Fuel Efficiency and the Yaris

[Pars]

Bailout, Thanks for the tip regarding the engine cut-out, it's saving me $200/year. I use to think coasting in neutral was the proper way to save gas, but once I learned that the engine cuts fuel-flow when coasting, I'm now always in gear while coasting.

[Yaris Newbie]

So, here's a question from another post that got some response there but might be more suitable here. I was referred here anyway.

Regarding Driving under load.
In rolling hills, where coasting downhill is possible, but it is obvious that I will need to climb the next hill with at least some pressure on the accelerator... should I just forgo coasting down the hill and maintain constant pressure on the gas pedal the entire time (down and up the hill)?

Given these points already made:
Driving slower (to a point) increases gas mileage.
Moderate drafting (please no safety debate) increases gas mileage.

Would it be better to go 50-60 alone or to increase speed to 70 or slightly more to gain a draft off of a transfer truck (18 wheeler)?

At what speed should (the rare times I use AC) I roll up the windows and turn on the AC?

Will a cold air intake improve MPG?

Is there a difference in running the AC at a lower fan speed compared to higher temperature (more red on the circular dial) compared to turning the AC on for a while then off for a while? Or is the compressor doing the same amount of work in all three situations?

[BailOut]

Originally Posted by Yaris Newbie

should I just forgo coasting down the hill and maintain constant pressure on the gas pedal the entire time (down and up the hill)?

On smaller hills, yes. On larger hills, no.

Originally Posted by Yaris Newbie

Would it be better to go 50-60 alone or to increase speed to 70 or slightly more to gain a draft off of a transfer truck (18 wheeler)?

While drafting does indeed offer decreased air resistance, it does nothing for rolling resistance. Going 50-60 alone is much better than drafting at 70. I only draft when I can find a proper vehicle going between 45 and 60 MPH.

Originally Posted by Yaris Newbie

At what speed should (the rare times I use AC) I roll up the windows and turn on the AC?

None. Windows down is always much more efficient than using the a/c. Mythbusters proved as much as well.

Originally Posted by Yaris Newbie

Will a cold air intake improve MPG?

Only if you drive like a testosterone-infested aggressive punk.

Originally Posted by Yaris Newbie

Is there a difference in running the AC at a lower fan speed compared to higher temperature (more red on the circular dial) compared to turning the AC on for a while then off for a while? Or is the compressor doing the same amount of work in all three situations?

The compressor is basically a binary unit, being either on or off. As such it doesn't matter what the fan is set on. If the a/c is on the compressor is clutched 100%.

[petesimac]

Bailout, I heard recently by the so-called experts, that one should roll their windows up when the speed of the car reaches 30 mph, as the drag reduces fuel efficiency -- have you heard this as well?

[Smokey159]

Quote:
Originally Posted by Yaris Newbie
Will a cold air intake improve MPG?

Only if you drive like a testosterone-infested aggressive punk.

LOL, horrible answer.

Before the hack, I did an extensive report on Simota's Carbon Charger... should've saved it.

But anyways, I got an increase in MPG of 1.5MPG. After doing the math, at $3 a gallon, it would take around a year and a half to pay off the investment of the intake. (this number obviously depends on how much you drive per year and the actual price of gas).

Only the "testosterone-infested aggressive punks" LOSE mileage because they want to hear the new sound the intake makes since you can only hear it when you apply more throttle.

Before someone tries to tell me I'm wrong, let me explain. Also keep in mind that I have been an engine builder for almost ten years and I am Dynojet certified to operate their Dynomometers and administer their Power Commander engine management systems.

OK, simply put, if you make an engine more efficient, you save gas. I'll preface this by saying YOU CANNOT CHANGE YOUR DRIVING TECHNIQUES and keep this statement true at the same time.

When you hear people say: "If you introduce more air to an engine, the ECU adds more fuel, making it less fuel efficient" you may tell them that they are HALF right. The fuel mapping DOES introduce more fuel, however this is to keep the air/fuel ratio correct (usually aroun 14:1). Now here is where they are wrong, if you introduce MORE air and MORE fuel to a motor, you make it more powerful, AND more efficient.

If a motor has more power, you don't have to press on the pedal as hard. Opening the throttle less will ALWAYS use less gas then the ECU has added to balance the ratio. As a result, you get better fuel mileage. Think about it this way, with the same amount of pedal, you go further.

Done deal, stop arguing about it. Buy an inexpensive intake and follow the following rules:

1) Reset the ECU after the install by disconnecting the battery for a few minutes, then reconnect it and start the motor. DO NOT REV THE ENGINE, just let it idle for about 5 minutes and then shut it off.

2)Don't buy a high priced intake, this will only make it harder to pay off. CAI are usually higher priced than SRI, but they offer little more in terms of engine efficiency in the real world.

3)Make sure that the design of the intake does not place the Air Intake Sensor too close to the throttle body, this will actually make the engine run rich. for example: Simota's carbon charger is as close as you want to get.

4) Do not change your driving habits, you will see a reduction in fuel economy if you want to hear it. This is harder than you think, it does sound cool.

