EcoModding for Beginners: Getting great gas mileage.

[Hasbro]

Originally Posted by aerohead

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.

My 04 Civic Si has the same i-vtec motor as the RSX except the RSX has a different dual intake runner. While the Si has a higher hp. top end of 160 vs. 155, the RSX has 141 ft-lb of torque vs. 132. All the "tuners" want the Si's manifold...

[Daox]

Originally Posted by petty

Got done several modifications but I was expecting more results after this.

Well, if it were incredibly easy, the manufacturers would have done it already.

[Unforgiven]

For what its worth... I see a couple of comments in here about how having more airflow into the compression chamber would hurt fuel economy rather than help it. For me, a K&N air filter did improve my economy during light acceleration. I believe this was a simple 2mpg gain for my vehicle, but dont have hard data on it. Just basic fuel economy from tank to tank numbers. Now on the flip side, if I do stick my foot into the floor (grins most wickedly) then I do lose a bit of mpg... but oh the rush...(coughs and tries to not show too much red). As a final side, K&N does claim better fuel economy with their filters. I wager there are others out there that also make that claim.

[slurp812]

Originally Posted by Hasbro

My 04 Civic Si has the same i-vtec motor as the RSX except the RSX has a different dual intake runner. While the Si has a higher hp. top end of 160 vs. 155, the RSX has 141 ft-lb of torque vs. 132. All the "tuners" want the Si's manifold...

Really??? I bet that RSX intake runner would give our EP3's a little better mileage. I could use the extra low end.

[Hasbro]

Originally Posted by slurp812

Really??? I bet that RSX intake runner would give our EP3's a little better mileage. I could use the extra low end.

That's what I was thinking. The top engine builder on an EP3 forum disagrees but didn't state the reason. They build for performance, though, so I'm not convinced that he is correct.
ephatch.com forum

[e1982]

Originally Posted by jcantara

Here's what I've learned / thought about regarding this:
On a normal gasoline engine, increasing the efficiency of the intake/exhaust is going to have limited success (if any) with MPG improvement. The reason why is because of the way gasoline engines work: The ECU (or carburetor) in a very simplified form, just tries to inject the appropriate amount of fuel for the measured amount of incoming air, usually 14:1 ratio of air:fuel. If you increase the efficiency of the intake, that would allow more air into the engine, and more fuel, and make more power, and you'd accelerate. However... you may just want to cruise, so you close the throttle a little bit to compensate and... all your efficiencies from improving the intake go out the window, because the throttle body is (by design and operation) a restriction, and inefficient. This is one of the main reasons why diesels do so well, no throttle plate. If you improve the path of the intake, you end up having to compensate out the improvement with the throttle any, because you would accelerate too fast otherwise. Any improvements seen from optimizing the intake/exhaust are probably more happenstance and involve running slightly leaner, because the ECU (or carburetor) are injecting slightly less fuel due to one reason or another.

These are just my thoughts and opinions and real-world observations. Feel free to disagree

I am from england and i was looking at your site to see if i could pick up any further tips on fuel economy, when i came across this thread, which i noticed a lot of common mistakes to do with internal combustion operation and principles. i once was on a site that claimed remmaps port polishing freeflow exhausts to name a few would not increase horsepower because the amount of air in the cylinder has not altered (excl turbos of course). first mistake an induction kit allows more air into the engine causing the ECU to administer more petrol FALSE (unless it is exhuast charged ie turbo or a supercharger) a racing filter or induction kit allows the engine to breath without being restrained by a small filter and intake box thus releasing hp, a throttle body is a restriant TRUE for carbuerretors False for EFI becuase the petrol and air is mixed in the cylinders not the intake manifold, has any of you seen a cat conv internals i have its a maze of metal guaze one over the other thats were you lose quite alot of power try this yourself put a thick material over your mouth and try to breath through it and then youll know what the cats doing to your engine like you lot say uneccesary strain on the engine causes loss of power and mpg if you actually to the cat off your car you wouldnt need to do any EOC, who thought of that must be retarded turning the engine off while your in motion you lot might be able to get away with it on your roads (straight wide) try doing that in about 80% of places in england and your gonna get had off probably with your life ie no abs no power steering no vacuum on master brake cylinder (may aswell bite brake disk with teeth). and one last thing have you ever noticed that on a winters morning when you turn the a/c on that the revs arent as high as usual this is becuase the air is colder thus more dense which inturn has more oxygen per litre so the car produces more hp on the same amount of petrol than it does on a summers day.

its good to see you americans starting to think about the enviroment also try to get obama to sign upto the world wide pollution treaty george bush was being an a**ehole about it and one last thing push him for a national health service we have one the amount of money your countrys got and you have to pay for medical treatment thanks for reading this post

all regards

[Eznoobpwned]

I thought the point of a Cold-Air Intake (CAI) was that cold air is denser, of course, so it expands more (pre-ignition density to post-ignition density change/ratio) when heated (say by the burning of fuel) and also increases the mass of the air expanding. I will admit I have no idea on the exact equation or the numbers involved, though the concept is fairly solid. For the sake of explanation, I will throw some bogus numbers out there:
Let's pretend that air expands 10% per 10 degrees C raised. Let's also pretend that fuel igniting in a cylinder burns at 500C. It's a nice mild day at exactly 10C (50F).

