| twosomeca |
Well, this is the first time I have ever seen this. I was down to about 1/12th of a tank of gas and had planned on getting gas while I was out. But I noticed that my range said 0 mi. I thought this was weird. I probably drove another 10 miles while it said 0. I was trusting in the gas needle display and the fact that the nearest station was about 6 miles no matter which direction I took. Everything worked out find.
I would have thought that the computer would recalculate mileage range based on existing gas in the tank and the current driving conditions. I know my bimmer does this, but I guess the MDX does not. Any thoughts? TIA. |
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| Echo2625 |
You're not serious are you?
No vehicle that I have ever owned has calculated the miles to empty to the very last drop! At some point it's going to read zero even though you haven't run out of gas.
It's not good for your fuel injectors to let the gas get that low in the first place. |
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| twosomeca |
quote:
Originally posted by Echo2625
You're not serious are you?
No vehicle that I have ever owned has calculated the miles to empty to the very last drop! At some point it's going to read zero even though you haven't run out of gas.
It's not good for your fuel injectors to let the gas get that low in the first place.
Yes, as a matter fact, I was serious. We have talked about this at length on one of the BMW boards I belong to. The computer seems to be VERY accurate with those cars. I am not being disrespectful to Acura. Just wondering about this. When the gas light first went on, there was still about an 1/8 of a tank according to the gauge. Unfortunately, I had a flat tire, so I put the spare on, took it to a tire store, dealt with that, and then went to deal with gasing up the car on the way home. It LOOKED as though I had enough to make it without any problems, according to the gauge anyway. What I thought was UNUSUAL was the computer calculated range, which state ZERO. |
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| twosomeca |
| Let me rephrase it. Why would the computer calculate the gas range at zero when the gas gauge still shows fuel in the tank? |
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| maddawg995 |
| I think its because the trip computer does not put the reserve gas into consideration. That's why it shows 0. Not sure how much gas is actually left when the range reaches 0 but I've heard it could be as much as 3 gallons. |
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| snoman |
Regardless of the technical accuracy of one metering system over another, Echo2625 has stated the one point that really matters ...
ya ought not let your gas tank get that low to begin with. It isn't good for the MDX.
Personally I start looking for a gas station when it gets to 70 miles left, and try to never go below 40.
(':trustme:') |
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| twosomeca |
quote:
Originally posted by snoman
Regardless of the technical accuracy of one metering system over another, Echo2625 has stated the one point that really matters ...
ya ought not let your gas tank get that low to begin with. It isn't good for the MDX.
Personally I start looking for a gas station when it gets to 70 miles left, and try to never go below 40.
(':trustme:')
You know what this is called? Unsolicited advice (thanks, but no thanks, btw). This was NOT my question. I mean, come on. If you don't want to answer the question and you want to try take issue with a fellow owner, you should know that you are wasting your time and you are probably pissing people off.
quote:
I think its because the trip computer does not put the reserve gas into consideration. That's why it shows 0. Not sure how much gas is actually left when the range reaches 0 but I've heard it could be as much as 3 gallons.
Thanks, that is interesting. I wasn't aware of that and it helps me out as my wife is the primary driver of this vehichle. I'll let her know. :) |
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| Echo2625 |
quote:
Originally posted by twosomeca
You know what this is called? Unsolicited advice (thanks, but no thanks, btw). This was NOT my question. I mean, come on. If you don't want to answer the question and you want to try take issue with a fellow owner, you should know that you are wasting your time and you are probably pissing people off.
Thanks, that is interesting. I wasn't aware of that and it helps me out as my wife is the primary driver of this vehichle. I'll let her know. :)
It's NEVER a waste of time to piss off a fellow owner! :2: :18: |
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| G. COLTON |
quote:
Originally posted by maddawg995
I think its because the trip computer does not put the reserve gas into consideration. That's why it shows 0. Not sure how much gas is actually left when the range reaches 0 but I've heard it could be as much as 3 gallons.
What RESERVE gas?
G |
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| G. COLTON |
quote:
Originally posted by snoman
Regardless of the technical accuracy of one metering system over another, Echo2625 has stated the one point that really matters ...
ya ought not let your gas tank get that low to begin with. It isn't good for the MDX.
Personally I start looking for a gas station when it gets to 70 miles left, and try to never go below 40.
(':trustme:')
As long as it is getting fuel the MDX (or any other standard vehicle) does not know/care whether or not it has a full tank or 1/4 gallon.
Regardless it is never a good idea to let the fuel cage and/or trip computer calculate low fuel because it may be inaccurate and you may be waiting at the side of the road for the fuel truck.
G |
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| csimo |
quote:
Originally posted by twosomeca
Well, this is the first time I have ever seen this. I was down to about 1/12th of a tank of gas and had planned on getting gas while I was out. But I noticed that my range said 0 mi. I thought this was weird. I probably drove another 10 miles while it said 0. I was trusting in the gas needle display and the fact that the nearest station was about 6 miles no matter which direction I took. Everything worked out find.
I would have thought that the computer would recalculate mileage range based on existing gas in the tank and the current driving conditions. I know my bimmer does this, but I guess the MDX does not. Any thoughts? TIA.
After reading your asinine remarks to others I'll tell you exactly what the computer was trying to tell you.
