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Old 08-05-2012, 09:27 AM   #1
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'97 TJ 4cylinder - Want more power!

Running stock height, 31x10.5 tires, looking for some more power both on road and off because I'm looking at putting a 2" lift and adding more weight with bumpers/sidebars etc. Recently put a throttle body spacer in and noticed a little bit of a difference. Any other suggestions?

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Old 08-05-2012, 09:32 AM   #2
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With a 2.5l you have a number of things that can help, it depends on your budget. How much are you willing to put into your need for more horsepower.

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Old 08-05-2012, 09:36 AM   #3
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This is my 2.5, I've done everything you probably want or need to do.


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Old 08-05-2012, 09:57 AM   #4
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Budget isn't much of an issue, living in the barracks so not spending much money, and i can save up for the more expensive parts.
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Old 08-05-2012, 11:30 AM   #5
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I'd suggest starting with a simple cold-air intake kit. There are plenty for your model or you can do like I did and modify one that I had laying around from a previous vehicle. I put one on that has the conical K&N filter and gained a some horsepower and more importantly 2-3 MPG back.
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Old 08-05-2012, 07:34 PM   #6
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Save money for a motor swap. The 2.5 is what it is. And that isn't a powerhouse. The only thing I can think of would be a turbo. But that can get pricey. And you'd still only be about as powerful as the I6
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Old 08-05-2012, 08:46 PM   #7
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Ive heard people talk about doing a motor swap but I'm not 100% sure on what all that entails, what would you swap to? Wouldn't you have to upgrade the drive train and tranny as well? Oh, its a Manual by the way.
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Old 08-05-2012, 08:56 PM   #8
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I can only say to not waste your $$$ on gimmicks like throttle body spacers, cold-air intakes, K&N air filters (ESPECIALLY not K&Ns!), larger throttle bodies, etc. The only sure way to noticeable power gains is by regearing your axles to a lower ratio, which wouldn't be worth it for only 31" tires, or to install a turbocharger or supercharger.
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Old 08-05-2012, 09:13 PM   #9
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Take a bit of time and drive your jeep. Keep track of the rpm ranges you normally drive in. Take it off road. Do the same thing. On mine I very seldom find my 2.5 with 31 tires and 4.10's is much over 3500 and is as low as 1500. Most of the things that are out there "work?" at higher rpm levels. Bigger cams, ported heads, headers, intake pipes. All might make more power but at higher rpms than you normally use. Gears on the other hand work across the board. From a slow crawl to top end on the freeway.
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Old 08-05-2012, 10:53 PM   #10
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Jerry is right. There's lots of stuff you can waste your money on, put your money into gears along with a header and cat back exhaust. Believe it or not the 2.5 revs higher and cleaner when you remove the fan. An electric fan works well and gives you control to shut it down when entering deep water. You can find gearing charts that will give you and idea of rpm levels. I believe 4.11's were stock with the 4 bangers, the highest ratio that you can install in your axles are 4:88's and it's worth every penny. The 2.5 is not the answer for big power stuff but, with the right combination you will have a jeep that will do most everything you're looking for, for a fraction of what a motor swap would cost. I wheel with the 4.0's all day long and have never been "that guy" that can't get done. I would strongly take advise from those that have built their 2.5's and have experience with each step of their build. I hope this helps.
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Old 08-06-2012, 06:28 AM   #11
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If you have some extra money just sell it and get one with the I6.
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Old 08-06-2012, 08:56 AM   #12
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Idk if I'll ever bring myself to sell this jeep. Love at first sight bro. I'll keep putting money in it until it literally falls apart while I'm driving it. And even then I'll probably ask to ride in it as they tow it to the yard.
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Old 08-06-2012, 09:36 AM   #13
