Author Topic: 2.5 vs 2.4 engine  (Read 20137 times)

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keithert

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2.5 vs 2.4 engine
« on: October 20, 2006, 09:19:35 AM »
I've had my 98 SE for about 6 weeks and am happy enough with it's power.  It is a 5 speed.  It won't win any races but does an ok job otherwise.   I know the 2.4 has more horsepower and is a completely different engine.  What are the pro's and cons of each engine?  Will a 2.4 with an automatic have as much power as a 2.5 with manual trans?  I've also read that the 2.5 has more toreque down low so it actually feels quicker than the 2.4.  I'm wondering because I might get a newer TJ and would like to stay with the 4 cyl due to cost and mpg issues.  I know the mpg isn't much different than the 6 but every bit helps.

frosty

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2.5 vs 2.4 engine
« Reply #1 on: October 20, 2006, 11:19:14 AM »
the 2.5 is a jeep engine designed for a jeep. The 2.4 is a dodge neon engine designed for a car.  The 2.5 has its torque at a much lower rpm where you really need it. its the same as the 3.8 vs 4.0 debate.  The 3.8 produces a little more torque but the 4.0 produces 85% of its torque at idle where you really need it.  With thats said I would take any variant of the two amc engines over a chrysler engine any day of the week.  The are both simple tough strong engines that are made of all cast iron.  Both the 2.5 and the 4.0 are known to go forever I am not so sure about the 2.4 it may be a decent engine as is the 3.8v6  But i will say that the jury is out and they dont match up as far as durability and longevity to the older amc engines

dunklervogel

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2.5 vs 2.4 engine
« Reply #2 on: October 20, 2006, 12:47:13 PM »
I've just heard the 2.4 has to get pretty high revs to reach a good torque that the 2.5 can put out at lower rpms..  in which case on a trail i'd think the 2.5 would be a better engine for a jeep.

Offline Jeffy

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2.5 vs 2.4 engine
« Reply #3 on: October 20, 2006, 12:55:55 PM »
The DC 2.4L is a completely different engine then the AMC 2.5L.  The AMC 2.5L was first designed to replace the GM Pontiac Iron Duke 2.5L that the CJ's had been using for years.  In 1984, the first Jeeps with the AMC 2.5L.  This included the CJ and the new Cherokee (XJ) and Comanche (MJ).  The engine was designed from the 4.2L AMC already had but with some differences.  The engine still uses push rods like the 4.2L.  Stock gearing was 4.10/4.11 for the manuals and 3.73:1 for the automatics generally but when parts ran short, some 3.54 gears were used for the auto's and possibly 3.73 gears were used on the manuals.  The engine has had different ratings over the years but the TJ's has 120hp (down 3hp from the YJ) and 140lbs-ft of torque.  The engine hits peak torque between 2600-3200RPM.  This is pretty low and is in the middle of the power band.

The 2.4L was designed to be used on multiple platforms.  The Neon, Caliber, Liberty, PT Cruiser, etc...  Unlike the 2.5L the 2.4L was designed to be a transverse engine instead of the conventional N-S setup a RWD uses.  The 2.4L also moved away from push rods in favor of OHC.  OHC involve less parts so there is less power wasted in moving the valves.  Typically, this also means that the engine is more balanced and can rev higher.  The down side is there there is less torque down low.  To hit peak RPM with a 2.4L you will need to rev to 6000.  That's 3000RPM more then the 2.5L.  The 2.4L does produce 147hp which is 27hp more then the 2.5L though.

The first 2.4L's came out with the same gearing as the 2.5L, 3.73 and 4.11's.  They were still using a 5-speed manual and a 4-speed automatic 42RLE.  Then they switched from the 5-speed manual and 4-speed auto to the 6-speed box for both. They also regeared the 2.4L to 4.56:1 in both models.  This only lasted a year, I believe.  Then they went back to 3.73 and 4.11's which is where it started till they phased out the 2.4L Wrangler.

As for the 3.8L, this engine was derived from the current 3.8L DC has been using in their Caravan and other cars.  The engine was revamped though.  A friend of mine bought a Rubicon Unlimited JK and drove it from MI to CA with the 3.8L.  He said he likes the engine better then his old 4.0L but not as nice as his 5.7L Hemi.  (His 97 TJ ahd a 4.0L before he swapped in a 5.9L.  His Unlimited had a 4.0L but was swapped out at AEV for a 5.7L Hemi.)

That said, another friend said had owned a 2.5L, and two 2.4L's one with 4.56's.  He never got very good gas mileage compared to his 2.5L.  His Jeeps were all relitively stock.

The biggest advantage of having an engine shared with a bunch of other model vehicles is that many parts are interchangable.  This means there is a higher likelyhood of performance parts especially with the Neon.  There is also the option of a turbo, lower compression rods, etc...
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keithert

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2.5 vs 2.4 engine
« Reply #4 on: October 20, 2006, 02:08:56 PM »
Jeff, thanks for the excellent and detailed write up.  Can any 2.4 owners speak up on how they like their engine?  I get about 17-19 mpg with my 2.5 that has 31's and 139k miles.  What are people with the 2.4 getting?

Liljeepz

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2.5 vs 2.4 engine
« Reply #5 on: October 20, 2006, 03:39:19 PM »
Quote
Both the 2.5 and the 4.0 are known to go forever I am not so sure about the 2.4

I never thought about this.... That dose worry me....



Quote
The biggest advantage of having an engine shared with a bunch of other model vehicles is that many parts are interchangable. This means there is a higher likelyhood of performance parts especially with the Neon. There is also the option of a turbo, lower compression rods, etc...


