Does a cold air intake add power on a 4.0?

Carve said:
I don't believe cleanability is a K&N advantage. It's a messy job with oil and solvents, and it should be easier to clean a regular filter. I do it all the time with my HEPA filter I have in my bedroom and it works fine. I run a humidifier that puts lots of calcium from hard water into the air, so this thing clogs up every month or so. I just soak it in some hot water mixed with detergent and vinegar, rinse well, and then run it through the dishwasher with dish detergent (by itself, of course). You can actually hear the smooth airflow afterwards, and then a month later, sure enough you hear my HEPA filter chuffing and sputtering, so it is continuing to filter out these microscopic calcium particles. There's no reason to think you can't do the same thing with the paper filter on your engine....I just don't bother because it's only $15 every few years for me. If I was racking up miles in super dusty conditions though and going through many filters per year, I'd probably give it a try.

But yeah....K&N sucks as a filter. I'd not use it in the dirty off-roading environment. It'll let too much dirt in, and also pack up too quickly, ultimately rendering it MORE restrictive in short order. For a seldom used performance car on the street though...sure...it'll get you a little extra power if you look after it.
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Pretty much all of the "washable" filter manufactures have openly stated that using the "oiled" filter is not recommended for extremely dusty conditions. They are meant for more humid/wet, low dust, environments. I put an AFE kit on my '06 Cummins when I was living in Western WA and had a noticeable gain of 1.5 to 2 mpg from the time I put it on. I was always wiping some oily residue from inside the tube with the oiled filter and there was clear evidence of some dust contamination almost every time. 6 years ago when I moved back to Idaho, I read an article about dry vs oiled filters and switched to their 7 layer dry filter and I have yet to find any dust or dirt contamination inside the intake tube since the switch.
 
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reddvltj said:
... I put an AFE kit on my '06 Cummins when I was living in Western WA and had a noticeable gain of 1.5 to 2 mpg from the time I put it on...
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A low restriction filter might actually offer an MPG bump in a diesel engine, but I don't think they do anything in a gasoline SI engine because the biggest restriction in your intake while cruising is the partially closed throttle plate. If you reduce restriction upstream of the throttle, you just have to close the throttle more to achieve the desired power setting.
 
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Carve said:
A low restriction filter might actually offer an MPG bump in a diesel engine, but I don't think they do anything in a gasoline SI engine because the biggest restriction in your intake while cruising is the partially closed throttle plate. If you reduce restriction upstream of the throttle, you just have to close the throttle more to achieve the desired power setting.
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There's a definite difference between forced induction and natural aspiration... I suppose I could have left out the mileage gains in that comment, the main focus was supposed to be the difference in usages for oiled and dry filter types. oiled is definitely not something you want if you're in dusty environments, but if you only ever play in mud and water the oiled filter does have the advantage of shedding any water vs it being absorbed by the filter media.
 
OK, can’t help myself :). To get to the core question, does a cold air intake add horsepower…yes, cold air is denser and thus under proper conditions can add horsepower.

But how much (again, this depends and a lot of people talked about filters)?

To try to see just how much, I created a cold air setup, but used an enclosed inline type filter (rated decently above the CFM required for the 4.0L) and put it in the same location as the typical cold air setups you see for the TJ. What this allowed was for me to add and remove a snorkel intake, and then measure the difference in intake temperatures, and thus to approximate how much horsepower increase I can expect with a snorkel.

I realize this doesn’t get to the difference between the cold air intake kits without a snorkel and the stock TJ setup, but my assumption is that the difference in air temperature under the hood between factory TJ air intake and a ‘standard’ cold air setup without snorkel should be even less significant between the ‘standard’ cold air intake set up and the one with a snorkel, and that I’m not looking at differences from different filter types.

So my test was multiple passes down the same stretch of relatively flat (as flat as I could find) highway with both the snorkel attached and not attached. Again, while I haven’t done full analysis, it is clear there is about a 10 degree F temp difference…so what does that equate to?

The general equation for difference in horsepower for given intake air temp difference is that it is proportional to the sqrt(T2/T1), with T referenced to absolute zero (so start at approx. -460 degrees F and add intake temp).

For my tests, we have sqrt(600/590) = 1.0084, which at best case (max horsepower) equates to about 1.5 horsepower.

Now I haven’t fully researched it, and again I am not considering differences in filters, as to me that is a different question, so I welcome criticism if I’ve made any errors.

In the end, yes a cold air intake can add horsepower, but from a pure cold air perspective, unless you can get a large temperature difference, the gains are minimal and so doubt noticeable.

And I’m sorry if this is duplicating anything anyone else added, although I love this forum, after page 3, I was just skimming!
 
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TheBoogieman said:
I made a "true" cold air intake, using the stock air box with no cover and filled it with ice. It sucks stopping all the time to refill the ice bucket, but the hp gains are undeniable. :geek:
p.s. I drilled a hole in the bottom, so the water drains out.
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Let me know when you are ready to graduate to liquid nitrogen, grasshopper. :cool:
 
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TheBoogieman said:
I made a "true" cold air intake, using the stock air box with no cover and filled it with ice. It sucks stopping all the time to refill the ice bucket, but the hp gains are undeniable. :geek:
p.s. I drilled a hole in the bottom, so the water drains out.
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My buddy used CO2 to cool his intake charge on his Skyrine. True story.

But so we are all on the same page, I see people talking about 3 separate angles here: K&N style oiled filters, CAI's aimed at getting, ummm, colder air into the intake manifold, and then we are evaluating an aftermarket swoopy style intake that "flows" better than stock. I think what OP is primarily evaluating here is the last topic. All aspects matter and are good to talk about, but just so we are all on the same page...
 
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SkylinesSuck said:
My buddy used CO2 to cool his intake charge on his Skyrine. True story.

But so we are all on the same page, I see people talking about 3 separate angles here: K&N style oiled filters, CAI's aimed at getting, ummm, colder air into the intake manifold, and then we are evaluating an aftermarket swoopy style intake that "flows" better than stock. I think what OP is primarily evaluating here is the last topic. All aspects matter and are good to talk about, but just so we are all on the same page...
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Well....if I could find the motivation to do it, I think the best setup is cowl induction. You get cold, outside-the-engine-bay air in an area that's high (to avoid water) and high-pressure when highway driving, for a little extra boost when you really need it

IMG-4104,medium_large.1551049470.jpg
 
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The cowl area isn't going to be under any pressure. It's open at the top AND bottom. One down side to a cowl intake like that is your are going to hear it a lot in the cab, although some people might not mind that much. Still, I agree it's a good option.
 
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SkylinesSuck said:
The cowl area isn't going to be under any pressure. It's open at the top AND bottom. One down side to a cowl intake like that is your are going to hear it a lot in the cab, although some people might not mind that much. Still, I agree it's a good option.
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I can't hear mine in the cab at all...

Jeep - 5.7 Hemi 7-7-2017 1517.JPG


(Note: Other factors may be involved... ;))
 
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Neat to see some actual results. I would still rather have better filtration over those minor gains though. There are just so many other things to spend your money on!
 
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