I have a '95 YJ with the 2.5L 4 cylinder and haven't done much with it yet.  I want to mod it so it will get more horse power.  However, I read that Hazel modded his 4 cyl. and driveability suffered.  If I put a cat back on it, a header, performance catalytic converter, and an intake, does anyone know how it will perform (better or worse)?  Well, if anyone has or is in the same situation as I am, please comment.  Thanks!  

I've had a 94 YJ 4banger for going on the last nine years.  

I don't want to tell you what to do or anything (because you probably won't do it).  

But with the 4Banger, I'd seriously only recommend upgrading with engine performance parts if the OEM original stuff wears out.  Then you can justify the "performance" upgrades as a truly necessary purchase.  

JP magazine did a test on a 4banger that it had upgraded across the board with completely new intake and exhaust -- headers, cat, cat-back-- & TB, etc.  Gained maybe 10% power for about a $1500+ expenditure.  This is gospel as far as upgrades go with the 4Banger (you'll spend lots of money and get little back).  

Seriously, you best bet with the 4banger Jeep is sell it for a 4.0L or, if you must keep it and want to run bigger tires -- say 33s -- regear your diffs to 4.88 (vs stock 4.10 with the 4banger manual).  Follow this advice; you'll thank me later!  

I do plan on doing those upgrades if it is worth it.  The horsepower and the torque on the YJ hazel had did go up, but he said it was better overall with the stock drivetrain, so I'm at a loss.  I wish I could get a hold of the newer 2.4L 4 cyl.  They have as much horse power as the 4.0L in the YJ's and are quieter and more economical.  It's horrible; I live in Wyoming and the winter sucks here.  I've been getting 10 mpg with my jeep which is sad considering it's a 4 banger (even with the added idling and heater use...).  

If anyone knows where I can get a replacement 2.4L that would be great.  Maybe it's just me, but I have tried to find 4.0L's on the search engines and can't find anything...  

My 2 cents, I have a 92 2.5l, 194000 miles. engine has never been cracked open. I have put a 160d stat, accell super coil, accell wires, bosch-4 plugs, and am currently changing the fan to electric, also I opened up my exhaust. cat back systems my buddys have not had luck with. go to a muffler shop. have 2.5 inch pipe and low restriction muffler put on. I won't header mine because of the bad luck I have had with headers. I have noticed a considerable difference with these small changes. A local engine shop says he can bore it cam it and open the valves for around 1200.00 and I will get 200+hp. I have found thow these 4 bangers are sensative to dirty injectors. have you cleaned your fuel rail and injectors?  

this is how i started....now i have a stroker and 4 links good luck and if you are worried about money DONT start  

Yes yj383 that is ultimately the answer. and I too will follow that brick road. I have V8'd other of my jeeps and purchased this one with the 4 because I new the 8 will soon come. But these dang little 4's are hard to kill. We are 4 wheelers! Money is no problem! HU  

I like the idea of doing the internals on the 4banger and squeezing 200hp out of it for $1200 or so.  

But then you still end up facing the 4Banger's AX5 transmission which probably isn't going to hold up to long to a 50-60% power increase before going south.

I'd personally do 33s, 4.88s, 4" lift, rear axle swap, and keep the 4banger engine stock until parts start to wear out on it.  The 4.88/33s setup will keep your mpg within reason, also (kind of important lately)

Good news is that that setup -- even with the 4banger
-- and a winch will probably get you through 95+% of the trails in the U.S. I am a big horsepower/torque fan myself, but the 4banger Wrangler S type Jeeps will get the job done in most cases.  

"That setup and lockers," I should add.  

Ah ya
no arguments with you there longdukdong. This is the delema some of us all face. This 92 is my 6th jeep in 23 years. Number 7 is out here also but it is a 2002 and my wife drives it. I have had 2A's, CJ5's, Willys pickups and a couple Wranglers. I have V8'd A few and found myself blowing apart drivetrain. I would not V8 mine now unless I was prepaired to go all the way. I agree. and I am going to crack mine open and do the upgrades to see what it gets. before spending 10 thousands on replacing everything. I agree all the way with the locker and geers. I am changing to 4:56's thow. I still don't run a huge lift and huge tires because of the mountain region and trails I run in and live in. I find myself helping out a lot of guys because the lift made them to top heavy. The winch is always the first thing that goes on. I call it "insurance". 20 years ago we went everywhere we go today with stock jeeps that had no lifts and highway tires and then we hearded them down the highway to work on monday. And now days we have to build them to the *** to get there.  

The transmission issue. Ax5 yes it will not hold up to a lot more than the stock 4 for long, but I picked up a spare and am rebuilding it and putting it on the shelf for when mine does go out. I would not keep it if I went v8. But I know some that have and still haven't replaced it. I suppose it also depends on who is behind the wheel.  

Does anyone have these modifications (save the header, I changed my mind...) on their 4-cyl. jeep?  If so, please let me know if it drives well and is better than prior to the upgrades.  

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SORRY GUYS COMPUTER PROBS. SINCE LAST POST I HAVE CHANGED MY 2.5 THROTTLE BODY WITH A 4.0 UNIT. THIS MAKES A DIFFERENCE. BE CAREFULL ON THE ELECTRIC FAN SWAP. THE 4 BANGER SITS FAR AWAY FROM THE RAD AND IT IS HARD TO GET A LOT OF AIR OVER THE ENGINE BECAUSE OF THIS. HOWEVER I DID NOT NOTICE MUCH DIFF BETWEEN THIS MOD AND PUT BOTH FANS ON. I RUN 32 11.50 MUD TRACS AND CAN CRUESE AT 60-65MPH IN 5TH GEAR. AND I GET AROUND 15 MPG. I LOVE THIS RIG IN THE MOUNTAINS. TRAILS ARE STEEP AND RUGGED HERE AND HAVE NOT HAD ANY ENGINE PROBLEMS ACCEPT WHEN THE IDLE MOTOR GUMMED UP ON ME. GOOD LUCK  

"BE CAREFULL ON THE ELECTRIC FAN SWAP. THE 4 BANGER SITS FAR AWAY FROM THE RAD AND IT IS HARD TO GET A LOT OF AIR OVER THE ENGINE BECAUSE OF THIS"

Your not trying to get the air over the engine, your trying to get it through the radiator. So custom applications the radiator is mounted in the bed of trucks with electric fan attached, no air gets to the engine via the fan with this method. that doesnt matter.