Help 3.7L V-6 from the Liberty is it fitted in JK?

sportman · 12-25-2007, 11:25 PM

I drove the 2005Y liberty over sand dunes and It was great fun, I drove through the same terrain with my 2007Y JK Rubicon and I feel there is not enough torque to bush the car in low speed or low RPM..I was in impretion that the JK has the same engine of liberty with incresed cc from 3.7 to 3.8L
I'm not sure what type of engine is in my Rubicon I like it on the highways but not suitibale for soft dunes where I need more torque in low RPM...I'm having 92Y YJ with 1-6 4.0L no way to compare..I really feel that jeep had make a great mistake

of selection the right engine..do you agree

**Prot** · 12-25-2007, 11:30 PM

The 3.7L and 3.8L engines are completely different, it is not merely a bump in displacement. Rev the 3.8L and it makes power. The power band for the 3.8L is mid to upper rpm's whereas the power band for the 4.0L is low to mid rpm. If you are in soft dunes, put the Rubicon in 4LO as the crawl ratio is sufficiently low enough to allow the engine to rev while the jeep slowly creeps forward. You can also regear the differentials, which I have done.

sportman · 12-25-2007, 11:40 PM

Quote:

Originally Posted by Prot

The 3.7L and 3.8L engines are completely different, it is not merely a bump in displacement. Rev the 3.8L and it makes power. The power band for the 3.8L is mid to upper rpm's whereas the power band for the 4.0L is low to mid rpm. If you are in soft dunes, put the Rubicon in 4LO as the crawl ratio is sufficiently low enough to allow the engine to rev while the jeep slowly creeps forward. You can also regear the differentials, which I have done.

regear the differentials? what type of gear ratio u put 4.88? or higher
yes I agree in 4LO the JK can push him self through soft sands..but do u agree that for offroading we need low to mid rpm engine not mid to upper rpm's just imagine I shifted to 1st gear and it die and had to star the engnition over and over...we need more torque in JK

SecondTJ · 12-25-2007, 11:52 PM

The 3.7L in the Liberty is completely different as said. That engine was derived from the 4.7L V8 engine.

The 3.8L in the JK is out of the minivan lineup (Grand Caravan, Town & Country, etc). It originally started out as a 3.3L back in the early 90's. It got bumped to 3.8 sometime in the mid-90's for the "top of the line" minivans.

sportman · 12-26-2007, 12:03 AM

It's under power in low RPM do u agree?
what the story of OHC and OHV..alway I heared about these tirms and what they have to do with power or torque?

DougieFresh · 12-26-2007, 12:52 AM

I don't know much about the differences in the engines, but did you have ESP turned off on the JK? And was there ESP on the Liberty?

When on low-traction surfaces a couple times I've forgotten to turn it off and it feels like there's no power because the ESP just keeps cutting power to limit wheel spin...

Just a thought...

sportman · 12-26-2007, 01:04 AM

Quote:

Originally Posted by dougbuch

I don't know much about the differences in the engines, but did you have ESP turned off on the JK? And was there ESP on the Liberty?

When on low-traction surfaces a couple times I've forgotten to turn it off and it feels like there's no power because the ESP just keeps cutting power to limit wheel spin...

Just a thought...

Good point doughbuch, to be honest till now i do not know how to swich it on or off..is it when the indicator light is on in dashboard that meens the ESD is on too or oposite, I had the ESD indicator flashing from time to time till I had other indicator light (in yellow) saying ESD BAS what that mean? I do not have manual with my car sorrry for so many Questions

BigJerm · 12-26-2007, 07:04 AM

yes there is ESP on the liberty. My girlfriend has a liberty and it is way faster, on road, than my JK. Of coarse my 35" tires dont help much with the speed but off road i wouldnt trade the gearing/torque for the speed

**Prot** · 12-26-2007, 08:38 AM

Sounds like you need to spend some time reading the owners manual about ESP and lockers etc.

Regarding regearing, see my signature. Going with 4.88's with 35's would have returned me to stock ratio, but I opted for 5.13 and am very happy with the results. For an engine to perform effectively, it has to be kept in its power band. To get power at a given speed, it has to be geared in such a such way that it is in its power band at that speed. Take a look at horsepower and torque curves of the 3.8L vs. the 4.0L to see what I mean.

rirrgang · 12-26-2007, 09:44 AM

Although I am no fan of the underpowered 3.8l, I challenge you to find a HP/Torque chart on both the 4.0l and the 3.8l. You'll find them not to different in torque curve. At least not enough to make to much notice out of.
I found this info.
Cut and pasted from another Jeep website.

XJ______________4.0 I6___190 HP___235 Torque____Curb Weight ~3500
07Unlimited____3.8 V6___205HP___240 Torque____Curb Weight ~4500
%Increase_______________HP +8%___Torque +2%____Curb Weight +26%

Obviously an 8% increase in HP and 2% increase in Torque will not offset the
26% increase in weight.
Are XJ owners looking for an upgrade are going to be rather disappointed with performance?

sportman · 12-26-2007, 10:30 AM

Maybe I was mistaken to criticizing the 3.8L v6 but the video prove alot

http://www.youtube.com/watch?v=wURso2yrNS8

and I figure out that the ESD was cutting my engine RPM and I was comparing my YJ fully modified with 4.88 gear ratio with Rubicon

opp I'm talking about 2 door version..

SecondTJ · 12-26-2007, 10:53 AM

Quote:

Originally Posted by sportman

what the story of OHC and OHV..alway I heared about these tirms and what they have to do with power or torque?

An OHC engine has multi-camshafts. They are either SOHC or DOHC. SOHC (single overhead camshaft) has 2 cams, one for both the intake and exhaust valves on each said of the motor. DOHC (dual overhead camshaft) has 4 cams, two on each side of the motor, one for intake, one for exahaust valves.

An OHV motor has just one camshaft in the center for all valves.

OHC motor's typically make more power at higher rpm's because they can breathe better, which OHV motors make more power at lower rpm's.

Quote:

Originally Posted by rirrgang

I challenge you to find a HP/Torque chart on both the 4.0l and the 3.8l. You'll find them not to different in torque curve.

Check out this post for a side by side comparison.

http://www.jeepforum.com/forum/2979664-post19.html

sportman · 12-26-2007, 12:12 PM

that what I was looking for to see both carves side to side

waaaaaw the JK feel powerfull on higher RPM..I think as I drove many jeeps before including XJ cherokee and 4.7 grand cherokee..I have to abmite that both engine do there job in deffernt way..JK v6 needs to spin faster to build out the torque required..while the I-6 straight has it available most the time..I have to get use to the change of both engine charactaristics coz i'm driving having both and not thinking to sale th YJ..u may ask why..because i do not wonna to miss it classic look and it's legand engine with leaf suspention ride..every one has it's ggod and weak points..and no comperason I should say there are totally differnt jeeps (YJ vs. JK)

**waterboarder** · 12-26-2007, 12:53 PM

I can't believe that JK basically went straight up the side of that hill. Good lord.

sportman · 12-26-2007, 12:58 PM

Quote:

Originally Posted by texasdog

I can't believe that JK basically went straight up the side of that hill. Good lord.

believe it that clip make me think twice and I will just give my JK second chance to prove it self with turning the ESD off

and pushing it hard make it rev above 3000 rpm