Pete799

And I think the 5.7's (at least some of them) have the feature that lets them run on 4 cylinders when cruising.

I believe this is called the MDS or multi-displacement deactivation system. It does wonders for your highway milage.

Josephus

MDS - Multi Displacement System
Not all 5.7 Hemi's have this available. As a matter of fact there are some significant differences between this and the Ram Hemi that is most commonly and affordably swapped into the JK.
I wish I could locate a shop that would do the MDS Hemi swap, but they all seem to have avoided the MDS.
I too would love to have 330HP and 22mpg towing a boat.

Anything higher than a 5.7 should have the axles swapped out for 1 tons. The Rubicon axles are fine for the 5.7

...This is all from what I've read on various forums. I still have the sucky 3.8 V6.

kntr

So, Im still wondering about the difference in power???

Has anyone driven both motors in a JK?

Gunslinger

No experience with them in a JK, but I test drove both in the Charger. I bought an SRT-8 with the 6.1L. The difference is quite significant in my big, heavy, 4 door sedan. Put in in a JK and that difference would be ridiculous. The 5.7 would be plenty I'm sure.

atomicmecha

Yeah, its the MDS that cuts out 4 of the cyclinders when crusin... its only avaible on select 5.7's. the 6.1 and 6.4 do not have that feature. so its a balance i guess, do you want plenty of power and good fuel economy, or an ass load of power and so-so fuel economy?

my vote is the 5.7... the 6.X looks bad ass under the hood, but the 5.7 just has so many more appealing features and looks more at home under the hood of a jk...

JackMac4

Let me put it this way, my Grand Cherokee WJ hauls ass with its 5.7 HEMI. If that HEMI hauls ass with that much weight, I think it'll do just fine with a JK that weighs a lot less.

HULKGREEN

Interesting photo I use it as my main screen for my pc !!

If you want your JK to FLY you would be better off with the 5.7.....

If you want your JK to be a ROCKET then choose the 6.1...........

And if you want to get crazy there is a company called XV motorsports that makes 3 diffrent crate engine 5.7 Hemi.......365hp.....and up to 460hp dynoed before shipment !!

im4degreesaboveu

i am pretty sure i read here a long time ago that burnsville offroad found a way to make the mds work.

JeeK

X2 the 6.1 is brutal force but consumption is brutal too

I think the 5.7 is the best go go go !!! do it!

kntr

What is the gas mileage of the 5.7 vs th 6.1?