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141K views 186 replies 51 participants last post by  Little green jeep_97 
#1 ·
After adding a lift and 33 inch tires a 4cyl is pretty heavily stressed and lacking power. short of re gearing, what are some ways to "beef up" my little 4 banger

Thread is not a how to manual.. it's merely to seperate fact from fiction.. and as such will aid me in choosing the next diy project of the week.

feed back:
please rate or place the the various mods in the order 1 - 5 of importance.. which if done first will do the most good. If you have done any of these.. then what was the degree of your success?


Got any other bright ideas?

1. cold air intake

2. 4.0 throttle body spacer

3. exhaust

4. ECU or Chip

5. O2 sensor
 
#65 ·
Go for it! Very simple swap. It took me longer to clean the donor 4.0 TB than it did to remove the old one & install the new one.

I'm still in awe of how it woke my 2.5 up. Like I said, I've been playing with motors for over ten years & swapped out countless TB's & never has one made this big of a difference.
 
#66 ·
Yes with a 4.0L TB swap on a 2.5L you swap out and keep the 2.5L sensors. Some models the map sensor or maybe the throttle position sensor might be the same part number as the 4.0 . But you defitnetly have to swap out the IAC housing .( Idle Air Control ). On the side of those housing they are marked with 2.5L or marked 4.0L. I do myself as mentioned before do run a 4.0L TB. The only thing I did is shave the top side of the throttle shaft for smoother air flow. Well for what its worth. O yes also bored out my intake manifold to 55mm match the bottom of the 4.0L TB. I just simply used a gasket to mark it, stuffed the intake runners with rags to prevent metal shavings from intering intake, used a drill with rasp and then finner sanding disk for smooth finish. Little by little round and round trying to stay as uniform as possible. Until reaching 55mm bore. Did use a measuring gauge for tight tolerance and measuring all around. Works great with the 4.0L TB, gsp throttle body spacer, and bored manifold. O yes for whats its worth I did wrap my intake tube with insulation to keep incoming air temps down.
 
#67 · (Edited)
We have finished with the following mods and each one helped significantly, and were pretty cheap, recommend all of them;

Cat delete; did the same time as muffler, cost; 12.00 for 2.25 pipe from summit, Got 45.00 cash back for the old bad cat.

4.0 Throttle body, went on fine, big power difference, 45.00 at the boneyard (seemed like too much :()

5.0 Injectors, (got them from a 5.0 Ford truck, Bosch yellow top, 60.00 for used from boneyard, 1 hr to do.

Efan; 30.00 fan, 35.00 sensor kit ("Derale") Big difference there too.

I am really happy with all these mods, and yes, were running 30x1050r15's with 4.10s. I fully understand with 33's will require gears, and poss SYE/driveshaft. Im happy weve stretched the 2.5 to be all she can be safely. Thanks to all for your input.
 
#69 ·
We have finished with the following mods and each one helped significantly, and were pretty cheap, recommend all of them;

Cat delete; did the same time as muffler, cost; 12.00 for 2.25 pipe from summit, Got 45.00 cash back for the old bad cat.

4.0 Throttle body, went on fine, big power difference, 45.00 at the boneyard (seemed like too much :()

5.0 Injectors, (got them from a 5.0 Ford truck, Bosch yellow top, 60.00 for used from boneyard, 1 hr to do.

Efan; 30.00 fan, 35.00 sensor kit ("Derale") Big difference there too.

I am really happy with all these mods, and yes, were running 30x1050r15's with 4.10s. I fully understand with 33's will require gears, and poss SYE/driveshaft. Im happy weve stretched the 2.5 to be all she can be safely. Thanks to all for your input.
Now that your cat is deleted have you noticed any power loss or exhaust popping?, my cat had been taken off prior to me buying my my 91 yj jeep and it pops almost everytime I let off gas also has flow master on it.
 
#68 · (Edited)
On the Crank sensor mod, did some looking into; If we alter the crank sensor position without altering the CAM sensor position ( Which I believe is in the distributor) it stands to reason it would send the ECM a fault like a jumped timing chain. Would have to adjust both and guess they were the same amount?! The newer engines with variable valve timing have a fit with crank/cam correlation and Im not sure I want to go there... Thoughts anyone??
 
#70 ·
2.5L Power Mods

Yea me myself I would not mess with the cam or crank sensor. There is safer mods to mess with if you decide to mess with any sensors. There is the IAT sensor mod. I believe one is a module you can buy that fools the sensor, which myself dont like. The second mod to the IAT is to actually and physically relocate it to a cooler location such as the intake tube or air filter box. This mod is supose to read cooler incoming air intake temps and therefore alter the timing a bit along with fuel intake. The other safer mod in my opinion is to alter the volts going to the map sensor. By increasing the voltage to map sensor it will slightly advance your timing along with giving you a wider and longer pulse width to the fuel injectors. I believe this mod is only good at wide open throttle. That can be a good thing.
 
