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?

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!

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

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.

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...

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%.

Glad to see the sense of humor is still alive!

probably because gas weighs 8 pounds per gallon. less weight = more speed

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!!!

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.

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.

OMG NO WAY! I DID THAT TOO! We Rock!

How did you do that?
If someone makes a kit I'm buying.

Thats deep WOW. good info

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.

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.

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!

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.

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.

Jeez, where's my foil hemet when I need it most.....

Probably in the closet with your bunny ears

Dave

You know, the last thing you hear with Zois is a grunt, Then the room starts to smell and everything goes black.

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!

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 =

Well I dont think this guy is coming back soon?

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

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.

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.

I already sent you a PM apologizing for our (my) rude behavior, something I attributed to end-of-week rummy-ness. Anyway,

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....

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 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)

Uh Joe, 5 gallons at 7 lbs is 35 lbs

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!

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

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 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.

I don't give a rats ass how it's spelled or what you do with it as long as you boycott Miracle Spit