Hi,

I seem to have come across a funny pattern, my car seems to drive better(more responsive, less hesitation during acceleration) when the fuel tank is close to empty and the fuel light comes on. I am yet to confirm the pattern for sure, but could there be a logical explanation for it?

 

Other than the fact the your car weighs a lot less due to not as much gasoline in your tank thus your car doesn't have to move that extra weight.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by VRDrvr &raquo;</TD></TR><TR><TD CLASS="quote">Other than the fact the your car weighs a lot less due to not as much gasoline in your tank thus your car doesn't have to move that extra weight.

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hahahahahahaahahahah.....thanks MR. Wizard..hahahahahahhaha

 

Well, it feels at least a thousand pounds lighter. Any better explanation to account for the rest of the performance loss ?

 

What was stated earlier about the weight loss is true. Why don't you believe him? Think of it this way.

Gasoline is a liquid which is heavy. Slightly lighter than water but heavy still. Good example is to take a gallon of water. Now take about 14 of those babies and there you go.

Simply less weight to pull because of it being a four cylinder which means less torque than say a V-6. We might be able to put out more HP eventually but most V-6's will still have more torque.

Yes I do know there are frickin exceptions!

And that is why your car feels faster when it has an empty tank.

One thing to think about, was your car cold when you noticed this. A cold engine likes to pull harder when pushed because it is cold and gets better air and such, not to mention more fuel. Just remember that racing around on a cold engine tears it up much quicker.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eswaroop2 &raquo;</TD></TR><TR><TD CLASS="quote">Well, it feels at least a thousand pounds lighter. Any better explanation to account for the rest of the performance loss ?</TD></TR></TABLE>

I really am not making it up...nor bullshitting you.

it takes hp and tq to move that weight, with less weight it will be faster.

 

Wow this situation is funny to me, because usually the exact opposite happens when the tank is low on fuel. Usually the car won't respond as well to an empty tank because the fuel pump can't get a full gulp anymore. Think of it like when you are drinking pop through a straw and it's almost empty, sure you still get some moisture coming into your mouth but not a heavy flow as before. Well congrats on the good outcome from usually a negative situation, but I highly suggest not continuing to do this over a long period of time, unless you are ready to replace your fuel pump in the near future. Just my $0.02

~P!cKl3$~

 

same feeling when fat girls get out your car... feels light as a feather

 

17 * 3.78 litres = 68 pounds, you ppl are saying that by adding around a 100 pounds, the driving charecteristics are changing? Maybe there would be a difference, but it drives worse with just me and a full tank than 4 people and an empty tank. It really drives shitty. And it was not like this before.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eswaroop &raquo;</TD></TR><TR><TD CLASS="quote">17 * 3.78 litres = 68 pounds, you ppl are saying that by adding around a 100 pounds, the driving charecteristics are changing? Maybe there would be a difference, but it drives worse with just me and a full tank than 4 people and an empty tank. It really drives shitty. And it was not like this before. </TD></TR></TABLE>

OK now we are getting somewhere..That is the info that we needed at the start
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I have no idea why

 

Gasoline in your tank helps cool down the fuel pump. With low gas levels your fuel pump is exposed above the gas. The fuel pump will heat up quicker and this sorta helps shorten its life span. With a full tank the fuel pump is fully submerged and the gas helps cool it down especially in the cold mornings. After long driving periods the gas in the tank isnt cool anymore, its sorta warm/room temperatue like... this is a reason why your car doesnt run as good when youve been driving around for awhile.

Also, for those who never fill up all the way when getting gas... your leaving oxygen in the tank. On cold mornings "dew" can build up on the sides of the walls in the tank that arent submerged. Dew can grow mold and such in your tank. Before you know it... you have a monster in your gas tank waiting for that special day to come out and eat you during your next fill up.

 

If this was happening to me, I'd try changing the fuel filter first. I dunno if it'll do anything, but it is involved with your gasoline, and is cheap to replace.

 

The fuel filter is as clean as new. I checked that out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by whoaitslen2 &raquo;</TD></TR><TR><TD CLASS="quote">Gasoline in your tank helps cool down the fuel pump. With low gas levels your fuel pump is exposed above the gas. The fuel pump will heat up quicker and this sorta helps shorten its life span. With a full tank the fuel pump is fully submerged and the gas helps cool it down especially in the cold mornings. After long driving periods the gas in the tank isnt cool anymore, its sorta warm/room temperatue like... this is a reason why your car doesnt run as good when youve been driving around for awhile.

Also, for those who never fill up all the way when getting gas... your leaving oxygen in the tank. On cold mornings "dew" can build up on the sides of the walls in the tank that arent submerged. Dew can grow mold and such in your tank. Before you know it... you have a monster in your gas tank waiting for that special day to come out and eat you during your next fill up. </TD></TR></TABLE>

But according to your explanation, my car should run worse when it is close to empty right?

 

Well...

Despite how great your gas is, there's still gonna be **** in it. And **** settles. Perhaps you're going to lose it cause all the **** is congregating at the bottom of your tank, and with the low amount of fuel your getting that sucked in your pump?

I see you've checked your fuel filter though....hmmm.

 

My fuel tank looks like new, there was not a speck of dust in it, (until I actually opened up the fuel pump, and a couple of flakes of dust fell in.), but the problem has been there before the open up.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eswaroop &raquo;</TD></TR><TR><TD CLASS="quote">

But according to your explanation, my car should run worse when it is close to empty right?</TD></TR></TABLE>

I didnt say if it will run better or not. It should run better because its not heavy but its also heating up the fuel pump. That causes it to stress out a bit more than normal but its not gonna seize up the motor or anything haha.

 

ok,

So what would actually make it run better? other than the weight loss factor?

 

Less fuel in the tank means hot fuel. The fuel pressure regulator will allow unused fuel to be returned to the tank. Maybe the fuel gets warm enough to atomize better? You may have a totally different problem goin' on here, so get your blinders off and check the basics before you start guessing what's wrong.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eswaroop &raquo;</TD></TR><TR><TD CLASS="quote">17 * 3.78 litres = 68 pounds, you ppl are saying that by adding around a 100 pounds, the driving charecteristics are changing? Maybe there would be a difference, but it drives worse with just me and a full tank than 4 people and an empty tank. It really drives shitty. And it was not like this before. </TD></TR></TABLE>


i know this doesn't help with your problem, but i have to point out a flaw in your calculations.....

17gal = approx 65 L
assuming the density of gas is about 0.75g/mL, then 65L = 48.75kg = 107.25 lb, not 68lb

 

Thanks, that is right! But the problem remains. Sometimes, the car drives well even on a 3/4th full tank...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mike813 &raquo;</TD></TR><TR><TD CLASS="quote">same feeling when fat girls get out your car... feels light as a feather </TD></TR></TABLE>bahaha

 

Well since a gallon of water equals 8 pounds and gas is slightly lighter then you could probably say it would be around 6-7 lbs/gal. and since 7 pounds of weight removed is equivelent to 1 horsepower then you can see where the feeling of extra power comes from. But what you said about the car feeling better with more people in the car is probably not about actual performance but has to do with your suspension and when the car is full it is really stiff cause it is weighed down, and seems to respond better. This probably does not have anything to do with the gas level. Just a little to think about

 

Ok,

I must maybe rephrase my question. Other than the reduction in weight, could there be some factor which might make it drive better with less fuel in the tank?

Like maybe, pressure buildup due to vapors in the tank which might offset any pressure loss, hotter fuel or something of that sort?

( there would be less chance of a vapor buildup in a full tank right..)