rxspeed87

only problem is the headers, what material I would use, and nice tight bend that I would need to make to get it into the intake manifold
still thinking though and might be able to pull something together if someone could possibly help stimulate my brain
and I would be willing to post results if I did this BUT i have no speedo right now could only go by feel and guestimated driving mileage being I only drive a few different places.

Valkyrie

Internal combusion engines are inefficient because of heat. Most of the energy they produce is in the form of heat, only a small percentage (I forgot how much) actually gets used for moving the car.

I don't mean that heat itself is nessicarily bad (it's unavoidable), but heat is usually a sign of friction, which takes away from a machine's efficiency.

But there is still no reason to intentionally heat up the air of a car's engine EXCEPT to get the car warmed up faster. And "warming up" the car ISN'T making it more efficient. Cars are designed to deal with the heat they produce by working in a normal operating range. The reason cars don't run as well when they're cold is because they aren't in the normal operating range yet. It doesn't mean heat makes them more efficient. If cars didn't produce any heat, it would be more efficient since all the energy is going into pushing the car, and you wouldn't have to heat the car up since its normal operating range would be the same as when you start the car.

Your theory that heat = pressure is also flawed. A car doesn't not run because of heat. Heat is simply a waste byproduct of the detonation of gasoiline and oxygen. Like I said, MOST of the energy that a car produces is heat because it simply isn't that efficient to burn gasoline in order to create pressure. There is nothing you can really do about this. If there was a way to burn some sort of fluid that released all of it's energy into the form of pressure, it would be far more efficient than burning gasoline, creating tons of heat for the smaller amount of pressure it creates.

Either way, if you were to heat the air going into the engine, you would lose efficiency because you would not be able to produce the same amount of power with the same amount of fuel. You would lose power and torque, and you would have to rev the engine higher to acheive the same speed. That would hurt your gas mileage, would it not?

As for a hot air box, you wouldn't need it. The engine produces more than enough heat already. Just put a high-flow cone filter in the car, and there would be more than enough heat in the engine bay to warm the air if you wanted to so badly (meaning besides when you're just starting the car). It would make more sense to just have a cold air box to take OFF rather than a hot air box to put on.

(or you could use a battery warmer or something)

Oh, and I'm fairly certain that heating up your intake air would make your engine MUCH more likely to knock. The hotter the air is, the more like your engine will knock, and on a rotary, that = bad.

Also, you couldn't possibly remove all the heat of a car's engine. You really can't gain efficiency by cooling or heating a machine. But you can make it far more powerful. ie, super computers. They're so powerful that they generate an insane amount of waste heat. By cooling them, you can run them a whole lot faster.

Efficiency is simply doing more with the same input (ie, NOT cooling the computer is a waste of hardware since you could do a lot more if you cooled it). And heating your intake air ain't gonna do that.

So explain to my why you want to heat up an already very hot engine?

Feel free to prove me wrong. Try driving a car with a cone filter exposed to the engine, and then try it with an insulating cold air box around it. See which setup gets better mileage.

I'd say the chances of the heated car being more efficient are about 1 in 4... because I could be wrong, but I doubt it.

Aaron Cake

iTrader: (1)

I doubt it would make much of a difference. The engine in the Insight is WORLDS apart from the RX-7. You can't even begin to compare them. The only reason I want to suck in warm air is that it more easily allows the "lean burn" mode of the engine to come into play in cold weather. When it's quite cold out, it can be harder to keep the engine in the lean burn state (running at ratios as low as 25:1). The hotter, less dense air requires less fuel to maintain these ratios. Lean-burn is not about power at all. It's totally about economy. In the RX-7, sucking in hot air will just cost you power, but probably will help your winter mileage VERY slightly.

