New gas = faster bike?

[yogurtpooh]

Hey, why is it that each time I pump new gas, my bike feels and sounds much more responsive? Now, I know you guys are going to think I'm crazy and that it's all in my head, but after a day, the bike returns back to it's "bogged" down state. With new gas, the RPMs climb effortlessly and feels way more responsive. My bike is around 17,000 miles or so. I only commute about 5 miles or less most days total, and most of the time, it's only in third or fourth gear because I'm in Vietnam, and most roads only allow for 20-30 miles an hour speeds.

Thank you

[alex.s]

nasty gas tank

[Somchai]

Lucas your feeling is right and totally normal, because since the gas is stored underground it's colder than the environment and cold gas gives higher energy or just say more power.

[cuong-nutz]

Poor gas vent?

[micoulisninja]

when I want some "natural" extra performance I put a whole gas tank in the fridge for 4 hours at least and for the next 15' I get better throttle response and quicker revving without any gas boosters or any other tricks... when temps here get to 35deg C or more it makes a huge difference...that's why I have two gas tanks lol

I 've seen greek tuners on the dragstrips use dry ice around the plenum and gas tank of turbo busas and claim that this can make a winner...
I think that gas also loses some of its octane grading with time so it is good to always have fresh gas in the tank... if it takes you 2 weeks to empty a tank it is impossible to have well burning gas during the second week...

[Lemonfresh]

Cold gas is denser gas. Denser gas has more energy per unit volume. Cooling off the gas before running it will create potential for more power.

OP you are probably feeling the effects of cool gas. You can always test this theory. Fill up a tank with fresh gas, let it sit in the sun and warm up and go for a ride. Drain the tank, hit up the gas station again and see how it runs with cooler gas.

Originally Posted by micoulisninja

I think that gas also loses some of its octane grading with time so it is good to always have fresh gas in the tank... if it takes you 2 weeks to empty a tank it is impossible to have well burning gas during the second week...

Octane has nothing to do with the energy content of gas. There are different grades of gas with different octane levels to prevent pre-ignition in high compression engines. Higher octane ratings raise the ignition point of the fuel/air mixture and nothing more.

I'm not sure about the gas in Greece, but here in the US we have 10% ethanol in the gas. Ethanol is hygroscopic and will absorb moisture from the air. Adding water to your fuel will not increase the energy density. If left to sit, ethanol will coat the fuel system with a nasty film and if left long enough solid clumps will form and plug the fuel system. This will definitely hinder the performance of your motorcycle. These are both good reasons to use a fuel stabilizer if your bike will be sitting or a great excuse to ride your bike more often.

[ninja250r81]

Does your fuel tank sound like a "cat meowing" when the bike has been ridden or in the shade??

If it does that's good, it means that the breather on the side of the tank is releasing the vacuum in the tank.

If not the fuel lines to and from the carbs and the breather need changing, something is blocked.

Cold fuel more power, only in a testing lab.

Realalistically, no real change becasue the engine is hot, the small amount of fuel that is passed to the carbertuer will warm up by the heat of the engine, even when you have coolant lines running through the carbs at operating temps 80-90 deg Celsius.

And that small amount will not increase power by a measurable amount.

Hot fuel, cold air :-)

[micoulisninja]

Originally Posted by ninja250r81

Realalistically, no real change becasue the engine is hot, the small amount of fuel that is passed to the carbertuer will warm up by the heat of the engine, even when you have coolant lines running through the carbs at operating temps 80-90 deg Celsius.

And that small amount will not increase power by a measurable amount.

Hot fuel, cold air :-)

Thankfully, European FI engines deliver differently and get hugely affected by that factor...power gains are non-existent to minor but response and revving get boosted...of course besides cold fuel, there are other tricks to keep engine heat away until the very last moment before fuel igniting in the chamber...