Dry Ice in Intake?
 

Well hello everybody, and Happy New (EM) Year!

I was thinking about water injection as a means to cure my 07 Civic's lackluster response in hot weather (a whole other story), when I contemplated means to improve gas mileage under light loads.

Can anybody think of any reason why dropping some cubes of dry ice (frozen CO2, no?) into the intake would not trick the ECU to interpret that as a low oxygen environment and reduce the fuel injection rate? My theory is that the dry ice when returning into gaseous CO2 would mix with the air rushing past it. The air/CO2 mix should have less oxygen in it and to keep the fuel/air mix right, the engine would have to reduce the amount of fuel injected, therefore causing a lean burn, right?

Think: Nitrous injection - but the opposite! :D

Maybe it would choke out the engine completely? Could this hurt the engine? Thanks for the feedback!

superchow -

I don't know, but I am *guessing* it would richen the fuel mixture on the assumption that the combustion will free the 02 in the C02 from the dry ice. I say this because the 02 sensor in the exhaust manifold would then measure an increase in oxygen levels, creating a "lean burn" reading. The car's ECU/PCM would then increase the amount of fuel injected to bring you back to stoichiometric AFR of 14.7:1.

I don't think it would hurt the engine because EGR already recirculates C02 into the combustion chamber (at much higher temperatures than dry ice CO2).

What are the "leftovers" after the dry ice has melted away? Water? Goop?

But someone who really knows pipe up.

CarloSW2

Is there a chance that the extra CO2 could prevent combustion?

Co2
 

I believe the outcome would in effect,be like lowering the displacement of the engine,with loss of power,efficiency,mpg,with all the original canibalistic internal losses.------------- The CO2 is already fully oxidized,will act as an inert gas,displacing valuable oxygen,reduce the charge density,lower BSFC.----------------- Beside all that,how could you possibly hope to monitor and adjust" stoiciometric" ratios.---------------- Co2 is used in fire extinguishers,and plenty believe we already have plenty in the atmosphere.-------------------------- I think you should look elsewhere for a solution to driveability issues.

aerohead - I read as much as I could find about the R18A engine in the Civic and one of its highly touted points is the low friction coatings in the engine block cylinders. I notice this every day when engine braking: It just does not want to slow down as much as other cars that I've driven. Yes, the engine would become less efficient. Even so I hypothesize that despite the negative effect of the oxygen being replaced by CO2 and thus reducing engine power and efficiency, the overall amount of fuel being injected would be lower than at with plain air.

Stoichiometric ratios - Less oxygen should mean less fuel, no? I'm proposing more "filler" to be pumped and less stuff that could react with gasoline. Where's a chemist when you need one! :confused:

Yes, using CO2 would be counterintuitive for ecological reasons... Any ideas for frozen inert gasses that could function as a substitute for dry ice?

Nothing would be left over. Dry ice is just frozen CO2, once it sublimates it is gone with the wind.

Even if it did help, consider that it takes a lot of energy to make, store, and distribute dry ice or to freeze any other compound.

Your EGR system already does this by keeping or rerouting exhaust (mostly CO2) back into the cylinder. The problem is that at low loads too much CO2 results in misfires for most vehicles, which results in other emissions spikes. The newer GDI engines allow for precise control of the incoming fuel mixture, which lets manufacturers run more EGR and relatively lean A:F ratios in order to improve BSFC w/o increasing emissions. Here's some more info.

You might want to re-think this one :-) How much does dry ice cost (not just money, but in energy) vs the amount of gas you expect to save? How long will the dry ice last in the summer? How much extra gas will you burn driving to wherever you plan to get the dry ice? How often will you have to stop and add a chunk or two to the air intake?

If all you want is to fool the ECU, why not just put a small microprocessor in the circuit between it and the sensor(s), and map whatever response you want?

Really, you should have waited until April 1st to post this one :-)

james - the resistor thing would cause it to lean out, but it wouldn't add "filler" to the combustion process... that's his point - if you add CO2, it displaces X volume that now cannot be filled by air/fuel.

