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Old 07-16-2008, 03:42 PM   #31 (permalink)
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[Traffic/mpg]

*Stop-and-go driving consumes up to 100% more fuel than highway driving.------------------------------------ *Fluctuating between say 40 mph(64 km/h) and 45-mph(72 km/h),can cost you 1 mpg.----------------------------------- Best economy is achieved around 35-40 mph ( 56-64 km/h ).--------------------------------- *It takes six(6) times more fuel to accelerate a car up to the posted speed limit from a dead stop,than it does from as little as 3 mph (5 km/h ).--------------------------------------- * Compared to a 40-mile trip(64 km ),a 4-mile trip (6.5 km) will cost you 40% in mpg.---------------------------------------- a 2-mile trip (3.2 km) will cost you 55% mpg.------------------------------ A 1-mile trip ( 1.6 km) will cost you 75% mpg.

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Old 07-16-2008, 04:02 PM   #32 (permalink)
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[Weight/mpg]

There is great variability in relationships published for weight,as with respect to its influence on mpg.Published research reflects "averages" for the time in which the research was conducted and results published.------------------------------------- I would place a very high confidence in the work of Gino Sovran,with General Motors Research Labs in the 1980s.-------------------------------------------------- For an intermediate- sized car of 1279 kg (2,813-lbs),Cd 0.45,Af 1.98 m squared, a 10% reduction in weight,was good for an average 4.51% improvement in mpg.Urban mpg would see the greatest benefit.Highway mpg would see the least benefit as I'll illustrate in the following example.----------------------------------- In the early 1990s,I added 1,300-lbs(a 65 % weight increase) ( 590 kg ) to my CRX,and it only reduced highway mileage by less than 4%,dropping from 52,to 50-mpg.
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Old 07-24-2008, 11:14 PM   #33 (permalink)
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Increase intake runners

Just wondering if increasing the intake runners will
have increase in fuel efficiency?

Not directly but indirectly by increasing low end
torque. Say by installing spaces between the throttle body
and the engine block?

Any thoughts?
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Old 07-24-2008, 11:59 PM   #34 (permalink)
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Quote:
Originally Posted by jamesw View Post
Just wondering if increasing the intake runners will
have increase in fuel efficiency?

Not directly but indirectly by increasing low end
torque. Say by installing spaces between the throttle body
and the engine block?

Any thoughts?
I don't think this would help unless it allows you to use a higher gear much more than you do now.

Some things that are likely to improve engine efficiency:
1) increase the compression ratio
2) use a heat barrier coating on pistons and combustion chambers
3) retard the camshaft a few degrees (but lose some torque)
4) optimize the ignition timing
5) raise the thermostat temperature
6) install zero gap piston rings (like Total Seal)
7) install a water injection system to add water at high loads
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Old 07-25-2008, 01:40 PM   #35 (permalink)
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spacing

Quote:
Originally Posted by jamesw View Post
Just wondering if increasing the intake runners will
have increase in fuel efficiency?

Not directly but indirectly by increasing low end
torque. Say by installing spaces between the throttle body
and the engine block?

Any thoughts?
I'm no engine guy.I've read a bunch of stuff.I think the root of your question comes down to the one-size-fits-all conundrum.If you go for low end,you loose top end.The transient regimes an engine is asked to operate within,seems to require trade-offs somewhere.You may have read of variable-length intake runners,which switch between two separate intake manifolds,depending upon a prompt from some fly-by-wire gizmo.It's an attempt to deliver "both worlds".I think economics constrains the engine designer,as the bottom line is always in sharp focus,and everyone does the best they can within the budget constraints for a particular model.I'm still focussed on load reduction and trying to keep the engine I've got in it's "sweet-spot." I may get under the hood one day,however my confidence in out-smarting a powerplant engineer, for performance and driveability in the real world is weak at best.For the rpm band modern engines perform at during cruise,I think the volumetric efficiency is good overall.You might want to think in terms of maintaining the best brake-specific-fuel-consumption(BSFC)for your existing setup as your target.Engines are a lot like algebra.Whatever you do to one side of the equation,you've got to do the the other.Engines are really complicated.I'll shut up.No doubt other,better qualified members will jump in on this one.If you've got access to a dyno,you'll be in a position to know about mods in a controlled environment.Short of that,it's going to take a lot of patience and time to figure out what your changes are doing.Best to you on the project.
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Old 07-29-2008, 10:31 PM   #36 (permalink)
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Quote:
Originally Posted by i_am_socket View Post
My girlfriend was complaining this weekend that I was driving "like a little old lady" doing just that in her car.