rxspeed87

some of what you say doesn't make sense to me but no worries hopefully we can get that explained

reason I'm saying heat makes a car more efficient is like most gasses I know of when they get hot they expand. so when you put the air and fuel into the motor they down into the cylinder get compressed and then get spark which makes the fuel go boom. that boom creates heat and then that heat makes the gasses inside the cylinder expand. this makes the motor run
now the reason I say heat makes a motor more efficient is with that heat that the combustion makes.
if your running the motor cold (lets say you just started it up or running colder thermostat) now when that fuel tries to ignite the surrounding walls inside the cylinder will absorb some of the heat which is then pulled away with the coolant. since it pulls away some of that heat though it is taking away that energy inside cylinder which prevents that pressure pushing on the piston (easier to think piston terms for me sorry).
yes friction causes heat to and I agree friction is bad.
but your common about cars don't run whell when cold because they arent in normal operating range. seems to shoot down your next statement of it doesn't mean hat maks them more efficient.
can you explain why a car running in normal operating temp (hotter then when first started) runs better and more efficient then a cold car?

as far as my heat = pressure theory that is how a car works though isn't it? gas gets burned which creates heat and that heat builds pressure. problems arise with an internal combustion motor through through transfer of heat to other places. like the cylinder walls (less heat during combustion so you get less pressure), you get hot exhuast gasses (again wasted energy being that heat isn't being used to create pressure inside the cylinder and instead is going out the tailpipe instead).

in a better world we would eliminate transfer of heat to the cylinder, piston, rotor, valves or whatever things inside the motor absorb heat and instead would keep all that heat inside the combustion chamber, also we would elimnate all heat going out the exhuast which is the biggest reason for it's inefficency.

with heating the air I would think it might help out a little being hot air again reduces pumping loss through the throttle system not being closed as much. kinda like a dirty air filter can reduce gas mileage becuase it is an obstruction creating a pumping loss. this is due to needa little more throttle to bring in the same mass of air. also heat is a form of energy heat is what creates the pressure inside out cylinder. sure if another means could do it without the heat as you said we prolly could be more efficient but that isn't how our cars work they work from the heat creating pressure.

would you care to explain that one? my car is a manual so if the clutch is pushing against the flywheel it is directly coupled meaning if I rev my car higher it goes faster.
so how am I to rev my car to make more power just to go the same speed?

about your comment on detonation sure it prolly would lead to detonation but I'm not running at wot and don't plan to be running at wot for a while.... again big sheets of ice

I have a cone air filter already. right now though underhood temps are not that hot partly due to getting rid of that nice underhoot temp creating device known as the stock exhuast manifold. so the air I'm sucking in really isn't all that hot as is.


trying to compare a supercomputer to a car in terms of power creation isn't the greatest way to explain things.
one big difference in a computer heat is a waste byproduct.
in a car the heat is a product that gets wasted.



so to sum up in sorta nutshell
our engines powered by heat. (if you disbelieve me look it up).
air and fuel go into combustion chambe then go boom. since energy can't be created or destroyed only converted or transfered what happens is the potential energy of the gas gets converted to heat by burning with the mixed in o2. this heat energy then gets converted to mechanical energy by pushing down on the piston. the inneficient part of that heat created happens with the heat going through the cylinder walls absorbing energy which should be used inside the motor to creat pressure and by going out the exhuast which again that is wasted heat being that heat is not used to produce pressure inside the exhuast but instead again just wasted.
there are other factors resulting from friction, pumping losses, and many other things but that is not what we are talking about in this little post so I'm leaving them out.


as to why a motor runs faster with a cai or even colder air for that matter is when at WOT you are able to pull in a greater mass of air being cold air is more dense though the volume of air stays the same. that more mass means more fuel gets burned and that mixture creates heat which then creates pressure since hot gasses expand.
but I'm not working WOT right now again big sheets of ice so I am not worried about WOT performance. I'm worried about efficiency. and getting a little better gas mileage if for nothing else because gas cost too much and this cold weather driving isn't going to make me want to do performance driving right now anyway.

rotorheaven7

You will get the same mileage in cold or warm weather. The oxygen sensor adjusts the amount of gas given by the fuel injectors to meet the amount of oxygen in the air. The computer makes your car run at the stoichiometric equilibrium.


You will however have more power with cold air because your car has the ablility to put more total air in your engine and therefore more total gas.

