Printable Version of Topic
Click here to view this topic in its original format
914World.com _ 914World Garage _ WHY? does my 911&914 rune better with 1/4 tank
Posted by: yellow914 May 9 2008, 12:23 AM
I noticed when I had a 74 carrera 2.7 that at about 1/4 tank I'd get more H.P.'s and now that I have a 75 1.8 914 I get the same thing way better throttle response??? I doubt it's due to weight...any ideas?
Posted by: jkeyzer May 9 2008, 12:45 AM
The gravitational pull of the fuel in the tank counteracts the torque of the engine when the tank is full. At less than half a tank, the effect is reversed. The net effect is that with a nearly empty tank, the fuel is actually accelerated into the engine, like a tiny turbocharger inside your fuel pump.
Posted by: yellow914 May 9 2008, 12:50 AM
The gravitational pull of the fuel in the tank counteracts the torque of the engine when the tank is full. At less than half a tank, the effect is reversed. The net effect is that with a nearly empty tank, the fuel is actually accelerated into the engine, like a tiny turbocharger inside your fuel pump.
Awesome!...it was driving me nuts....I noticed like a 20% plus increase!
Posted by: ericread May 9 2008, 03:04 AM
The gravitational pull of the fuel in the tank counteracts the torque of the engine when the tank is full. At less than half a tank, the effect is reversed. The net effect is that with a nearly empty tank, the fuel is actually accelerated into the engine, like a tiny turbocharger inside your fuel pump.
Sooooo, the gravitational pull of the fuel... I have posted some BS remarks before, but this tops the chart! Let's see now, gravitational pull of an object is directly proportional to it's mass. Therefore, the mass of the gasoline would be so significant as to exert it's gravitational pull over the Earth's gravity and other large objects...
A very entertaining explanation, but it just doesn't hold water... er, gas.
Let's see... A gallon of gas weighs about 6 pounds. So a 12 gallon tank would weigh about 72 pounds. For shits and giggles, let's say that the weight of a gallon of gasoline = about 0.45 Kilograms at 60 degrees F (temperature is actually an important variable here). Thus, you have a mass of about (72 pounds times .45) 32.4 Kilograms.
So the 32.4 Kilograms of mass (the gasoline) is interacting with a significant gravitational force. Let's see, the other really big gravitational force is the Earth, which has a Mass of about 6,600,000,000,000,000,000,000 (6.6 sextillion) short tons (6.0 sextillion metric tons), or 6.0 × 1024 kg.
So in a contest of gravitational forces between the Earth and the gas, the Earth clearly wins. In fact, if it were true that there was a significant gravitational pull of objects which have a minor mass, say like a 50 story building, then the gas would be pulled to the building rather than to the engine. In fact we would all be pulled to the building. Bummer.
Nope. But it was fun to dissect. I haven't done this math in about 25 years, since I taught astronomy at a planetarium, so I may be off by a decimal point or so.
But it really doesn't matter, the gravitational pull of non-significant objects (say, smaller than the moon) just don't have any measurable effect, and thus, doesn't asssit in your car's performance.
Let's do this again sometime
Posted by: zymurgist May 9 2008, 05:55 AM
The gravitational pull of the fuel in the tank counteracts the torque of the engine when the tank is full. At less than half a tank, the effect is reversed. The net effect is that with a nearly empty tank, the fuel is actually accelerated into the engine, like a tiny turbocharger inside your fuel pump.
Agreed. Any astronomer will tell you that the more the universe expands, the faster that expansion is occurring. Therefore one can conclude that the emptier the vessel, the faster it goes, so your fuel tank will reach maximum velocity just before yout engine is starved for fuel.
Posted by: SGB May 9 2008, 08:44 AM
The gravitational pull of the fuel in the tank counteracts the torque of the engine when the tank is full. At less than half a tank, the effect is reversed. The net effect is that with a nearly empty tank, the fuel is actually accelerated into the engine, like a tiny turbocharger inside your fuel pump.
Agreed. Any astronomer will tell you that the more the universe expands, the faster that expansion is occurring. Therefore one can conclude that the emptier the vessel, the faster it goes, so your fuel tank will reach maximum velocity just before yout engine is starved for fuel.
