Cold Air vs. Not and MPG?

[Infidel Edition]

I'm at work and I'm board, so I've been looking at some tech articles on Cold Air Induction systems and their MPG savings claims. :rolleyes:
But I also had been looking at mod's to cool down my under the hood temps and found several references to hotter engines burn less gas...

... which led to the physics of cold air vs. hot air and why there is a difference in fuel consumption.
As I read it, cold air is more dense and therefore holds more oxygen per volume than hot air. More oxygen means more burn... and implied more fuel consumption.

However, all the CAI systems tout that they not only give you HP, but MPG too.
:poke:

Then I started thinking, it's freaking hot under my hood after a long road trip! And I was going to work on a ventilation system... as the floor gets a little warm too up by the firewall.

I also pondered the idea of ceramic coating the inside of my exhaust manifold (did this on my K5 years back ~ there's a ceramic spray for like $20 that does a decent job).
Why not also ceramic coat the inside of my intake manifold to maintain the cooler air temps... or even the exhaust wrap on the intake?

So is it Hot = better MPG?
...Or Cold = better MPG?
...................... and why not get HP too!
WT* is the sweet spot?

Just some random thoughts from my slow arse day in the dungeon at work:rolleye0012:

[Mudderoy]

I'm at work and I'm board, so I've been looking at some tech articles on Cold Air Induction systems and their MPG savings claims. :rolleyes:
But I also had been looking at mod's to cool down my under the hood temps and found several references to hotter engines burn less gas...

... which led to the physics of cold air vs. hot air and why there is a difference in fuel consumption.
As I read it, cold air is more dense and therefore holds more oxygen per volume than hot air. More oxygen means more burn... and implied more fuel consumption.

However, all the CAI systems tout that they not only give you HP, but MPG too.
:poke:

Then I started thinking, it's freaking hot under my hood after a long road trip! And I was going to work on a ventilation system... as the floor gets a little warm too up by the firewall.

I also pondered the idea of ceramic coating the inside of my exhaust manifold (did this on my K5 years back ~ there's a ceramic spray for like $20 that does a decent job).
Why not also ceramic coat the inside of my intake manifold to maintain the cooler air temps... or even the exhaust wrap on the intake?

So is it Hot = better MPG?
...Or Cold = better MPG?
...................... and why not get HP too!
WT* is the sweet spot?

Just some random thoughts from my slow arse day in the dungeon at work:rolleye0012:

A few years ago I was looking at various ways to improve mpg. I was thinking of a cold air system. A vendor that sells cold air told me not to bother. Now I've been collecting mpg data for some time now, and if someone wants to send me one to test out, I'll be happy to report the mpg changes, and send it back after the test.

[Paddletrucker]

Can't really speak with authority on Cherokees, but I'm a fuel mileage obsessed fanatic on my semi, because it's how I make my living. One mpg in those things can mean up to .15 cents/mile, or in my case $300-$350 per week. So, I've tried all kinds of various things to improve economy.

In my experience, it will give you horsepower or mileage. Rarely, RARELY both. In theory, sure it's true. It can happen. It practicality, however, I've almost never seen it. In my diesel pickups and in my semi, it comes down to three things...aerodynamics, speed, and a proper shift technique (not applicable if you've got an auto tranny). Slow down, clean up the outside from drag and resistance, and shift smoothly. Almost anything else is a sales technique to sell stuff. In my pickups and in my semi, every 5mph I slow down equals 1/2mpg, or for every 5mph I slow down, I give myself a 5 to 7 cent per mile raise. Sure, I've got all kinds of mods on my engines for power to climb hills under heavy loads, but the only thing that's ever RELIABLY given me better mileage EVERY TIME IT'S TRIED, is slow down, shift smoothly, and take stuff odd of the outside that may looks good, but causes drag.

I've tried intake mods, exhaust mods, injector mods, aftermarket turbos, etc. etc. etc. Still though, those three things is what works, with slowing down being the most effective.

[Infidel Edition]

A few years ago I was looking at various ways to improve mpg. I was thinking of a cold air system. A vendor that sells cold air told me not to bother. Now I've been collecting mpg data for some time now, and if someone wants to send me one to test out, I'll be happy to report the mpg changes, and send it back after the test.

~I wasn't going to actually pay for anything... I was going to redneck it into a engine compartment air circulation sort of thing.
...a.k.a. stick a vent and some air ducting from the box to the side.


In my experience, it will give you horsepower or mileage. Rarely, RARELY both. In theory, sure it's true. It can happen. It practicality, however, I've almost never seen it.

I've tried intake mods, exhaust mods, injector mods, aftermarket turbos, etc. etc. etc. Still though, those three things is what works, with slowing down being the most effective.

That's kind of what I thought. But with so many people getting "hyped-up" about them, I thought maybe they were the magic pill.
...not to mention, it is freaking hot under my hood ~ which means the air intake is pulling hot air into a hot engine.