#73 ·
Hmmm. How do you do this MAP sensor mod? Speaking of MAP sensor, where the heck is it on the 2.5's? Most of the time they're in the TB, but my original 2.5 TB didn't have provisions for one. I might give that one a try next.

I just finished up relocating the IAT sensor to the airbox. An old 2nd gen Dodge Ram trick I've been doing for years. Crude, but effective none the less.



As for the CPS mod. I'm not sure about it on the 2.5's. I haven't looked into it. I've done it on 2 of my personal 5.9 Rams & numerous buddies 5.2/5.9 equipped vehicles with good results. It won't cause any issues with the cam sensor/pickup coil since your not moving the timing out of it's threshold enough to trip anything. You can't mod it far enough to hurt anything on the Magnum motors. It's not physically possible due to the bell housing. None of this applies to the 2.5 tho. I haven't even laid eyes on the 2.5's CPS. It could have waaaay more room for adjustment than the Magnum motors.

It would be worth a VERY CAUTIOUS try IMO given the high success rate on the Dodge V8's. But, to be honest with you guys, my little 2.5 has responded well to the small amount of mods I've done to it so far. I probably won't even mess with it. I can't wait to ditch the fan & try some 5.0 injectors. I have long been anti TB spacer, but all the 4 banger guys say they help. I find that hard to believe given the engine is MPFI, but they're cheap enough on ebay.

Fun little motors to work on, Even if the return is small. The more the better I say. :D
 
#75 ·
Hmmm. How do you do this MAP sensor mod? Speaking of MAP sensor, where the heck is it on the 2.5's? Most of the time they're in the TB, but my original 2.5 TB didn't have provisions for one. I might give that one a try next.

I just finished up relocating the IAT sensor to the airbox. An old 2nd gen Dodge Ram trick I've been doing for years. Crude, but effective none the less.

http://s42.photobucket.com/user/bigmacdak/media/IMG_20131022_224631_229_zps1046d518.jpg.html

As for the CPS mod. I'm not sure about it on the 2.5's. I haven't looked into it. I've done it on 2 of my personal 5.9 Rams & numerous buddies 5.2/5.9 equipped vehicles with good results. It won't cause any issues with the cam sensor/pickup coil since your not moving the timing out of it's threshold enough to trip anything. You can't mod it far enough to hurt anything on the Magnum motors. It's not physically possible due to the bell housing. None of this applies to the 2.5 tho. I haven't even laid eyes on the 2.5's CPS. It could have waaaay more room for adjustment than the Magnum motors.

It would be worth a VERY CAUTIOUS try IMO given the high success rate on the Dodge V8's. But, to be honest with you guys, my little 2.5 has responded well to the small amount of mods I've done to it so far. I probably won't even mess with it. I can't wait to ditch the fan & try some 5.0 injectors. I have long been anti TB spacer, but all the 4 banger guys say they help. I find that hard to believe given the engine is MPFI, but they're cheap enough on ebay.

Fun little motors to work on, Even if the return is small. The more the better I say. :D
Here's a good link to do the map sensor mod you asked about, http://jeep-xj.info/HowtoMAPsensor.htm
 
#79 ·
Mine is a 95 & it's up on the firewall. The '98 model 4.0 TB I put on had provisions for a TB mounted MAP, so I just blocked it off with a rubber cap.

I might have to try a home brew snorkel myself. I don't thing I'd ever need it, but it would be a good project. One of the guys on here posted a pic of one that was built out of 3" exhaust pipe, bent on a mandrel bender. It looked very nice.
 
#88 ·
The results are there, but nothing astronomical. You'll notice it better on a cold day if you have other mods that compliment it. TB, Kitty delete, that sort of stuff. It's worth doing. Pretty simple.
 
#89 ·
Well if there is no downside, and on my Lil 4 banger I can feel 1/2 a pony increase or decrease then maybe I just might really consider this mod and ponder on it. My questions to this mod would be, do I relocate all the way to air intake box or a milder location such as the intake tube, further out or in the middle of air tube or closer to TB ? Humm ?
 
#95 ·
We will keep that in mind if we decide to do that mod, leaning towards doing it once I get some free time. First things first on my lil rig. I gotta replace the power steering sensor, it seems to be leaking. Always filling the power steering fluid along with feeling a slight bog when crawling and turning steering wheel. Then I am going to replace the distributor swicth plate. My rig seems to buck on the first start up of the day. Looked at many other things and just wanna make sure its all running just right. O I adjust my adjustable air plate on air filter intake box, opened it up just a bit more along with down sizing my plug gap to .037 and she fires up alot quicker. She also seems to reach top speed real quick. I think I found a new sweet spot as far as air intake charge, along with a hot strong spark. Via accel coil, accel wires, NGKs at .037. with just the right air charge. Now gotta keep eye on MPG. Performance wise feels great. Thanks guys on input on that IAT relocation.
 
#96 ·
No problem. It's one of those do it your own leisure mods. I still need to do a complete tune up on mine. The plugs are just about toast. The wires look like new, but I would feel dirty about not changing them with the plugs. Haven't looked at the cap or rotor yet. Might do it this weekend.
 
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