Does a cold air intake add power on a 4.0?

Richard49 said:

Oh,and still remaining neutral here; cooler air is denser, so more will fit into a given volume.
There is that to consider.

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There are numerous things that come into effect. cool vs hot, humid vs dry air. The price of tea in China.
My jeep runs much better on a cold dry day vs hot and humid. It almost feels like I lose about 50hp on a hot humid day.
And....dyno number can be manipulated. Not that I'm saying the OP did that.

Reading through this thread is puzzling. Are some of you not reading the first post and understanding that he did the runs himself? Or are you accusing the OP of manipulating the dyno runs?

He made multiple back to back runs in each configuration, and the runs in one configuration were consistently higher than the other and greater than the variability between runs of each configuration on its own. To chalk that up to error would require much greater anomaly than that the K&N setup adds power. I'm taking the data with the assumption that the OP is honest and not trying to mislead us...and if that's the case it's definitive that the engine DID make more power with the aftermarket intake. What remains to be known is why - was it truly a result of decreased resistance to flow or was it a temporary effect on the mixture that the PCM will adapt to?

freedom_in_4low said:

Reading through this thread is puzzling. Are some of you not reading the first post and understanding that he did the runs himself? Or are you accusing the OP of manipulating the dyno runs?

He made multiple back to back runs in each configuration, and the runs in one configuration were consistently higher than the other and greater than the variability between runs of each configuration on its own. To chalk that up to error would require much greater anomaly than that the K&N setup adds power. I'm taking the data with the assumption that the OP is honest and not trying to mislead us...and if that's the case it's definitive that the engine DID make more power with the aftermarket intake. What remains to be known is why - was it truly a result of decreased resistance to flow or was it a temporary effect on the mixture that the PCM will adapt to?

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Doesn't matter. Jerry talked to a guy.

Why do we care about whether or not they add 10 HP or not? These are 4000 lb bricks, it's not going to make any actual performance improvement under any realistic conditions.

The shuggs said:

Why do we care about whether or not they add 10 HP or not? These are 4000 lb bricks, it's not going to make any actual performance improvement under any realistic conditions.

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some of us want a more detailed understanding than just taking "no" at face value from someone on a forum. Even if the answer is still "no", it matters to some whether that's because it literally makes zero, dyno-verifiable difference, or whether it makes some difference that's only perceptible on the dyno and not in real life.

freedom_in_4low said:

some of us want a more detailed understanding than just taking "no" at face value from someone on a forum. Even if the answer is still "no", it matters to some whether that's because it literally makes zero, dyno-verifiable difference, or whether it makes some difference that's only perceptible on the dyno and not in real life.

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What I'm saying is that if the answer was that it unequivocally added 10 HP, would that make an on-road difference in how a TJ drives given its miserable power to weight ratio, and terrible aerodynamics?

The shuggs said:

What I'm saying is that if the answer was that it unequivocally added 10 HP, would that make an on-road difference in how a TJ drives given its miserable power to weight ratio, and terrible aerodynamics?

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It probably wouldn't, but that's still not the question being asked or answered in this thread.

freedom_in_4low said:

It probably wouldn't, but that's still not the question being asked or answered in this thread.

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That's why I asked a better question.

The shuggs said:

What I'm saying is that if the answer was that it unequivocally added 10 HP, would that make an on-road difference in how a TJ drives given its miserable power to weight ratio, and terrible aerodynamics?

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Agreed and as I have redundantly stated repeatedly over and over again ad nauseam, bolting an aftermarket intake on to a stock engine isn't something I recommend to 99% of TJ drivers. It isn't going to help push your TJ with oversized tires and not enough gearing up a hill in 5th with your foot on the floor at 3k rpm. It isn't going to make you crawl any better over a rock. It can potentially filter worse and could possibly be more likely to suck in water. 10rwhp from only bolt on n/a mod is nothing to scoff at though.

