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Old 10-20-2013, 09:18 AM   #1
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What's everyone doing to squeeze out some more power?

I recently purchased my first Wrangler, a 99 TJ 2.5 liter 5 speed, not the first one i've driven but the first one ive owned. So far so good besides my little ignition issue i posted about in a different thread, but otherwise than that all is well.

My question now is, short of throwing in a whole new engine, what's everyone doing to squeeze some more power out of these little 4 bangers? It's perfectly adequate for getting up to highway speed, but with the 33's its got on it, it bogs down to nothing, close to stalling, in the medium depth mud wholes and decent grade hill climbs. Is it just a forgive and forget sort of lost cause? What's everyone doing?

-Grizz

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Old 10-20-2013, 09:32 AM   #2
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Was it regeared after the big-o tires? You're not going to get any more power or mileage out of the engine, but you can regear it to take advantage of what its got.

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Old 10-20-2013, 09:46 AM   #3
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There is the classic formula. More air + more fuel - exhaust pressure = more power. Change the air filter, change your fuel filter, new high performance spark plugs, and a less restrictive exhaust is a good start. Might be only minimal increases but they are relatively cheaper fixes.
X2 on a re-gear with 33s. I only went 31 so I didn't have to change suspension or re-gear.
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Old 10-20-2013, 09:49 AM   #4
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I bought a 4 banger TJ. Regeared with 32" tires still bogged on me. So in less than a month I traded it for another TJ but rubicon.
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Old 10-20-2013, 10:35 AM   #5
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There is the classic formula. More air + more fuel - exhaust pressure = more power. Change the air filter, change your fuel filter, new high performance spark plugs, and a less restrictive exhaust is a good start. Might be only minimal increases but they are relatively cheaper fixes.
X2 on a re-gear with 33s. I only went 31 so I didn't have to change suspension or re-gear.
By changing the air filter I hope you mean replacing the dirty stock filter with a new one. CAI's are absolutely useless because the stock air filter allows more air in than the engine needs and CAI's allow more dirt in than you would want.
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Old 10-21-2013, 09:14 AM   #6
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By changing the air filter I hope you mean replacing the dirty stock filter with a new one. CAI's are absolutely useless because the stock air filter allows more air in than the engine needs and CAI's allow more dirt in than you would want.
On a cheap aftermarket CAI you would be correct, also a CAI on a jeep makes no sense for what the vehicle is designed for, but that's not for me to judge them on. A well designed filter, factory replacement or aftermarket, will offer more surface area for air to travel thru therefore it will be less restrictive. A cheap one has bigger holes to allow more air (and dirt). I just figured it goes without saying.
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Old 10-21-2013, 09:20 AM   #7
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The TJ's OE air intake system was specifically designed to be non-restrictive, it can easily flow more air than the engine can consume at wide-open throttle and redline RPMs. That is why Atthehop said what he did, he was right on. Some car engines have restrictive air intakes so they can benefit from free-er flowing air intake systems but that isn't the case with the Wrangler TJ. Making the TJ's air intake "less restrictive" won't help in the least.


Grizzly1200, the previous owner probably did not regear the axles once he installed the 33" tires. If your transmission is the usual 5-speed, regearing your axles to 4.88 will make a dramatic improvement to your 2.5L's performance.
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Old 10-21-2013, 09:21 AM   #8
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On a cheap aftermarket CAI you would be correct, also a CAI on a jeep makes no sense for what the vehicle is designed for, but that's not for me to judge them on. A well designed filter, factory replacement or aftermarket, will offer more surface area for air to travel thru therefore it will be less restrictive. A cheap one has bigger holes to allow more air (and dirt). I just figured it goes without saying.
there is no cai that is currently made that cleans the air better than the oem paper element

and the oem paper filter allows roughly 100 cfm more than our motors can consume at WOT

cowl induction with a paper filter seems to be the only suitable upgrade over the oem airbox
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Old 10-21-2013, 09:25 AM   #9
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Until you can regear, just use 4L. I have the exact same setup and 4L works well in those situations. Just go easy on the skinny pedal.
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Old 10-21-2013, 11:08 AM   #10
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Old 10-21-2013, 11:54 AM   #11
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This^
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Old 10-21-2013, 12:46 PM   #12
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nothing you can do to get more power out of it besides a motor swap or a turbo setup...neither of which are cheap.

as other mentioned, you can regear it to take advantage of what power it does have but thats about it. Go with 4.88's and you should get by just fine in the city. You'll still struggle a bit on hwy inclines but wouldnt be "terrible".

good luck
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Old 10-24-2013, 01:57 PM   #13
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Thanks for the input everyone. Looks like some regearing is in my future....
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Old 10-24-2013, 02:16 PM   #14
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Buying a 2.5L and wanting power is like buying a Jeep and wanting better mpg. Oxymoron....
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Old 10-24-2013, 02:54 PM   #15
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Regear. Got a 2.4 with 4.88 gears on 33" tires and I can hit 90 now. I can finally see my 6th gear
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Old 10-24-2013, 02:55 PM   #16
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Regear. Got a 2.4 with 4.88 gears on 33" tires and I can hit 90 now. I can finally see my 6th gear
You have a 6 speed? Automatic?
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Old 10-24-2013, 03:22 PM   #17
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The other thing to do to get a "gain" is change the power to weight ratio. Put your TJ on a diet and it will be more nibble and accelerate quicker. Heavy bumpers, armor, hardtops, fat chicks, etc all bog it down.
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Old 10-24-2013, 04:06 PM   #18
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Old 10-24-2013, 04:14 PM   #19
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It's the rear fender skirts that make the 64 Chevy fly. Someone should design skirts to cover the wheels and tires on a TJ to increase power and mpg. It would make more money than the companies that sell CAI's.
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Old 10-24-2013, 06:27 PM   #20
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it's the rear fender skirts that make the 64 chevy fly. Someone should design skirts to cover the wheels and tires on a tj to increase power and mpg. It would make more money than the companies that sell cai's.
lol

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