Armchair theory - extreme cold air intake.

[djct_watt]

Originally Posted by cfeng

I'll try my best to explain this.

A turbo or supercharger system is adiabatic. It increases pressure to force more air into the engine.

The system described by beer jammer is technically another forced induction system, however instead of being adiabatic, it is isobaric, where pressure does not change since the air molecules are squeezed together by cooling.

The flaw with beer jammer's idea, which probably other people see, is that using an air conditioner as a forced induction system involves more imperfect energy transfers where energy is wasted. It employs an air conditioner which cannot surpass carnots predicted efficiency (lose about 20-30% here), then it would need some heat exchangers (20-50% loss, governed by newton's law of cooling). It would be much more efficient to use a turbo or a supercharger.

So well put, it's near impossible to add to it. But considering the HUGE inefficiencies of using an A/C, I'm fairly certain that the cooling effect would still result in a NET LOSS of power. It'd be like having a cigarette lighter powered coffee machine boil water to power a steam generator that is connected to the crankshaft.

[cfeng]

if not designed properly, there could be a net loss of power. even if designed well, the car would operate less efficiently, more fuel would be consumed per unit of power.

[eTiMaGo]

Originally Posted by djct_watt

So well put, it's near impossible to add to it. But considering the HUGE inefficiencies of using an A/C, I'm fairly certain that the cooling effect would still result in a NET LOSS of power. It'd be like having a cigarette lighter powered coffee machine boil water to power a steam generator that is connected to the crankshaft.

I don't think the OP realizes just how much power the AC saps. you could try this, start the car, AC off, then start driving at part throttle in second gear, then turn on the AC and feel how much the car lurches...

But, upon thinking about this more, there is *one* way in which this idea could work. Suppose in a normal driving scenario, you are not at full throttle all the time, sometimes you are slowing down, sometimes you are just cruising at part throttle. These would be the times when the AC compressor is engaged and generating a charge cool air, but this cool air does not go into the intake, there is a valve to prevent this. But, once you go to full throttle, the AC is disconnected by the pulley clutch, the cold air valve mentioned above is opened, so you get a small charge of cooled air into the intake, And, whatever air follows is still cooled to a certain amount by the still-cold evaporator... It would be a very short-term effect, but it *could* work. I sorta experimented with the same thing in an effort to use the AC without wasting fuel, only engaging it when I am in DFCO. It works, but not very efficient :p

[djct_watt]

^ true. But then again, the gains (if any) would be VERY minimal with an NA engine.

[eTiMaGo]

yeah you obviously can't expect a NOS-like effect!

[djct_watt]

AC just kicked in yo!!!!

[Beer Jammer]

Wow! I guess I stirred up a load of controvesy here..

Anyway, as stated in the OP, this is 'Armchair Theory' and I have no intention of setting this up in any way or think that doing this would make my yaris super quick. The basis of this post is that 'Colder air in the intake allows the engine to perform better.' which is a very universally agreed concept and why products like the K&N Typhoon are highly recommended. My fervent mind just thought about this in a more extreme way.

I am agreeing with everyone here in that feeding the intake with a/c conditioned air will not increase performance and part of my OP stated:

I know that the a/c saps power, but would routing its output to feed both the cabin and the engine air intake work to offset this reduction in power and make the engine give better mpg when you use a/c

So the theory is that on a hot day you are using your a/c anyway, so why not channel some to the engine? It will never make the yaris perform as good as turning the a/c off, but it may reduce the difference, so the big boys like Mercedes, GM, Toyota and the rest could have the time and money develop this to a way to increase the efficiency of their a/c systems and be more 'green' ?

[djct_watt]

It wouldn't do much based on the volume of cooler air supplied. The net result will be a less cool cabin with a negligible difference in economy.

[jcemitte]

what if instead of routing direct air from the a/c directly into the intake, what if you took the freon from the a/c system and made some kind of housing that has the freon cooling the air flowing through it effectivly cooling the air? would the motor compensate for the colder air?

i had a armchair theory about this once but a little different.

since basically a turbo or supercharger increases the psi in the intake to force air in the motor. ive heard off off roaders using there a/c compressor for on board air, so why couldnt you plumb that into the intake. or if its cheaper whynot put a little compressed air tank in your trunk and just use it like a shot of nos?

both not very plausible theories and at that point just buy a turbo or some nos lol.

[cfeng]

One interesting point is that many engineering applications try to recycle heat into engines using regenerators for higher efficiency, not cool their engines. This theory described in this thread works the opposite, however tries to achieve more power.

Rankine and brayton cycles involving turbines are made more efficient by heating the working gas.
http://www.energysolutionscenter.org...ombTurbine.htm

Some one might want to start a thread of another arm chair theory of achieving higher efficiency by preheating air and fuel for higher efficiency. Others can knock it down saying it causes detonation.

[PHXDEMON]

Originally Posted by djct_watt

The idea makes sense, but it would make no difference, and would end up reducing net efficiency. Let me explain to you why I am bursting your bubble.

1) The amount of CFM (cubic feet/minute) an air conditioner can move is insubstantial next to the amount of air an engine pulls in. It'd be like p***ing in the wind.

2) The gross inefficiency of an any and all air conditioners mean that it takes more power to run the air con than it gains by cooling the air. Simply put, you'd see more power simply by turning it off.

If it's cooler air you're looking for, then the traditional meth injection, nitrous, or other compressed gasses will substantially reduce temperatures. Also, intercooling works too, but really is only worth it on a FI type application.

/thread

[cfeng]

In no way will this theory give you more efficiency.

However the two points above need to be reconsidered. Think of having a very inefficient supercharger on the yaris, you will have more power but with a loss of efficiency.

[TEHxFALLEN V1.2]

Here's my theory:

Connecting a very sophisticated box that holds ice cubes in the "ice box" chamber would cool down temperatures in the stock airbox. Check out the dyno chart.

[djct_watt]

The crudeness of that picture just makes it THAT much more awesome.

[cfeng]

HAHAHAHAHAAA

[cali yaris]

LOL, good one.

People DO ice down the intakes when trying to get an "extra special" dyno pull.

Speaking of which, has anyone done back to back dyno pulls with the AC off and on?
Do we actually know in measurable terms what effect it has on the motor's power/efficiency?

This whole thread is based on a premise that the AC's single pulley makes a really big difference. I'd like to know what hard data supports that. (And yes, I can feel it with my butt just like everyone else).

[Y@R15]

this is also true the A/C is only effiecent in the 60+MPH range. in this speed having the windows down would kill your MPG as well. what your talking about it trying to gain by saving. you cant gain power and MPG when you have the A/C on. now a way to i think see a little less fuel consuption would be to use an aftermarket A/C pulley. like the crank and altinator pulleys. other then that. your not gonna see anything by useing the A/C air... i think i confused myself.

[Yoda]

Originally Posted by cali yaris

LOL, good one.

People DO ice down the intakes when trying to get an "extra special" dyno pull.

Speaking of which, has anyone done back to back dyno pulls with the AC off and on?
Do we actually know in measurable terms what effect it has on the motor's power/efficiency?

This whole thread is based on a premise that the AC's single pulley makes a really big difference. I'd like to know what hard data supports that. (And yes, I can feel it with my butt just like everyone else).

I did this last year but I can't seem to find the dyno graph. It was about 2.5 whp lost as I remember. I did the first run with the a/c on not knowing it was. Then turned it off for the second run and showed gains.