere else, like New England...I'll have to look that up and get back to you. I know that they are also tested in the lab, but I thought it was also in 2 differing cities.

 

[mtlelantra]

So let's just go back...

Regardless of what numbers he puts up, for the sake of argument let's say they're fine and River got ~29 mpg.

EPA fuel economy on that car is 21 city, 30 highway.

If on that 29 mpg trip he did any more than 10% city driving, then his car had better fuel economy than is estimated. So even by his own calculations his argument fails.

---------- Post added 09-24-2010 at 01:06 PM ----------

I thought that I read somewhere that the cars are tested in San Diego and somewhere else, like New England...I'll have to look that up and get back to you. I know that they are also tested in the lab, but I thought it was also in 2 differing cities.

The EPA lab is in ann arbor, and the lab test is a federally regulated standardized test... Actually, it's usually the car companies that run the test using the standardized method... EPA retests only a few of them for accuracy. But it's regulated by law, so if a car manufacturer artificially inflates numbers, they can get fined by the EPA. So it's usually in the manufacturers' best interest to estimate a bit low. Then they can't get flak from the EPA, and customers are happy that they get MPG > estimates.

 

[Silentwolf]

^Aye.


I just wish I could get rid of this crappy FL gas.

 

[SuperGLS]

Alright everyone, let's act like adults. I just wasted a good 15 minutes cleaning this up and I don't want to have to do it again.

I've filled up the tank to 15.5 gallons on a couple of occasions.

Lately I've been driving speed limit or speed limit+5 because I got a speeding ticket in July and my gas mileage has increased 25-30 miles per tank (so like an extra gallon worth). Good stuff.

 

[BobMs_wht2k2]

^Aye.


I just wish I could get rid of this crappy FL gas.

I have to second that. I hate crossing over the state line. We try to fill up north of Valdosta before crossing over because we KNOW the gas in FL sucks. About 10% worse economy with that crap y'all have.

---------- Post added 09-24-2010 at 02:03 PM ----------

Alright everyone, let's act like adults. I just wasted a good 15 minutes cleaning this up and I don't want to have to do it again.

I've filled up the tank to 15.5 gallons on a couple of occasions.

Lately I've been driving speed limit or speed limit+5 because I got a speeding ticket in July and my gas mileage has increased 25-30 miles per tank (so like an extra gallon worth). Good stuff.

Then, like our "friend", you have been ripped off.

 

[mtlelantra]

you think you can accurately tell how many gallons you used on a tank of gas. Thats insane.

Let me explain it to you with an example using numbers, see it that helps...
The size of the tank does not matter so long as you fill up the same way every time.
You go to gas station A, on pump 1. You fill up until it clicks off and not top up.... say it fills up 10 gallons. nice round number. You clear the odometer. You drive. Let's say you drive 240 miles, and you go back to gas station A on pump 1. You fill up until it click off and not top up, exactly like before. say it fills up 8 gallons. This means on your trip of 240 miles, you used up 8 gallons of fuel.
240/8 = 30 miles per gallon.
Who cares how big the tank it. It could be a 30 gallon endurance fuel tank, and was 2/3rd full when you first filled that 10 gallons.

 

[SuperGLS]

Perhaps I have been ripped off, though these were on occasions where I was sputtering to make it to the gas station. But what are you going to do? Tell the attendant you want $2.74 back? No, of course you aren't.

How far does the fuel travel before it gets to the tank? I'd be interested to remove a fuel tank and then fill it and the "tube" going into it completely and then see exactly how much it holds. Am I saying Hyundai is incorrect? No. But, you never know how these things are measured and what methods are used.

I also drive until I'm nearly out of gas each tank (unless I know I'm not going to encounter another gas station) add gas beyond the auto-stop. Yeah, I'm a rebel like that...

 

[BobMs_wht2k2]

Perhaps I have been ripped off, though these were on occasions where I was sputtering to make it to the gas station. But what are you going to do? Tell the attendant you want $2.74 back? No, of course you aren't.

How far does the fuel travel before it gets to the tank? I'd be interested to remove a fuel tank and then fill it and the "tube" going into it completely and then see exactly how much it holds. Am I saying Hyundai is incorrect? No. But, you never know how these things are measured and what methods are used.