His idea is bascially water injection with CO2 instead.

Here's the problem - aside from cost, which has fervently been pointed out already, the rate at which the CO2 sublimates would increase with ambient temperature... it would nearly be impossible (given your theoretical setup) to keep track of how much CO2 you're adding to the combustion process, and you may even add enough of it that there wouldn't be enough room left for the air and fuel to create a strong enough combustion process to actually keep the engine running. Chances are, after the engine warmed up, you'd starve it, and it would shut off.

Another issue with doing this - you're making the air/fuel mix very sparse in such a large area, which makes it harder to ignite... ideally, you want a richer mixture nearer the spark plug, and a leaner mixture everywhere else, or at least a homogenous mixture everywhere.

Adding random (or even controlled) amounts of CO2 to the mix, if you add enough, will make it so that parts of the a/f mixture are all over the place. You'd have to control the timing for the gaseous CO2 to be injected, so that it would limit access to the areas closer to the piston, and air/fuel could be drawn in on top of it... what you'd have essentially done is lowered the effective stroke of your engine, more accurately, lowered the displacement... there are easier, cheaper, more reliable ways to do this.

Granted, the overall cost of energy involved in this setup would be prohibitive. But, I must mention that the Civic has a resonance chamber plumbed before the air filter almost in front of the front left wheel well. I am guessing that there would be about 2-3 feet of air intake (I haven't measured, sorry). Air enters right behind the driver side headlight, drops down below the battery, to the resonance chamber, then back up to the side of the engine where the air filter is located.

Theoretically dropping a couple of cubes of dry ice into the air intake would get stuck in the resonance chamber and not really close to anything hot.

I have never played around with dry ice, and I do not know how quickly it sublimates, but surely it could last long enough to drive a few hundred miles? Long enough for a personal record breaking run?

I have the feeling like this idea will not take off until I go from theory to practice. :thumbup:

I do not have an idea if this would be even financially viable - probably not! - but after seeing racing cars using dry ice to cool off the air to their radiators before the air passes through the radiator, something must have been planted in my mind.

Oh, and for everyone asking "why?": I am very shy of actually chopping around on my vehicle because a) it is relatively new, and b) it is the only vehicle in our household and my wife would not appreciate walking to work in the pacific NW rainy winters. Therefore I am limited to non-invasive mods - if there is such a thing.

Thanks for the feedback entertaining my wacky ideas. If not here, then where, right? :rolleyes:

superchow -

From what I've read, no one seems to think that there will be harm to the engine.

Aside from all the other caveats, it sounds like you could at least do a test. Leave the car parked in neutral and let it idle while the dry ice is off-gassing into the intake. This wouldn't be a complete test, but you could at least see if the engine bogs down under a controlled/safe idle/min-load condition. You could also press the accelerator and see if it runs "normally" at different RPMs. If you don't like what you see or hear, just turn the engine off and pull out the dry ice.

I don't blame you for thinking in terms of non-invasive mods. I'm a proponent of the "reversible mod", and the politics of sharing one car can be verrry complicated.

CarloSW2

What about using a compressed CO2 canister instead? Same gas, but better control. You could even put a nice valve on it to regulate the output.

Hmmmm, the effect of CO2 in the intake is a more complex a problem than it seems at first glance. I don't think it is a given that it would cause the engine to burn leaner at all. The CO2 might make the engine run richer. The extra oxygen detected in the exhaust by the oxygen sensor might make the engine management system think there was insufficient fuel for complete combustion, causing it to richen the mixture.

Second, CO2 is a major greenhouse gas. So as well as using more fuel to drive the same distance you would be adding even more greenhouse gases to the environment from the dry ice.

Third, it takes a lot of energy (electricity) to make dry ice. That puts even more pollutants, including more greenhouse gases, into the air from the generating plant.