Thanks for the feedback

[bigjim350]

Only time ive heard of people getting mpg and hp gains out of a cold air intake is when it is also used with a free flowing exhaust and a tuner.

[gary63]

the way to get more mpg out of your motor is to get it to make the same or more hp at a lower rpm. Example if you are turning 2000 rpm at 60mph you will use more fuel than if you can get your motor to move you at 60 mph at 1800 or 1500 rpm.To do that you have to get the motor to burn all of the fuel that goes into the cyl.that way you are not wasting fuel and you make more hp.So colder AIR will get more oxygen into the cyl. so can burn the fuel easyer and more with less waste.Now if the motor is hot when the cold air goes into the cyl. it will start to expand witch is now trapped in a closed chamber with the same amount of fuel that it had before but more air that is now expanding making more prisher witch gives you more comprition and more comprition give you more hp..So you get more hp with the same amount of fuel and running at the same rpm so themotor is not working as hard you get more mpg. not saying you will get alot it all depens on how go your motor can burn the fuel.

[bigjim350]

If your motor is running 2k rpm at 60, it doesn't matter how much more hp you get. You can add another 1000hp and it will still run 2k rpm at 60. That has to do with gear ratios not hp

Sent from my nerdy smartphone

[bluedragon436]

If your motor is running 2k rpm at 60, it doesn't matter how much more hp you get. You can add another 1000hp and it will still run 2k rpm at 60. That has to do with gear ratios not hp

Sent from my nerdy smartphone

But it would be a heelaciously fun time having a 1000hp XJ, and getting to that 60 with my XJ and 33's... , or what would be left of em'.... LOL

[ArmyGuy45]

I know this is a XJ forum but when I put a full breathing kit (intake and exhaust) on my Rubicon JK I got up to 23 mpg on freeway vs 21.

http://i1161.photobucket.com/albums/q520/ArmyGuy1911/Image0073_zpsdec498ea.jpg

Vs

http://i1161.photobucket.com/albums/q520/ArmyGuy1911/Image0079-1_zps45e04036.jpg

[Infidel Edition]

OK... so cold air with more open exhaust.
I have the stock '89 Remix system.
The TB is what 55mm. The stock 90+ is tapered to ??upper 50's somewhere and people hoan them out to what 62mm?
Anyway, is the exhaust diameter larger too?
And if I pulled 1 from the local junkyard... would it bolt on?

.... my exhaust from the cat back is rusted to sh!+ ~ so if I have to replace it.... just thinking outloud:watermelon:

[bigjim350]

Do you plan on wheeling the jeep? If so a cold air intake would be a bad idea, especially if wheeled around mud or deep water. Also oiled type air filters, like k&n, aren't a very good idea anywhere other than the street.

Sent from my nerdy smartphone

[Infidel Edition]

Do you plan on wheeling the jeep? If so a cold air intake would be a bad idea, especially if wheeled around mud or deep water. Also oiled type air filters, like k&n, aren't a very good idea anywhere other than the street.

Sent from my nerdy smartphone

My primary objective is street ~ specifically over mountain passes that get snowy in the winter... and occasionally snowy in the early summer too.
With occasional beach trips... so sand.

Oregon can get some diverse weather and driving options for jeeps

[ArmyGuy45]

Do you plan on wheeling the jeep? If so a cold air intake would be a bad idea, especially if wheeled around mud or deep water. Also oiled type air filters, like k&n, aren't a very good idea anywhere other than the street.

Sent from my nerdy smartphone

Why is oil filters bad for 4x4? I would think the dust and oil would be better filtration than paper. On my Rubicon I always cleaned my filter on every oil change.

[bigjim350]

The dust and dirt will restrict the flow on an oiled filter much quicker than a dry filter. But I'm not suggesting a paper filter, just not a oiled filter.

Sent from my nerdy smartphone

[ArmyGuy45]

The dust and dirt will restrict the flow on an oiled filter much quicker than a dry filter. But I'm not suggesting a paper filter, just not a oiled filter.

Sent from my nerdy smartphone

So foam?

[bigjim350]

A few people make very good dry cotton filters. My favorite would be AEM. They have stock type drop in replacement filters as well as universal cone type filters.

Sent from my nerdy smartphone

[4.3LXJ]

I have an AEM, love it

[XJ Wheeler]

Just to throw a wrench into your thoughts. Cowl induction & snorkel? Both have the ability to pull cooler air without the risk of coating the filter in mud or flooding it.

[89Laredo]

I'm doing cowl on mine eventually...
I'm kinda sceptical about "cooler air" with the tube going right over the head though...

[Infidel Edition]

I have an AEM, love it

What's an "AEM"?


Just to throw a wrench into your thoughts. Cowl induction & snorkel? Both have the ability to pull cooler air without the risk of coating the filter in mud or flooding it.

I was planning on a scoop opening toward the windshield as I drive in the Pacific NW and don't need that much extra water spraying my engine down.
So, by pointing it toward the windshield and then adding a small lip and screen on the hood where I cut the hole is to ensure water doesn't sneak past....
That should drop the under the hood temps.