It was trying to say... hey fool no reasonable person should be driving this vehicle with an empty gas tank. You are damaging the fuel pump and injectors. Stop being so cheap and irresponsible and put some damned gas in the tank.
I guess your BMW is too politically correct to tell you what you need to hear.
My apologies to the rest of the fine folks here... this guy just rubbed me the wrong way and needed to hear the truth. |
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| NewMDXOwner |
quote:
Originally posted by G. COLTON
What RESERVE gas?
As long as it is getting fuel the MDX (or any other standard vehicle) does not know/care whether or not it has a full tank or 1/4 gallon
G
:confused: Isn't that the amount left in the tank when the gage reads "Empty?" As far as I have had cars, there has always been gas left in the tank when the gage reads "Empty."
Try running the cars dry often enough and you'll burn out the fuel pump due to overheating. This is in addition to all the muck you'll be sucking up from the bottom of the tank. Bad idea! |
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| TheWorm |
The computer is factory-programmed with an offset of 20 miles...it shows -0- but there is really ~20 left according to your current driving pattern (recent, NOT average MPG). Presumably it's so you don't run it all the way to -0- and damage the pump (overheat b/c the fuel is the pump's coolant) or run dry by pushing it too far.
I guess it doesn't need to be mentioned again that it's unwise to do so :D
I know you can change the offset in Nav-equipped X's, but don't know about touring w/o nav. |
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| twosomeca |
edited - cismo isn't worth it. ;) BTW, I love my bimmer, you gotta problem with that? :p
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| G. COLTON |
"Reserve" gas is that which is provided to be used when the fuel in the primary tank has been expended. The VW bug used to have a "reserve." The driver would move a handle when the primary tank was empty. Do not know of any manufacturers that provide a reserve tank, or even reserve sump these days.
If you run your vehicle totally out of fuel and operate in this condition for a prolong peroid of time damage can occur to the fuel pump. I suspect that running for 2 or 3 hours without fuel would cause damage, but it sure is good for gas mileage. Now if only I could find a vehicle which will not automatically stop when out of fuel I will buy it.
As long as fuel from an almost full or almost empty tank is running through the fuel lines NO DAMAGE will occur. If you believe this statement to be incorrect please provide exact mechanical details to show how damage occurs.
G |
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| csimo |
quote:
Originally posted by G. COLTON
As long as fuel from an almost full or almost empty tank is running through the fuel lines NO DAMAGE will occur. If you believe this statement to be incorrect please provide exact mechanical details to show how damage occurs.
G
There are many pumps that use the fuel for cooling... both internally and externally. Some pumps are designed to be immersed in fuel for cooling in addition to using the fuel going thru the pump as coolant.
There are cars that will not run the tank completely dry for this very reason... well none will pump the tank completely dry, but some are designed to keep the pump covered with "sloshed" fuel even when they won't pump anymore.
I don't know about our MDX pumps, but there are some out there that won't survive running out of fuel more than a few times. |
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| G. COLTON |
quote:
Originally posted by csimo
There are many pumps that use the fuel for cooling... both internally and externally. Some pumps are designed to be immersed in fuel for cooling in addition to using the fuel going thru the pump as coolant.
There are cars that will not run the tank completely dry for this very reason... well none will pump the tank completely dry, but some are designed to keep the pump covered with "sloshed" fuel even when they won't pump anymore.
I don't know about our MDX pumps, but there are some out there that won't survive running out of fuel more than a few times.
I really doubt that there are many people out there that have a problem with "running out of fuel more than a few times." Anyway, once they run out of fuel I would think that the owner would shut off the engine and then they are no longer running and no longer need fuel for cooling or for lubrication.
The pumps that require fuel for cooling generally are large capacity pumps and not the small pumps used in automobiles. Not all electric automotive fuel pumps are even immersed in the fuel tanks. Some have historically been mounted on other vehicle locations.
G
G |
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| csimo |
quote:
Originally posted by G. COLTON
I really doubt that there are many people out there that have a problem with "running out of fuel more than a few times." Anyway, once they run out of fuel I would think that the owner would shut off the engine and then they are no longer running and no longer need fuel for cooling or for lubrication.
The pumps that require fuel for cooling generally are large capacity pumps and not the small pumps used in automobiles. Not all electric automotive fuel pumps are even immersed in the fuel tanks. Some have historically been mounted on other vehicle locations.
Wish you had really read my post and replied to what I actually posted.
You said "I really doubt that there are many people out there that have a problem with "running out of fuel more than a few times"." Probably not, but then I know people who manage to run out on a semi-regular basis. They seem to feel some sense of accomplishment by taking the needle all the way to "E" or beyond.
You then said, "Anyway, once they run out of fuel I would think that the owner would shut off the engine and then they are no longer running and no longer need fuel for cooling or for lubrication." What would make you think the damage hasn't already been done?
You then said, "The pumps that require fuel for cooling generally are large capacity pumps and not the small pumps used in automobiles. " Really? How many of todays automobiles use electric pumps in the tank? 90%+ would be my guess... maybe more. Do you think they do this for the fun of it? Do they do it to make the pump easier to get at? Why would they do such a thing? Think about it.
Then you said, "Not all electric automotive fuel pumps are even immersed in the fuel tanks." I didn't see anything I posted that said that. Nothing at all even to indicate anything close. I don't use absolutes in messages unless warranted. To say "all" of anything is probably wrong and I didn't use the words you implied. Where did you come up with such a thing?
