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Discussion Starter · #1 ·
Everyone has an opinion....what I really want to know, other than the desire to hear your exhaust, is there any performance enhancement, or is it just...I wanna hear some noise....same thing about adding cold air...is it just noise, or is there really a benefit....new to me 2012 sport...so I'm new to this....
 

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Surprisingly I did see a notice a power increase after putting on the Magnaflow Rock Crawler exhaust. I would like to say I've been there and done that with the power adders and placebo effect of more noise on my old TJ. So when I put the Magnaflow kit on, I was only expecting more noise.

However, this is my experience. The '12 JK has 4.10 gears, and is turning 38" tires. I drive a stretch of freeway through the mountains fairly often, and with the stock exhaust, it would hold OD only on flat ground/no headwind, and so I would normally just lock OD off. Most hills would need 4th and the steep ones would need 3rd. After putting on the Magnaflow, I was surprised to notice the Jeep was now climbing all but the steepest in 4th gear. And it can hold OD much easier on the flats/small grades. The Jeep gets about 1+ MPG better too. I was very suprised!
 

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No. Unless you have seriously modded the "air pump" that is the Motor..... modding the free flow of air IN (CAI) OR the free flow of air OUT (CAT-Back) - there is no appreciable difference that even IF it happened the computer would adjust to compensate.
That said, Modify the Motor and then you will see Modest measureable gains by freeing up air flow.
Yes there are many opinions and everyone has a right to theirs, what they don't have a right to is making up the results.
Dyno's tell the story. New Heads, New Cam, Power adders, Complete computer remapping and then - open up the intake and exhaust.

Uggh old topic ......and yes the "SS" after Rubi is because I've been building and Racing Cars since I was 15 years old.
 

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Exhaust is just a mod for the sound on most vehicles, you won't see any noticeable gains. That said, every vehicle I've owned since I was 16 has gotten exhaust systems because I like the sound.
 

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Discussion Starter · #5 ·
More air in, more air out....unless the efficiency of the air pump is maxed out already...just what I thought.....
 

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More air in, more air out....unless the efficiency of the air pump is maxed out already...just what I thought.....

Modern OE exhaust systems are extremely efficient. And more air in/more air out doesn't mean anything unless you have the fuel system to back it up. At best, we're talking like a 10 HP gain (which you'll never feel) way up near redline. The only way to get serious power out of one of these engines is forced induction or maybe a tune but even then a tune is more about drivability improvement than power gains typically.
 

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Don't forget, for some, replacing the exhaust is about clearance. I really didn't want any noise. But my stock muffler was getting beat up.
 

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Don't forget, for some, replacing the exhaust is about clearance. I really didn't want any noise. But my stock muffler was getting beat up.
This was my case, I ended up putting a hole in my muffler so it found itself on the chopping block. I now have my thrush welded (flowmaster replica) mounted just in front of my evaporation can and dumping before the axle. It is tucked up really well and no more crushed tailpipes/muffler stabs.
 

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even IF it happened the computer would adjust to compensate.
What do you mean the computer would "adjust to compensate"? You say that as if the computer would adjust to negate any gains provided by the intake/exhaust.

In closed loop conditions, the computer would compensate for changes in airflow by adding/removing fuel to maintain the desired air:fuel ratio (would be stored in long term fuel trims). So if intake and/or exhaust improves airflow, the computer will compensate exactly in the way that is desirable, adding more fuel to match the extra air, improving power during closed loop operation (part-throttle daily driving type situations, less throttle would be needed to maintain speed, throttle would be more sensitive/responsive, etc).

In open loop situations, the computer would not compensate for anything, because it's not using the O2 sensors for feedback. In open loop conditions (heavy acceleration, etc), the end result would be that the air:fuel ratio is slightly leaner than the OEM tune intended. On OEM tunes, fuel ratio is often a bit on the rich side at full throttle for a safety buffer (avoid detonation, etc). By adding some extra air, you end up with slightly higher cylinder pressure, and slightly leaner fuel ratio, closer to ideal for max power. That's how bolt-on intake/exhaust can produce full throttle gains without a custom tune.

Add a custom tune on top of that, and the open loop fuel ratio can be precisely/purposely adjusted to a good ratio for power, likely getting a bit more power than the somewhat accidental leaner fueling you get without the custom tune.


Yes there are many opinions and everyone has a right to theirs, what they don't have a right to is making up the results.
Dyno's tell the story
Fortunately, a member of the forum has put the effort into producing dyno results for various combinations of CAI and/or exhaust, so there's no need to speculate on whether it will produce any gains or not: http://www.wranglerforum.com/f274/banks-dyno-day-326377.html
 

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So on our systems for the JK platform that we dynoed we did see nominal gains, being either high single digit or low double digits through out the power band.
In regards to CAI, I dropped a K&N into my 2013 JKU, they show gians but in the higher RPM's.

I often get people asking if I did an HEMI conversion. :beerdrinking:
As mentioned one of the biggest benefits of an aftermarket muffler or system is to get a smaller footstep with the muffler and to tuck it up and out of the way.


Everyone has an opinion....what I really want to know, other than the desire to hear your exhaust, is there any performance enhancement, or is it just...I wanna hear some noise....same thing about adding cold air...is it just noise, or is there really a benefit....new to me 2012 sport...so I'm new to this....
 
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