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Old 07-30-2012, 04:18 PM   #1
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2.5 performance mods

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

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Old 07-30-2012, 04:43 PM   #2
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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!

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Old 07-30-2012, 05:16 PM   #3
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What squeeze said. However I have the intake, 4.0 tb, and replaced the 02 censor and it makes it bearable... Until I hit a hill, or hook up my trailer!
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Old 07-30-2012, 05:17 PM   #4
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Quote:
Originally Posted by Squirrel cage
What squeeze said. However I have the intake, 4.0 tb, and replaced the 02 censor and it makes it bearable... Until I hit a hill, or hook up my trailer!
Note: I have the 4.0 throttle body, not a spacer.
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Old 07-30-2012, 05:37 PM   #5
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Regear Regear REGEAR
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Old 07-30-2012, 05:41 PM   #6
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Stroke it
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Old 07-30-2012, 06:16 PM   #7
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You forgot to add swapping in a electric fan for the clutch fan.
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Old 07-30-2012, 06:21 PM   #8
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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.
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Old 07-30-2012, 06:22 PM   #9
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Dont waste 500+ on useless items, put that towards a regear!
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Old 07-30-2012, 07:40 PM   #10
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Dont waste 500+ on useless items, put that towards a regear!
Exactly. The 2.5L is a fantastic motor, durable as heck, good torque curve, fairly reliable. It does not respond well to mods. There is a good idiom that applies, like squeezing blood from a stone.
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Old 07-30-2012, 09:34 PM   #11
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Quote:
Originally Posted by mbaseel
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?
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Old 07-30-2012, 09:59 PM   #12
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The banks cat back is great. Has a nice low rumble. Wasn't the greatest until I put the header and high flow cat on it though. Sounded kind of ricey before that.
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Old 07-30-2012, 10:04 PM   #13
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I put a intake,4.0 throttle body,and a efan and it helped some.still was not happy.I ended up swaping my engine for a 4.0.
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Old 07-30-2012, 10:25 PM   #14
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yup you're right.. and i'm looking now for the fan $25 taurus
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Originally Posted by Nickabis View Post
You forgot to add swapping in a electric fan for the clutch fan.
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Old 07-31-2012, 02:59 AM   #15
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Dyno tests have shown as much as 40hp over stock with all of the available mods.. I will say that 19lb injectors that have a multi-ported nozzle do give the engine more umph. Cleaner burn pattern.
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Old 08-01-2012, 09:17 AM   #16
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If you haven't yet check out 4bangerJP.com - Index
Alot of good info..
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Old 08-01-2012, 11:26 AM   #17
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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.
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Old 08-01-2012, 11:16 PM   #18
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Thumbs up

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 not got my head wrapped around the TB yet.
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Old 08-01-2012, 11:27 PM   #19
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Quote:
Originally Posted by Frenz
I am buying an e fan $40 pep boys.
do yourself a favor and spend the little extra to buy the wiring harness with the adjustable temp.
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Old 08-01-2012, 11:43 PM   #20
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Quote:
Originally Posted by BlackedOutYJ View Post
do yourself a favor and spend the little extra to buy the wiring harness with the adjustable temp.
gotchya ty
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Old 08-05-2012, 11:20 AM   #21
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Quote:
Originally Posted by ctlucas93
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.
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Old 08-05-2012, 08:43 PM   #22
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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.
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Old 08-06-2012, 08:44 AM   #23
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Quote:
Originally Posted by Xpress
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
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Old 08-06-2012, 09:02 AM   #24
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1 e-fan
2 lose the AC
3 4.0 throttle body
4 gear the hell out of it, 4:56 or 4:88
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Old 08-06-2012, 10:19 AM   #25
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Do any of yall have a p/n on the Bosch 19lb injectors
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Old 08-06-2012, 11:28 AM   #26
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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.

Quote:
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While that would make sense, a spacer also allows the air to heat more causing lese dense mixture atleast I would think so
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.
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Old 08-06-2012, 11:53 AM   #27
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You can throw all kinds of parts at it, but when the day is done a gear swap is the only thing that will make a real difference.
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Old 08-06-2012, 02:58 PM   #28
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Do any of yall have a p/n on the Bosch 19lb injectors
I'm curious of this myself, as I believe the 0280150943 Bosch/19 pound yellow tops I have are the WRONG part number.
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Old 01-09-2013, 05:47 PM   #29
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Does any of this apply to the 90 2.5l TBI? Not the exhaust, but the 4.0 TB, 19lb injectors, etc?
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Old 01-10-2013, 12:28 AM   #30
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Does any of this apply to the 90 2.5l TBI? Not the exhaust, but the 4.0 TB, 19lb injectors, etc?
Unfortunately no, you and I have the same motor. I only did the header and e fan. Most everything else is for the mpi motor.

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