"John's" car has a WAI system pulling 100C air off from around his exhaust manifold, giving a 400C temperature change. If I'm thinking the math right, that gives a 44:1 expansion ratio {400 degree change = 40*(10C increases)*1.1 [AKA 10% increase] = 44} Does that sound right?

"Jane's" car has a CAI system pulling outside 10C air in, giving a 490C temperature change or a 53.9:1 expansion ratio. {490 degree change = 49*(10C increases)*1.1 [AKA 10% increase] = 53.9}.

Like I mentioned earlier, there is also the increased air mass / volume ratio of a CAI over a WAI. Doesn't a cars computer measure the volume (L or Cu. Inches) of air going past the intake not the mass (kg/L or Lbs/Cu. Inch)?

As for the atomizing/vaporization of fuel, the inside of the cylinder is hot as hell after only a very short time once the engine has started. Except for those first seconds to minutes (depending on conditions/fuel systems/engine types) after starting a cold vehicle, a WAI's benefits are lost. My dad's old carbed Toyota Pickup ('85 I believe) has a "Warm Air Return" or something along those lines which is something of a hybrid WAI/CAI system. When the engine is cold, a thermostat closes the main intake and opens the WAR/WAI section to allow the engine to warm up quicker and helps atomize the fuel in the carb. Once the engine is warm, which in turn warms up the carb, the thermostat opens the main intake/CAI system again and closes the WAR/WAI system off.

[Andyman]

There is a thermodynamic formula for gases that some of you might like to know. You can read about it in physics books or some places on the web. It is called the ideal gas law. Here is one place to learn more about thermodynamics:

Thermodynamics - Wikipedia, the free encyclopedia

Here is the ideal gas law:

PV=nRT

P: pressure
V: volume
n: number of molecules (related to the mass of a gas)
R: a gas constant
T: absolute temperature in degrees Kelvin

If the absolute temperature of an ideal gas doubles while the volume stays constant, the pressure will double. If the absolute temperature doubles while the pressure stays constant, the volume will double. In an engine, the pressure of the gas trapped in a cylinder is raised about three to four times when the gasoline burns. It might go from 180 PSI absolute pressure to about 630 PSI when the piston is near the cylinder head. I guess the absolute temperature goes up about three to four times also. There may be changes in the n factor (number of molecules) during combustion because of chemical reactions. The fuel mixture is not an ideal gas but most gases behave reasonably similar to an ideal gas.

It's not clear what intake air temperature is best. A higher temperature reduces pumping loss by requiring a larger throttle opening for the same power. It also increases the speed of combustion. On the other hand, a higher air temperature will increase heat lost to the engine. I suspect that the best temperature may be higher during light loads than at heavy loads. I know that old thermostatically controlled air cleaners would deliver cool air to the engine at full throttle but that may have been to help power instead of fuel economy. If the engine uses water injection, the best temperature might be higher than if it doesn't. I think that testing an engine's efficiency is the best way to determine what air temperature works best. It may not be the same for all engines.

The pressure increase is greater when the fuel mixture is colder, so power is increased. Fuel used is also greater because of increased density of cold air. There is a formula to calculate the theoretical efficiency of an Otto (gasoline) engine. It says that the efficiency can be calculated from the compression ratio. The air temperature is not in the formula. You can read about the formula here:

The Otto Cycle: Compression Ratio vs. Efficiency

It includes a chart. It shows the theoretical efficiency would be 50% with a compression ratio of about 5.7. It would reach 60% with a compression ratio of 10. The actual efficiency is less because of many factors that cause energy losses.

[resultkk]

current global economy should be getting rectified soon. these informations are highly recommended.

[slurp812]

Originally Posted by Hasbro

That's what I was thinking. The top engine builder on an EP3 forum disagrees but didn't state the reason. They build for performance, though, so I'm not convinced that he is correct.
ephatch.com forum

Well, I bet they don't shift at 2500 RMPs like I do! I don't doubt its faster the way it is.