It's fine to have a discussion about the subject. It's another to imply that I said things I didn't say. Read the messages carefully. |
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| twosomeca |
You said, I said, so you said, so then I said, and I know that people do this on a semi-regular basis.
:rolleyes: |
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| cvyluv |
| Am I the only one who became somewhat irritable after reading all these posts????? :3: :3: :3: |
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| csimo |
I apologize to those that had to endure this thread. I just get too aggrivated at times. Accuracy is important to me.
Once again I extend my apologies. |
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| dj-mdx2 |
Why can't we all just get along? Let's stop adding fuel to the fire, since this thread is running on empty, and everybody's getting gassed out. (Puns intended)
Peace!
:20: |
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| DaleB |
| This thread would have ended up more worthwhile if the links had materialized in the last post....but I'm patient.....:1: |
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| maddawg995 |
The X hold around 19.4 gallons. Of those 19.4, lets say 17.4 of it is considered the actual amount of gas you should run on. When those 17.4 gallons is used, that's when the computer reads 0 but in actuality, you still have 2 gallons in "reserve".
On my old '02 CRV, whenever the fuel light comes on, I still have 3 gallons of reserves to run on. I'm guessing that's how the MDX trip computer calculates things too.
quote:
Originally posted by G. COLTON
"Reserve" gas is that which is provided to be used when the fuel in the primary tank has been expended. The VW bug used to have a "reserve." The driver would move a handle when the primary tank was empty. Do not know of any manufacturers that provide a reserve tank, or even reserve sump these days.
If you run your vehicle totally out of fuel and operate in this condition for a prolong peroid of time damage can occur to the fuel pump. I suspect that running for 2 or 3 hours without fuel would cause damage, but it sure is good for gas mileage. Now if only I could find a vehicle which will not automatically stop when out of fuel I will buy it.
As long as fuel from an almost full or almost empty tank is running through the fuel lines NO DAMAGE will occur. If you believe this statement to be incorrect please provide exact mechanical details to show how damage occurs.
G
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| NewMDXOwner |
quote:
Originally posted by G. COLTON
As long as fuel from an almost full or almost empty tank is running through the fuel lines NO DAMAGE will occur. If you believe this statement to be incorrect please provide exact mechanical details to show how damage occurs.
G
Colton:
I was hoping you would provide exact mechanical details to show why NO DAMAGE would occur. My wife is the primary driver on the MDX and she has a bad tendancy to wait till the gas tank is almost empty before she fills it up. Never ran it completely dry, never got stranded, mind you, just almost empty! Well, take a wild guess! It did burn out the fuel pump. The coil was shot, or at least that's what Acura tells me. Luckily it occured right before warranty runs out so we didn't have to pay for it.
Since you seem to be so sure, I was hoping you could provide some sort of mechanical details on why the pump shouldn't fail, just so I won't be so paranoid about her gas tank anymore. |
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| csimo |
Here's an excerpt from an article on "Honda Fuel Pumps & Fuel Injection Repairs". The paragraph is from "Why Fuel Pumps Fail".
http://www.autohausaz.com/honda-aut...fuel-pumps.html
"Your Honda's fuel pump relies on fuel passing through it for lubrication and cooling. Consequently, fuel starvation can be another factor that accelerates wear and may even cause pump damage under certain operating conditions. "
Make your own decisions. Everyone is entitled to their own opinon but it makes a big difference if the opinion is based on fact or an old wivestale. My opinion is that it's is just plain foolish to let your fuel tank run below 1/4 tank. I'll stick with my plan and let those that run the tank down repeatedly scratch their heads and wonder why when they have fuel pump problems. |
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| afs12065 |
In addition to the information already presented with regard to fuel acting as a lubricant/coolant for an electric fuel pump, there is also the issue of sediment and other materials that end up at the bottom of the tank over time.
From the aforementioned website :
"Accelerated wear may also occur if sediment or rust gets past the inlet filter sock. In some instances, a pump will fail because contaminants entered the pump and jammed it, causing the motor to overheat and burn out."
As a fuel tank approaches empty the "slosh effect" becomes greater - liquid has more room to move around and the materials that make it into the tank (and settle at the bottom) can be ingested into the fuel pump and fuel filter. This can cause premature fuel pump failure if severe enough and can accelerate the rate at which the fuel filter (further upstream) becomes clogged. If you couple this with running a tank down close to empty - thereby reducing the amount of cooling the pump receives while pumping dirt and grit from the bottom of the tank at higher operating temperatures - one could guess that these conditions will lead to a shorter life span on electrical and moving parts compared to those that are not subjected to such conditions.
As a rule of thumb (just because I think it is a good precautionary measure and has always been how I've operated) I always fill up at a reputable, high volume gas station and never let the needle get below 1/4 tank... have never lost a fuel pump on any brand of vehicle for what its worth... That's just my $.02 I guess. :-) |
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| JTM |
quote:
Originally posted by TheWorm
I know you can change the offset in Nav-equipped X's, but don't know about touring w/o nav.
You could program the offset on the trip computer (non-navi) as well. |
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| squaw_ski_bum |
quote:
Originally posted by NewMDXOwner
This is in addition to all the muck you'll be sucking up from the bottom of the tank. Bad idea!
