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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
 
#2 ·
I can't speak from experience as I'm still building my jeep, but most guys and girls on here will tell you just to regear. At the price you'll be putting out for all the things you listed, you'll be better off regearing to get the most power. Just figured is prepare you for the same answers I got!
 
#8 ·
I have intake, 4.0 throttle body and throttle body spacer, pacesetter header, high flow cat, banks cat back monster exhaust, and mustang 19lb injectors and it gave me 5th gear back... If all of that is worth it to you go for it. But from experiencing the minor differences of all of these things together even after a full rebuild on my top and bottom end I say save for the re-gear.
 
#11 ·
mbaseel said:
I have intake, 4.0 throttle body and throttle body spacer, pacesetter header, high flow cat, banks cat back monster exhaust, and mustang 19lb injectors and it gave me 5th gear back... If all of that is worth it to you go for it. But from experiencing the minor differences of all of these things together even after a full rebuild on my top and bottom end I say save for the re-gear.
How's the banks cat back for you? Does it sound good?
 
#17 ·
1. 4.0 Throttle body and spacer
2. 19lb Bosch Yellow Top Four Hole Injectors
3. Ford Taurus Electric Fan
4. MSD Ignition Coil
5. 8mm Spark Plug Wires

I have all these mods and I can do 75 MPH no problem running 31-10.50-15s, AND I use 5th gear and get 18 MPG. Fan and throttle body make the most difference right off of the bat.
 
#42 ·
2.5 performance mods help please!

1. 4.0 Throttle body and spacer
2. 19lb Bosch Yellow Top Four Hole Injectors
3. Ford Taurus Electric Fan
4. MSD Ignition Coil
5. 8mm Spark Plug Wires

I have all these mods and I can do 75 MPH no problem running 31-10.50-15s, AND I use 5th gear and get 18 MPG. Fan and throttle body make the most difference right off of the bat.
Thanks to all for your investment in this thread.
Were working with a 95 YJ 2.5 5 spd.
Yes I know gearing is in mu future once we do 33's, but want the horses we can get for cheap.

I've already done cat delete, fm super 44 muffler,

Heading for electric fan, have a 4.0 throttle body to install, Possible timing adj.
A couple questions for your intelligent chime in....

1 Looks like ford Taurus is a simple fan swap? I can handle proper wiring ok
Is that the best junkyard fan to look for?

2. Injector swap from junkyard, 4.0 litre? Mustang bosch yellow? Years?

3. Do I have to modify intake for the bigger throttle body?

4. Im considering slotting bellhousing to advance timing at crank sensor. Anyone gotten into that??

Side note, Had a 99 TJ 4.0 and put an air-raid spacer with the swirl interior and definitely helped midrange. That alone helped the 4.0
 
#18 ·
I am buying an e fan $40 pep boys. also excited about "tri county gear's.. inertia ring" that is sitting here waiting to be installed. the motor is on the engine stand waiting for the mods. injectors coil & wires yeah baby :thumb: not got my head wrapped around the TB yet.
 
#21 ·
ctlucas93 said:
1. 4.0 Throttle body and spacer
2. 19lb Bosch Yellow Top Four Hole Injectors
3. Ford Taurus Electric Fan
4. MSD Ignition Coil
5. 8mm Spark Plug Wires

I have all these mods and I can do 75 MPH no problem running 31-10.50-15s, AND I use 5th gear and get 18 MPG. Fan and throttle body make the most difference right off of the bat.
I can do 75mph in 3rd no problem with a stock 4cyl on 31"s too!

Also, think about what the Jeeps throttle body does, it has no fuel injection at the throttle body, thus no reason at all for a spacer.
 
#23 ·
Xpress said:
TB spacers supposedly make the air more turbulent. In theory, it doesn't matter where the fuel is mixed, more turbulence throughout the intake means a better mix.
While that would make sense, a spacer also allows the air to heat more causing lese dense mixture atleast I would think so
 
#26 ·
Here's a list of parts for 1991-1995 MPFI 2.5L engines:

-19lb injectors
-Electric fan
-4.0 throttle body
-Throttle body spacer
-High flow intake
-Borla headers
-Full exhaust system
-Hotter running ignition coil
-Regear for your tires

Like I mentioned, some advocates of this setup has seen as much as 40hp over stock in engine output, and some 35ft lbs of torque. That's plenty to make your humble 2.5L into an engine that can roll with a bit more authority. 123hp vs 163hp, modern 4 cylinder engine territory.

Of course if you really want to get power out of a 4 cylinder then I suggest stroking to a 2.9L and turbocharging, ontop of the above power upgrades.

And for those who whine about parasitic drag increases on the alternator from the e-fan, it's not present while the fan isn't running. Above 25mph there's really no need for a fan, as the air flow through the radiator is adequate to keep everything cool. 25mph+ = no electric fan on, which in turn = no additional parasitic drag on the alternator.



Not really, no. Your intake manifold isn't really HOT in the first place. Plus, more spooling air inside means that it will cool down more before it gets sent in. NOT THAT a 10* temperature difference is going to make your engine run any better or worse. The turbulent air is what you're after.
 
#28 ·
I'm curious of this myself, as I believe the 0280150943 Bosch/19 pound yellow tops I have are the WRONG part number.
 
#32 ·
Being as mine has 48k miles on it, there won't be a swap coming anytime soon. Fingers crossed.....


It's a beach buggy most of the time, less weight with the top off anyway. 😀 31's with a 2" lift going in right now. I hope it doesn't turn into a chore driving down the highway to the Cape this summer.
 
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