Seriously...why 330 hp Jeep Hemi and 350hp Dodge and Chrysler Hemi??? - JeepForum.com
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Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > WK Grand Cherokee & XK Commander Forum > Seriously...why 330 hp Jeep Hemi and 350hp Dodge and Chrysler Hemi???

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Unread 11-01-2007, 06:53 PM   #1
HurriJeff
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Seriously...why 330 hp Jeep Hemi and 350hp Dodge and Chrysler Hemi???

C'mon.. Someone's gotta know the answer.. Why are the Ram trucks and Charger 5.7's rated 20hp more than same engine in my Jeep ??

I know dual exhaust on those others but is that really all there is to it ? Same ECM programing? <shrug>

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Unread 11-01-2007, 06:55 PM   #2
ttusqrl
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I don't care, just gimme the 20 extra
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Unread 11-01-2007, 07:55 PM   #3
gornoman
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The duals could easily make that difference. Maybe better intake airflow also since those trucks don't deal with water fording as a design criteria.
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Unread 07-17-2011, 06:31 AM   #4
mikeb33
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Quote:
Originally Posted by HurriJeff View Post
C'mon.. Someone's gotta know the answer.. Why are the Ram trucks and Charger 5.7's rated 20hp more than same engine in my Jeep ??

I know dual exhaust on those others but is that really all there is to it ? Same ECM programing? <shrug>
I don't think it is the same ECM programming. I think the intake, exhaust and programming are the differences. This is good since these are easily changed.
If you change these 3 on a Charger, you may gain 20HP. If you change them on a WK Jeep, it may yield 40 HP! WIN!
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Unread 07-17-2011, 11:08 AM   #5
Omelet
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I am sure the exhaust manifold makes a difference too. Ours are terrible!
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Unread 07-17-2011, 01:58 PM   #6
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The difference is typically caused by inlet and exhaust restriction which changes for each vehicle application. Almost everything else is the same on either engine. Keep in mind that the rated HP is taken at max operating conditions (wide open throttle, near max operating RPM) which means that to the average customer, 99% of the time there should be no difference in power output between the Jeep and the Dodge Hemi engines.
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Unread 09-21-2012, 11:00 PM   #7
phottomatt
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I know this is a year old thread but instead of starting a new one i thought I would hijack this one. Anywho the answer is ECU programming. Now, the new question is can we get the WK reprogrammed?
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Unread 09-22-2012, 09:19 PM   #8
90grandoneer
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Here's one big difference that, I am sure, accounts for most of it. http://www.jeepforum.com/forum/f67/b...-7-wk-1174042/ Also, as said above, the duals may help a little, but can be adjusted for with a good low restriction, straight through 3 in. cat. back. I am guessing mine is putting about ~420 at the engine and ~370 at the wheels, the way I've got it set up. See my signature. Still have a few things I can do (heads, throttle body and UD pulley) to pull another 40-50 hp out of it. There are also about 3-4 different intake manifolds for the Hemi. Mopar Magazine did a test on all of them.

To answer your question, phottomatt, you'll have to get either a Diablosport or Superchips tuner to reprogram the PCM. If you're after economy the DS is a little better, if you want full control of the trans., the SC is better.
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Unread 09-22-2012, 09:25 PM   #9
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Funny thing is there not even true duals,it's a single exhuast with dual tips.
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Unread 09-22-2012, 11:10 PM   #10
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Thanks 90grandoneer, haha, you answered the question I MEANT to ask. I knew there was a way I just was interested in the best options.
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Unread 09-23-2012, 01:49 PM   #11
90grandoneer
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Pm, I've got both of the most popular tuners for both my Hemi vehicles and, as I said, the DS is a little better for economy. I never use the SC tuner on my Magnum anymore, but do change back and forth on the Jeep. I had been running the SC for quite awhile, solely because of the cool Trans. App. that is an option with it. I do that mostly because of the lousy stock shift schedules and torque management setup for the 545RFE. The DS now offers limited (1st, 2nd, and 3rd only) so it is a little better now, in that regard. The Maggie has a NAG1 tranny with full autostick, and is 1000 times better than the Jeep, IMO.

Other differences, if you're thinking of picking one or the other up are, the SC has some adjustments that can be manipulated for the off-roaders, and the DS allows you to update to the latest CALID flash files (about $100-150 to have done at the dealer) for the PCM/TCM, and gives you the ability to have custom tunes made. This seems to be mostly for the high performance engines, but some have said it works good for mildly modified engines too. Even with my mods., I've never invested in one (~$200-300, I understand), and am happy with modifying the canned tunes. In addition to some of the tuning mods. also incorporated in the SC tuner, the DS tuner allows you to adjust WOT fuel mixture and timing, which is helpful if you do a little racing. Hope this helps a little for you.
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Unread 09-23-2012, 01:53 PM   #12
Moto4x4
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Quote:
Originally Posted by gornoman View Post
The duals could easily make that difference. Maybe better intake airflow also since those trucks don't deal with water fording as a design criteria.
Quote:
Originally Posted by Omelet View Post
I am sure the exhaust manifold makes a difference too. Ours are terrible!
I would say these are your best bet why your have less HP.

On my STi going from 2.5" to 3.5" exhaust and changing headers can make another 60hp at the wheels
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