Don't get me started on my Thrush welded muffler and 3" tailpipe giving me a 15 hp increase.
Does a cold air intake add power on a 4.0?
- Thread starter Jezza
- Start date
I do like the logo, that's gotta count for something?
Dogma strikes again. Even if the dogma is "correct" in a practical sense (stock air box is best for most), it's technically wrong.
Air filters are restrictions. They are an area with a bunch of tiny holes. For an air filter to be less of a restriction it needs either
a) more filter area. or
b) bigger holes.
K&Ns have bigger holes, so they flow better at the expense of filtration effectiveness. We all know this.
As to the tune adapting the losing power, this can be explained by the trim tables. Slap on a better-flowing filter and intake and you've got more air and a leaner mixture. Lean makes more power (at the risk of damage), so the computer "corrects" this over time and some of the gains are lost. But not all of them.
That said, the main benefit of aftermarket intakes is sound. Intake roar = power!
Air filters are restrictions. They are an area with a bunch of tiny holes. For an air filter to be less of a restriction it needs either
a) more filter area. or
b) bigger holes.
K&Ns have bigger holes, so they flow better at the expense of filtration effectiveness. We all know this.
As to the tune adapting the losing power, this can be explained by the trim tables. Slap on a better-flowing filter and intake and you've got more air and a leaner mixture. Lean makes more power (at the risk of damage), so the computer "corrects" this over time and some of the gains are lost. But not all of them.
That said, the main benefit of aftermarket intakes is sound. Intake roar = power!
I don't know about that computer stuff? I haven't seen or paid much attention to that. My long term trims change pretty quick, what else is there? I don't really know but there aren't many people posting dyno charts two weeks later or are there? On a thread like this I'd expect dyno charts to go along with comments like the computer will adapt over time.
If there’s a resulting lean A/F, the O2s are going to add to the STFT and correct to stoich immediately. Eventually the LTFT will learn or adjust based upon the amount of correction in the short term. I still feel the diminished gains over time is most likely a perceived condition or due to environmental variables.
Agree. As someone whose career practically revolves around the characteristics of airflow, it doesn't hold one drop of water to tell me the stock intake has "no restriction" or is effectively completely open. That's simply not how flow works. I could probably accept "as unrestrictive as is practical or cost effective or as the NVH engineers would tolerate".
Air moves because of a difference in pressure. To say there's no restriction would be to say that the pressure at the throttle plate is exactly the same as the pressure at the entrance to the intake horn, and physics would respond by saying there's no air moving through the intake tract. If air is moving, there is a pressure difference, and if there is a difference in pressure then there is resistance and if there is resistance then there is opportunity to reduce it.
Any pressure drop in the nozzle (P6 to P5), filter (P5 to P4), box and hose (P4 to P3) results in less pressure available at the throttle plate (P3) to push air into the vacuum created by the piston increasing the volume of the cylinder. Conversely, reducing the restriction between P6 and P3 means there is more pressure available to move air from P3 to P0.
From the PCM's standpoint, it's expecting a programmed volume of air based on input from the TPS, MAP, and engine speed (then making a correction based on IAT), but since P3 has shifted closer to atmospheric pressure, there will be more air than the PCM thinks there is and the mixture will lean, requiring the STFT and LTFT to adjust to bring it back...in closed loop. In open loop, I don't know what mechanisms there would be to make this adjustment (haven't had time to read the PDF posted before).
To reach the final answer of this debate we have to ask:
1. Does the reduced resistance of the aftermarket intake result in an increased P3, driving more air into the cylinder?
2. Does that increased air charge result in increased engine power output?
3. Does the power increase result from more total air/fuel charge, or by a temporary shift in AFR? (or, does the gain stick or does the PCM adapt it's way out of it)
4. Is that gain significant enough to be perceptible by the driver?
5. Is any perceptible gain justified by the loss of filtration?
1 is answered by fluid mechanics, and it's YES.
2 is answered by @Jezza dyno runs, and it's YES.
4 is probably no, and 5 is definitely no except in racecars where power gains at high RPM and WOT can be utilized and frequent engine rebuilds are expected.
The only thing remaining to be answered is #3.
OP
Looks like a toilet ring for someone with hemorrhoids.
Should be more peak HP than the "CAI." Maybe another 5-10? Looking forward to the results!
Bad design. It needs to project above the hood at least 18 inches!
OP
Bet it's still more power than factory!
I was thinking something more of a pocket P type thing... so he could give that Jeep some lovin'!
+15rwhp over stock?
Please actually run that and PLEASE let it make more power than stock!!!
Can you hook up a vacuum gage to it this time?
OP
I don't know when I'll get around to it, but I will. I may even dyno again with the stocker and the K&N and video the whole thing uncut for the doubters. I have my HP Tuners here as well I will log each pull.+15rwhp over stock?
Please actually run that and PLEASE let it make more power than stock!!!
Can you hook up a vacuum gage to it this time?
Can you hook up a vacuum gage to it this time?
yes PLEASE this. Right in front (upstream) of the throttle body, if possible.
Head Lice
TJ Addict
Have been on the rollers many times with both Dodge/Cummins trucks and my H-D FXRS . . . . many variables.
Appreciate your time, effort, and posting your results.
Contentious issue with some folks here.
Thanks.
Anybody even mildly interested in airflow, intakes and porting would enjoy David Vizard's book "Tuning BL's A-series Engine." He's written allot including small block stuff but I think the A-series book is one of the best for airflow. There's an entire page of ram pipe designs with detailed information about 11 types and corresponding flow. Tons of dyno and flow charts with minute changes in port shape and design and the results. I've might have mentioned the book before, even though it's old the information isn't dated.