"So you don't want me to save you gas and money?"
"No, I want to get there."
"We'd get there in just about the same time with traffic and lights."
"I don't care, you're driving me crazy."

Yeah.
You are nicer than me, I would have let her walk!
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Old 07-30-2008, 07:47 AM   #37 (permalink)
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Aerohead, I think
u r right.

Read up a bit more about the length & tuning em. If we simply lengthen
the intakes, it could mess up the resonance. Seems like best mods
are still aero mods.
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Old 09-06-2008, 10:32 PM   #38 (permalink)
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Quote:
Originally Posted by spyderbite9001 View Post
Sorry to burst ur bubble man, but your looking at the wrong equation. For air resistance yes, it is a function of the square of your velocity (v^2) however, when we talk about gas mileage we should be more concerned with the power req'd to gain/maintain the objective velocity. To calculate the req'd force or power we look at the equation

Power = Force Drag * V supposing that
Force Drag = (1/2)*density fluid*(v^3)*area*drag coefficient

and therefore the growth in power needed, which directly translates to gas mileage, is in fact, exponential.

Reference: Drag (physics) - Wikipedia, the free encyclopedia
No, sorry. Fuel mileage is "distance/fuel." This is distance/energy as far as we are concerned, since fuel is energy for us. Invert this for energy/distance. Then notice that energy is equivalent to work. This leads to work/distance. Work is force*distance, so now we have (force*distance)/distance or force. Therefore, mileage is proportional to the inverse of force. Air drag force is proportional to the square of speed, so mileage is a function of the inverse of the square of speed.

Besides, what you have for power (which is correct by the way) is still not exponential, it's just a power function with a different power, 3 instead of 2. If it were exponential, it would increase as a fixed number raised to the power of speed.

You're missing the fact that while power required to overcome aerodynamic drag does increase with the cube of speed, distance covered increases with the first power of speed, so energy required to overcome aerodynamic drag to cover distance increases with the square of speed.

Last edited by PA32R; 09-06-2008 at 10:58 PM..
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Old 09-06-2008, 11:43 PM   #39 (permalink)
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Aerohead, modern CTV's have improved greatly. My wife drives a Honda Jazz/Fitt ctv and it is rated at beeter FE than the manual, and is smooth as.
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Old 09-11-2008, 11:32 PM   #40 (permalink)
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Quote:
Originally Posted by SVOboy View Post
Section 4: Modify your vehicle
Vehicle modifications are some of the most difficult and hardest to quantify changes you can make. Some of them are great, others might seem like more effort than they are worth, and some will be just too hard to do. Pick and choose.

3 - Increase tire pressure
This is one of the easiest ways to increase mileage. I currently have my 44 max psi tired inflated to 50 psi. This doesn't mean that you should do it, but it has been done by many people. When overinflating, inflate a bit at a time to test handling and feel before you settle somewhere comfortable. Be prepared for a bit rougher of a ride, but you will see the fuel economy increase!

There is also the possibility of running a solar car battery charger, though I haven't heard of anyone experimenting with this yet. Make sure to only remove the belt in case you need to reattach it at some point to deal with rain or darkness!
This article delivers great pieces of information. I am actually planning on increasing the mileage of my car. Got done several modifications but I was expecting more results after this.

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