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  1. #41
    Join Date
    Mar 2006
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    Denver, Colorado
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    312

    Re: 2.5L performance?

    If you change the 2.5 TBI to the 4.0 TBI do you need to change the fuel pump as well to keep up with the extra demand of fuel?

  2. #42
    Join Date
    Feb 2004
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    I'm here just for TwistedCopper!
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    5,098

    Re: 2.5L performance?

    Quote Originally Posted by drewman
    I went to take a picture but my camera batteries are dead. as soon as I can find the cord to my battery charger I will charge the batteries and take a picture then post it. In the mean time just look at the front of the filter housing. there is a hole where the air enters the housing. this is where the restriction is. it is similiar to the other one and comes out the same.
    My '94 doesn't have a restrictor there...it has the intake "snout" that runs up behind the grill and turns down at the front end, but no restrictor......

  3. #43

    Re: 2.5L performance?

    Quote Originally Posted by BaconYJ
    If you change the 2.5 TBI to the 4.0 TBI do you need to change the fuel pump as well to keep up with the extra demand of fuel?
    i wouldnt think so because your PCM is for a 2.5 so the amount of fuel will be the same...also, the injectors are also the same i believe...
    completely offensive, denominational, gender-biased, very original...sig line

    1995 Jeep Cherokee Sport w/ 4.0 HO. 3 inch lift put on by previous owner. shooting for 5 inch spring packs in the back instead of 3 inch shackles...

  4. #44

    Re: 2.5L performance?

    Quote Originally Posted by drewman
    I went to take a picture but my camera batteries are dead. as soon as I can find the cord to my battery charger I will charge the batteries and take a picture then post it. In the mean time just look at the front of the filter housing. there is a hole where the air enters the housing. this is where the restriction is. it is similiar to the other one and comes out the same.
    i believe you are talking about the resonator in front of the air filter...
    completely offensive, denominational, gender-biased, very original...sig line

    1995 Jeep Cherokee Sport w/ 4.0 HO. 3 inch lift put on by previous owner. shooting for 5 inch spring packs in the back instead of 3 inch shackles...

  5. Re: 2.5L performance?

    I'm don't know what a resonator is or does but it sure looks a lot like the restrictor between the filter and the tb. I charged my camera batteries last night and will try to post a pic tonight.

  6. #46
    Join Date
    Nov 2005
    Location
    Murfreesboro, TN
    Posts
    660

    Re: 2.5L performance?

    Got that picture yet?
    The poster formerly known as Red93...

    '93YJ 4.0HO, 33x12.50r15 Maxxis Mudder Buckshots, 4.5 RE extreme-duty lift w/ 1" BL, 4.11 gears, Aussie locked front, 1in transfer case drop soon to be replaced by SYE/cv shaft, 2 memphis 10's pushed by a memphis pr500, custom bumpers made by me

    http://www.myjeepspace.com/wrangl3r93

    http://www.tnvjc.org

  7. #47

    Re: 2.5L performance?

    i just got my first jeep, 87 comanche 2.5. having said that ive been a mechanic and fabricator since, well as far as i can remember.
    isnt the 2.5 a general motors motor?
    i was under the impression that the 2.5 is what they called the iron duke motor. it this is the case there is a lot of stuff available for this engine! cams, pistons, roller rockers even performance heads.

    can some one tell me if i'm right or wrong?
    thanks
    jeff

  8. #48

    Re: 2.5L performance?

    Quote Originally Posted by warpedredneck View Post
    i just got my first jeep, 87 comanche 2.5. having said that ive been a mechanic and fabricator since, well as far as i can remember.
    isnt the 2.5 a general motors motor?
    i was under the impression that the 2.5 is what they called the iron duke motor. it this is the case there is a lot of stuff available for this engine! cams, pistons, roller rockers even performance heads.

    can some one tell me if i'm right or wrong?
    thanks
    jeff
    It's an AMC Design with lots of GM parts to my knowledge.

  9. #49

    Re: 2.5L performance?

    4.10 gearing if you want to go over 50 mph

  10. #50
    Join Date
    Sep 2006
    Location
    Murfreesboro TN
    Posts
    160

    Re: 2.5L performance?

    I'm all about more torque rather then mass amount of horsepower. I think i'd redo the gears, rather then go out and spend big bucks on things that would improve it. But most of those improvments won't come into effect until 33's or better.
    Silence will bring even the mightiest of men down to their knees.

  11. Re: 2.5L performance?

    Quote Originally Posted by currupt4130 View Post
    I could pull 65 on the highway on 35's no problem with a 4 spd, thats pretty much the same as regearing. now on 38's the 4 banger is lacking a little bit even with 5.13's. I can get her to 50, but to tell you the truth, im scared to go over that with it now
    I just picked up a np435 myself, and plan on staying with my 4 cyl 2.5, I have a dana 300 to mate up to the back, I just have a few questions about the np435 swap. you used your ax5 bellhousing, and what adapter kit from advance, the one for the nv4500 and modified it? i talked to them and they said that is what to do, because they dont have a kit they told me specifically for thr np435....you reuse the fork and throwout bearing, does the kit come with the piot bushing? what mods were necesary for the adapter to work with the np435? what clutch did you use? and flywheel/flexplate?
    thanks for any info you want to send my way man
    dewitt

  12. #52
    Join Date
    Dec 2006
    Location
    San José, Costa Rica
    Posts
    1,693

    Re: 2.5L performance?

