EcoModding for Beginners: Getting great gas mileage.
 

This is an article from my website, www.crxmpg.com, which discusses some of the most basic ways to get better mileage. Certainly you can't do it all, but you can

So, what is EcoModding?
The term hasn't been around for too long, but it basically means changing your car or your habits to squeeze the most efficiency out of it, whether it's for the environment or saving a few dollars.

How does one EcoMod their car?
Well, it's really not all that difficult. The range of EcoModding techniques are quite wide, from easy to very difficult. I'm hoping to address them all, but with the emphasis on the safest and easiest. I will also concentrate on some general tips to help people save gas. EcoModding your car isn't always the best way to reduce consumption, sometimes lifestyle changes end up in everyone's favor.

Why should I do it?
There are many reasons that EcoModders do their thing: fun, challenge, environmentalism, and thrift. Depending on the type you are, you will find yourself gravitating to certain groups of techniques. I myself am an environmentalist, so you will see that showing up, be warned!

I will organize this as best as I can, but it may get a little confusing. Please bear with me and feel free to email if you find something amiss.

Section 1: Drive Less
I put this section first because it is the best way to reduce your gas consumption. If this isn't an option, skip on down, but I think it's well worth a look for everyone.

1 - Live closer to work
Living near your job will not only reduce your gas consumption, but will reduce stress, be safer, and give you more free time. If you're spending 10 hours a week commuting, consider a change.

2 - Carpool
Carpooling will not only reduce consumption, but will reduce vehicle wear and tear, saving you a lot of money overall. Carpooling reduces road congestion, and really isn't all that bad. Make a friend at work and commute together, it'll be nice not to have to drive all the time!

3 - Bike
If you live close to work, biking can create entire days when you don't even turn on your car. Even if you don't live close to work, chances are that you live close to something you do. For those short trips to the bank, the post office, etc., consider getting on the old bike and getting a workout. You'll enjoy yourself more and won't be using any gas! Also, keep in mind that short trips are the hardest on your gas mileage. Eliminating all those below-average, around-town trips will boost your mileage without even touching your car.

4 - Combine short trips
You've probably heard this a million times, combining trips will save you gas, simple as that.

Section 2: Change your vehicle
Regardless of how you drive or how much you drive, getting a more economical vehicle will help. Check out the 100 Greenest Cars at Yahoo!

1 - Buy a smaller car
This is usually the cheapest and easiest thing. Think about how much size you really need and how often you actually fill your car to capacity. So what if it's a little squished in the back when you have to haul extra people? That's never hurt anyone in the past. Moving to a smaller vehicle will save you money in just the vehicle cost, let alone the fuel savings. Just make sure your smaller car isn't a sports car!

2 - Buy a hybrid
They're all the rage right now, and for good reason. Honda and Toyota hybrids can regularly dominate their non-hybrid competition. For a bit more money, you get all the comfort of a bigger car and all the economy of a smaller car. Hybrids are generally some of the best cars on the market for pollution and reliability. Don't let the skeptics get you down about battery replacements and pollution, these claims are greatly over blown.

3 - Buy a motorcycle
Though a motorcycle would be difficult to use as a sole means of transportation, small motorcycles such as the Kawasaki Ninja 250 can be had for about 2000 dollars and will return fuel economy great than 75 MPG and great performance. If you do go this route, don't forget your gear and your safety course!

4 - Buy a scooter
Just like number 3, but even better mileage! If you live in the city, this is the perfect solution for a lot of people. Honda currently makes the best scooters out there, and a Honda Metropolitan will return over 100MPG. Just don't buy a 2-stroke and remember the gear and the safety course!

Section 3: Change your driving habits
This is the most important thing you can do when working with an existing vehicle. There are a ton of strategies, but I will try to simplify them to serve as an introduction.

1 - Get instrumentation
The most important thing you can do is get some instant feedback so that you know what's going on with you car. If you are driving an OBD2 vehicle (1996 and up), go to www.scanguage.com and pick yourself up a Scanguage II. You can also find them on ebay for a little cheaper, but they are indispensable. For older, fuel injected cars, check out the MPGuino. It is more limited in terms of compatibility, but very worth it if you are compatible.

2 - Slow down!
Air resistance increases exponentially with speed, so slow down! The difference between 55 and 75 is astronomical.

3 - Plan your route
One of the easiest things to do is choose a better route to work. In many cases, you may find that you use less gas but get lower mileage, or go further but use less gas, depending on which route you pick. This is why tip 1 of this section is important. Check out this article for more information.