Posted by: ericread May 9 2008, 08:58 AM
The gravitational pull of the fuel in the tank counteracts the torque of the engine when the tank is full. At less than half a tank, the effect is reversed. The net effect is that with a nearly empty tank, the fuel is actually accelerated into the engine, like a tiny turbocharger inside your fuel pump.
Oh, I forgot to mention one other thing. Besides the gravitational pull thing, I need to mention the error in the statement "the fuel is actually accelerated into the engine, like a tiny turbocharger inside your fuel pump".
Everybody knows that you can't turbo a 914...
Posted by: DNHunt May 9 2008, 09:15 AM
It seems to me it might have something to do with the choice of measuring instruments. Butt dynos are are notoriously inaccurate. It may be open for discussion but, my opinion is they may vary in the neighborhood of + or - 20%.
Posted by: purple May 9 2008, 09:51 AM
Glad to see the sense of humor is still alive!
probably because gas weighs 8 pounds per gallon. less weight = more speed
Posted by: ericread May 9 2008, 10:00 AM
I absolutely love the term "tiny turbocharger inside your fuel pump"!!!
It gives me visions of tiny exhaust pipes and wastegates!
Whatever it is, I want one!!!
Posted by: ConeDodger May 9 2008, 10:10 AM
You know, Randall recently did an experiment with something like this. He found that the car was definately faster with fuel in it than without. Unfortunately so did the rest of us. 
Posted by: ericread May 9 2008, 10:11 AM
You know, Randall recently did an experiment with something like this. He found that the car was definately faster with fuel in it than without. Unfortunately so did the rest of us.
Posted by: brer May 9 2008, 10:17 AM
Octane settles over time so when you get to the bottom of the tank you get all the juicy bits.
Posted by: ericread May 9 2008, 10:28 AM
Octane settles over time so when you get to the bottom of the tank you get all the juicy bits.
I have optimized my tank so that I only feed my engine from fuel the bottom quarter of the tank. No matter how full the tank is, my engine only receives gas from the bottom quarter. This allows me to always access the juicy Octane bits.
Posted by: purple May 9 2008, 10:30 AM
OMG NO WAY! I DID THAT TOO! We Rock!
Posted by: brer May 9 2008, 10:32 AM
How did you do that?
If someone makes a kit I'm buying.
Posted by: Heeltoe914 May 9 2008, 10:35 AM
The gravitational pull of the fuel in the tank counteracts the torque of the engine when the tank is full. At less than half a tank, the effect is reversed. The net effect is that with a nearly empty tank, the fuel is actually accelerated into the engine, like a tiny turbocharger inside your fuel pump.
Thats deep WOW. good info
Posted by: ericread May 9 2008, 10:44 AM
Let's face it. There are no quick fixes to milage or performance. You have to use the gas magments if you want significant increases.
Posted by: ConeDodger May 9 2008, 11:04 AM
Let's face it. There are no quick fixes to mileage or performance. You have to use the gas magnets if you want significant increases.
Word! (after I made a little spelling correction)
I used one of those turbo devices in my intake once and my stocks went up by 70% I am now a believer. I religiously watch late night and day-time cable to find out the latest innovations. Billy Blanks is a God to me...
I hear the latest is to rub pickle juice on your tires to get more miles out of them. It is an incredible use for something that goes to the sink in most cases. The tire companies don't want you to know that. In fact they will probably buy this website and shut it down to keep this information under wraps...
Posted by: purple May 9 2008, 11:23 AM
Let's face it. There are no quick fixes to mileage or performance. You have to use the gas magnets if you want significant increases.
Word! (after I made a little spelling correction)
I used one of those turbo devices in my intake once and my stocks went up by 70% I am now a believer. I religiously watch late night and day-time cable to find out the latest innovations. Billy Blanks is a God to me...
I hear the latest is to rub pickle juice on your tires to get more miles out of them. It is an incredible use for something that goes to the sink in most cases. The tire companies don't want you to know that. In fact they will probably buy this website and shut it down to keep this information under wraps...
See, my previous owner stapled bacon to my tires before selling the car to me... sadly, all it does is make the tires slippery...
I seriously want to change my forum name from purple to Bacon_Tires now.
