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Old 07-08-2008, 02:38 PM   #1
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Best way to increase power in a 4 cyl 98 tj?

Just wondering what the best way is to increase power in my 4 cyl....going up inclines is a pain and a lot of the time 3rd gear is not enough and 2nd it revs the engine too much....when its windy outside i cant go above 50-55 on the freeway. So i need more power!!!

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Old 07-08-2008, 02:45 PM   #2
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Do what I did to my 02 install a chevy v-8

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Old 07-08-2008, 02:57 PM   #3
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is your rig stock? tire size?.. tranny (A/M)? lift? Any engine mods?
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Old 07-08-2008, 02:59 PM   #4
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Its stock with 31.10.5 tires. with a manual and no engine mods. And a V8 would be a little too much...and im sure way expensive
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Old 07-08-2008, 03:10 PM   #5
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You're kind of stuck between a rock and a hard place with your 2.5L engine. The real truth there is not much you can do to substantially and reliably increase its power. None of the gimmicks like throttle body spacers do anything either. 31" tires are slightly larger than what comes stock on a Wrangler and even those have caused a power loss due to their larger diameter and a few other issues larger tires cause. You could regear to 4.56 ($1200 or so) which would give you a big boost in power by slightly higher rpms (but there's not that much difference between your current 4.10 and 4.56) but most wait until they go to 33" tires when they regear all the way down to 4.88.

The 2.5L is a small engine not known for having any excess power. Installing headers and a different intake, etc. would help a tad but it's still not going to provide a real satisfying bump in power. Or you could go back to a smaller tire like 29-30" which will raise your available power a tad.
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Old 07-08-2008, 03:20 PM   #6
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basically this is my most cost efficient recommendation but it costs more in general.
Do the math and you will find big expensive upgrades are the most cost effective ones.
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Old 07-08-2008, 03:32 PM   #7
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They also make a variety of chips for the 4 banger that I have heard do good. I ran into a guy on a trip that claimed that the mods to his 4 made it close to a stock i6. He had a chip in it, new exhaust system, throttle body spacer, and a cold air intake system. He didn't mention anything about regearing but I'm sure he had because he didn't seem to have much trouble on the trail. Having had a 4 banger in the past I understand your aggravation with lack of power. I traded to a i6... but of course it is an i6 in a different Jeep. The 4 banger died a horrible gruesome death probably because I was running 33x12.50's on a bone stock 2.5L.
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Old 07-08-2008, 03:38 PM   #8
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If you consistently race or drive at wide-open throttle and high rpms, then a chip is for you since that's where where they work. But for the rest of us, chips are useless as are throttle body spacers due to the type of throttle body our Jeeps use. To me, those mods are useless while the others like intakes and exhausts don't do enough to make them worth the $$$.
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Old 07-08-2008, 03:47 PM   #9
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Jerry I would agree with you on that one. That's one reason I didn't add that stuff to my 4 banger. It did just fine off-road but the highway is what bit the dust, of course I don't do much highway so it was not an issue for me.
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Old 07-08-2008, 03:51 PM   #10
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perhaps stroking the 2.5 if some one makes a stroker for them?. As i said, boost is the only worthy cost effective option for smaller engines. It's good but doesnt help offroading much. Honestly though if you want power and torque trading it in for a 6 would be your best option since it will be more reliable and you will get low end torque.
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Old 07-08-2008, 04:01 PM   #11
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i have a 99 4 banger on a set of 31's and i did some of the mods to the engine. the only reason i did any of them is because i got a great deal. after an intake, and exhaust it only cost me $250. if i paid in full it would have around $650. i did notice some power gain and better gas millage, i don't have to down shift going up hill or going around someone on the highway. the next thing i would do would be to re-gear.
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Old 07-08-2008, 04:27 PM   #12
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Tripp, where are you getting your experience from?

Just curious?

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perhaps stroking the 2.5 if some one makes a stroker for them?. As i said, boost is the only worthy cost effective option for smaller engines. It's good but doesnt help offroading much. Honestly though if you want power and torque trading it in for a 6 would be your best option since it will be more reliable and you will get low end torque.
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Old 07-08-2008, 04:42 PM   #13
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Naws baby yo
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Old 07-08-2008, 04:48 PM   #14
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Originally Posted by tazmann910 View Post
Tripp, where are you getting your experience from?Just curious?
i've been tuning cars even before i got my first car and i've also installed few turbo systems. I bought an intake, headers, full cat back.. etc.. spend half of what a turbo would have cost me and ended up getting maybe 15 hp. I was gonna install a turbo but my crankshaft crapped out. The way they designed it is the big pulley thats mounted on the crank shaft is held in place by a huge bolt a keyway all on a tapered shaft. Well whoever did the timing did not tighten it well so it was free to turn and was only held in place by the keyway which chewed up the crank shaft and the pulley... I dont have the tools to replace the crank shaft so we welded it together. i was told it should hold however will not hold when you add high performance upgrades such as 12 pounds of boost which is why i got rid of it. I've rebuilt 2 smaller motors and few lawnmower engines. I might not have any big experience with my jeeps engine but i know how to boost junk. Basically i memorised the steps on installing a turbo kit so i know how stuff goes together and how to make it work lol

This is where my hands on experience comes from. Books and stuff.. that's another story.
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Old 08-07-2010, 02:04 PM   #15
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Thumbs up 2002 Tj

i dont know how much of a differnce it would make between a 4.0 an a 2.5l but my tj has 31's and i got a kn intake, oil filter and a flomaster muffler and it was a huge differnce. if i can find some good headers that wont crack on me ill prob do those to. under 500 and a noticable difference.
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Old 08-07-2010, 07:11 PM   #16
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My 97' 4 Banger is pretty fast. I get up to 75-80 On the highway with my 31" BFG All Terrains just fine. When its windy more like 70-75. I have a manual so i just down shift some times up steep hills, other than that the 2.5L works pretty good for me.
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Old 08-08-2010, 11:34 AM   #17
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I got up to 80mph the other day. I was going down a 7% grade, even used 5th gear. However I used 3rd all the way up at about 40mph so my average speed was 60!

97TJ, 2.5 31.5 tires. jj
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Old 08-08-2010, 12:02 PM   #18
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Drop in k&n filter didn't make any difference in mine. With no wind I can get up to 75-80, but that's it. On windy days I'm lucky to hold 65. I figure I'll swap a Chevy V8 or regear eventually.
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Old 08-08-2010, 12:17 PM   #19
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Drop in k&n filter didn't make any difference in mine.
Of course it did, the K&N air filter is letting more dust and dirt get past it and into your engine.
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Old 08-08-2010, 02:49 PM   #20
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you know when its an old thread when yo see a post buy triple88a.
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Old 08-08-2010, 03:53 PM   #21
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I've read a few posts where some have added an electric fan in place of the stock belt driven one. Nothing mentioned other then the fact they noticed an increase in power and a little better gas mileage. I might try one they aren't too exspensive.
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Old 08-08-2010, 05:41 PM   #22
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lower gears will help a lot.
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Old 08-08-2010, 05:44 PM   #23
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Best way I know is to add 4 more cylinders hehe

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