4 - Stop idling
When you idle, you are getting 0 MPG. Idling the car in the cold does not help warm it up, it actually takes longer. Just drive gently after starting up.

5 - Avoid rapid acceleration and hard braking
These sort of actions waste gas. Instead of braking hard, coast from as distance. Use your brakes as sparingly as possible. Also, be aware the slamming the gas will only dump more fuel on than is necessary. Conservative acceleration will generally return the best fuel economy.

6 - Anticipate changes in traffic
If you know that a light is going to become read or turn green, slow down in advance and give it time to do so rather than gunning the gas up to the stop. In heavy traffic give yourself a bit of space before starting up, try to keep moving slowing rather than alternating between fast speeds and stops. This is one of the best tips for driving, as it will prevent you from making many unnecessary stops.

7 - EOC (Engine Off Coast)
Engine off coasting is the way to go to increase fuel economy to astronomical amounts. This is very difficult and can be unsafe, so be very careful when using it. Also be aware that long EOCs can reduce catalytic converter heat and increase emissions (though the time period or relative emissions increases are unknown.
Before EOCing, you need to be aware of how your car will preform under the circumstances. The basic drill is to put the car in neutral, turn the engine off, and turn the key back to run (to give you the use of the speedometer as well as the ability to turn the wheel). EOCing will cause you to lose both power steering and power brakes. You will have a limited power brake reserve, but this depends on each car.
For your first EOC, find a deserted road with a long open stretch and then key off, turn to run, and begin coasting. While coasting, test your steering and your brakes. If they do not feel comfortable, don't EOC! You don't want to risk anyone's life in this pursuit. If steering is okay and the brakes work well, you are ready to EOC in normal driving. Just remember to be very alert and not to EOC in environments likely to have unexpected occurrences. Stay safe!

8 - Draft at a distance / use the corridor effect
On the highway you will notice that SUVs & other large vehicles are basically moving walls, pushing all the air out of the way. If you get in behind one, air drag will be cut astronomically. Now, don't get too close, try to leave 100 feet, or else the trucker will become angry and neither of you will be safe. Even at 100 foot drafting has benefits.

The "corridor effect" describes the flow of air that is set up by a flow of fast moving traffic (ie. several lanes of busy freeway traffic). In those conditions, even driving in the right lane with nobody ahead of you traveling your exact speed, you'll see measurable aerodynamic benefits. IE. driving at 55 mph on a deserted road vs. 55 within a flow of traffic, all else being equal the traffic situation will yeild better fuel economy.

9 - Pulse and Glide
P&G is an interesting technique, taken from the hybrid drivers, which involves alternating EOC and acceleration. P&G is most effectively done at slower speeds, where air drag is not as much of an issue. To P&G you pick a target speed (say 40) and accelerate past it (to 50) and EOC until your speed drops (to 30), you then start up again and accelerate back to the upper target. Rinse and repeat for awesome mileage. Note: This is best done when no one is around and is very annoying to keep up!

10 - Driving with load
In hilly terrain, it can kill FE to be constantly gunning it up hills. DWL involves picking a fixed throttle and slowing down up hills and gaining speed down. Rather than holding speed, you are holding the pedal. This is a very affective way to deal with hills, though you often will need to bend the rules to not slow down traffic too much.

11 - Reduce engine loads
High fans, loud stereos, A/C, and heat add load to the engine and reduce fuel economy. It is much better to roll down your windows than to turn on A/C in almost any circumstance, so keep this in mind. A/C can reduce fuel economy 5-30%.

12 - Turn off 4WD
If you can, turn it off when it is not necessary, it increases driveline losses.

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.

1 - Swap the engine
This depends greatly on your mechanical ability. If you can do it, pick out an engine, and throw it in. This is akin to getting a new car and can give you huge boosts in mileage. I won't go in depth, however, because I'll assume that if you know how to do it you can pick out an engine. Perhaps in a later article I will detail the options for Hondas. (Feel free to bug me if you want it done.)

2 - Swap the transmission
Very similar to the above. An auto to manual, like I did, will realize the biggest change. I picked up about 50% on my mileage with this swap. Figure out the gearing on various transmissions and see what suits your needs. You can also swap gears around from within transmission, but then it just gets more complicated! Check out this link for more.

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!

4 - Warm air intake
The WAI will not work for everyone, but it is worth noting because it is a very good mod for Saturn owners. For whatever reason, Saturns really respond to warm air intakes, so take advantage of it of you can. A WAI is generally constructed by extending the stock intake to suck air from closer to the exhaust manifold (where air is warmer). Once again, experiment before you finalize anything.