Posted by: jkeyzer May 9 2008, 11:34 AM
You know that extra power you get under 1/4 tank? Well think of it this way - if you have a full tank instead, instead of extra power, the ram-fuel effect is minimized and you get lower emissions and extra fuel economy instead.
This is why the Toyota Prius has a fuel bladder - basically no matter how much fuel is in the tank, it is always "full", leading to max mpg!
Posted by: ericread May 9 2008, 12:32 PM
Let's face it. There are no quick fixes to mileage or performance. You have to use the gas magnets if you want significant increases.
Word! (after I made a little spelling correction)
I used one of those turbo devices in my intake once and my stocks went up by 70% I am now a believer. I religiously watch late night and day-time cable to find out the latest innovations. Billy Blanks is a God to me...
I hear the latest is to rub pickle juice on your tires to get more miles out of them. It is an incredible use for something that goes to the sink in most cases. The tire companies don't want you to know that. In fact they will probably buy this website and shut it down to keep this information under wraps...
I agree with all of the above, but why is Billy always yelling at me??? Please make him stop.
As for the pickle juice on the tires, I always save my spare change to purchase high-grade Dill Pickle juice, the best there is!! I call it my Dill Dough...
Posted by: ConeDodger May 9 2008, 01:24 PM
Let's face it. There are no quick fixes to mileage or performance. You have to use the gas magnets if you want significant increases.
Word! (after I made a little spelling correction)
I used one of those turbo devices in my intake once and my stocks went up by 70% I am now a believer. I religiously watch late night and day-time cable to find out the latest innovations. Billy Blanks is a God to me...
I hear the latest is to rub pickle juice on your tires to get more miles out of them. It is an incredible use for something that goes to the sink in most cases. The tire companies don't want you to know that. In fact they will probably buy this website and shut it down to keep this information under wraps...
I agree with all of the above, but why is Billy always yelling at me??? Please make him stop.
As for the pickle juice on the tires, I always save my spare change to purchase high-grade Dill Pickle juice, the best there is!! I call it my Dill Dough...
I love it... It is just so gratifying to me to see a creative mind go to waste.
Posted by: KELTY360 May 9 2008, 01:35 PM
Let's face it. There are no quick fixes to mileage or performance. You have to use the gas magnets if you want significant increases.
Word! (after I made a little spelling correction)
I used one of those turbo devices in my intake once and my stocks went up by 70% I am now a believer. I religiously watch late night and day-time cable to find out the latest innovations. Billy Blanks is a God to me...
I hear the latest is to rub pickle juice on your tires to get more miles out of them. It is an incredible use for something that goes to the sink in most cases. The tire companies don't want you to know that. In fact they will probably buy this website and shut it down to keep this information under wraps...
I agree with all of the above, but why is Billy always yelling at me??? Please make him stop.
As for the pickle juice on the tires, I always save my spare change to purchase high-grade Dill Pickle juice, the best there is!! I call it my Dill Dough...
I love it... It is just so gratifying to me to see a creative mind go to waste.
Reminded me of one of the classics:What a waste it is to lose one's mind. Or not to have a mind is being very wasteful. How true that is.
-- Vice President Dan Quayle winning friends while speaking to the United Negro College Fund, 5/9/89.
Can't go wrong with the Quaylemeister.
Posted by: geniusanthony May 9 2008, 01:40 PM
My theory is this, Your engines (both of them oddly) were jetted too rich. The engines were recieving too much fuel due to the raised fuel level in the tank exerting additional PSI at the pickup in the base. With less fuel in the tank, the pressure in the lines is less, meaning less fuel in the engine. The benefit of lowered pressures is a leaner, hotter mix in the combustion chamber. I want to warn you ALL, do not allow the fuel level to get too low, if you do the engine will become dangerously lean and make expensive sounds. You may notice that it will be running at its best right before it goes boom. In fact, after reviewing all this data, My official recommendation is that none of us drive our cars ever.
Good day to you all.
Posted by: Joe Mama May 9 2008, 02:29 PM
Jeez, where's my foil hemet when I need it most.....
Posted by: DNHunt May 9 2008, 02:44 PM
Jeez, where's my foil hemet when I need it most.....
