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Unread 09-21-2006, 08:19 PM   #1
Laxstar46
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The JK 3.8 not hatin legit question

KK guys well Ive been lookin into these JK's and Gotta say i really like them. I was a big fan of the 4.0L but i think this 3.8 will be just as good if not better. Now here's my question. I'm lookin at the jeep website they give the 4.0 L 190 hp and 237 ft lbs torque. The 3.8 has 202 hp and 240 ft lbs. they also say that the 3.8 is a better engine cuz it will have more torque available in the higher rpm range. this is what jeep states.

Now i work with a guy that has a 98 sport tj. He is tellin me that even tho this is what jeep says the 3.8 puts out he says the 4L still has way more torque. His only info to back that statement up was "well the 3.8 is a V so it stinks". which isn't very factual.
I did some reading online and what i came up with was reasoning sorta like this. If two engines that are relatively the same displacemnt and are being given a comparable fuel mixture and that most parts of the engine are similar. Then the Inline engine will have an edge in torque over the V. But i also gathered that this is not a standard across the board for all engines on the market.
So i'm figuring that the 3.8 must be designed different in someway that makes it hvae just about the same torque with more hp than the 4.0L.
I'm also looking at the ratings that jeep puts up and when looking at those the 3.8 actually has a bit of an edge over the 4.0. Can someon explain to me how inline engines compare to V styel engines with torque and why (if at all) the 4.0 is so much better an engine than the 3.8.

I'm gettin an opinion from you guys cuz when i look at jeep they support what i'm thinking and that's that the two engines are practically the same. But the guy i work with sez no the 3.8 is junk but he had not factual info to back it up. i also don't believe him cuz about three weeks ago i lost my gas cap and he told me that my jeep would blow up cuz there would be air in the gas tank. i basically told him that theres air in the tank all the time or the tank would implode under air pressure from the outside. he then got mad threw a tantrum and told me "fine don't call me when ur jeep is gone" and just acted liek a child. so i turn to the guys on this forum for my answer because i think i hvae a good understanding of it but i want some outside opinions.

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Unread 09-21-2006, 08:21 PM   #2
Rocky529
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The 3.8 has more torque, but that comes at a high RPM, an RPM that won't be reached off-roading.
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Unread 09-21-2006, 08:23 PM   #3
Karamba
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Quote:
Originally Posted by Rocky529
The 3.8 has more torque, but that comes at a high RPM, an RPM that won't be reached off-roading.
off-roading != crawling. How about sand or mud? I would like to see you idling through mud...

You do not consider 1:2.5 transfer case to be not off-road worthy? So if you use 4:1 case with a higher revving motor, it will actually move slower then a 4.0 coupled with ~1:3...

It will be reached just fine.
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Unread 09-21-2006, 08:35 PM   #4
Laxstar46
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i see is that a general rule that a V style engine makes the torque at a higher rpm while a inline has the torque at a lower rpm.

i'm glad to see good response cuz if u read the guy i work with really is someone i'm ashamed to see drive a jeep to be honest. I'm 17 i bought a tj when i was 16 and now that i'm gettin ready to graduate we (the family) are lookin into a new on 07 or 06 havnt decided yet also depends on time when we will go and iff there is a good selection of 06's. but the jeep i have i have kept stock to save money since i only work at a convenience store and i talk to a lotta guys wit jeeps. They are all real great real nice no one is a jerk cuz i drive a stock 2.4L. they all are like "well better than no jeep" and i agree well this guy i work with does nothing but talk smakc all day long like he knows everything about jeeps. His 98 tj only has a 2 in spacer lift nothing else. And he tlaks down to all toher jeep guy and gals like he is some sorta god. in all honesty he's a disgrace to jeep. i laughed i worked wit him the other night and some guy wit a old cj7 iwth some 38 in boggers pulld up and told him off for how he was actin.

but that's my story back to the info i'm just tryin to learn more bout engines and just mechanical stuff in general
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Unread 09-21-2006, 08:37 PM   #5
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If your family wants it, the 4 door Wrangler is the best bang for the buck as far as space/convenience is concerned.
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Unread 09-21-2006, 08:41 PM   #6
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Does anyone have access to torque/hp curves for the 3.8 and 4.0? The only information I've seen from Jeep states that the 3.8 "maintains higher torque at speeds above 3,400 rpm." Based on this limited information and the information that I've read about the 3.8 (which generally states that the 3.8 is a torquey OHV engine), I would assume that the the 4.0 makes slightly more torque than the 3.8 up to 3,400 rpm. After 3,400 rpm the 3.8 will make slightly more torque.