Adding CO2, in the form of dry ice OR compressed CO2 seems like a bad idea on several levels, in my opinion.

If you want to fool the ECU, lie to it directly. Unplug the oxygen sensors, plug them into some circuit/computer, and have that "black box" tell the ECU whatever you want it to see. For instance, if you want to lean things out a few percent have the box tell the ECU there is less oxygen in the exhaust than is actually present. If you don't push it too far you may be able to force the engine to run a bit leaner. Push it too far and the car won't run very well. I don't know exactly how the ECU reads the oxygen sensors (measures voltage, resistance, capacitance, whatever), so you would need to do some research to figure out how to make a controllable "fake" oxygen sensor for the ECU to read.

Don't expect to pass an emission inspection with this in place though!

Wackiness Points earned, you have answers already
 

Superchow,

You would be a good scientist, I am not sure about you making a good engineer :D

Your answers are summed up by roflwaffle and jamesqf. Christ has taken care of demolishing the practicality.

A leaner mixture would be already equivalent to one having CO2 filler. If there is insufficient fuel to burn all of oxygen in the mixture, it does not matter if it is O2 or CO2, it (non-fuel part/excess O2/air) won't burn. Also as jamesqf pointed out, gaming/fooling the ECU is done best through modding ECU sw /instrumentation.

I don't have an answer to the cooling brought by the dry ice, but somebody else more qualified should answer (and let me just meddle with interpretation of others' post :p but what the heck, are not newbies allowed this to add to their post count? ;) )

Cheers,
hummingbird

These should be fairly easy to find, too, since they're commonly used as fire extinguishers (preferred for electrical fires, IIRC). Which I think says something about the practicality of the original idea :-)

instarx - there is an emissions trick to this - You're leaning the engine out, which creates higher NOx gas emissions, and adding CO2 to the mix actually will clean the NOx via the catalytic convertor.

BTW - the O2 sensor will not mistake CO2 for O2, it's a different compound, that creates a different signal. The O2 sensor is trained to see a certain amount of O2 after a burn cycle (little or none is preferred), so you're giving the O2 sensor exactly what it wants, by displacing oxygen intake. It will read that there is substantially less air than the "normal" volume, and start pulling fuel until it gets a bottom line.

OP - you may still run rich - the ECU can only pull an amount of fuel that would cause your engine "normally" to go too lean to recover. It's a failsafe feature that prevents unmodified engines from leaning out far enough to actually kill themselves. This is also why no racer (normally) uses OEM software. They modify the fuel curves, usually stating something like "pig rich" in the interim.

I wasn't trying to say for sure that you couldn't do it, I was explaining exactly what was more than likely to happen. With no direct way to meter when or how much of your CO2 enters the air stream, you've ended up with an uncontrollable cycle. This is not conducive to good testing procedures.

Ideally, to pull this off, you'd have to meter it so that all of your CO2 gas enters the cylinder in a pulse, BEFORE any air/fuel goes in, so you can keep ideal combustion in the cylinder. (The air/fuel mix would end up stacked on top of the CO2). You can give it a shot, in that resonator box, but I don't think you're going to see much of anything happening, and if you do, you're going to see damage to your engine from leaning out the fuel mix due to a lack of *dynamic compression*.

Everyone - If I understand correctly, and I think I do - He's not really looking to lean the air/fuel mix, more-so, he's trying to lower the amount of fuel used by limiting the amount of combustion space it has to work in. Think Atkinson cycle. Adding CO2 limits the amount of combustion space he has, which technically limits the usable displacement of the engine... bad terminology owns this thread, in that he's not trying to lean it out at all.. he'll still be running close to stoich, for the amount of usable air volume he has in the combustion chamber (if the ECU can compensate that far, if it can't, he'll be running rich, as instarx suggested, b/c of too little air, and the ECU not being able to trim fuel enough to compensate.)

Nitrogen could be used instead.

Carrying around this much inert gas in any form is likely to be a problem.