I also drive until I'm nearly out of gas each tank (unless I know I'm not going to encounter another gas station) add gas beyond the auto-stop. Yeah, I'm a rebel like that...

a.) Yes you have been ripped off, and I agree you;re not going to ask for $3 back, I just wouldn't go back to that station. WE ran into something similar on our out west vacation with the truck. We have a 25 gallontank, pulled into a station in Flagstaff with a little over 1/8th tank. The last 6 fill ups would have required 20-22 gallons and was fairly consistent. This one took 25.6 gallons. WE knew we had been ripped off, but what are you going to do when you're 1900 miles from home?

b.) http://www.elantraxd.com/forums/sho...lantra-on-one-tank-of-gas&p=600699#post600699 Explains all you want to know about how much theoretical fuel an Elantra could hold.

c.) Like has been stated previously, running your tank almost dry is the WORST thing you can do to your fuel pump/filter.

 

[robs02elantra]

In other news, I've just had my first post edited by James...at least first that I can remember.

 

[evilcalvin]

How bad on the fuel pump is it really? Real question. I like Supergls run to empty all the time. As you can imagine doing 40,000 miles a year driving to and from work 95% freeway will toll roads that are traffic free, I visit the Costco, Shell and Chevron pumps often. Often getting 14 or more gallons and on many occasions 15+ gallons in the tank as I too top off.

By the way it was wrong of me to threaten you Bob. Nobody likes being told they are stupid, least of all me. That being said, I think there is truth on both sides of this arguement that gas pumps are not infoulable and that Hyundai is only accounting for the gas tank which is a full 10+ feet in tube-run to the intake. Also the fuel tube as well. Nascar even admits that car teams can sqeeze extra fuel into longer running fuel lines

 

[BobMs_wht2k2]

Go back and re-read my reply. I'm accounting for fill tube and fuel lines. MAximum of 2 tenths a gallon combined.

Like I have said a hundred times before: Fuel pumps use the fuel in and around them to keep them cool and lubricated. When an intank pump runs dry, you have run it out of coolant and oil at the same time. Would be like running your engine without both for a short period of time. Yes, you can get away with it for a while. But long term all those times it was overheated by sucking up the bottom of the tank with nothing around it to keep it cool will shorten the life of the pump significantly.

In the early days of fuel injection/intank pumps, running a car with more than 50k miles on it empty would literally kill the pump. I learned my lesson the hard way.

EDIT: Remember, nascar is running 1/2" fuel lines, and 3/8" return lines. We're running a tick over 1/4" feed line, with no return.

 

[evilcalvin]

does that trip thingy you plug into the data port under the dash read some help here?

 

[hyunelan2]

Lately I've been driving speed limit or speed limit+5 because I got a speeding ticket in July and my gas mileage has increased 25-30 miles per tank (so like an extra gallon worth). Good stuff.

Just wanted to quote this and re-emphasize the role that air pressure plays in fuel mileage. When you are going slower, there is less air resistance pushing against the car. As you increase speed, it has a similar affect to driving up a hill. Slow and steady is how those hypermilers got 1000 miles out of a tank of gas on the new Sonata.

 

[BobMs_wht2k2]

does that trip thingy you plug into the data port under the dash read some help here?

I think this is what you meant:

Does that trip thingy you plug in under the dash help you with gas mileage?

My response is to that translation.... No. The under dash scanners merely record what it is you're doin, or if you use the ones with an active display they will show you specific functions going on in the engine. what they might help with is helping you change your driving habits bby showing you how poorly you;re driving.

 

[evilcalvin]

so they can display gas mileage as you drive like the newer cars do?

 

[BobMs_wht2k2]

DEPENDS On what you actually get, but yes many have a rudimentary function that will calculate miles per gallon. You will want to check it against what you're actually doing (miles driven divided by gallons needed to fill up. Only works when starting from a full tank). The vette has both instant and average. The average if I reset each tank is close.

EDIT: PErsonally I've never used those types of things. I have always kept a running total of mpg's per tank. Lets me know if somethign is different.

 

[hyunelan2]

The scangauge is pretty popular on a lot of other forums. http://www.scangauge.com/

Does things like GPH, which can't be easily calculated. Your mpg ratings are only going to be as good as your cars sensors though (i.e. you use the wrong wheel/tire combo and it has no way to know that).