To say that the 3.8's torque comes at a high rpm, which won't be reached off-roading seems a bit misleading. The 3.8 matches the 4.0's torque peak a mere 200 rpm higher.

Now, the JK (particularly the Unlimited) is heavier than the TJ and the throttle has been recalibrated for a less sensitive response, both of which could lead to the JK feeling a bit more sluggish off the line (as some reviewers have reported), but these are factors independent of the engine.
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Unread 09-21-2006, 08:41 PM   #7
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The stroke of an engine is one variable. A short stroke engine is usually less desirable than a long stroke engine when it comes to making torque. A short stroke can be higher revving than a long stroke.
I don't know the bore and stroke of the 4.0 and the 3.8.
Intake runner length and exhaust diameter also have an effect on torque production.
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Unread 09-21-2006, 08:41 PM   #8
Laxstar46
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that knda came out wrong my parents are lookin to buy a rubi 2 door 06 or 07 for me as my h.s. grad present. well not buy they just gnna help me with like every other payment or somthing
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Unread 09-21-2006, 08:43 PM   #9
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Quote:
Originally Posted by Laxstar46
that knda came out wrong my parents are lookin to buy a rubi 2 door 06 or 07 for me as my h.s. grad present. well not buy they just gnna help me with like every other payment or somthing
If I were you, I would get a 2006 Rubicon ...or if you like the JK's styling, wait until 2008.
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Unread 09-21-2006, 08:45 PM   #10
Laxstar46
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the only prob is with the 06 rubi would be that what dealers have now is well what they have and till we go out to really get serious about buying there might not be a 06 rubi that i would be interested in. also neone know when the 2 drs are shipping all the dealers ahve 4 doors. and y wait till 08? (not being smart alleck just wondering)
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Unread 09-21-2006, 08:52 PM   #11
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Quote:
Originally Posted by Laxstar46
the only prob is with the 06 rubi would be that what dealers have now is well what they have and till we go out to really get serious about buying there might not be a 06 rubi that i would be interested in. also neone know when the 2 drs are shipping all the dealers ahve 4 doors. and y wait till 08? (not being smart alleck just wondering)
It is not a wise move to buy the first year of a re-designed vehicle - and to top it off, it is being built in a brand new facility. Let them work out all the bugs that the new JK will have. This is just my opinion though. Gotta watch your way of phrasing sentences around this forum lately.
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Unread 09-21-2006, 08:57 PM   #12
Laxstar46
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KK i understand what you're saying and I will definately watch how i say things. lol i only joined the forum thirty min ago or so. So if i made anyone mad with poor grammar or anything else I am sorry will not happen again.
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Unread 09-21-2006, 08:58 PM   #13
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The torque will be derived from several things; stroke, bore, volumetric efficiency (pumping efficiency due to intkae and exhaust design and cam profile) and ignition timing.
The only effect that the cylinder configuration will have is miniscule... the inline 6 has more main bearings, hence, higher friction, but it is inherently stronger... discounting a bearing girdle on the V6. Assuming all parameters are the same then the two configurations will produce the same torque and power.
Unless someone can produce the torque/power curves for each engine it's silly to argue about it... the peaks are not important, area under the curves is.
Gearing and gear selection that keeps your engine rpm at the highest VE (max torque) is ideal. High reving doesn't hurt off-road performance if you are geared correctly for the task at hand.
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Unread 09-21-2006, 09:11 PM   #14
Laxstar46
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Sounds good i think I understand that. I was just asking cuz the only comparison i had up until now was a guy just tellin me how stupid i was for even thinking the jk with the 3.8 was a decent jeep. When he was asked why he feels that way and some real fact info on why it stinks he just walked away. So i figured id find a jeep forum and talk to some ppl that really know their stuff. And I am not dissapointed at all. I appreciate the help you guys. tyvm
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Unread 09-21-2006, 09:12 PM   #15
Rocky529
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Quote:
Originally Posted by Laxstar46
KK i understand what you're saying and I will definately watch how i say things. lol i only joined the forum thirty min ago or so. So if i made anyone mad with poor grammar or anything else I am sorry will not happen again.
Your grammar is fine, I said that to defend what I said. Anytime a comment is made towards the JK, there is a risk of the thread turning into a 5 page flame war. This forum has to move towards tech. related issues.
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