Dude, where do you think the fuel pick up is in the tank? 1/4 of the way up from the bottom?
Why do people think that somehow fuel tanks have a magical bottom layer that is below the fuel pickup / outlet point? This is a common myth that I hear so often that I have to laugh. If any muck denser than the gas got into the tank, it would end up at the bottom, and promptly get sucked out into the fuel filter, no matter if the tank was full or empty.
FWIW, I find that the range meter in my 2002 is an approximation, at best, and gets confused sometimes if I refill before the tank is near empty. On one trip to LA the range meter said 0 and the gas gauge said 1/4. I did about 75 miles before pulling in for a fill up. I trust the little warning light that comes on at 3 gallons to empty, not the range meter. |
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| Mr. Mom |
| Maybe some are confusing their yacht with their Acura. :) |
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| csimo |
quote:
Originally posted by squaw_ski_bum
Dude, where do you think the fuel pick up is in the tank? 1/4 of the way up from the bottom?
Why do people think that somehow fuel tanks have a magical bottom layer that is below the fuel pickup / outlet point? This is a common myth that I hear so often that I have to laugh. If any muck denser than the gas got into the tank, it would end up at the bottom, and promptly get sucked out into the fuel filter, no matter if the tank was full or empty.
Something tells me you've never looked in the bottom of a fuel tank. I have a relative that owns a scrap metal business and have seen thousands of them. Now these were all metal tanks and newer ones are plastic, but other than rust I'm sure the gunk is the same.
Gasoline is not a stable compound. Let it sit and it precipitates varnish, gunk, and a variety of other bad things. Mix in some water and you end up with homogenized gunk after some driving. Not good stuff.
You never know what you're pumping out of the gas station's tanks. They're even worse.
Take the time to actually look in some old tanks and then you won't make believe that it's all clean and nice in there.
Ever take apart an old carburetor? What was in the bottom of the float bowl? That junk got there even after going thru the fuel filter! |
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| Mr. Mom |
Ok, who wants to be the first to run their X on ¼ of a tank or less for 6 months and end this speculation? :p
Ski is right; the pick-up is on the bottom of the tank, not a floater as on a boat. |
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| tlhurlbut |
Having spent 33 years as a state trooper, dealing with people who have run out of gas, I found that the top half of the gas tank costs less than the bottom of the tank. When you figure the missed appointments, frustration, hours lost sitting at the side of the road, wondering who might stop to help, paying for road service to come "give" you a gallon, buying a gas can to get a gallon of gas so you can limp to the next gas station, possibly damaging your fuel pump, wearing down your battery trying to start the car, and many other issues, the danger of being disabled along a busy freeway, the risk of being hit sitting on the side of the road, getting your new X hit sitting because you're out of gas, stopped in a remote area, and many more issues, the bottom half can be very expensive. I rarely go below a 1/2 tank unless I'm around town and close to a station. With a 1/2 tank, you normally have enough "reserve" to deal with any traffic jams that might happen.
Just a thought for many happy X trips. |
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| NewMDXOwner |
quote:
Originally posted by squaw_ski_bum
Dude, where do you think the fuel pick up is in the tank? 1/4 of the way up from the bottom?
Why do people think that somehow fuel tanks have a magical bottom layer that is below the fuel pickup / outlet point? This is a common myth that I hear so often that I have to laugh. If any muck denser than the gas got into the tank, it would end up at the bottom, and promptly get sucked out into the fuel filter, no matter if the tank was full or empty.
FWIW, I find that the range meter in my 2002 is an approximation, at best, and gets confused sometimes if I refill before the tank is near empty. On one trip to LA the range meter said 0 and the gas gauge said 1/4. I did about 75 miles before pulling in for a fill up. I trust the little warning light that comes on at 3 gallons to empty, not the range meter.
Come on bum! Do you really think the velocity caused by the pump suction would be enough to drag any sediment collected at the bottom into the fuel line, even if the pickup is at the bottom of the tank? If so, why do we ever have any sediment left in the tank at all?
The situation is like this. Like it or not, you always have craps collected at the bottom of the tank. When you drive a round, fuel will slosh and create surface waves. With a full tank, the waves do not penetrate far enough to dredge up this muck, sort of like the water a few hundred yards from the beach. The waves are there, but the water still looks clean.
Now, when you run the tank to empty, the gas will slosh more, and the wave action of the surface will be enough to mix up all that muck with the gas and that's when the fuel pump will be able to suck it into the fuel line.
Another thing you ought to think about, if you can think at all, is the fact that people in cold weather do not run their gas tank below 1/4 tank in the winter. When they do, they occasionally suck up moisture into their fuel line, and that would freeze causing the car to quit. According to your logic, such a thing could never happen because water is heavier than gasoline and should have been sucked out as soon as it gets in the tank, right?
Next time, perhaps you should think first and laugh later, right? |
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| Dr. Ken |
Several months ago I was to cheap to buy gas for $1.99 (premium) since I knew of a station that was about 5 cents less further down the road. Well, it was further than I thought and my range display showed 0 miles for several miles before I reached the gas station. I was really sweatin' it. Imagine my surprise when I could only put 18 gallons in the tank! I have since learned, as many of you are talking about, that the range calc is only approximate, even though the gas needle was below empty. Of course I would gladly pay $1.99 at any station now.