Probably in the closet with your bunny ears
Dave
Posted by: ConeDodger May 9 2008, 03:50 PM
You know, the last thing you hear with Zois is a grunt, Then the room starts to smell and everything goes black. 
Posted by: KELTY360 May 9 2008, 03:54 PM
You know, the last thing you hear with Zois is a grunt, Then the room starts to smell and everything goes black.
Posted by: bandjoey May 9 2008, 04:04 PM
Hell...You're onto my 2 best kept secrets...I bought welding magnets and attached them to the rear firewall at the fuel line exit to pull the jucy octaine bits back faster (hence tiny turbo charged) and sprayed PickleX juce all under my car for the slipstream effect! Here's the proof. 1+1=2. There. Once again proving Mathimatically the increased effect of 2 extra items for the car. Pass me the bottle please! 
Posted by: kwales May 9 2008, 07:29 PM
You guys got it all wrong...
The real reason that the car runs better is that 3/4 of the tank is filed with an air/moisture mix. The moisture in the air is dissassociated and absorbed into the gas. For each molecule of moisture, the gasoline absorbs two atoms of hydrogen to add tremendous amounts of extra power to the fuel, and a free atom of oxygen to boost the power like squirting in a dose of nitrous oxide......
That's what you are experiencing....
And, if you pee into the tank and drive by Algores house, you can counteract some of his blatant excessive use of electrical energy and pwer (10k a month)used by his home.....
Kenwhoknowsthesethings
Posted by: ericread May 9 2008, 08:40 PM
You guys got it all wrong...
The real reason that the car runs better is that 3/4 of the tank is filed with an air/moisture mix. The moisture in the air is dissassociated and absorbed into the gas. For each molecule of moisture, the gasoline absorbs two atoms of hydrogen to add tremendous amounts of extra power to the fuel, and a free atom of oxygen to boost the power like squirting in a dose of nitrous oxide......
That's what you are experiencing....
And, if you pee into the tank and drive by Algores house, you can counteract some of his blatant excessive use of electrical energy and pwer (10k a month)used by his home.....
Kenwhoknowsthesethings
I am unable to provide any mathematical equations which confirm or deny the above, with one exception:
1 + 1 =
Posted by: porschecb May 9 2008, 09:24 PM
Well I dont think this guy is coming back soon?
Posted by: ericread May 9 2008, 09:29 PM
Posted by: Slider May 9 2008, 09:39 PM
you mean that all of this isnt true??
ohh man there goes my 5 page essay on improving fuel economy and performance. with bacon and magnets.. darn
Posted by: yellow914 May 9 2008, 09:55 PM
Okay it was an honest question...and no I don't want to buy your bridge! 
I have to admit you guys are very funny....
....
Posted by: ConeDodger May 9 2008, 11:00 PM
Okay it was an honest question...and no I don't want to buy your bridge!
I have to admit you guys are very funny....
....
Sorry... I guess we were having fun at your expense. Welcome to the World! I suspect that your sensation of more HP at 1/4 tank is entirely random and has no correlation.
Posted by: jd74914 May 9 2008, 11:08 PM
If its not your imagination, you may be feeling the effects of less weight in the front. By a 1/4 tank you are probably down 70# from a full tank.
Posted by: ericread May 9 2008, 11:39 PM
Okay it was an honest question...and no I don't want to buy your bridge!
I have to admit you guys are very funny....
....
Sorry... I guess we were having fun at your expense. Welcome to the World! I suspect that your sensation of more HP at 1/4 tank is entirely random and has no correlation.
I already sent you a PM apologizing for our (my) rude behavior, something I attributed to end-of-week rummy-ness. Anyway,
Posted by: LarryR May 10 2008, 12:40 AM
I would say that since the 914 and 911 both have fuel tanks in the front you could get additional lift in the front causing you to plant the rear tires more firmly.
I cant see how this would effect a chassis dyno but I can see how it might give a perceived additional horspower on the street.
I do llike the acceleration due to less weight theory though. 
How about the turbo swirl effect of the gas once there is room for it to move about kind of like a tornado in your fuel tank. All of this force directed towards its outlet ... the fuel line so there is so much force that it compresses and creates a more dense fuel in the line and thus a more compact fuel delivered....
