Toyota Echo modifications
 

Hey guys. This is my first post so please be gentle. I have a 2002 toyota echo (manual) and I am averaging about 51 mpg over the last year mostly due to conservative driving techniques. Being in Arizona I also don't deal with the cold temps...

Anyways, I was wondering if anyone has done any modifications to the air intake for an echo? Despite the formulation for problems using my mechanical engineering degree (which I am working toward), I have found that warmer temperatures give me better gas mileage. I have found this correlation by sticking my hand out the window and a little help from the scan gauge ;) So, using this idea, wouldn't a cold air intake be detrimental to mpg?
I am wondering if I should design a heating system, using wasted engine heat of course, to heat the air before it goes in the intake. I would make it removable for the 110 degree F summer heat we get here...

Also, I was wondering if anyone has taken off their muffler and made a pipe that goes straight back. Two purposes: to hear the engine (since you can hardly tell if it running when sitting in traffic with no tachometer) and to possibly give a very very slight boost in mpg.

Thanks for any input:
Jason

If the air going into the intake is colder than your normal intake, the amount of horse power your motor develops will be greater. And I suspect MPG *might* increase as well.

Secondly, I wouldn't suggest messing with the muffler...

Back when i had my civic i used a hot air intake to good effect. I made it with a length of flexible aluminium duct and fitted one end to the air intake and wedged the other end behind the catalytic converter, just under the exhaust manifold. Intake temps got up to 80c during the daytime and she ran lean as! Mpg went up by a few, about 5 or 6 iirc. Unfortunately i have hills, school runs and very changeable weather to contend with so it made it hard to pin down the exact mpg gain. But you are in AZ so you should be ok!

I know that mathematical knowledge says the colder (more dense) the air going into the engine, the more horsepower. However, whenever it is colder outside, even when my engine is warmed up, I do get less mpg. Has anyone noticed the same thing?

warmer air = less dense = less fuel injected to maintain stoichiometric mixture = better fuel economy

Cold air for power, warm air for fuel efficiency is generally the rule. How warm depends on each engine.

Theortically it takes so much power to push a car down the road. Hot less dense air with less Oxygen just takes greater volume(larger throttle opening) to make the same amount of power as cold dense air (smaller throttle opening). Fuel remains the same either way.

I think every sensor is a little different and that what will determine if you car will do be more FE with hot or cold air, and every car same make model and year may be different. Buy a new O2 sensor and I'll bet your FE will change. If hot air makes better FE, your engine is running leaner. If your fuel to oxygen ration remains constant the FE will as well.

I think better FE when warm or summer is more a factor of air temperature as it relates to bearings & transmission regardless then engine intake air temp. And don't forget warm dry air is less dense for the car to push through as well, no clue how much though.

while all your logic makes perfect sense, i have to disagree. i put a warm air intake on my jeep and noticed an immediate difference, even in the middle of winter. can i explain it? nope, because i use the same logic you are using, but i know it made a difference in my Jeep

Warm air helps vaporize fuel, allows the throttle plate to be open more and it takes up more space so you end up with slightly higher compression ratio, so if you want to build a thermostatically controlled warm air intake look at pretty much any carburetted car and you will find a warm air intake tuned to about 110F.
The Toyota Echo and first generation of Toyota Prius share a great deal, alloy wheels and low rolling resistance tires will help you with better mileage, not sure if the prius had a factory belly pan or not, but the that first generation prius apparently had some issues with the electric drive motor, so you might get a good deal on wheels and body parts if you check around.

Look at it this way, fuel evaporates faster if you toss some on a hot piece of metal versus a cold piece of metal. Regardless of every other consequence of hot versus cold ambient temperatures and their effects on mileage, at some point fuel will freeze if the temperature is low enough and spontaneously ignite if the temperature is high enough.

In my old VX a hot air intake was easy and it made a 10% difference in mileage, in cold weather, in otherwise identical circumstances. It enabled lean burn over a wider range of operation.

In the 02 Insight a radiator block made a 10 MPG difference in winter driving when temps fell below freezing. One of the large factors between winter and summer driving is the temp of the coolant when it enters the engine. That temp can vary by as much as 80 or more degrees depending on ambient temperature. This is because there is no regulation of coolant temp as it exits the radiator. When its 100 outside the exit temp is about 130. When it is -20 that same temp may only be 40 degrees. New radiators make the difference greater and can actually hurt your mileage, especially in winter. Colder temperatures exacerbate the problem because the thermostat restricts the flow of coolant and that slower coolant loses more heat as it passes through the radiator.

regards
Mech