GregSL-SE

In older cars a "heat sheild" box thing is around the exhaust manifold with a hole in the top(about 1.75"), there's a flexible tube that runs from there to the air cleaner assembly, whala- you have heat to get much better gas milage, and accelerated warm-up. So you can get one of those tubes at an autoparts store. If your running a stock exhaust with heat sheild, all you would do-in theory- is cut a hole in it(holesaw) stick the tube in and do the same at the air box.
Keep us up to date on the mileage improvements!

rxspeed87

I will try to figure something out
just need to get a little more time
but being I am using a header and not so stock intake ducting and filter little more fun :-)


"You will get the same mileage in cold or warm weather. The oxygen sensor adjusts the amount of gas given by the fuel injectors to meet the amount of oxygen in the air. The computer makes your car run at the stoichiometric equilibrium. "

even though the o2 does adjust to keep the car at stoic I am thinking that this might help reduce some of the pumping losses in the motor. at least hoping

rxspeed87

I will try to figure something out
just need to get a little more time
but being I am using a header and not so stock intake ducting and filter little more fun :-)

rs_1101

yea.. with a nice tailwind.. :-D

ey.. i was reading through this, and after much much deliberation, i decided, youre prolly going to spend more money researching a hot air box than you will save in the gas you dont buy. given the density of air, it will not help warmup the car any though that method.
i also feel obligated to inform you that youll be using just about the same amount of gas either way. with colder air, youll require less throttle to operate, less air volume at higher density = x amount of fuel. in hotter weather, youll need more throttle more volume of air at lower density = the same damn amount of fuel to maintain a speed of 'S'. in a car with a basic feedback system, it makes little/no difference.
cake is right, as always, and my honda had a similar system to his lean burn, on my ep3, it has a low end vtec that operates a lean burn below 2200 rpm. the fc3s isnt that advanced. all youre going to do by using a hot air box is increase chance of detonation and waste your time..
but go ahead and try it.. post if it works.

rxspeed87

money to research?
can't be that much to research since I'm kinda doing that right now :p
as far as building don't see it being that expensive if I can figure out what to build it with.

but to further what I am trying to say with you talking about hot/air less density/more throttle vs cold air/less dense/less throttle.
engines tend to run more efficient with larger throttle openings least from all the bsfc graphs I have seen more throttle is more efficient. and it seems to make sense being that more throttle opening should reduce a pumping loss by letting the throttle be open more

kinda like how many ppl here have noticed an increase in gas mileage due to removing the cats and putting a header on there instead? why? less pumping loss
or changing that dirty caked on airfilter (I speak from experience on this one due to mod boggin in my celica) for a new one helping out?
as well as other things. they all reduce the pumping loss that the motor has to go through.

what I'm hoping though I admit I'm not sure and was hoping for correction on this, is that with hotter air being you woudl have to open throttle more to let the same mass of air through is it would reduce pumping loss.

Tofuball

That is called a "Stove"

Aaron Cake

iTrader: (1)

We have an Insight nonbeliever. These are not my pictures. They are those of another owner. I don't carry a camera in the car any more.

116MPG over 95 miles


A 114MPG trip, and a 91MPG lifetime mileage:


117MPG over 95 miles


On an RX-7, yes. On an Insight, it's a completely different story.

I don't mean to be a jerk, but it's not even close to the lean-burn system of the Insight.

Take a look at http://www.insightcentral.net/encyclopedia/index.html for lots of into on the engine.

rs_1101

cake im not trying to pick a fight!! lol i was messin with ya! anyways the systems are similar. take a look at the ep3's fuel map. its 3 dimensional. it adds a load as a dimension under 2200 rpm at cruise it uses practically no fuel by leaning out the mixture to about 17:1.. its not as cool as your badass hybrid system, but they operate on similar principles., its still honda remember?
anyhow.. i was just messing with you with the tailwind comment.

i guess i can see some point in reducing pumping loss. can anyone tell how much loss there is?
youre going to have to show at least a 20%mpg increase for me to go with any of this. cuz last summer, i remember using just as much fuel as i use now.

rxspeed87

hey man with gas prices right now I could handle it being a 5% increase

but during summer it woudl come off easily.... I bought the car to have right?
as far as how much pumping loss are reduced I wouldn't have a clue hoping someone else would chime in on this