Posted by: yellow914 May 10 2008, 04:46 PM
Hey Guys (and girls)
I took no offense to the replies....believe me I know it's all apart of being in a fraturnity and I'm happy to be here.
By the way I've also filled my tires with Helium waddya all think?...kidding...just kidding..lol.... 
Posted by: Joe Ricard May 10 2008, 05:17 PM
OMG NO WAY! I DID THAT TOO! We Rock!
I pull fuel from the bottom of my tank all the time. Maybe because it is a RACE CAR.
We noticed a handling difference from like 3 gallons of fuel and a little over half tank which is about 8 or 9 gallons.
7 pounds x 5 gallons is 57 pounds on the front of the car. and tossing side to side.
Fill your tires with nitrogen. Fill your car with helium unless you have rust holes (it will escape)
Posted by: vsg914 May 10 2008, 05:46 PM
Uh Joe, 5 gallons at 7 lbs is 35 lbs
Posted by: ConeDodger May 10 2008, 09:10 PM
Hey Guys (and girls)
I took no offense to the replies....believe me I know it's all apart of being in a fraturnity and I'm happy to be here.
By the way I've also filled my tires with Helium waddya all think?...kidding...just kidding..lol....
I just wanted to make sure we had not offended you. It happens. You just witnessed the humor of a bunch of engineers, professors, and innovators who happen to also be 914 enthusiasts. If something doesn't seem to have a logical base we can get off on the humorous lane. Please take no offense.
I think the assertion that your experience is due to the weight of the fuel is possible. I have also been more acutely aware of my engine's performance when my fuel is less than 1/4 tank. I own both a 911 and a 914 and let's face it, the fuel gauge is less than optimally accurate. Just this week my Carrera had its yellow warning light on with 1/2 a tank indicated. I alternated between thinking I should ignore it and stopping finally to fill up. The car sometimes kills when it is cold and I am off throttle. That was it for me. I had to fill it up before driving home. The point is, I was paying very close attention to the performance of my motor because I was worried about running out of gas.
I'm not sure why you have this sensation but it seems to have no logical basis in actual performance advantage. The purpose of having the engine and fuel tank at opposite ends of the car is at least partially balance (and necessity). The assertion that the front end of both is lighter with less fuel while true would require testing to determine a real performance advantage. Even with Joe's Mississippi math!
Posted by: scotty b May 10 2008, 09:25 PM
Pay no attention to the class clowns. You will find the answer you seek in
Mayonaisse
Posted by: Pat Garvey May 10 2008, 09:38 PM
Pay no attention to the class clowns. You will find the answer you seek in
Mayonaisse
Umm, err - Scotty, there are 2 n's & 1s in your secret substance. That is, unless it's TOTALLY secret, which could be construed as a terrorist compound.
Oh, it's French? You use it on fries? You slather it all over your body & wait for ants? Sorry, didn't realize you used THAT stuff! Never mind.
Pat
Posted by: ericread May 10 2008, 09:41 PM
Pay no attention to the class clowns. You will find the answer you seek in
Mayonaisse
Was that the "Class Clown" or the "Ass Clown"?
On another note, I fear we are going to need to have a class on "Conversational Mathematics". It appears that due to a limitation of appendages, most of our board members cannot count to over 21.
Posted by: Pat Garvey May 10 2008, 09:47 PM
[quote name='ericread' date='May 10 2008, 09:41 PM' post='1030557']
--><div class='quotetop'>QUOTE(scotty b @ May 10 2008, 08:25 PM) </div><div class='quotemain'><!--quotec-->
Pay no attention to the class clowns. You will find the answer you seek in
Mayonaisse
[/quote]
Was that the "Class Clown" or the "Ass Clown"?
On another note, I fear we are going to need to have a class on "Conversational Mathematics". It appears that due to a limitation of appendages, most of our board members cannot count to over 21.
[/quote]
I can go to 22, because I have an extra appendage. Won't admit to where it is, though.
Posted by: scotty b May 10 2008, 10:16 PM
I don't give a rats ass how it's spelled or what you do with it as long as you boycott Miracle Spit
Powered by Invision Power Board (http://www.invisionboard.com)
© Invision Power Services (http://www.invisionpower.com)