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If you have some extra money just sell it and get one with the I6.
What a douche thing to say. The guy wants to modify the Jeep he has and then you come in and tell him to sell it and buy a different one. A lot of help you were. Ignore comments like this on here man. I've seen this quite a bit actually since I've joined a couple of months ago. Especially regarding the 2.5 motors. Guys come in and say "Oh don't modify it, just swap a "real motor" like the 4.0 in it". The 2.5 is just as reliable as the 4.0 contrary to what some people might have to say. No it doesn't have the power but there are ways to increase power like others have already stated in here. It'll never be a powerhouse motor but that's not what it was made for. Good luck with your endeavor on this forum and hopefully you don't have to worry about douche comments like this one anymore.
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Old 08-06-2012, 02:13 PM   #14
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I think what your really looking for is more low and midrange torque. Altho I could be way off base on that. The best way to increase torque is to increase displacement up to 2.9, increase compression up to 10 to 1, increase valve lift and slight duration increase to 220 degrees, advance the cam 99 to 102 degrees intake centerline and run tighter 104 to 106 degree lobe centers for a higher midrange. Change timing curve for more initial advance 12 to 14 degrees, total 36 to 38 degrees all in by 3500 rpm. Aftermarket stand alone fuel injection computer to handle the changes. Remember you are building size wise half of a 5 liter ford mustang at 2.5 and at 2.9 it is half of a 6.0 chevy. This is just some ideas that work in other engines I have built but they were V8's. Principle is the same though. Small cam a bit of compression and a bigger pump. All equals more torque and power. Just how much you want depends on your wallet. Still say gearing would be my first choice though.
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Old 08-06-2012, 10:46 PM   #15
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When I bought my 99 it had a blown piston in the 2.5. I had a choice to go for a swap or stick with the 4cyl. I purchased a ProMar 2.5 (marine engine builders out of New Jersey) long block. Then I went with a ceramic coated header, hi-po cat converter, turbo muffler, Air Raid Cold Intake Kit & spacer. 2 yrs later my friend suggested I get the head machined and go with a camshaft with increased lift. Since then I have many people impressed by the "oomph" out of the 2.5. I tow my dirtbikes in a 6x12 cargo trailer and thats with 31" swampers with no problems (unless heading in to 30+mph winds then I have to stay in 4th). Sometime before years end I would like to punch up the ignition and maybe throw a fresh cat converter and muffler on ( 65k miles on them ). Also, there's a company that sells a propane conversion kit for the 2.5, but not the 4.0. Why propane? Longer oil life and currently approx $1.89/gal equivalent.
But anway, the 2.5 is fine- just let it breathe, make sure your gearing/tires is correct and remember: The 1st Jeep had a 4cyl !!!!
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Old 08-06-2012, 11:07 PM   #16
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Gearing, my man, GEARING! That is the only thing that will legitimately make the 2.5 more powerful. I suggest 4.88's. I would also get an Atlas II Transfer case with 4.3:1 gearing. It is pricey, but worth every penny.
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Old 08-08-2012, 06:30 AM   #17
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Honestly I'm kinda liking the sound of this turbo idea, cost aside. I've got 4 years here in the states, plenty of time to build this puppy up. One thing I'm still kind of confused about is the gearing, how do you find out what the current ratio is? And how do you go about changing it.
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Old 08-08-2012, 11:58 AM   #18
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You most likely have 4.10's in there. Your going to want to look into what axles are there. If it is all stock then d30/d35's. For a turbo and some real hard wheeling you would most likely want to upgrade your axles. A 44 in the rear and a super 30 kit in the front. Of course it all depends on just how much you want to get. 505 performance did one and added 40 hp. But it was set on safe. With a stroker/ported head/cam/turbo/intercooler/tuner. You could easily boost into the 200 hp range. But it would cost bucks.
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Old 08-09-2012, 08:52 AM   #19
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I know the front axle is still stock, the previous replaced the rear end so no clue whats under there.
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Old 08-10-2012, 07:12 AM   #20
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TJ/LJ FAQ!/ axles/trans, alignment - Newbies, this one's for you!

