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Unread 03-14-2009, 05:03 AM   #1
turf-pro
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1997 TJ Wrangler 
 
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2.5L performance upgrade......

I am in need of a little more zzzip from my 4 cylinder. It runs great, for having 100k on it, but turning 31's is tough on the mountainous highway. I am not hard on my jeep, just enjoy some "light" off roading.

Can you put a 4.0 intake on a 2.5L? If so, I need details...

Please give any other tuning advice.


Thanks, turf-pro

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Unread 03-14-2009, 05:17 AM   #2
drtywtr
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not on a 1990 yj. they have tbi (throttle body injection) stick with the old stand by intake and exhaust. mild gains but you are never going to turn a 2.5 into a drag racer no matter how hard you try
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Unread 03-14-2009, 05:19 AM   #3
1C41N0
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Yes, if you have TBI you can put a 4.0 TB on a 2.5, but make sure you swap the idle air controller (IAC), or it'll run like crap. Keep it tuned up. There's not much you can really do to gain HP on a 2.5, it's a matter of making what it has more useable. Cheap mods are hotter coil,($70) high flow air filter$30 60 degree elbow, filter and grommets. Then you can put a less restrictive exhaust and an electric fan. If you put larger tires the main thing is to regear according to the size of the tires 4.56 or even 4.88. Anything else is just not worth it. The best gain is to do an engine swap. If you're thinking a 4.0 swap, consider a V6 or V8 if you want to get into it. The work is about the same, but a V6/8 swap is more costly because you can't use much of the old drivetrain. Basically to improve what you have, get that little engine some more air to breath, and then reduce the workload on it. They're an awesome reliable little engine, I love mine. I only running 235's, and no lift/gear changes. I don't think the 1990's are TBI, even though, the rest of this post contains the main points.
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Unread 03-14-2009, 05:39 AM   #4
JeeperDon
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The best performance upgrades for a 2.5L are made by General Motors.
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Unread 03-14-2009, 05:53 AM   #5
drunkencitywork
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www.4bangerjp.com lots of stuff just for 4cyl
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Unread 03-14-2009, 06:19 AM   #6
stu1021
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Quote:
Originally Posted by JeeperDon View Post
The best performance upgrades for a 2.5L are made by General Motors.

Amen brother !!
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Unread 03-14-2009, 07:10 AM   #7
sjwrangler
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I did the hot coil, wires and plugs, as described on another thread, and I could notice the difference. Less downshifting. Getting the rusty old coil out took some time.
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Unread 03-14-2009, 07:27 AM   #8
jonzjeepyj
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Also another cheap upgrade is....

Switching from 17lb injectors to 19lb ford injectors. It's a direct drop in replacement and gives your little 2.5 better
fuel delivery due to the increase in preasure as well as a 4 pintel (port) design. The stock 17lb injectors only have
one pintel. It allows your motor to perform better at the higher rpms when the ECU leans out the fuel delivery. This is
above 3200 rpms. Remember your power band on the little 2.5L is 2800-to-3500rpms. When revving the motor to pass
on the highway or climbing hills it really pays off. The motor keeps pulling all the way through 5000-to-5500 rpms. WoW!
At lower rpms you can enjoy a much smother and I do mean MUCH smother idol and a faster throttle response. I do suggest
you also do the 4.0 TB upgrade at the same time to get the full benefit out of it. I also tossed my stock muffler and replaced
it with a glasspack. I did some experimenting with the exhaust. I removed everything and ran it for awhile. Loss of power
and way too loud. Next I put back in the stock Cat. The power came back and much quieter but still to raspy and not toned
down enough. The glass pack toned it down and gave it a better sound with no flow restrictions. I'm very happy with the sound
and performance of this set up. Believe me, I'm 41 and don't like loud vehicles. You would think the glasspack would be
too loud but in reality the cat does most of the quiting and the the glasspack tones it.

I bought all my upgrades off ebay. The injectors were from a Donner Volvo. I got 5 (Volvo's are 5 cyl, I got a spare LOL)
19 lb injectors shipped to my door for $12.20. The 4.0 Throttle Body was $29.99 + $7.95 S+H ($37.94) The glasspack was
19.99 at a local parts store. Money well spent IMO. The bet $70.13 I spent on my Jeep besides regearing.

Some say the the ECU relearns the extra fuel and Air intake. I agree to a point. I does relearn the extra capacities and has
them available when needed and also adjusts to the new air and fuel mixture that is also available but it does NOT go back to
stock. I have had min on now for a better part of 6 weeks and it has been well over 50 warm up/start cycles and I still have
all the benefits of these upgrades.

Good Luck
John

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Unread 03-14-2009, 07:29 AM   #9
jonzjeepyj
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Quote:
I did the hot coil, wires and plugs, as described on another thread
That is going to be my next upgrade!

John
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Unread 03-14-2009, 07:38 AM   #10
stu1021
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Quote:
Originally Posted by jonzjeepyj View Post
Also another cheap upgrade is....

Switching from 17lb injectors to 19lb ford injectors. It's a direct drop in replacement and gives your little 2.5 better
fuel delivery due to the increase in preasure as well as a 4 pintel (port) design.
Except the OP's heep is a '90 which has only one injector - in the TB.
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Unread 03-14-2009, 07:43 AM   #11
jonzjeepyj
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WOOPS! I Missed that. That will teach me to read their stats first before posting. LOL Thanks for catching that.
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Unread 03-14-2009, 07:59 AM   #12
stu1021
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Quote:
Originally Posted by jonzjeepyj View Post
WOOPS! I Missed that. That will teach me to read their stats first before posting. LOL Thanks for catching that.
I only caught it 'cause mine is the same year and had the TBI before I installed the Chevy MPI upgrade......with the 4.3L engine under it
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Unread 03-14-2009, 08:32 AM   #13
KEEFFIE
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my brother did the " screaming demon" upgrade on his 4 popper. he said he noticed the inprovment. he can ALMOST keep up on the roads now.lol almost. oh not sure if there is differnt packages avail for the 4 popper but his was wires,cap,rotor,coil,and we also bought new splitfire plugs and intake at the same time.
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Unread 03-14-2009, 10:06 AM   #14
wendell
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With my 02 wrangler with the 2.5, I was running 31's and swapped in 4:56's. It made a big difference with this combo. I disagree, general motors doesn't have a cure for anything when it comes to a jeep. I wouldn't put a chevy engine in a chevy much less my my jeep.
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Unread 03-14-2009, 10:14 AM   #15
KEEFFIE
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Quote:
Originally Posted by wendell View Post
I wouldn't put a chevy engine in a chevy much less my my jeep.

i also disagree with your findings. mine has a chevy motor and am more then pleased with it and the power, no major probloms.
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