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Old 07-31-2013, 01:55 PM
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3.8L HP upgrades

Just picked up my first JKU a '11 Sport S 6sp 3.73 gears and was wondering if anyone has any opinons on uping HP. Tried a couple of searches but did not really find much other then alot of opinions between the 3.8 and the 3.6.
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Old 07-31-2013, 02:58 PM   #2
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Old 07-31-2013, 03:14 PM   #3
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I threw everything at mine. Programmer, CAI, Throttle Body Spacer, Exhaust. Helped some but now much. Supercharger is about the only way to go.
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Old 07-31-2013, 03:37 PM   #4
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Supercharger is the only way to go in order to get useful power gain. The downside is 6K in cost and it opens up a whole host of new issues. Sure you reprogram the computer but Jeep and computer were never designed to run with a supercharger so you might see little quirks and issues. Another downside is most shops don't know how to deal with an engine that has such a large aftermarket modification and might even refuse to work on it.

If you are willing to spend the 6k on a supercharger setup my advice is to take that money, sell your 2011 and buy a Jeep with a 3.6 in it. Superchargers give the 3.8 pretty much the same power as the 3.6 with less mpg. If you are all about modifying and hot rodding engines, go for it and put the supercharger on it.

This advice comes from somebody who bought a 2009 jeep with an aftermarket supercharger on it. I love the jeep and can't imagine it with less power. I paid pretty close to stock book value for a JKUR so I feel I got a good deal with all the mods. All that being said, I also have a plan to sell it in about 5 years if they come through with a diesel.
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Old 07-31-2013, 03:51 PM   #5
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Forced induction or motor swap. Or re-gear to 4.10, 4.56, 4.88, 5.13 depending on tire size.

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Old 07-31-2013, 06:49 PM   #6
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I think it would be much more wise to do a regear. I know its not what you asked...but more gear will utilize the power it does have, better. Disclaimer: I have no idea what I'm talking about.
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Old 07-31-2013, 07:06 PM   #7
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Regearing is the best option.

The problem with the 3.8 is it was pushed to it limited for the most part to begin with. So gaining HP out of the motor can only be achieved by adding a supercharger. The intake is not restrictive so adding a CAI does little to nothing. A larger viper throttle body only causes thrown codes and in some rare cases puts the vehicle in limp mode. Even the exhaust isn't very restrictive and a Cat back does little if your not replacing headers back. The Tuners help throttle response but little in hp gains. And if you did it all, it would be nearly as costly as a Supercharger which gives real gains. One place did a dyno once after adding a CAI, Headers and exhaust with a tuner running and all they got was 10hp gains and that was at max RPM's. At driving RPM's it was more like 2 to 3 hp.

Saying all that, Their is better hp in the 3.8, but it is at higher RPM's. The problem is at normal driving speeds/RPM's there just isn't any hp or torque. That is why many re-gear. The JK was just under geared for the 3.8 motor and especially the Automatic transmission. So by regearing, it puts the motor in it's optimal RPM to hp band. Regearing just does wonders for the pre 2012 JK's.
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Old 07-31-2013, 07:11 PM   #8
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OP - what size tires do you have? I think if you have stock-size tires and 3.73's and you already think the 3.8 doesn't have enough power, you are going to be disappointed with the 3.8 no matter what you do with it besides forced induction, which really isn't cost-effective.
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Old 08-01-2013, 07:44 AM
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It currently has the stock 255s but I was planning to put 33s. I have not jacked it up and spun a tire but according to the spec sheet on jeep.com it has 373s. If I went to 410s would it be that much different I would I need to go like the 456s. I will jack it tonight and confirm the 373s.
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Old 08-01-2013, 02:51 PM   #10
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You're talking about a 3% difference between the 32 you have and the 33 you plan on. Regearing is expensive and won't make that much of a difference, 3.73's and 33's is a pretty reasonable setup. Either get used to the 3.8 or trade it in.

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