USNMaA, check out this thread. It has lots of useful info that may help.
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Old 08-10-2012, 02:02 PM   #21
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Get a snorkel, beautiful cool air for your engine, improves performance, and makes your lil 4 beater look like a the MONSTER of your community. haha not hating, I have a 4 beater myself and want to get a snorkel
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Old 08-10-2012, 02:21 PM   #22
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looking for some more power both on road and off
add more cylinders. that's the only thing that's going to noticeably increase power.
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Old 08-10-2012, 02:36 PM   #23
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For my old 4 cylinder, I regeared to 4:88 ran 33's and I put a throttle body from a 4.0 onto the 2.5, it fit like a champ. Gave it a little better throttle response. That's about all I did for performance and it suited me fine.
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Old 08-11-2012, 05:19 PM   #24
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So I've decided, over the next 4 years I will addon (in no particular order) air intake, turbo, regear to 4.88, 2" or 3" susp. Lift, 33"s(haven't decided on brand or tread), rhino line the inside(And possibly outside) and lastly the matching rear bumper w/ tire carrier and Stinger hoop to my front one.
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Old 08-11-2012, 05:29 PM   #25
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Get a snorkel, beautiful cool air for your engine, improves performance, and makes your lil 4 beater look like a the MONSTER of your community. haha not hating, I have a 4 beater myself and want to get a snorkel
There is one single valid reason to add a snorkle and improved performance is not it. My guess is that of a hundred snorkle owners, one may have a truly valid need for it. Not to mention the reason a snorkle doesn't actually improve performance, despite the advertisements, is that the TJ's OE air intake system is more than capable of flowing all the air the engine can consume at WOT and redline RPMs. Offering more air via a large diameter snorkle tube than the engine is consuming is pointless. Kind of like expecting to be able to run faster by breathing through a larger diameter pipe held in your mouth. The only (!) way to make an engine consume more air than it normally consumes is via a supercharger or turbocharger.
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Old 08-11-2012, 05:34 PM   #26
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With those major plans I would just sell and look for a Rubicon. It has an I6 to cover your needs for more power. And more importantly Dana 44 front and rear.
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Old 08-11-2012, 05:43 PM   #27
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With those major plans I would just sell and look for a Rubicon. It has an I6 to cover your needs for more power. And more importantly Dana 44 front and rear.
Like I said earlier, not sure if Ill ever be able to bring myself to sell it.
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Old 12-01-2012, 03:46 PM   #28
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Dude, like it was said earlier , you'll hear people say "sell urs and buy another jeep with an I6", dude i say screw that ! Irun a 4 banger with 33s , cold air intake (not a snorkel) , 4.0 throttle body, spacer , jet stage 2 chip , gutted cat and chambered glasspack and im completely happy with mine ! Although , they are right regearing is my next step you should definitely go that direction , if i could trade in all my mods for one thing it would be gears ! Im tellin ya listen to jerry man , you'll be happy you did, even if you only go to 4:56s! get ahold of adamsdriveshaft.com they sell gear kits for 425 bucks for both housings and install kits . these are the guys i dealt with when ordering my sye kit and driveshaft , amazing customer service bro ! Happy Wheeling! See ya out on the trail someday!
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With those major plans I would just sell and look for a Rubicon. It has an I6 to cover your needs for more power. And more importantly Dana 44 front and rear.
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Old 12-01-2012, 04:49 PM   #29
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hey man take it from me, ive got a 97 2.5 with a 2.5" lift running 32's. ive tried it all. throttle body spacer, cold air intake, performance coil and plugs. all of it together helped, but mostly only past 3500 rpm, and not really very much anyhow. the only way to get utilize the power you have is gearing. lower the gears at the diffs. it might be pricy but its cheaper than a turbo kit, and less likely to screw something up. plus while your having the gears done you could get lockers or limited slips put in while your in there. thats my next big mod project, gearing.
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Old 12-01-2012, 08:46 PM   #30
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I have an auto transmission could I put 4.88 gears and still take highway?

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