Best HP/$$$ mods for 1998 2.5L inline-4

Jul 25, 2003 4 Replies

Hello:



I have a 1998 Jeep TJ SE that I imported to California from Canada. While in Canada I installed a 2.5" BDS lift and put 33"x9.5" BFG MTs on the stock wheels and it was great in the snow, but the tires are pretty useless here.



I've recently started towing my 5x8 motorcycle trailer (for a roadracing bike) back and forth a lot. With the small 2.5L inline4 motor and big tires, I'm starting to wish I had a little more HP on tap.



When these tires wear out, I'm going to 31-inchers for the lower weight and better match to the stock 4.10 gearing, but that's probably not for another year or two.



Between now and then, what are the best HP/$$ mods I can do on the Jeep engine? I want something safe, cheap, and simple. I'm not looking to make my 128000km engine blow prematurely, I don't want to run higher octane fuels, and I don't want to spend too much time or $$ installing a blower or anything like that.



The engine is completely stock. Stock filter, stock throttle body, etc. I can't remove the catalytic converter because I'm in California and need to smog the damn thing.



Got any suggestions? Has anyone done dyno testing to show what mods made the most amount of improvement? Thanks for all your help.


I put a bunch of engine mods on mine, and got very little increase in horsepower. It's louder though, and the fuel mileage is definitely better. That should in principle keep the enviro-Nazi faction in my town happy with me. ;o)

In your place, I would forget about engine performance mods and regear, so you can get your performance back to approximately the same level and keep those 33 inch tires. Get the biggest (highest ratio) gears you can.

Earle

Swap out the stock TB for one from a 4.0 I6. That will free up some HP. Just keep the original for when you need to pass emissions.

Stay away from air swirrly things, they just suck cash.

A CA legal cat-back system and header would also help.

Then there is porting and polishing, but that's in the $$$$ category.

The 4.0L TB swap brought some good gains for me. I also have an AirAid intake (lots of discussion there) and a PowerAid throttle body spacer (a.k.a. money-sucker).

Eric

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