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Unread 03-14-2013, 04:53 PM   #1
nightwrencher
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What's the pros/cons of putting a later model I4 in a YJ? want MPG

Hello, I am new to jeeps. I used to build GM musclcars and liked to cram big V8's where they don't belong. I guess I'm getting old, I have a YJ I4 w/ a million miles, and I am contemplating a later model I4 drivetrain. I don't necessarily need more power, but I am looking for some decent mileage if possible (w/o sacrificing the off-road gearing). I plan on using this for trail riding mainly, but I don't want it to cost an arm and a leg to get there. I don't know anything about the chrysler family of engines and drivetrain interchangeability between models, so can someone give me the basics. I understand I need to carry over PCM and make some adaptions, but but what drops in without major surgery and I can source from a junkyard donor? I don't need a 6 and if I can connect it to my AX5 that would be even better since it's rebuilt.

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Unread 03-14-2013, 09:09 PM   #2
ratmonkey
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You'd find better economy in a v8 fuel injected motor swap since it would be the same amount of work.
The 2.4 isn't any better than the 2.5 for economy and power and it doesn't mate to the ax-5, almost nothing other than the 2.5 does.

Most do indeed get much better economy from v8's than the stock jeep offerings.

Otherwise, just throw in a reman 2.5.
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Unread 03-15-2013, 10:56 PM   #3
nightwrencher
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thanks for the insight. I guess I can search the yards for some sort of GM engine. either V8 or V6 as long as it's common and got SFI. I know there are adapters out there, am I right in assuming I need a RWD engine? I also wanna stick w/ a manual tranny. obviously I need to do more reasearch, but having trouble finding anything more than dropping a SBC w/ auto-trans. prob gonna rebuld the I4 for now, but there's always scheming.
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Unread 03-16-2013, 02:49 PM   #4
1982cj8
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I am sure you could adapt the 2.4 to your trans but while the 2.4 has more horsepower it is high in the rpm range and the 2.5 has more torque. For trail riding the 2.5 is a better option. Typically for most people the 4.0 gets as good or better mileage than the 4cyls. You could source all of the items to switch to a 4.0 and probably get the trans at the same time.
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Unread 03-17-2013, 05:44 PM   #5
nightwrencher
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cool, i guess 4.0 is a good option unless I come across a deal on a gm drivetrain, but those rarely include manual trannys. I'm gonna run the 2.5 into the ground but just need a game plan and MPG is the only thing that sucks about this rig. my train of thought is updating to a newer engine w/ more efficient management/components/etc will give more streetablilty whithout sacrificing trail riding. the diesel option seems intriguing, but gotta learn more.
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Unread 03-18-2013, 04:46 AM   #6
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They're all going to cost money and not save enough fuel to pay for the mods in any reasonable time frame.
An i6 swap is just as much work as most v8 swaps.

What kind of economy are you getting now? What size tires and what ratio gears do you have?
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Unread 04-03-2013, 01:11 AM   #7
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keep the stock motor, work on new sensors, tune up, and improve compression.

dont forget to go easy on the pedal!
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Unread 04-06-2013, 07:51 AM   #8
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Unread 04-06-2013, 08:29 PM   #9
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Unread 04-07-2013, 07:45 AM   #10
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Quote:
Originally Posted by nightwrencher View Post
I used to build GM musclcars + I have a YJ I4 w/ a million miles + I don't necessarily need more power = I guess I'm getting old
Do the math, yeah, thats a downhill roll for sure, and you're almost at the bottom. Hell yes you're getting old. There are pills though. I'm twice your age and still not old.

I agree with most of the above guys that prety much any normal motor swap has the same work, so why bother with another low power 4 cyl. You have the last Jeep made with a 'normal' dashboard and gauge system, before the world went OBDII and CAN BUS, so that part is easier too.
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