Years ago I drove a Ford pickup, and when the needle was on empty, it was empty. Absolutely no reserve. So today's manufacturers can make their guages more accurate if they really wanted to. |
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| G. COLTON |
quote:
Originally posted by Mr. Mom
Ok, who wants to be the first to run their X on ¼ of a tank or less for 6 months and end this speculation? :p
Ski is right; the pick-up is on the bottom of the tank, not a floater as on a boat.
I frequently, maybe 50% of the time do not get fuel until the iettle fuel low light comes on. It makes no difference to the fuel system if I have 1/4 tank, 1/2 tank or whatever until I get to the point that the pickup is starting to suck air. At this point I am in trouble.
For the most part squaw_ski_bum is correct. The pickup is on the bottom. Yes, crud does collect but the "fullness" of the tank has no bearing on this. Even with the baffles in a gas tank it sloshes regardless of it being 3/4 full or 1/4 full.
And from what I read on this board some MDX owners frequently hear fuel sloshing.
For you cold weather folks, what is the thought that keeping 1/4 tank prevents mositure from being picked up? I have seen water get into the fuel lines right after a fillup.
G |
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| NewMDXOwner |
quote:
Originally posted by G. COLTON
For the most part squaw_ski_bum is correct. The pickup is on the bottom. Yes, crud does collect but the "fullness" of the tank has no bearing on this. Even with the baffles in a gas tank it sloshes regardless of it being 3/4 full or 1/4 full.
And from what I read on this board some MDX owners frequently hear fuel sloshing.
For you cold weather folks, what is the thought that keeping 1/4 tank prevents mositure from being picked up? I have seen water get into the fuel lines right after a fillup.
G
Of course the gas slosh in the MDX is always there. But try a little experiment. Put some sand in a glass and fill it to the brim with water. Now see if you can "swirl up" the sand by shaking the glass sideways. Now dump the water out and leave only a little water around and try to do the same. Don't tell me there is no difference. |
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| bk123 |
interesting thread :D
i wonder if the reported MPG is inaccurate based upon the claim that not all the gas in the tank is used in the Miles Remaining calculation.
today, i was driving the X and it reported 7 miles to empty based upon the calculated 13.4 MPG we are getting on this tank (684 totla miles on the odometer). when i gassed it up, it took 18.5 and it has a 20.4 gallon tank. |
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| G. COLTON |
quote:
Originally posted by bk123
interesting thread :D
i wonder if the reported MPG is inaccurate based upon the claim that not all the gas in the tank is used in the Miles Remaining calculation.
today, i was driving the X and it reported 7 miles to empty based upon the calculated 13.4 MPG we are getting on this tank (684 totla miles on the odometer). when i gassed it up, it took 18.5 and it has a 20.4 gallon tank.
I have checked the miles per gallon calculated by the trip computer against real miles per gallon based on actual fuel used over several tanks. The miles per gallon is usually quite accurate. It is the miles until empty that is in question. I have not checked exactly how Honda does this but I would not expect them to use MPG calculations. They are probably checking what they think is fuel remaining in tank and dividing that by current MPG.
I used to have a Blazer that also showed how many gallons of fuel used. It was very accurate on this and also on the MPG. Once on a long trip I compared the computer fuel used vs the actual used. The computer said I had used 157 gallong and I had actually used 155 gallons. If I was to reset the fuel used entry each time I filled the vehicle I always had a very good idea of how much fuel was remaining. Even if you do not have a fuel used display this is easily calculated in your head using the MPG and miles driven.
G |
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| G. COLTON |
quote:
Originally posted by NewMDXOwner
Of course the gas slosh in the MDX is always there. But try a little experiment. Put some sand in a glass and fill it to the brim with water. Now see if you can "swirl up" the sand by shaking the glass sideways. Now dump the water out and leave only a little water around and try to do the same. Don't tell me there is no difference.
To make your experiment accurate you need to have the same geometry. Try using a pyrex or similiar dish about 2 inches deep and 12 inches square. Put about 1/32 in of sand in the bottom and 1 3/4 in. of water on top. Accelerate the solution fore and aft as in accelerating your vehicle and stopping. How vigorously you shake will depend upon how heavy footed your are.
Actually sand is not representative of the crud in the bottom of your tank. The sand will have a much higher specific gravity and will not agitate as well. You really need a substance with specific gravity only a little heavier than water.
G
G |
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| squaw_ski_bum |
quote:
Originally posted by csimo
Something tells me you've never looked in the bottom of a fuel tank. I have a relative that owns a scrap metal business and have seen thousands of them. Now these were all metal tanks and newer ones are plastic, but other than rust I'm sure the gunk is the same.
Gasoline is not a stable compound. Let it sit and it precipitates varnish, gunk, and a variety of other bad things. Mix in some water and you end up with homogenized gunk after some driving. Not good stuff.
You never know what you're pumping out of the gas station's tanks. They're even worse.
Take the time to actually look in some old tanks and then you won't make believe that it's all clean and nice in there.
Ever take apart an old carburetor? What was in the bottom of the float bowl? That junk got there even after going thru the fuel filter!
Yes I have taken apart plenty of carburetors - I used to own a Fiat and a VW bug.
Any junk in the gas ends up on the bottom of the tank, no matter if the tank is full or near empty. Every time the car is driven, any gas slosh will cause the gunk to get stirred up into suspension in the fuel, where it gets sucked up.
