Caffeinated21

You can't get energy from nowhere. There is a certain amount of energy required to get to a certain speed, specifically, one half of the mass times the velocity squared. Add to this engine tire friction, wind resistance, and, finally, driveline friction, and you have the amount of energy it takes to get to a certain speed. So, if u want to use less gas, you can A. lighten the car. B. make the car more aerodynamic, C.) get low rolling resistance tires, or D.) lower the internal friction of the engine by, namely, lowering the revs. in THEORY, if you had aftermarket gears you could get similar gas mileage at low speeds by shifting at extremely low RPMS and getting into 5th or 6th gear quickly, but i dont think that is the case here. IF you don't get this explaination, i give up. Go sign up for a physics class at the local JC, or, shit, email a physics prof. and ask them to explain.

PilotKD

You're the moron. More air = more fuel.

Go ride a ten speed bike in a high gear (lower gear ratio) and tell me how your legs feel while trying to accelerate. With a higher ratio you use less energy to accelerate.

I think you need to do some reading on manners.

Caffeinated21

You're anecdotes about a ten speed bike really have alot to do with a car...because, don't u know, human muscles work just like car engines! A guess ill try once more...full throttle at say 2000rpm lets less air into the engine than say, hald throttle at 6000. YOu could consider throttle openning as a percentage of the max power obtainable in whatever gear. Once again, if your making decisions on what makes a car more efficient based on how u ride a bike, you're a moron...

Wisconsin S2k

[QUOTE=Warren J. Dew,Apr 19 2005, 05:37 PM] He could also be shifting earlier.

Wisconsin S2k

when you open the throttle more (ITB) your car introduces more fuel to compensate for the increased air you are letting in, otherwise your mixture would become too lean. this is proven by the fact that at idle, your air/fuel ratio is around 16:1. start to accelerate under load, and that drops to as rich as 12:1. Obviously from this information, if we were pressing the throttle more, that extra air MUST be compensated for by more fuel.

And caffeinated, I'm going to ask you to stop calling people morons and making childish remarks. It won't be tolerated any further in this thread. If you won't contribute in a mature manner, then remove yourself from the conversation.

CrazyPhuD

Okay....so let's remember the simplest answer is often the correct one here....and this one is pretty simple.

Fact.....every time there is a combustion in a cylinder you use gas.
Fact.....more revolutions in a give time frame = more combustions by the engine.
Fact.....Higher gear ratios will result in a higher RPM at a given speed...

Well if these three things are true then how can anyone get better gas milage with shorter gears?
Well part is perception...one knock on the S2k is that you need to rev it have any real power, with shorter gears you feel like you have more power at lower RPMs this may mean that you don't feel the need to rev as high to get the power you want. Also you have more gears(except once you're in sixth). Where you may have been at the top of third at a given speed now you may be at the bottom of fourth. I believe that were you to actually measure it, you would find that with a gear change you the average RPM has gone down for city driving which allows you to be more fuel efficient in the city. The Highway average RPM will go up however causing a loss of MPG for highway use. Given prior reported MPG estimates from gear changes this is consistent with existing data.

The primary concerns with weight, rolling resistance and drag are not related to making the engine more efficient and thus improving fuel economy. Instead by decreasing weight, drag, and rolling resistance, you decrease the amount of power that you need to accelerate and maintain speed. This reduction in power requirements allows for a smaller more fuel efficient engine to be used. This is where you gain the most from reducing weight, rolling resistance and drag, not in making the engine operate more 'efficiently'.

jyeung528

^
exactly, lets say u cruise at 40mph in city.

with stock gearing you would shift as follows:

1st gear, rev up to 4rpm, get to about 12mph...Shift to 2nd
2nd gear, rev up to 4rpm, get to about 27mph...Shift to 3rd
3rd gear, rev up to 4rpm, get to about 40mph. done.

with aftermarket gear, (estimated numbers since i don't have aftermarket gearing) you would shift as follows:

1st gear, rev up to 4rpm, get to about 10 mph...Shift to 2nd
2nd gear, rev up to 4rpm, get to about 22 mph...Shift to 3rd
3rd gear, rev up to 4rpm, get to about 33 mph...Shift to 4th
4th gear, rev up to 3rpm, get to 40 mph. done.

gas is saved!!!

however, go on highway, and its worse for aftermarket gearing, however, like i said before, average gas mileage isn't mainly attributable to average mpg on the highway, rather it is mainly determined by the amount of gas consumed to get the car up to speed from a STOP, as this is when the car expends the most gas...thus controlling this would be the biggest factor in increasing gas mileage.

jyeung528

^
actually, that example doesn't tell the whole picture.

the amount of rev's doesn't tell the whole story.

when you go DOWNHILL, you are definately saving gas, however, ur RPM's still climb UP.

The reason why you save gas with aftermarket gears in the city, is because driving with higher gear ratio is like DRIVING DOWNHILL. ur revs still CLIMB, but there is less effort to get the car rolling. thats it.

YellowS2kPwr

I do something like:


1st gear, rev up to 4rpm, get to about 10 mph...Shift to 2nd
2nd gear, rev up to 3rpm, get to about 16 mph...Shift to 3rd
3rd gear, rev up to 4rpm, get to about 30 mph...Shift to 4th
4th gear, rev up to 3rpm, get to 40 mph. shift to 5th

And still get 16 mpg

CrazyPhuD

^^^^ checked your air filter lately?

Also for the down hill issue...that a throttle imput issue, either the ECU registers less throttle = less gas or the MAP sensor notices less Airmass = less gas.

If gears make you lighter on the throttle then that can also potentially save you gas. It wouldn't me