Let's get a rough idea of how much volume one would need. Assume a 2.0 L engine. If the car's average RPM is 2000, and there is one intake cycle every other rotation (4 stroke engine), then the motor will suck in 2000 L per minute. Assume the maximum perturbation is replacing 10% of that with the inert gas, which would be 200 L per minute. A scuba tank (80 cu ft at 3000 psi) is equivalent to (2265 L at 3000 (PSI)/14.7 (PSI/ATM) = 204 atm) so at 1 atm that would be 2265*204 L = 462060 L. At 200 L per minute this method could run for 2310 minutes, or 38.5 hours. In other words, it is within the realm of engineering feasibility to inject this much inert gas under more or less normal driving conditions.

Does it make sense to do so? That depends on how much energy it takes to load that scuba tank with nitrogen, and how much energy is wasted carrying around the extra weight. One also has to consider the lowered intake temperature which would result from expanding the compressed gas, although by routing the nitrogen line alongside the exhaust manifold it is probably possible to compensate pretty well for that effect.

What about ducting the air intake from somewhere cooler?

I'm wondering what drawing the cool air from in front of the air con outlet would do for engine power/and FE in hot weather. Be noisy in the cab, like an angry vacuum cleaner.

Tar seal is melting here in NZ yesterday and today its a hot one too. The road and tyres make a ripping sound as you go through the soft stuff. From a FE perspective the rolling resistance is high, and it pays to drive outside of the grooves made by other vehicles.

I've noticed when my engine is cooler from driving in the shaded forest or descending a mountain that I have way more power than when the motor is really hot like after climbing a mountain.

I'm getting the best FE now though, 75mpg US average tanks on mountainous roads with a lot of braking and tons of engine off time...I travel for 6 minutes without having to turn on!

Some cars do better with a high IAT like the Saturn. Mine did not. When the IAT got over about 110 it started to retard the timing and the FE would decrease. We get temps high 90-100+ and my IAT would reach temps of 130-140 or more. My high tech solution was to put a wet sponge in the bottom of the air box. This cooled the temps to my optimum temps and lasted for the hour commute. :turtle:

Christ -

Okay. I was thinking that the O2 in CO2 would separate during combustion, but you are saying that won't happen. That makes sense since that's already one of the emissions of combustion.

CarloSW2

A wet sponge?

One of those mounted infront of an incar air vent was my idea for a swamp cooler a/c system.

If you got hurt playing football they gave you a wet sponge.

Carlos - let me say this - I'm no chemist, by any means, so I won't say that it absolutely CAN'T happen...

I will say that afaik, it shouldn't happen, b/c in order for the compounds to separate, the O2 would have to have something to bond to during the combustion process, and since most of the O2 at that point (running lean) will just be extra compounds that have no "match" so to speak - that shouldn't happen.

Or, come to think of it, oxygen. This wouldn't save fuel as a retrofit in an existing motor. However, it could let a car with a very small motor produce bursts of energy, for acceleration or climbing hills, somewhat similar to a turbocharger. The atmosphere is 20% oxygen so adding 10% by volume pure oxygen to that would raise the oxygen level by nearly 50% (that is, to nearly 30%), which would let the motor burn 50% more fuel per cycle without changing the compression. (Ignoring for the moment complications such as the tendency for this high oxygen mix to ignite earlier.) Carrying around a tank of strong oxidizer would be a safety concern though, and the tank would have to be as far away from the gas as possible. If the oxygen tank ruptured in a crash, assuming the pressure related damage was contained by design, there would be a brief period of severe fire and explosion danger while the local oxygen levels are high, but this would dissipate quickly. It wouldn't be like a ruptured fuel tank, which leaves flamable liquid on the ground for a long time. Of course if both the oxygen and fuel tanks rupture at once, and there is any heat or sparks, it would be more boom than burn.