RTFM - I did - the fuel pump and filter is inside the tank, and the pick up is right at the bottom.
In diesel you can get bacterial growth if the fuel has been sitting in the tank for a long time, this will cause problems once the vehicle or boat starts moving and it gets stirred up and clogs the fuel filter. But we're talking gas here, and I go through about a tank of gas a week in both cars, so it isn't sitting long enough for anything to precipitate out. |
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| squaw_ski_bum |
quote:
Originally posted by NewMDXOwner
Come on bum! Do you really think the velocity caused by the pump suction would be enough to drag any sediment collected at the bottom into the fuel line, even if the pickup is at the bottom of the tank? If so, why do we ever have any sediment left in the tank at all?
The situation is like this. Like it or not, you always have craps collected at the bottom of the tank. When you drive a round, fuel will slosh and create surface waves. With a full tank, the waves do not penetrate far enough to dredge up this muck, sort of like the water a few hundred yards from the beach. The waves are there, but the water still looks clean.
Now, when you run the tank to empty, the gas will slosh more, and the wave action of the surface will be enough to mix up all that muck with the gas and that's when the fuel pump will be able to suck it into the fuel line.
Another thing you ought to think about, if you can think at all, is the fact that people in cold weather do not run their gas tank below 1/4 tank in the winter. When they do, they occasionally suck up moisture into their fuel line, and that would freeze causing the car to quit. According to your logic, such a thing could never happen because water is heavier than gasoline and should have been sucked out as soon as it gets in the tank, right?
Next time, perhaps you should think first and laugh later, right?
Nice analogy with the waves, but it doesn't work. Waves are surface energy created by wind over the water. Your point about deep vs. shallow water is correct so far as the ocean goes, but a gas tank is a different situation.
A better analogy would be to take a gallon plastic milk jug that is 1/4 full of milk (a gas tank 1/4 full.) Pour a bunch of chocalate syrup in (junk in your gas) and watch it sink to the bottom. Simulate driving by shaking the jug. Pour yourself a glass of chocolate milk to drink while you contemplate the following thought experiment:
Suppose, for the sake of this thought experiment, that the hypothesis of junk accumulating at the bottom of the fuel tank is correct, and that indeed it is a good idea to not get below 1/4 full or that junk will get sucked up into your fuel pump and filter. What then happens with each successive fillup? Answer: the junk accumulates, and pretty soon you don't dare get below 1/2 full... then 3/4...
As for cold weather, I lived in upstate New York for 5 years, and then New Hampshire for 5 years after that, and while I did freeze my ass off on -40F mornings I never had a frozen fuel line. Over the last 15 years I have spent many winter days in Tahoe, including living through an entire winter with the MDX, and never had frozen fuel lines. So maybe I'm lucky.
Bottom line (or bottom of the fuel tank) is - if you're getting water or junk in your gas, you need to buy gas somewhere else.
Another point, for those who were concerned about failure of the fuel pmp due to running it dry: RTFM. In the MDX, as well as any modern car with an electric fuel pump, the pump will come on for a few seconds (2 in the MDX) to pressurize the fuel lines when the ignition is turned on. The fuel pump will then only run if the engine is running. See page 11-28 in the service manual if you need to see it for yourself. |
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| NewMDXOwner |
quote:
Originally posted by squaw_ski_bum
Nice analogy with the waves, but it doesn't work. Waves are surface energy created by wind over the water. Your point about deep vs. shallow water is correct so far as the ocean goes, but a gas tank is a different situation.
A better analogy would be to take a gallon plastic milk jug that is 1/4 full of milk (a gas tank 1/4 full.) Pour a bunch of chocalate syrup in (junk in your gas) and watch it sink to the bottom. Simulate driving by shaking the jug. Pour yourself a glass of chocolate milk to drink while you contemplate the following thought experiment:
Suppose, for the sake of this thought experiment, that the hypothesis of junk accumulating at the bottom of the fuel tank is correct, and that indeed it is a good idea to not get below 1/4 full or that junk will get sucked up into your fuel pump and filter. What then happens with each successive fillup? Answer: the junk accumulates, and pretty soon you don't dare get below 1/2 full... then 3/4...
As for cold weather, I lived in upstate New York for 5 years, and then New Hampshire for 5 years after that, and while I did freeze my ass off on -40F mornings I never had a frozen fuel line. Over the last 15 years I have spent many winter days in Tahoe, including living through an entire winter with the MDX, and never had frozen fuel lines. So maybe I'm lucky.
Bottom line (or bottom of the fuel tank) is - if you're getting water or junk in your gas, you need to buy gas somewhere else.
Another point, for those who were concerned about failure of the fuel pmp due to running it dry: RTFM. In the MDX, as well as any modern car with an electric fuel pump, the pump will come on for a few seconds (2 in the MDX) to pressurize the fuel lines when the ignition is turned on. The fuel pump will then only run if the engine is running. See page 11-28 in the service manual if you need to see it for yourself.
Why is there a difference in what caused the waves to happen? Waves are just a result of surface instability, i.e. a tug of war between inertia and surface tension. As such, it has very little to do with the size of the container (that's an answer for Colton too), but everything to do with how deep it is.
