2012 3.6 Performance Mods!
10-19-2011, 07:46 AM
#11
JK Freak
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I know I do not have a 2012, but I will say this...
Switching to a muffler that is "too free flowing" will cause some low-end power loss, but it is not that drastic.
I had a MBRP muffler and the low end on that was fantastic! I switched over to a Cherry Bomb Extreme for the noise, and I immediately felt a loss of low end power, but the mid-range power definitely increased, along with the high end.
Switching to a muffler that is "too free flowing" will cause some low-end power loss, but it is not that drastic.
I had a MBRP muffler and the low end on that was fantastic! I switched over to a Cherry Bomb Extreme for the noise, and I immediately felt a loss of low end power, but the mid-range power definitely increased, along with the high end.
).Changing the cats is not something I would do unless it came from a company like ripp that dyno tuned that portion of the exhaust. Im talking about just swapping out the muffler essentially. I have done catbacks on motorcycles, mustangs, and my last JK all with great results. I dont see any reasons on the surface why a catback system on the 3.6 would be any different as long as the correct muffler is selected.
The last JK I had was running the MBRP setup and I loved it. So I called and emailed them when I got my '12 and offered mine up for R&D. They are still dragging their feet.
The last JK I had was running the MBRP setup and I loved it. So I called and emailed them when I got my '12 and offered mine up for R&D. They are still dragging their feet.
Here's what I have wrote in multiple other "exhaust" related threads where people claim free flowing exhaust causes power loss:
Originally Posted by Imposter_LRF
However, I do not necessarily agree with your "loss of torque" from low backpressure. From Professor David R. Dowling (Ph.D. in Aeronautics, teachs experimental, computational, and theoretical fluid dynamics and acoustics in automotive applications for the University of Michigan) in my company's Exhaust System Acoustics and Backpressure Handbook (and training), "There is no 'optimum' cold end backpressure - less is always better" And... for naturally aspirated engines, "rule of thumb: 0.21% power loss per kPa of backpressure increase"
BTW, "cold end" refers to the "cat back" exhaust system.
BTW, "cold end" refers to the "cat back" exhaust system.
Originally Posted by Imposter_LRF
Now...as I stated before, your "hot end" is the BIGGEST contributor to backpressure by far. Changing this, especially in VVT engines, will screw with your engine performance. I agree with you 100% on that and that the flow velocity decrease in the hot end has negative effects on OEM tuning in naturally asprirated engines (Aftermarket tuning and turbocharged/supercharged engines aside because...well...we aren't talking forced induction here).
Reduction in the backpressure of "cold end" exhaust systems will ALWAYS increase HP. It might sound like crap, be illegal from a noise regulation standpoint, look terrible (some jerry rigged systems I have seen
), or just be plain silly (6" exhaust stack on a diesel truck that isn't flowing enough for 3" pipes to be relevant), but it will be better than the OEM COLD END exhaust system in regards to performance.Also, flow velocities play a huge roll here with your guys' hot end exhaust with the "goofy" turn around loop. First of all, the turn around loop is to make the exhaust system equal length at the Y pipe. This has PROVEN BY THE OEM (Chrysler) to increase power/torque (and is simple fluid dynamics). Also, with the y-pipe, there is a scavenging effect due to the equal length legs. This is where the flow velocities come into play. As a pulse of gas passes the Y portion (not the individual legs, the actual point where it comes together), it will cause a pseudo "vacuum" down the other leg to "pull" the exhaust out of the system.
So...my recommendation to you guys...Don't mess with your Y-Pipe or catalytic converters UNLESS it is a dyno tuned system. The stock ECU calibration is made for this "hot end" and you will wreck havoc on your powerband if you mess with it without tuning changes.
Therefore...make your free flowing "cold end" exhaust system, make it as free flowing as you want (and within reason, if I see you with a 6" tip on there MrJones...I will hunt you down and...well...make fun of you
).Hope this helped and not confused people. Please feel free to post up any questions or concerns you may have and I will answer them, even if it is not in regards to a Dynomax system.
Good lord that took forever to put together...
10-19-2011, 09:01 AM
#12
JK Freak
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Thanks
10-19-2011, 09:43 AM
#13
JK Freak
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Since you are so close, if you ever need any exhaust help, let me know as I have a shop full of exhaust tools at my disposal Good to know this. I do have a question in order to lift the 2012 we need to move the cross over pipe back a few inches. Teraflex makes a exhaust spacer which is inserted where the exhaust is bolted to the exhaust manifolds. Will that make any noticeable difference in performance?
Thanks
Thanks
If it changes one side and not the other, you will only see minimal changes in performance, not even noticeable. Your peak power/torque would be at equal length, but changing that length slightly does not dramatically reduce power until you get to a point where one side is significantly longer/shorter.
10-19-2011, 10:48 AM
#15
JK Freak
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10-19-2011, 09:42 PM
#16
JK Enthusiast
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Originally Posted by Imposter_LRF
I have the Dynomax RockCrawler and absolutely love it. However...I am biased
Nice low tone and not very noticeable in day to day driving.
10-20-2011, 01:44 AM
#17
JK Freak
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Originally Posted by CGnTtown
Any drone what so ever? I have the VT cat back and their is never any drone which I like. But it's not very loud at all and the exhaust note doesn't change and get louder when I get on the gas like I thought it would with the valve in their.
No drone on mine at 55, can hardly tell its their. Very slight at 70+, but its not loud unless you downshift. Went on a roadtrip this summer with the girlfriend and a few friends and at one point while going 70+ everyone but me was sound asleep...if that tells you anything about the severity of drone at those speeds (very minimal drone).