In theory a car could also be fitted with equipment to concentrate oxygen directly from the atmosphere while it drives. Depending on the amount of energy this takes, it might end up energetically favorable if the normally aspirated motor was enough for 95% of driving, and it used that time to top off a small oxygen tank. No idea which separation technology would be used though, because commercial oxygen separation is cryogenic and the equipment is very large - that technology is not likely to miniaturize well. In any case, the waste product of the separation is just the other normal atmospheric gases, so releasing them back into the air should not count as pollution. Hmm, carried to an extreme, where the car runs entirely on separated oxygen, there could be some substantial pollution related benefits - no Nitrogen to form NOx and on a lean burn the extra oxygen would convert any CO all the way to CO2. That could allow the elimination of the catalytic converter(s), which would recover some of the weight of the oxygen separating equipment. Or go whole hog and carry equivalent tanks of both fuel and oxidizer, both of which to be filled at the "gas" station. That would be one heck of a dangerous gas station though!

If you put the CO2 into the intake "upstream" of the intake air measuring device (MAF, MAP sensor, carb venturi) then the fuel system will see the CO2 as air. It will add fuel to go with that air--which will result in a rich mixture. It may very well be richer than the O2 sensor downstream can cope with. So you'd need to add the CO2 "downstream" of the air meter. That will be very difficult with a MAP-based injection system (such as older Hondas have), because pretty much the whole manifold from the intake valves to the throttle plate is the air meter... Easier with an air-flow based system, which I think most cars today use.

The drop in intake temperature will also cause a richer mixture, as the fuel system will "see" colder intake air, which is denser and needs more fuel. (BTW, cold air intakes generally hurt fuel efficiency unless the "regular" intake temps are very high indeed. Though there are exceptions, as always!)

The CO2 is very unlikely to be dissociated in the combustion process. It is one of the products of combustion, after all.

Another idea would be to find a nice warm source of CO2 and add that into the intake, down stream of the air metering devide. You could probably tap it from the exhaust, in fact. Perhaps you could call it "Exhaust Gas Recirculation"? ;)

...Sounds like the OP has found a nifty complex way to re-invent EGR, only in a less controlled fashion.

-soD

I have read a very interesting article on Autospeed.com about exhaust gas recirculation (linky). The tweaking process is what seems daunting to me. The author gets bonus points for control of the system, but I am looking for the "swamp cooler" approach. BTW: Wet sponge in air filter box = Brilliant!

I became suspicious why my idea of this crude leaning of the air hadn't been tried before. Just think how the car manufacturer's could have cheated during the EPA testing procedures... Then again, they were also gunning for cleaner emissions, which this would not necessarily accomplish.

No, this is an unabashed attempt at "cheating" to get better mileage, emissions be damned. And trying this in my econobox once is still more environmentally friendly than driving a Suburb-Hum-hoe every day. Heck, I commute by bus most days - even during these cheap gas price days.

At least the wet sponge may solve my lackluster low end torque during hot days. That's what I call lateral thinking. Thanks to all who chimed in. :thumbup:

You could design a water reservoir that drips constantly on to the sponge.

Like an inverted caged pet feeder.

Make 2 and use one for a swamp cooler air con, I'd love to know if it really works. Dryer climates benefit more from swamp coolers than tropical humid or wet places.

Removing the crankcase fumes from going back in the engine via air intake, and fixing a mini pod filter MAY also cool the engine considerably. Some motors dont like it though...

blueflame -

Ha ha, now all we need is the hamster making electricity running in his wheel :D !!!!!!!! If I used the wet sponge method, I'd make a cool "WSpower" decal to make someone think I had a performance mod in my car.