Then for the air intake, I was going to redneck a hole on the side that could be modified into a snorkel or capped with louvers...

[89Laredo]

What's an "AEM"?


google broken? Lol
http://www.aemintakes.com/
Same as k&n just different construction.

[Infidel Edition]

google broken? Lol
http://www.aemintakes.com/
Same as k&n just different construction.

Hey now... Google had 12,200,000 results for AEM. :sign0181:

PS. Would flames shoot out my tailpipe like the Porsche in the pic on their page? That'd be cool.
... but the PD would probably ticket me.
......... and the O'person in DC would likely pass some sort of anti flames in the tail pipe emissions standards!

[4.3LXJ]

What's an "AEM"?



I was planning on a scoop opening toward the windshield as I drive in the Pacific NW and don't need that much extra water spraying my engine down.
So, by pointing it toward the windshield and then adding a small lip and screen on the hood where I cut the hole is to ensure water doesn't sneak past....
That should drop the under the hood temps.

Then for the air intake, I was going to redneck a hole on the side that could be modified into a snorkel or capped with louvers...

It is a type of dry air filter Big Jim mentioned. It filters well and does not use oil. Washable and reusable. If you just get a of dust on them like we can down here on group trips, you can just shake them out and put them back in.

http://i649.photobucket.com/albums/uu215/warriorsuspension/IMG_0483.jpg

[bigjim350]

google broken? Lol
http://www.aemintakes.com/
Same as k&n just different construction.

Don't be a :ass: And no its not the same as a k&n. Maybe you should google to see how they are different....

Sent from my nerdy smartphone

[89Laredo]

I wasnt... He asked a generalized question so I gave a generalized answer.

"Different construction"
EX: Different material that doesnt require oil... :poke:

Im pretty sure I remember them making an oiled filter at one point too, they must make only the dryflow now, couldnt find them on their site.

[joshuahabib]

i just fab a air intake for my 93, will let you know the difference.

[Infidel Edition]

i just fab a air intake for my 93, will let you know the difference.

OK ~ the grownup sized is the air filter (looks a little limp :mock:) on the driver side...
What's the jr. sized filter on the passenger side?

Does the filter vibrate on the inside of the fender...

[joshuahabib]

lol the little one is for the breather for the oil, and no
i have a bracket that holds it into place. :thumbsup:

[Infidel Edition]

lol the little one is for the breather for the oil, and no
i have a bracket that holds it into place. :thumbsup:

Cool &~ welcome to the forum...

[joshuahabib]

thank you

[gary63]

just for the record k&n can be used dry it filters better with oil.We have use k&n around here for years and we are in the desert with alot of dust and sand that is kicked up when driving.

[cpttuna]

For what it's worth. There are 5 XJ's in the family. My wife's 01 gets the best mileage I believe because her jeep has the best homemade cold air intake. All the jeeps have the same tires,exhaust setup, are all autos etc. I believe the cold air helps.

[Infidel Edition]

For what it's worth. There are 5 XJ's in the family. My wife's 01 gets the best mileage I believe because her jeep has the best homemade cold air intake. All the jeeps have the same tires,exhaust setup, are all autos etc. I believe the cold air helps.

On the cold air end...
What does the letter inlet look like?
Or does it just pull from the front corner?

[cpttuna]

I hope I understand your question. The silver colored dryer vent material runs down to the vicinity where the hole is for the factory fog lights. this is where the bulk of the cooler air comes in.

[Infidel Edition]

I hope I understand your question. The silver colored dryer vent material runs down to the vicinity where the hole is for the factory fog lights. this is where the bulk of the cooler air comes in.

"fat finger" I meant "O" outer ... not "litter" ~ and then my phone must have fixed my spelling :stars:
But yes, that does answer the question.
... did you remove the lights? Or just use the gap around the edge?

I was thinking of something along those lines since the factory box is right there and it'd be the most convenient spot.

[cpttuna]

I do not have fog lights. I used the opening.

[Carves]

This is apparrently the original air intake point on the early models ... and blocked off on the later models.

Might be useful to you ???


http://i1143.photobucket.com/albums/n629/carves-oz/Vehicle%20Bits/Engine/Airintake50a_zpsc82e7e7e.jpg

[89Laredo]

I wonder why they blocked it off... The inlet is still there, now it is trying to suck air from around a wall. My 97 wasnt blocked off.
Im doing a cowl intake on Mine. Not very hard and seems to be the best place to get cool air. Keeps water out too.

[Infidel Edition]

I'll have to check.
Maybe I just haven't dug around that much.
...there isn't anything currently connected there. Just sucks from the front corner area

[cpttuna]

i made a hole where the bottom of the air box was.

[Infidel Edition]

i made a hole where the bottom of the air box was.

That's pry what I'll do... But I have that vacuum thing nuzzled right there to deal with.
Pry drill a hole and move it over to the side of the box.