Another thing you ought to consider is that the pump is drawing an essentially constant amount of gas for a constant speed. There is definitely a difference in picking up foreign materials if you are drawing it through a 1 foot depth of fuel versus a 2 foot depth.
As for the "the junk accumulates, and pretty soon you don't dare get below 1/2 full... then 3/4..." argument, I don't think that deserves an answer :)
Now comes the real fun RFTM part. To be honest, I don't really want to know what RFTM is, nor do I want to know why people would feel macho throwing 4-letter words in a conversation behind an anonymous handle. :) But enough of that, the key is that "the pump will come on for a few seconds (2 in the MDX) to pressurize the fuel lines when the ignition is turned on" Now what happened when the car is out of gas, and it cannot pressurize the fuel lines just because the gas isn't there? The manual didn't tell me whether the pump would shut off in that case or not. Would you care to speculate or help us read the manual a little more? |
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| G. COLTON |
squaw_ski_bum, I think that you are butting your head against a stone wall here. Obviously you are trying to explain concepts to youngsters who do not have the automotive experience to understand the mechanics of the systems. Also there is a lack of knowledge of physics to be able to understand the actions of waves.
There is really no harm in their beliefs so it is probably best to just forget about explanations.
G |
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| NewMDXOwner |
quote:
Originally posted by G. COLTON
squaw_ski_bum, I think that you are butting your head against a stone wall here. Obviously you are trying to explain concepts to youngsters who do not have the automotive experience to understand the mechanics of the systems. Also there is a lack of knowledge of physics to be able to understand the actions of waves.
There is really no harm in their beliefs so it is probably best to just forget about explanations.
G
Colton:
It's useless for me to explain the law of physics to high school dropouts. So good bye! By the way, my doctoral dissertation was in two-phase flow and instability, just the subject here. Sheesh! What made amateur mechanics think they know everything!!!! |
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| squaw_ski_bum |
NewMDXOwner,
Waves in the ocean are caused by wind over the surface. That's not an accurate analogy to what happens in your gas tank. In your gas tank, the ENTIRE volume of liquid is subject to acceleration in various directions as the car accelerates forward, decelerates, turns corners, etc., not just the surface.
The pump draws a constant amount of gas, period. Engine speed has nothing to do with it. The fuel pressure regulator maintains constant pressure to the injectors and returns any excess to the fuel tank. So while you're sitting there at idle, some of your gas is going around and around from the tank, through the pump, to the regulator in the engine compartment, and back to the tank.
Please explain why, if one shouldn't allow the tank to get below 1/4 full for fear of sucking up accumulated junk at the bottom of the tank, that said junk would not continue to accumulate over time?
RTFM is "Read The Fine Manual" (substitute your favorite adjective starting with F.) Nothing macho about it.
The key to the fuel pump behavior is that it runs for 2 seconds when the ignition is turned on. Since you asked, here's a little more help reading the manual: Quoting from page 11-28 (2001-2002 manual)
"Fuel Pump Control: When the ignition is turned on, the PCM grounds the PGM-FI main relay which feeds current to the fuel pump for 2 seconds to pressurize the fuel system. With the engine running, the PCM grounds the PGM-FI main relay and feeds current to the pump. When the enigne is not running and the ignition is on, the PCM cuts ground to the PGM-FI main relay which cuts current to the fuel pump."
This has two very obvious benefits. One, the fuel pump does not continue to run and wear itself out if it is sucking air or there is no demand for gas. Two, if you are in an accident that damages the engine, the fuel pump doesn't continue to run squirting gas at ~50 psi through potentially broken fuel lines all over a hot engine compartment.
Finally, there's no need to sink to gratuitous insults. The relative anonymnity of the internet tends to bring out the worst in people. You may disagree with me, you may even be right, but you will be far more effective in getting your arguments across if you stick the the facts and leave the name-calling and insults out of it. |
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| NewMDXOwner |
quote:
Originally posted by squaw_ski_bum
Finally, there's no need to sink to gratuitous insults. The relative anonymnity of the internet tends to bring out the worst in people. You may disagree with me, you may even be right, but you will be far more effective in getting your arguments across if you stick the the facts and leave the name-calling and insults out of it.
I agree with you about the etiquette, or lack of it, on the internet. But if you would notice, I wasn't the one who started the insults.
First, I don't think it's appropriate to address people who you don't know as "Dude" in a disrespectful manner.
Second, I don't think it's appropriate, when you don't have a good argument, to start refering to people as "youngsters ..." just because someone here has been "hanging around repair shops." Well, I know a receptionist who hangs around a doctor's office all day. Maybe she can give that person an appendectomy?
If I appeared terse in my reply because of the annoyance I felt, I'm sorry, but I think somebody on this board suffered from an inflated ego that should be cut down to size. |
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| dj-mdx2 |
quote:
Originally posted by dj-mdx2
Why can't we all just get along? Let's stop adding fuel to the fire, since this thread is running on empty, and everybody's getting gassed out. (Puns intended)
Peace!
:20:
Probably not PC, not to mention vain, to quote oneself, but I find my earlier post apropos of the present situation timely and pertinent.
Relax guys and gals! Let's all watch Episode 3 this Thursday and remember to fill 'er up on the way home! :xnuts: |
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| squaw_ski_bum |
quote:
Originally posted by NewMDXOwner
First, I don't think it's appropriate to address people who you don't know as "Dude" in a disrespectful manner.