5 - Block your grill
The air drag caused by the radiator is rather large, so grab that corrugated plastic and block your grill. Be careful to make your first block easily removable and watch the temperature gauge to make sure you don't overheat. It's important to find a balance between cooling and aerodynamics, even a partial block will help.

6 - Rear wheel skirts
These snazzy looking covers will help smooth airflow across the car by closing the rear wheel wells. These are affective, though not mind-blowingly so. A must do for anyone with a lot of highway driving or someone interested in aero mods.

7 - Smooth undertray
Covering the entire bottom of the car with corrugated plastic will reduce air drag caused by the roughest surface on most cars. This mod is difficult mainly because you have to get under the car and work on your back securing everything. If you do this, make sure to leave easy access to oil and anything else you might need to get at normally.

8 - Take off the alternator belt
This is a pretty hardcore thing to do. By removing the alternator belt you disable the alternator and remove all electrical load from the engine. This means that you will be running down the battery constantly, so to do this you need to minimize electrical loads and run a battery charger at home to keep the battery topped off.

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!

Note that deeply & repeatedly discharging a regular starting battery will destroy it in short order. You won't save any money (if that's your goal) in the long run if you have to keep replacing your battery. Only proper deep cycle batteries should be deeply discharged, and you will have to do the math to decide whether or not it's a "paying" proposition in your case.

9 - Replace your radiator fan
If your fan is belt-driven or otherwise inefficient, pick up a new, electric fan to help reduce engine load. This is an especially good modification for those with belt-driven fans, and can save quite a few horsepower.

10 - Remove power steering
For many smaller cars, powering steering is more of a luxury than a necessity. My CRX does not have it and I've always been glad of that fact, it makes me feel more connected to the road to have manual steering. That being said, for cars with power steering there are often ways to disable it or to convert the car to manual steering. Also, electric power steering has become an option in recent years. Power steering is just another one of those little things that will rob you of a few HP here and there.

11 - Boattail
This is further down because it is difficult to do, even if it is good for a lot of improvement. A boattail reduces drag caused by turbulence at the rear of the car, which accounts for a large amount of a car's aero drag. Check out Basjoos' car in the gallery for some interesting ideas.

12 - Low rolling resistance tires
Much like increasing the tire pressure, LRR tires reduce rolling resistance by using a harder rubber material. They are more expensive and harder to find, but keep them in mind next time you're shopping for a car.

New Poster.. Old Trickshttp://www.clicksmilies.com/s1106/grinser/grinning-smiley-003.
 