    Quote Originally Posted by drewman View Post
    I went to take a picture but my camera batteries are dead. as soon as I can find the cord to my battery charger I will charge the batteries and take a picture then post it. In the mean time just look at the front of the filter housing. there is a hole where the air enters the housing. this is where the restriction is. it is similiar to the other one and comes out the same.
    I have a '94 YJ 2.5L, and I also have the 2 restrictions; one on the front hole of the filter box, and the one on the part tubing going back. I removed both today, so I will be able to tell you sometime in teh future if I notice any effects (I still have not found any noticeable effects, but I understand the computer needs to re-learn the conditions, and this takes a couple of weeks).

    As for other mods, I have a K&N filter, Gibson Hi Flow Cat-Back, Accell Coil with 8mm wires (my engine was coughing a little, and I had to replace the coil anyway, so I decided to go for a little better coil), Bosch sparkplugs, and I already ordered a Helix Throttle Body Spacer (once it arrives, I will go ahead and install that also). I also want to replace the 2.5L throttle body for a 4.0L throttle body, but I have been unable to locate the 4.0L version... Still have to visit a junkyard (if I can find one), or something similar. Any suggestions on where to get one near Miami, FL?

    Felipe

  13. #53
    Join Date
    Dec 2006
    Location
    San José, Costa Rica
    Posts
    1,693

    Re: 2.5L performance?

    Quote Originally Posted by northshore29 View Post
    have any of you tried those performance chips that trick your pcm to think the air temp is colder than it really is? i imagine it would just ruin your gas mileage dumping that extra fuel, but w/ a 4.0L throttle body, ram air intake, and maybe a header i'm thinking i could get an extra 15-25hp. if anyone has a wild hair and extra $600-$700 to try it let me know how it goes.
    I saw some of these chips on eBay starting at $6.99, another at $59.99, and others up (new from dealer). I asked all of them to send me technical data proving the increase in HP that they claim (dyno or other), and they al refused to send data, which only leads me to believe the claims are a little (so as to not say COMPLETELY!) bogus...

    As they say... If it sounds too good to be true, it probably is. But having said that, at $6.99 you cant really go wrong.

    Felipe

  14. Re: 2.5L performance?

    check out this month's JP magazine, big write up on modifying the 2.5/4.0, basically leave the 2.5 alone, with exception of avenger s/chargers. Bolt on parts do nothing for the 2.5l, sometimes they actually reduce power. If jeep could've gotten more ponies from it, they would of.The throttle body is sized to provide hp's AND torque. If jeep could've just made one t-body for both, they would of, it would've been cheaper. Adding three ponies is not worth your time nor is it noticeable, assuming you actually get them.And you may even lose some low-end. Your 2.5l wiil serve you well, leave it alone and regear your axe's.
    '03 WJ stock form
    '95 YJ detroits F/R 31 bfg m/t's 2" b-lft, rs9000, elec idle cont, arb snorkel, 4 KC's, custom rear bumper, twin tube frt, 8000lb warn, cable act frnt ax,frnt diff guard...
    '81 CJ-7 fiberglass tub/hood, built AMC 360, 38.5 boggers, 6" sprlft,...
    '79 CJ-5 90% resto'd, 32" bfg mt's, new bestop, rebuilt 4.2l, trans, t-case,...

  15. #55

    Re: 2.5L performance?

    Quote Originally Posted by hummer-recovery-inc View Post
    check out this month's JP magazine, big write up on modifying the 2.5/4.0, basically leave the 2.5 alone, with exception of avenger s/chargers. Bolt on parts do nothing for the 2.5l, sometimes they actually reduce power. If jeep could've gotten more ponies from it, they would of.The throttle body is sized to provide hp's AND torque. If jeep could've just made one t-body for both, they would of, it would've been cheaper. Adding three ponies is not worth your time nor is it noticeable, assuming you actually get them.And you may even lose some low-end. Your 2.5l wiil serve you well, leave it alone and regear your axe's.
    While I'll agree that no single mod will have a huge impact for a 2.5L, doing several can. The most bang for the buck is a electric fan conversion. Instead of trying to squeeze more power from the motor, it frees up some that were already there but being used

  16. #56

    Re: 2.5L performance?

    I will also agree that re-gearing is the best choice

  17. #57

    Re: 2.5L performance?

    i'll second regearing and the electric fan(free up some poni's)

  18. #58
    Join Date
    Feb 2004
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    5,098

    Re: 2.5L performance?

    Quote Originally Posted by TwistedCopper View Post
    While I'll agree that no single mod will have a huge impact for a 2.5L, doing several can. The most bang for the buck is a electric fan conversion. Instead of trying to squeeze more power from the motor, it frees up some that were already there but being used


    Now, if JP Magazine had an opinion on which Cotton Dockers went with my Air Nike's and Old Navy Fleece pullover, I might pay attention to them.

  19. #59

    Re: 2.5L performance?

    Quote Originally Posted by Sparky-Watts View Post


    Now, if JP Magazine had an opinion on which Cotton Dockers went with my Air Nike's and Old Navy Fleece pullover, I might pay attention to them.
    I'd go with Khaki. Khaki goes with just about anything.

  20. #60
    Join Date
    Feb 2004
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    Re: 2.5L performance?

    Quote Originally Posted by TwistedCopper View Post
    I'd go with Khaki. Khaki goes with just about anything.
    Khaki does go with my hair...and sorta goes with the grey in my beard, but it just sounds too much like "caca" to me.


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