Dude, I'm from CA where we're all dudes. Except for hte dudettes.
This is a forum where we can all learn from each other if we take the time to listen (figuratively) and stick to presenting our points in a reasoned manner. (But thanks for the support, G. Colton.)
Seriously, if you have a reference to support your arguments, I'd be interested to look it up. It has been a long time since I took Fluid Dynamics. |
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| nightguy |
quote:
Originally posted by squaw_ski_bum
Another point, for those who were concerned about failure of the fuel pump due to running it dry: RTFM. In the MDX, as well as any modern car with an electric fuel pump, the pump will come on for a few seconds (2 in the MDX) to pressurize the fuel lines when the ignition is turned on. The fuel pump will then only run if the engine is running. See page 11-28 in the service manual if you need to see it for yourself.
But ideally the pump is submersed in gasoline for cooling. The brief time it comes on isn't going to hurt anything but to continue to make the pump operate with low gas without cooling or to actually run it dry would be bad.
I don't understand this contamination issue either. Modern fuel is super-refined. There's a filter at the station pump, a screen on the fuel pump intake and an in line fuel filter. I did read about some kind of vandalism recently where it appeared somebody contaminated the gas causing about a dozen cars not to start. But short of that I don't understand where the 'junk' comes from.
The junk in the carburetor was likely caused by varnishing. Most people don't let gas sit around in their tanks long enough anymore for this to happen. Today's refining technology makes it less likely too. We're not talking about a 2 cycle carbureted engine here. :rolleyes: |
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| Sinecure |
Well, this has been an entertaining post to read. I'm kind of pissed off that I had to read 4 pages of posts just to discover that no one has posted what I've learned this weekend (well, Squaw Ski Bum came close - BTW, I ski at Alpine mostly, but same idea and I love Squaw too).
I was at the track with my motorcycle yesterday. Before leaving I filled my tank. When I got near the track I had 1/2 tank but needed to fill my 5 gallon fuel can for use in the bike during the day (gas at the track is very expensive - although you can get 100 octane). I gave the attendant $20 but that was more than enough to fill the 5 gallons so I put a couple of extra gallons in the X after filling the can. At the end of the track day I still had a couple of gallons in the can so I dumped that in the X as well. At that point I had nearly 3/4 tank indicated.
Well, when I got down just below 1/4 tank, I noticed that my computer was reading 0 miles range. Not surprising since I'd travelled over 300 miles on one "tank" if you don't consider my little additions.
So, if you add a small amount of fuel without filling up, I can see how it might get faked out. I'm still driving on the same tank this morning, and I plan to fill up at lunch time. By the time I get to the gas station, my needle will be near the red line and I expect the fuel light will be on (it still wasn't when I arrived at work this morning).
In the past I've found the range computer to be pretty accurate. I've gotten it as low as 7 miles and when I filled up, the car took over 19 gallons (at the time I thought it only held 16 or 17!).
OK, now you can all go back to arguing over sludge, fuel as a coolant, pumps, etc.
Oh, maybe I'll contribute my $0.02. I was always told to be wary of filling up when the fuel truck is at the gas station. When they fill the station's tanks, they disturb the water that sometimes gets into those tanks, mixing it with the gas that you are pumping, thereby increasing the chance of you pumping some water into your tank and fouling your engine. It made sense to me so I don't fill up if the tanker truck is at the station. |
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| ypsimdx |
Being from the wholesale petroleum industry, I can say that it makes little difference if the fuel truck is there or not. Water in the UST is minor, if it is there at all. If you are fueling with branded gasoline, the stations are inspected often enough to make sure there is no water in the tank. Most modern stations have automatic tank gauges that also have water sensors.
I would fill up whenever the price is at our advantage, or whenever you need it. Whichever comes first. |
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| Sinecure |
quote:
Originally posted by ypsimdx
I would fill up whenever the price is at our advantage, or whenever you need it. Whichever comes first.
:2: :eek: I live in the SF Bay Area. Home of some of the most expensive gas in the country. We're paying $2.80 for super right now. If I waited for the price to be at my advantage, as you put it, I'd have to ride my bike to work! :eek: :3: |
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| ardvarkus |
What a waste of bandwidth...
To the original questioen- I have a 2003E39 M5 and a 2001 MDX
The remaining mileage in BOTH vehciles is based on similar algorithms- BMW tracks fuel levels and fuel consumption in L/Hr, converting this to miles remaining. I regularly run it down to zero miles, and past by a few miles. So it is not precise. , no matter what the marketing will have you believe.
The MDX appears to use averag mpg with each fill up- the past mpg sets the total miles and then the present mpg is used to adjust this number as the tank is used.
There IS a way on all MDXs to adjust an offset to this number - nav and touring. (Someone else commented on this, but by that time the blood was in the water and the participants lost intrerest) Do a search. The factory setting is very conservative and will leave your 20 -30 miles after you hit zero. Adjust it down if it bothers you.
On the M5 I can have, say 20 miles left when crusing on the freeway- but once I get on surface streets and my mpg drops, the miles quickly drop. It can go from 20 to 0 in less than 10 miles. The acura system seems much more 'damped' but then again an M5 can get 9mpg or 21mpg...the mdx cannot change consumption that much.
Back to your regularly scheduled pissing match..
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