CarloSW2

140hp- really cram those little guys under the hood

I find that it works very well. Just need instrumentation to verify the IAT and timing. Unless the commute is long you don't need elaborate setup(Keep it simple. KIS) it will work for about an hour on 100+ days. As always your mileage may very.

dry ice
 

superchow,is your driving urban,or highway,or a mix?------If your going to "cheat",I think it would be easier on the highway than around town.Anytime you're in traffic,driveability issues will be an issue.---------- You might see 150-mpg at a constant 35-mph with a Pogue vapor carburetor(yeah they're real!),but they can't handle throttling.-------------------- The dry ice cooling you mention,is it for race cars compensating for heat-of-compression do to superchargers or turbochargers? If so,I suspect the fuel line is snaking through a "cool-can",which is a heat-exchanger type device filled with ice water,and along with inter-coolers,helps bring the charge temp down for better density (more charge more horsepower).---------------------- Modern electronic fuel injection attempts to balance MPG and driveability,with high sampling rates,and tremendous internal "look-up" menu scenarios,to anticipate conditions the car might experience.---------------- If you throw the ECM a curve-ball,by way of bogus input from sensors "seeing" artificial environments( CO2 ) it just may not have a fuzzy logic to make the best of all possible operating regimes.There's a lot of ROM in there.

When commuting, it is all 25 to 40 mph city/suburban streets. But this mod was intended for longer contsant high speed (50-70 mph) drives. We drive every so often to Portland, which is a 200 miles round trip. Even though it is 70 mph for 75% of the way, I can get away with puttering at 55-60 most of the time. It would just be too much effort for the gain I imagine for commuting - especially since it would be my wife who'd have to do this. Riiiight.....

I believe that I have basically achieved 90% of what is possible from the car in its stock form. After it is paid off and the novelty has worn off, I may consider 'basjoos"ing it to move to past "impulse power" and into "warp 1.0". But that involves too much time and money (and intermarital strife) to be worth saving a few dollars at the gas pump. Maybe when gas reaches $10+ per gallon the relationship may be in favor of modding, but even then the KISS answer would be to drive less.

Then again - since when do men take the easy way to do things. :thumbup:

If your goal is to "cheat" in order to get a lifetime best mpg run, there's a much easier way. Just drive up to Mt. Rainier. Start at the top of the pass, and record mpg on the way down. Saves lots of complications like possible damage to your fuel system, plus you get to spend a day hiking or skiing.

Somewhere I've got a photo of the Insight's display, showing 150 mpg average for a ~70 mile run. The trick is to start at Carson Pass, about 8500 ft, and take the picture when you get to the valley, near sea level :-)

Come on 90% of what's possible.:p Don't give up.:turtle:

If you want to cheat just put what ever you want in the gas log and just keep telling yourself that it's real.. :eek: It's not a lie if you believe it right.:p

dry ice would take loads of money and emissions to make sounds like a non-starter to me

Ah, but there is this thing called "accountability"!

I stand to my FE numbers, horrible as they may be. In the long run it'll give me a good idea of the fuel consumption of the car over many years. My time is too precious to waste it posting false mpg numbers. I also try to keep a record of the conditions during each tank, just to see what did make a difference.

To using pure oxygen in the engine for a power booster - you could try this using the breathing apparatus that some older people use... it's battery-electric, and creates a decent amount of (non-medical grade) "pure" oxygen.

Just so you know - the process to create cutting/welding "pure" oxygen is much cheaper than medical grade "pure" oxygen... both are "pure"... but neither is 100% oxygen.

if your gonna put anything in the intake throw in some hydrogen

Dry ice into intake?
 

To put dry ice into the intake of a Civic?

It could work to boost compression, however what about build up on the ice on the engine?

If there was a C02 turbo charging system as described, the dry ice could be made from the cars own exhaust, and sublimation emissions from the dry ice should be enough to cool the engines temperature, simulating the cold weather performance.

I would recommend keeping the ice sublimation emissions source (dry ice from exhaust) far away from engines intake to reduce damaging it. You might consider putting the dry ice behind the engines heat source to reduce drag. Also don't forget to change the oil first to cold weather oil.

Check out the Carbon Dioxide Recycler at:

myspace.com/allantugwellroberts

And Allan Tugwell Roberts on iTunes