3.6 Exhaust Loop - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 10 Old 11-14-2013, 10:18 PM Thread Starter
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3.6 Exhaust Loop

Alright i've read and searched about this for a couple days and just cant seem to come up with a definitive answer. Some have said that they have seen no loss in power by deleting it, as well as a bit of mpg gained. Others have said that "Chrysler put it there for a reason". but no one can show a dyno sheet comparing the 2 . i honestly cant see the need for a loop, it cant help the power that much by adding back pressure, in everything ive ever owned or been taught about pretty much says the faster the exhaust gets out the better, the less restrictive the better. So if anyone has experience with deleting it please feel free to chime in. Thanks

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post #2 of 10 Old 11-15-2013, 07:38 AM
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I have heard that it was to equalize the tube lengths. Supposedly Chrysler spend a lot of r&d time on it for better performance.
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post #3 of 10 Old 11-15-2013, 04:24 PM Thread Starter
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I cant imagine they would waste time scavenge a few horsepower. Knowing that they are building a jeep not a performance vehicle.

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post #4 of 10 Old 11-15-2013, 04:56 PM
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Most of us Jeep owners are clamoring for more horsepower. Since we will likely never sees V8 option this was there answer. I think Jeep tried to get the most they could out of a small engine and still maintain fuel economy. Up here in the altitude mine is pretty weak but if I wind it up it will smoke a 3.8 liter pretty easily. Someday I hope to install a V8 in this rig!!
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post #5 of 10 Old 11-15-2013, 05:15 PM Thread Starter
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I know im not going to get alot of power if I delete it and I know im not gonna lose alot if I delete it. I just have to change my y pipe for my lift anyway, and I was just seeing if anyone knew if it was actually beneficial one way or the other

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post #6 of 10 Old 11-15-2013, 05:25 PM
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Quote:
Originally Posted by WEST BY GOD View Post
I cant imagine they would waste time scavenge a few horsepower. Knowing that they are building a jeep not a performance vehicle.
They just like to spend extra money on engineering, tooling and manufacturing for tens of thousands of vehicles?

I'd think if they had the slightest inkling that "it was for nothing", they'd save the few million over the long haul and just run a straight pipe. CFD and Flow analysis is far from the "hot rodding" train of thought you seem to be relying on.

Is it going to turn your engine into a dog? Nope, not even the slightest. Do it if you don't want to, instead of complaining about how people haven't done back-to-back dyno tests for you to look at, how about you lead that up for the rest of the community and post up your results?

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post #7 of 10 Old 11-15-2013, 05:43 PM Thread Starter
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First off I am not complaining, I was stating that I had not came across any dyno proof. I thought maybe I had overlooked it somewhere. As far as me providing that information, I dont have that ability as any dyno is a few hours off. But as far as seat of the pants results and mpg comparison, I can and will take care of that and share my results when I do the delete.

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post #8 of 10 Old 11-15-2013, 06:17 PM
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Equalizing the lengths might have to do with emissions.
When tuning an exhaust pipe the length is so determined that the sonic waves that develop in the pipe help scavenge the burnt gases from the cylinder.
This reduces NOX emissions and increases power.
So it comes to reason that equal lengths of pipe yield best results.
At least that's why we did it in motorcycles.
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post #9 of 10 Old 11-16-2013, 01:04 AM
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Originally Posted by WEST BY GOD View Post
in everything ive ever owned or been taught about pretty much says the faster the exhaust gets out the better, the less restrictive the better.
You're talking about two different things here. Think about putting your thumb over the end of a water hose. Does the water come out of a smaller opening at a higher velocity? Of course. Although the smaller opening is more restrictive than the full opening, thus increasing back pressure and velocity.

Conventional wisdom has always been to go conservative on tube size in small displacement applications at comparatively low RPMs. This may not make the best HP numbers, but it will optimize the torque generated (which is what we want for off road, and for seat-of-the-pants impressions).

You're not looking to move a huge volume of gases. You're looking to move the gases out of the combustion chamber as quickly and efficiently as possible, creating a low pressure chamber in the cylinder during the valve overlap so a more dense fuel/air charge is drawn into the combustion chamber. Pulse timing in the exhaust stream is very important to that efficiency.

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Originally Posted by legi0n View Post
Equalizing the lengths might have to do with emissions.
When tuning an exhaust pipe the length is so determined that the sonic waves that develop in the pipe help scavenge the burnt gases from the cylinder.
This reduces NOX emissions and increases power.
So it comes to reason that equal lengths of pipe yield best results.
This is what I'm talking about. That pulse timing aids in an efficient burn. That improves torque, emissions, and MPGs. IMO, the last two were probably the real motivations for the visually funky design.

Interestingly, Magnaflow and AFE have both come to the market with replacement down tubes that are straight. But unless I am imagining something, they have increased the tube size to slow down the gas evacuation in that section of the system, "tricking" the system into functioning like a longer, but smaller, tube. By slowing the gases in a shorter tube, they bring the exhaust pulses back into correct timing and maintain the efficiency of the original design.

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post #10 of 10 Old 11-16-2013, 06:13 AM
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Quote:
Originally Posted by legi0n View Post
Equalizing the lengths might have to do with emissions.
When tuning an exhaust pipe the length is so determined that the sonic waves that develop in the pipe help scavenge the burnt gases from the cylinder.
This reduces NOX emissions and increases power.
So it comes to reason that equal lengths of pipe yield best results.
At least that's why we did it in motorcycles.
Remember that Ducati & Husquavarna used the loop pipe in there exhaust systems for a while to equalize tube length and improve flow. I spaced mine with TF spacers just in case and it works fine. I think it would take at least 15 HP to tell a difference anyway.
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