Cold Air Intakes?

It's a proven thing.

Warm air will give less power but use less fuel. Opposite for cold.


Just look at mileage for summer and winter.

Most airplanes have charts/graphs for fuel consumption at various altitude, power settings, and temperature combinations. And I'm not talking about just large jets here but everything down to home-built kits.

The colder the air,the denser it is so therefore it will take more fuel for any given volume of air. The ratio of air to fuel will be the same but because it's much denser you'll get more power from it. But more gas is used.

The warmer it is.. it'll be less dense. The air/fuel ratio must stay the same so now it'll be less fuel for any given amount of air.. so you'll get less power and burn less fuel.

When you lean the mixture you're changing the air to fuel ratio.. with cars that's generally done automatically for you (open/closed-loop etc) so they can stay as close to a stoichiometric a ratio as possible. That just means the ideal mixture (I think it;s around 20 parts air to 1 part gas).

The difference in my truck,especially in the winter, could be significant. -30 outside and +20 under the hood once the engine gets to operating temp. Mileage could be almost as good as in summer. I usually get about 25% worse mileage between October and April.

I assume the 'intake heat' you mention in an airplane must be carb heat. When you apply carb heat you're supplying the carburator with WARM air from around the engine to get rid of any ice forming in the venturi. Now, when you select that warm air, you usually have to lean the air/fuel ratio because now the engine is running too rich from too much fuel.

 

It's no trouble, but remote air intake is a lot quieter, that's what all those big plastic resonators are for.

Gee... then that same theory would also apply to cold air intakes, too.

Of course you could be absolutely right. I only have my truck as my experimental test bed. The average mileage for the last thousand miles is 23.5 mpg on Winter blend gas, even with almost no freeway driving.


Greg

 

What do you guys mean be tuning? His is this done? Is something like a urd maf sensor calibrator help with the tuning problem

 

Using regular pump gas, 14.7 to 1 is stoich....perfect burn
Airplane fuel is different

 

You gas mileage guys are too much... I want POWER!!!!

 

Yeah it sounds weird to be saying I want less power in a 4banger..

..But when it's winter and -30 outside and my mileage is 30% higher than summer..I feel I can lose a few ponies to stretch out my tank.

Besides I gained a bunch from the new header! So it should all even out..

I'm actually working out a plan to be able to go from a cold air intake (stock) to a warm air intake on the fly.

 

^^just teasing...I forgot to add the

But.. you're right. I'm not used to that severe cold weather and 30% difference is huge on the wallet. I really want a header, esp. after hearing good results from you and tooter, I'm just not sure yet if I want to do more... turbo, supercharger. And I like your idea on having a convertible cold air / warm air intake.

 

Why would 100 octane low lead aviation gasoline be any different on air/fuel ratio???

Many small aircraft can be FAA certified to operate on automotive pump, gas for those who keep their planes at a private landing strip, on a farm for example. I've seen several planes with the FAA automotive fuel certification label.

 

The intake air temp is nowhere near the whole reason for decreased efficiency in cold weather. Your engine will still have to warm up, and so will all the lubricating fluids in the entire vehicle. I notice very little (if any) difference in efficiency after the vehicle warms up, during cold weather. I do admit it's never been -30F here in my lifetime.

You will never recover that 25 to 30% loss by warming the intake air, if it even really helps at all. Even if it does help a bit with leaning the mixture, why wouldn't the loss of power offset that?

Anything anybody says, or does, without proof under scientific test conditions, is of no consequence to me at all. I only accept scientific proof. I'm not really going to argue, but it'll just go in one ear, and out the other...

 

I never stated that I would recover all the lost mileage due to winter. I know, probably better than you, that idling, winter gas, winter tires, colder roads, denser air etc and etc all in a small way suck mileage away.
You haven't read my earlier posts on this subject. There IS proof that warmer air gives better mileage.. you seem to know alittle bit about flying.. go look at cruise charts. They'll give the charts at varying air temp at any given altitude with fuel flows.

We're not talking about leaning the mixture here. Lean or rich mixture has to do with the air/fuel ratio. With cars and trucks the mixture is done automatically. If I go with a warm air or cold air intake.. the truck will adjust the mixture accordingly. What's going on here is the AMOUNT of air/fuel going into engine. Warm = less dense .. cold = more dense.

I also have observed the mileage fluctuate between summer (+30) and winter (-40) after many years of living and working up north.

Anyway, you are right in respect to this not being scientific, which is why I plan on documenting my whole process next year when I get my warm/cold air intake built. According to my scanguage at -30 air temp my air intake is at -22C (not sure were it gets the temp at.. I assume it's at the MAF). I want to try to get the intake air up to 0C at -30 outside temp. That's a huge difference in temp.

Sounds typical of some internet posters I guess.. we were having a great discussion on here with some great ideas and information being shared.

 

Thank you for your correction.... 14.7:1 is stoich for ALL automotive pump gas!

 

That's why I mentioned aircraft, the pilot has to make mixture adjustments. If our trucks had fixed jet carbs, then really hot or cold air would lean or richen the mix. With fuel injection the ECM adjusts for conditions to maintain 14.7:1.

Same thing that happened with modified exhaust, and intakes on motorcycles, and cars with carbs (especially after emission regs started). More air flow with fixed jet carbs made the mix too lean, and burned valves, scorched pistons was the result.

I still say any gain from the warm air (i'm still not convinced of any gain) will be offset by the loss of power.

 

That's my point but I think you've missed it..

Here's some numbers:
Let's assume the intake can keep the fuel air mixture at 14.7 parts of air to 1 part gas. (It can't and won't keep it exactly there..it will automatically richen or lean the ratio accordingly but it will never be bang on).

Let's say at +30C there is 100 parts of air (just a fictional number to be used as an example) that fit in the entrance of the intake at any given time. That means, at 14.7:1 that there will be 6.8 parts of fuel used.

Now, let's say that at -30C there is 130 parts of air (again just a fictional number.. I have no idea how much denser air is at that temp) in the same exact spot. Remember that the truck automatically adjusts the mixture to 14.7:1. So now we have 8.84 parts of fuel going in to get burned.

See what I'm saying? What's going on here has nothing to do with leaning or enriching the mixture... just the density of the air due it's temperature. The mixture is going to be taken care of by the truck.

 

I DO understand the idea behind what you are saying. I just used the the fixed jet carb thing as an illustration, and the aircraft as well.

I know modern vehicles match the fuel flow to the air flow.

However, engines with fixed jet carbs didn't. Add air flow, and they'd be lean. Take away air flow, and they'd be rich.

 

Yep. You're totally right. And I understand where you're coming from, but fixed jet carbs aren't pertinent to this discussion because we take the mixture out of the equation since it's a constant figure. The only variable is the density of the air due to it's temperature.

 

Subd

 

Um then how do you explain this? From chevy's website their 4.3L V6 ecotech 4WD has 285 HP and 305 ft/lbs of torque. It has an EPA estimated 17mpg city and 22mpg city. So according to this, this engine get better or just as good mpg as my 2.7L I4 and more power.

So there is more power with same fuel economy. More get up and go did not decrease mpg. Im sure more examples could be found.

 

You left out the part where the chevy will do that for a year but your Toyota will do it for 30 yrs...............

 

It's true but that wasn't my point