Hi, this is my first post. I've probably been around a little longer than most so I hope I can be of some interest. I've been looking over your site and I keep seeing "take off the alternator belt" as a "mod" trick. Back in the old days (I can say that cause I was there!) Drag Racing was King and one of the tricks back then was to leave the alternator belt on, but put a switch on the dash so you could turn it off from inside, thus reducing the "drag". Running an alternator that was turned off, as I recall, gave the same result as throwing it away (HP Gain back then)(except for the poundage), was a lot easier to accomplish (what else is on that same drive belt? the water pump?) and it was still there when you needed it! Just thought I'd throw that in. And I think they make elec. water pumps now too don't they? The water pump is a major drag on the engine. Ya kinda need one though. Also, I've been running my tires higher (around 40 to 45 lbs) for years. 1 reason is that I've always seemed plagued with slow air leaks and this sometimes cures them and when it doesn't it keeps me from having to refill the tire as often... BUT it also wears out the centers of the tires quicker. Best to be aware of it before it starts just happening. Another quicky (and cheap!) is opening up the air cleaner housing to allow more air into the engine with less restriction. This is more important when accelerating than when just going down the road, for that it's hard to beat Ram Air. Tuned Headers are my next favorite mod. Tuned ones are actually made to extract the exhaust fumes and $ for $ they're the cheapest way of increasing HP (which used wisely means more mpg). I was once Head mechanic at a Radiator shop. The advertised specs in those days for a radiator fan said the fan has no cooling effect on the radiator at all after 30 mph. Just a thought. I have swapped engines. It may be interesting to some that in 1974, the Chevy Van came out with the 2 barrel carburetor 350 cu in engine and the 4 barrel carburetor 350 engine. The 4 barrel version got better mileage. Sometimes a smaller engine uses MORE fuel. It all depends on the vehicle it's going into. Gotta keep these things in mind when you're planning a major undertaking like an engine swap. Smaller is not always better. I see no mention yet of using taller tires. They can add significant mileage savings on mostly highway driven vehicles. As can changing gear ratios... Don't know how to do this in a front wheel but it sure does work in Rear wheel drive vehicles. I've done the transmission swap thing to! Auto to stick. Major undertaking, congratulations to anyone else who's successfully done it. It was my first real mod on a car (well, I was part of putting a 427 SOHC engine in the back of an old Econoline Pickup Truck before that, but I was only 15 then!) I was 17. Knew a guy once that swore that by putting these big magnets on his upper and lower radiator hose it gave him a big mileage boost... I don't think so! For any head porters out there I think a reversion dam or 2 could possible add to the air/fuel atomization process on anything but a direct injection engine. Timing is done by computer these days, so a proper chip would do wonders too. I wonder if anybody still drills holes in the top of their pistons so that the compression stroke actually puts pressure behind the sealing rings to increase combustion pressure retention anymore? It was only good for Drag cars though cause it gets clogged with carbon pretty fast. Has anyone tried triple angle valve jobs yet? Or is that a thing of the past or regularly done nowadays, I've been off doing other things in my life. And how about "other gas injection"? I've ridden in a couple of nitros cars.... amazing, but couldn't some other "gas" be used to help with say "low end torque"? You know, you could use a taller gear (and taller tires) for the highway if you could replace the torque power lost with some other kind of "gas" that was injected at the proper time and the proper rate (computers are great for that stuff aren't they?). Anyway, just some ramblings from an Old Timer, hope it peaks you interest. I've had thousands of hours of fun working on Cars/trucks/boats/airplanes/motorcycles/bicycles and probably more ...oh yea... lawnmowers (not so much fun there!) and except for the occasional Owie and the Tool Addiction" I've enjoyed the Hell out of it. Have fun! That IS what it's all about. John

It is interesting reading about the contrasting theories of "increased Hp/efficiency results in better mpg" ie less restrictive intake or exhaust, or the "reduced hp = greater throttle opening req'd which reduces pumping losses and results in better mpg" ie warm air intake.

As noted, some of those intake and exhaust mods only work with old school, non computerized engines. Less restriction on intake or exhaust does not always equal better efficiency on modern computer controlled engines.

Do you have an example to back that up?

SVOboy, great write-up!!!

You might want to add...

Section 1: Right after walking or cycling, use transit if available - if we don't embrace it enough to expand it, we're pooched

Section 3 - 7 EOC: You might want to mention precautions for slushboxes

Section 4: Maybe put pumping up tires first and engine swaps much further down the list

Example of what? I was just commenting that there are two ways to approach better mpg. I think they both work.

An example of intake or exhaust modification that works only on carburated vehicles.

I tend to agree with this.

Limiting the intake and reducing the exhaust results in higher MPGs.

If you limit how much the engine can "combust", you reduce your fuel consumption.

I tend to think that increasing airflow to the engine HURTS your mpgs.
Likewise for the exhaust...

Smaller exhaust pipes and thinner wheels == better MPGs :cool:

You must also think of the efficiency of the modifications. If you spend a lot of time and money on minor increases in MPG, and have higher emissions because of it, it's not worth it. I would keep toward the easier modifications and add the more challenging mods as time and money/necessity allows.

I checked out an article on www.crxmpg.com, the one about Acceleration and Fuel Economy (http://www.crxmpg.com/accelmpg.html) and have a comment.

When I hear of a jack rabbit start, I think of someone running to the redline, or banging the gears to the point of barking with each gear change. More like someone interested in a 0-60 time than a 60mpg.

I have tried both methods mentioned in the article and like the "brisk" acceleration technique. Basically, I try to get into top gear as reasonably quickly as I can, without sacrificing other factors, like speeding up just to have to slow down.

Several factors I always keep in mind when driving my truck (5 speed) is to get rolling in first gear, then quickly shift to 2nd. If possible, I prefer to keep rolling, and just start off in 2nd. First gear is the strongest, and therefore, the worst economically. I run 2nd until I can reasonably get into 3rd and and prefer to do a bulk of my acceleration in 3rd, then skip right to 5th.

I appreciated that someone took the time to actually gather some numbers, kudos, SVOBoy.

Though it doesn't change your point, air resistance doesn't increase exponentially with speed: r=ce^(ks), it increases as a power of speed: r=ks^2. Here, r is resistance, c and k constants, s is speed.