This is not a smack down post, I just want to clear this up because many people don't truly understand some of the concepts.

[BailOut]

I heard that, too, and a few of us on CleanMPG quickly debunked it. Using an SGII one can drive around at various speeds and watch for an MPG change with the windows up or down. You wont' find one.

Then do the same thing with the a/c on or off and watch your average MPG instantly drop by 10-15%.

We know that the windows down affects drag, but it does so at a fraction of an MPG. Between all my measuring efforts the only time I have ever noticed the drag is when I'm FAS'ing one section of my commute home. In that section I already have a lot of rolling resistance and not much of a grade to maintain my speed before the next climb, and if I have my window fully down with a strong wind catching in it I can lose an additional 2 MPH from 60 by the bottom of that 1/2 mile hill. That's not exactly earth-shattering.

This correlates with what the Mythbusters show found both in their initial testing and their re-vistiing of the myth.

[sherryberry]

I thought I saw a mythbusters episode that tried to see if you get better mileage with a/c or window down. Believe that the one w/ a/c ran out of fuel faster than the one with window down but I could be wrong since it's been a while since I've seen it.

[Canuck]

Originally Posted by sherryberry

I thought I saw a mythbusters episode that tried to see if you get better mileage with a/c or window down. Believe that the one w/ a/c ran out of fuel faster than the one with window down but I could be wrong since it's been a while since I've seen it.

But all it really proved was that for those vehicules (they were SUVs) ith those conditions, the windows down were more efficient than AC. I would not extrapolate to all cars. And there is a comfort thing too. windows down at 100kmh is really no fun.

[eTiMaGo]

hehe mythbusters rocks

[sherryberry]

Originally Posted by eTiMaGo

hehe mythbusters rocks

i watch it all the time. Or at least I try to watch it as much as I can i like explosions

[Pars]

For those who have the scangage. Is it possible to tell how much gas the car is using up while idling with the AC running?

Since it's hot outside and I don't want to disturb the little one's sleep, I might have the car idling for over 1/2 hr on occassions, just to make sure the little princess sleep isn't disturbed. The price for disturbing a babe's sleep is too high, so I'm not worried about the fuel cost, but it'd be nice to know.

[BailOut]

Pars,

Please remember that the cost of burning fuel goes far beyond the price you pay at the pump. If you would like her to have a future free of the Arab stranglehold on oil - and the wars that come with it - we must cut back on our fuel usage harshly, and if you would like her and her own progeny to inherit a planet worth having the lessening of our usage and consumption of all resources is totally necessary.

With that said, you can use the SGII's GPH (gallons per hour) monitor to see the fuel usage at idle.

[fenwayfanatic94]

surprised how much i know, surprises me how much more i could do. good information.

[NimbleYarisOwner]

Brian,

Can you give me more details on the solar trickle charger???

thanks allot!

[BailOut]

Hi CheapYarisOwner,

There's not much to the solar trickle charger other than the link I gave in the "FE Mods" section: Long Link

... and that you have to drill a small hole in the firewall in order to mount it directly to the 12V battery. I just matched a drill bit to the cable's size and drilled it just to the right of the heater hose. You can't plug it into the 12V adapter inside the cabin as it puts out just enough power to initialize the entire chassis side of the ECU, which uses more juice than the panel provides, thereby creating a drain.

I also had to use a small round file on the back corner of the area of the dash that's right in front of the gauges in order to make the cord lay the right way and not be pinched.

It's not a miracle device, producing just 200mA at 12.3V in direct sunlight, but it accomplishes two things:

1) It replenishes the missing electricity from your battery that was a deficit when you parked it. I have a good climb right before I get to my office and my voltage readout usually shows 12.4V - 12.6V as I park. A full battery in the Yaris usually reads ~12.8V.

2) Once your battery is topped off it keeps it topped off, ensuring that 100% of the battery is available to you at the next start.


These things mean that you'll never have a dead battery (unless a major failure occurs) and when you start up your alternator doesn't have to engage for so long because all it's making up for is the energy used to turn the starter, rather than that plus all the juice you bled off during the down time. The less the alternator places a load on the engine the less fuel your engine needs to burn.

In real-world usage I've found that this solar trickle charger gets me back up to 12.8V in about 2 hours in good light (roughly 1/100 of a Volt every 3 minutes). On a cloudy day it can take up to 6 hours. Of the 2 parking garages I've been in things were odd because one was open to the outside but it was night when I was there, and the other was underground but very well lit, so much so that it still charged about the same as a cloudy day.

[Maypo]

Thanks, BailOut, for a fabulous amount of useful information; and other responders for adding ideas and opinions. I am going to try some of the new 'tricks' for myself.

A few comments on what I read here:

1) From BailOut's original list of hypermileage suggestions the one I am skeptical about is the "slow acceleration" gambit. Years ago, BMW did some testing to determine the optimum throttle-position and rpm shift-point for fuel efficiency. They tested all the combinations of 1/3 and 2/3 throttle-positions, with 3000 and 5000 rpm shift-points, and concluded that low rpm (3000), combined with heavy throttle (2/3) application was most efficient. Also, during the years of the famous Mobil Economy Run, it was discovered that the best methodology for fuel efficiency was full-throttle acceleration to some predetermined speed, followed by coasting. Anyway, I have not heard or read anything to the effect that BMW 's conclusion has been superseded by newer technology.