I recommend against them for most people for the above reasons. Not everybody is in that 99% though. Some people want to bolt on a bunch of engine mods on there TJ and rev it to redline. Some people want to mud bog or embarrass Honduhs at the stop light. Some people like building stroked out or turbo I6's. Some people just like tinkering. Not everybody has the same build and some people can't wrap their head around that and go around saying TruTracs are garbage and not worth anything anywhere anytime because they don't daily drive their rig and wheel exclusively out west on rocks and know nothing of trails out east-—-oh wait, I got a little off track there

OP started this thread by posting data. Some people jumped in with their opinion which is fine and welcome. Some people just shouldn't get all butt hurt when we don't all agree with them or treat their esteemed opinion as fact. I have very much valued Jerry's opinion on most things Jeep. Still do, and still will. I just wish Jerry would do a little better at remembering not all his opinions are facts just because he said so and not everybody builds their Jeep for the same purpose as he chose.

TL/DR:

Does adding 10rwhp at redline matter much for a TJ? Almost always no. Did adding an intake get OP 10 rwhp on his TJ? Yes.

The shuggs said:

What I'm saying is that if the answer was that it unequivocally added 10 HP, would that make an on-road difference in how a TJ drives given its miserable power to weight ratio, and terrible aerodynamics?

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Those 10 extra horses would help my 31's lay longer stripes!

The shuggs said:

Why do we care about whether or not they add 10 HP or not? These are 4000 lb bricks, it's not going to make any actual performance improvement under any realistic conditions.

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It's been proven at the track many times by many in the automotive industry that for every 100lbs removed is like adding 10 HP. Lets work that inversely for the Jeep crowd... for every 100lbs added, you take away 10 HP... so that bumper and winch you just added, those heavier tires, that armor plating, etc...

Maybe it makes a difference, maybe not. Will a winch get you recovered from all the situations you might experience on a trail? (same answer)

Jezza, I just realized, you don't need a dyno to hook up a vacuum gauge and try it with different intakes. It would work fine on the street just the same. You could even give us your butt dyno tingling readings afterwards as well!

SkylinesSuck said:

Jezza, I just realized, you don't need a dyno to hook up a vacuum gauge and try it with different intakes. It would work fine on the street just the same. You could even give us your butt dyno tingling readings afterwards as well!

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We don't need to know what makes his butt tingle...

Artsifrtsi said:

We don't need to know what makes his butt tingle...

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Y'all are making me reconsider replacing my POs K&N CAI....













I'M JOKING......ok... I said J-O-K-I-N-G

Jezza said:

Answer is yes.

I have seen this question asked and answered before. Typically the answers I see range from very little to none. I had a hard time believing that there was no power to be had, so I did a little test today while I had the TJ on the chassis dyno.

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Jezza said:

Does a cold air intake add power on a 4.0? Yes, in my testing it was good for around 10HP at the wheels. Is that power worth the money or the possible lack of filtration? I don't know, you be the judge.

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The OP made it clear he was curious and had the resources to test the question, so he experimented. The OP also never said to run a K&N filter. He's simply providing data, so the power question is no longer "butt of the seat" information. I for one would not run the max power configuration, but I can appreciate the thirst to be in the know!

However, understanding the rest of the story would be interesting, that is:

- What particle size passes through a Mopar stock filter?
- What particle size passes through the K&N?
- Does the stock computer null the HP gain over a period of time?

These combined would make a truly informed decision.

Jerry Bransford said:

View attachment 318662

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I don't have a dog in this air intake thing but if you have a relationship with this guy would you mind asking him to shed some light on the driveline-induced oscillating vibration some of us get, and how that might be related to the addition of the transfer case output dampener added in 2003?

williambmac said:

My jeep runs much better on a cold dry day vs hot and humid. It almost feels like I lose about 50hp on a hot humid day.

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I know it's butt dyno but I'm as certain as I can be that I could feel this on my 99 (at least cold vs hot, don't know if I can tell wet vs dry because it's usually more dry as it gets more hot). It's made me think at various times pretty seriously about the cowl intake mod with an insulated tube but I haven't been able to push through my trepidation of taking a large holesaw to my firewall.

I'm not as certain with my 06 as I was with my 99, but it may be because I had the 99 in Colorado and could drive to work in 60° and drive home at 100°...our daily swing in OK is half that at best and I don't commute anymore.