Misuse of "exponentially" is a pet peeve of mine, sorry.

I agree!
But nice post SVOboy.
I just don't understand how warmer air can increase efficiency.
However I have not done any research myself.
Since Cold Air Intakes take in denser air, which stuffs more oxygen in the explosion chamber, I guess it the computer puts in more fuel to compensate. Maybe that is why.
There probably is a whole thread on this somewhere, so sorry for not searching. I'll check later.

These mods have the effect of leaning out the mixture on open loop cars because they let more air in. Modern ECUs will match that extra air with extra fuel.

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 agree. My experience proves what you said, you just put it down in words.

My experience with a lower restriction intake ( I have 2 ) is better throttle response, which means improved acceleration. But there is no direct correlation with improved FE, IMO. If anything, it harms FE - at least with the lovely feeling of "right-foot-itis" - the power is fun.

Used wisely, one can briskly reach cruising speed, which can contribute to a FE improvement. Again, wisely using the performance capabilities of a vehicle to best FE advantage.

Here's my thoughts on this one, and it relates to my above post too:
The ECU (or carburetor) will inject an appropriate amount of fuel for any given amount of air (ideally, in real life it varies obviously, but that is the goal). An engine needs X mass of air/fuel to go a certain speed, regardless of the density of the air. If you are using less-dense air (hotter air is less dense) the engine will need the same mass of air to get the same amount of power, so you'll need to have the throttle open more (less restrictive) to compensate and allow in more of the air. There are other reasons why hot air is more efficient for cars, but that is probably the primary contributor.

Carburetors add fuel based on the volume of air that rushes through them, but they don't on their own compensate for air density.

Warm air improves mpg because it promotes fuel atomization and allows for wider throttle openings per desired power.

Carburetors also do not compensate for air restriction. This is where air filter manufacturers pull their claims of improved fuel efficiency. A clogged air filter will cause a carbed car to run pig stinking rich.

An ECU in closed loop mode will maintain a 14.7:1 ratio regardless of how clogged the air filter is (short of total blockage). Whether your throttle plate or a dirty filter is providing manifold vacuum, your engine does not care, and is burning at 14.7:1 regardless.

Thanks for all the WAI feedback.
This warm air thing seems to have no one single answer.
Here is my current summation:
The greater the temp of the air, the lower the density.
Lower density air has less molecules per volume.
Less fuel is needed to keep the 14.7:1 ratio of air to fuel.

Also, the WAI could just be explained away as magic. That is usually my answer in an arithmetic class. Stumps the professor every time . . . :p:D

I will be starting a new thread on the topic of WAI & CAI. Please check it out.

Also as was mentioned by one poster, warm air helps liquid gasoline to atomize, i.e. become a vapor, and only vaporized gasoline burns. To the extent that some of the gas is still liquid at the time of ignition, it is wasted.

My understanding is that there is a delicate balance with any given engine design regarding how warm the intake air should be; warmer for some, cooler for others.

It's simple really, accelerate slowly and cruise around 50 - 60 MPH. That right there should easily save anywhere from 5 - 10 MPG or more depending on how you drove before.

Beyond that is probably a little too much to ask of most people, hell even asking that is like asking someone to loan you a billion dollars, just not going to happen.

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.

Well the simple question is ... do you pay for her gas?

If you do, then drive the way you want. If you don't drive the way she wants, and save money when you drive your car ...

Clairify some facts.
 

I'm a hotrodder from way back. I have 30 engine swaps under my belt as well as 15 complete engine rebuilds and 5 custom intakes designed and welded by me.

1 - bigger air intake makes ZERO difference for anything but WOT at high rpm's. In other words unless you are looking for higher HP at high RPM Wide Open throttle (I.E. BAD gas mileage) this change will do absolutely nothing for getting better gas mileage. Also do NOT waste money on those "high flow" air filters. they will do nothing for your car.

2 - Exhaust headers. Bad idea. Again only good for high rpm WOT horsepower. Exhaust manifold logs with a restriction increase low rpm torque and actually increase gas mileage.

3 - Remove ALTernator belt... Get better gains by adding underdrive pullies to your car. This gives you a greater torque gain by slowing down ALL accessories and giving you a bigger boost than the ALT will.

4 - The electric "superchargers", spiral intake inserts, and other crap that claims increases in gas mileage all are 100% fake. dont buy them. I have a guy locally that has the stupid gas magnets, the gas "catalyst", the spiral intake, a cold air intake, and the electric bilge pump fan "booster" all on his car and he still cant understand why he sees no difference in Gas mileage.