2) BailOut bemoans the ending of the 55 mph NSL (National Speed Limit), but most of us do not. While limiting the entire populace to an artificial maximum speed saves fuel, it wastes a truly non-renewal resource: time. Also -- in retrospect -- it has been shown that highways were less safe, when the speed limit was established based on politics, instead of engineering principles (not a surprise, actually).

As an aside: Back when the draconian NSL was in effect, myself and several friends conducted our own 'fuel economy vs. speed' testing, by fitting a fuel meter to the gas-line on one of our Fiat X1/9s and driving up and down I5 at varying speeds to chart a fuel-use curve. We discovered that our peak fuel economy was achieved @ 75 mph (39mpg), and the 33 mpg we recorded @ 55mph was duplicated @ 85mph. Thus, the Federal Government was costing us time and fuel.

Although technology has pretty much locked fuel efficiency to standard highway speeds, I suspect there are still vehicles whose fuel economy is little affected by 'keeping it to 60.' In fact, my previous car, a Nissan 350Z, got 33 mpg @ 60 and 30 @ 70 -- a trade-off I was happy to make.

3) Some of the comments in this thread are about modeling better driving behaviors, and I am all for that. (I have a personal program of turning my headlights off when I am stopped at a red light and facing oncoming traffic, i.e., in a left-turn lane, as a courtesy. After 6 years of this, I have been rewarded by like treatment exactly twice, so, this project won't be ending anytime soon.) However, driving slower than prevailing traffic to 'control traffic,' or feel good about saving petroleum is not the kind of behavior I would want to model, nor is it likely to have a net benefit in the moment. Minimum overall fuel is consumed when speed changes in traffic flow are minimized. At the sane time, safety is enhanced and stress is reduced. All of which is why -- as far as being socially-responsible behind the wheel goes -- I recommend behaviors that facilitate traffic flow. (Even the Defense Driving that is hammered into us falls short, in regard to efficiency.) And, while that includes al lot of the ideas and suggestions already mentioned here, it doesn't include forcing others to slow down below prevailing speed.

Happy motoring!

[BailOut]

Smokey159,

While I appreciate you taking the time to work this up I have a few issues with your findings.

My primary issue is your claim of 1.5 more MPG. You show no mileage logs, offer no data points such as the length of your testing both before and after the installation, ambient temperatures during testing, the condition of the OEM filter before you swapped it out, etc. Please quantify your results.

Secondly, you neglected to mention how intakes perform differently at varying altitudes. As you are in Kentucky are we to infer that all your testing was done near sea level? Did you test at any other altitudes?

[Smokey159]

Altitude? 1500 feet.

If you're calling me a liar, I'll give you the short log I have. I'm not as anal about keeping logs as you are I'm sure. I can tell you that only the exact same trips were performed in my before and after trips, if I had to deviate, I took my truck. The comparisons consisted of 200 miles each, with a 60-40 combination of highway and city driving respectively. Temps were anywhere between 60 and 75 degrees.

My car had less than 5000 miles on it when I did the change, so the stock air cleaner looked practically new. I still have it if you want a pic.

Does 1.5 MPG sound like a lot to you? Personally I was a little disappointed. Quantifying my results to your standards is not necessary for me to find out whether it helped my MPG. I tried to keep as many variables constant as possible while keeping it a real world scenario. I have no interest in whether or not people are skeptical to my findings because I am not here to sway anyone. The facts and physics of internal combustion engines in today's vehicles have been proven enough, it is an ancient technology.

The fact of the matter still remains no matter if my testing had flaws or not. A properly designed(*key point) intake that increases airflow will allow the engine to operate at a higher performance level(also assuming the ECU can still manage a good air/fuel ratio). This has been proven time and time again by dynomometers. However, I will say that there is a point in performance gains where it is necessary to add more fuel than normal which leads to a loss in MPG, but this scenario is WELL beyond a simple intake modification.

Again, more power leads to an overall more efficient vehicle, keeping all other things constant, including driving habits. I'm sure you've noticed how much gas can be wasted by just the smallest increase in throttle. I believe I read something you wrote about exploiting fuel mapping(which I completely believe) that falls closely with what I'm talking about. Increasing the performance of a 4 stroke engine allows you to ride in fuel mapping areas for lower throttle positions, thus saving fuel.

Bailout, I understand that you have a different opinion about these sorts of things, and I'm fine with that. I don't expect you to change your opinion just on my words, you're too set in your ways to let a post influence your beliefs(that's not meant to be an insult). However, there are people out there that will look at your views, and look at mine, and decide how they feel about it. I'm only out to share my own experince with people.

That being said, I won't add to this thread anymore, and let others create their own beliefs. I absolutely will not get into a "back and forth" with anyone.