5 - dont screw with the ECM unless you know what you are doing. One guy locally leaned out his car and got great gas mileage until he burned all his valves and popped a hole in a cylinder.

I have only 15 years of experience building cars and engines from parts on up, so take my advice with whatever value you want.

Incorrect. The car will ATTEMPT to get to the ratio desired in the AF table for that set of conditions. MOST of the time it is running rich except for cruise plateaus on the AF table.

Very rarely does your car run at 14.7:1.. at least from the 30 or so ECM's I have been in are set for. But then I only program GM cars. It may be different for imports. But even then I cant see how they could ever keeep the AF near that all the time. you always are running rich on acceleration.

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

[Transmissions/mpg]
 

Hello all.I'm very late getting to the general discussion sticky on ecomodding.SVO and others have thrown out some great stuff and of great value to anyone considering mods.I have some tid-bits to add,and I thought I'd add them individually.-------------------------------- Transmissions have a tremendous effect on an engine's ability to transfer power most economically down the powertrain to the drive- wheel(s).I'm not saying that you can just run down to the corner parts store and get a different tranny to shove in your car,but it's important that everyone understands the significance the transmission plays in mpg.------------------------------------- So far,a 12-speed transmission has demonstated the best gain (15%).They exist only in the lab.----------------------------- The Continuously-Variable-Transmission(CVT) is a form of trans thought to promise a 15% improvement in mpg.The Subaru Justy has used this transmission for a few years,and it delivers worse mpg than other cars in it's class.-------------------------------- Presently,Mercedes offers a 7-speed trans,and Lexus just introduced an 8-speed. We'll have to wait to see how they stack up.------------------------------------- The premise for all the gears,is to let the engine remain close to it's "sweet-spot",where it achieves it's highest Brake-Specific-Fuel-Consumption(BSFC),the point of load and rpm,where the least fuel per horsepower/hour or kW/hour are produced.

[Road Grades/mpg]
 

This material is from George Wallace,one of Chrysler Corporation's computer whiz-kid's research, that helped them win them the Mobil Economy Run competition, more than once.Wallace recognized from pre-competition tests conducted at the Proving-Grounds,that small-engined cars were"fussy" about hill-climbing,and cooked up the following strategy to deal with road grades during the competition.------------------------------- On level roads,or grades up to 1% they'd drive 55-mph(88km/h).----------------------------- On a 2% grade,they'd fall back to 50-mph(80km/h).------------------------------------- At 4% grade,they'd drop to 40-mph(65km/h).------------------------------------ At 6%,30-mph(48km/h).-------------------------------------------------- The US,EPA claims that maintaining the speed limit up a 3% grade can cost you 32% in mpg.--------------------------------------- Driving the posted speed limit up a 7% grade can cost you 55% in mileage.

[Rolling-Resistance/mpg]
 

All the show cars and concept cars that get great mpg have special,low-rolling-resistance(LLR) tires.These particular tires are not in production and are not for sale,however,for the tires that are available to the general public,there is a "range" of coefficient of friction(Fr) for the tires available.------------------------------------------A 10% reduction in rolling resistance will net about 3.8% improvement in mpg,for comboned city/hwy driving.------------------------------------ Neglecting your tires,and letting the cold inflation pressure drop 25%,will cost you 1 mpg.-------------------------------- overinflating your tires 25% will net you a 1% improvement,but could destoy the tire,throw you out of control,and kill you,your passengers,and anyone else around you.------------------------------------ Tire manufacturers recommend that you never exceed the maximum pressure embossed on the tire sidewall.--------------------------.Also,it takes about 5-miles (8 km ) of continuous driving to get your tires up to their equilibrium temperature and highest economy.If your car is OBD-2,and should choose to monitor your mods with a Scan-Gauge,bear in mind,that any testing done without a 22-mile (35 km ) warm-up drive,will yield erroneous data,compared to a fully-warmed-up vehicle.In addition to the 5-miles necessary for the tires,all your lubricants will be below their equilibrium temps(and best performance) without at least 22-miles(35 km ) of warm-up.

[Temperature/mpg]
 

75-degrees F is considered"ideal" for testing,according to EPA.------------------------------ At 50-degrees F,you can expect to lose 5% mpg.----------------------------------- At 20-degrees F,you can expect to lose 11% mpg.

[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.

[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.

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?

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

spacing
 

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.

You are nicer than me, I would have let her walk! :eek:

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.

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.

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.

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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Car News by Patti.