This I like! I need to look into good engine mods for the 2.4L!
Will the 4.0TB work on the 2.4 since its a totally different engine?

Offline Jeffy

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2.5 vs 2.4 engine
« Reply #6 on: October 20, 2006, 03:58:57 PM »
Quote from: "Liljeepz"
Quote
Both the 2.5 and the 4.0 are known to go forever I am not so sure about the 2.4

I never thought about this.... That dose worry me....


I wouldn't worry about it.  The engine's used all over the place.  If the engine does have a problem with the design then it would have come up already.  Rememeber that the engine was used for a few years before the TJ ever got it.  I think it might be evolved from the 2.0L, 2.2L of the Neons.  In any case the engines are plentiful and are probably cheap too.
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"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

Chad

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2.5 vs 2.4 engine
« Reply #7 on: October 21, 2006, 12:08:11 AM »
I get like 12-14 mpg with 31's on my 2.5L i've got about 50k miles on the engine what the hell, how come your gas mileage is so much better?

YJmechanic

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2.5 vs 2.4 engine
« Reply #8 on: October 21, 2006, 05:21:08 AM »
jeffy not to kill your write up because as usual you have the insight to more info than i can imagine but one problem and i have heard this many times before.  but the 2.4 in the jeep is not a neon motor.  the 2.4 in the neons and the jeeps are totally different motors.  the 2.4 in the jeeps is actually from the stratus coupe and is actually a mitsubishi motor.  i thought the same thing untill i contacted my dealer reps with questions about using an srt4 turbo setup and found out where the motor came from.  also as a general buying guide.  42rfe is a great trans but if you see the tag 42rle it is a horrible trans.  we have replaced about 200 in the last couple of years with low milage.  jeep doesn't even use the trans any more because of all the problems.  just thought i could give some insight.

now as far as 2.5 vs 2.4  i have driven tons of both and i have to say my opion is that the 2.4 doesn't belong in a jeep. it is flat as day and revs out in two seconds.  it was designed for cars and that is where it belongs.  no offense to 2.4 owners though

Liljeepz

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2.5 vs 2.4 engine
« Reply #9 on: October 21, 2006, 09:01:07 AM »
:sad: I'm stuck with this POS because I didn't know any different when I bought it just over two years ago! Thanks a lot DC!  :angry:
Dose any one know of any good wright ups on this engine? Options, reviews... any thing? Or even good replacements? I already have 50k on this engine and it will be well over 100k by the time its my toy and I can play with it. I don't want to get rid of the 4 cyl but I don't want to keep the 2.4 when it has 35's and all these other great mods. :roll:

I know it dose great for me now... but when I'm more experienced I may want something else and I would like the knowledge before I get to that point.

Offline Bounty Hunter

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2.5 vs 2.4 engine
« Reply #10 on: October 21, 2006, 11:52:51 AM »
Quote from: "Chad"
I get like 12-14 mpg with 31's on my 2.5L i've got about 50k miles on the engine what the hell, how come your gas mileage is so much better?

Shoot, I get 18city and 21hwy with my 2.5L on 32"s, and the speedo has been corrected.

Back down to 225's now while I do a SOA and throw on 35"s and 5.38's.

Offline Jeffy

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2.5 vs 2.4 engine
« Reply #11 on: October 21, 2006, 12:06:09 PM »
Quote from: "Liljeepz"
:sad: I'm stuck with this POS because I didn't know any different when I bought it just over two years ago! Thanks a lot DC!  :angry:
Dose any one know of any good wright ups on this engine? Options, reviews... any thing? Or even good replacements? I already have 50k on this engine and it will be well over 100k by the time its my toy and I can play with it. I don't want to get rid of the 4 cyl but I don't want to keep the 2.4 when it has 35's and all these other great mods. :roll:

I know it dose great for me now... but when I'm more experienced I may want something else and I would like the knowledge before I get to that point.


I'm not sure if Allpar.com would have a good writeup but there should be on there.

Like we always say, gears are your friend.  Properly geared you should be fine even with 35's.  I'm a bit tossed between wanting to run 5.38's or else doing a SC or engine swap.  Going too low with the gears will limit my high end.  Although I doubt I'd want to go over 85mph.  It gets a bit scary at those speeds when a crosswind picks up.  If I was considering an engine swap, I'd probably gear only to 5.13's instead of 5.38's although I could live with 4.56's too.  I'd really like to swap my axles for a pair of Dtrac D60's, I think and keep my 35's.  I'd be able to go up to 37's or 38's but I really like 35's.

When I was mostly stock and ran 32's I would get +21MPG.  My best was 25-27 but back then 60mph was considered fast and so I didn't have to push it hard.  This is the biggest problem.  I think if I was able to drive at 55-60mph without having everyone in this Prius pass me, I'd get into the 20's again.  That's with 35's and 4.56's.  From what I've seen though the 2.5L gets better mileage since most are driven around town and you don't have to rev it up to get enough torque.  3000rpm vs. 6000rpm is a big difference.
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"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

Liljeepz

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2.5 vs 2.4 engine
« Reply #12 on: October 21, 2006, 12:52:28 PM »
Saving money now for a axle swap, I was tossing the idea around for a bigger lift fist, but axle's with lockers would help a bit more. I just have to remember I have a 2" lift and can't do the very hard trails with out a lot of damage. I'm running 31's now, I can't complain about the power but it is high rpm power I don't get going tell 3k+.
1K-3K is rough tho.

JeepersCreepers

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2.5 vs 2.4 engine
« Reply #13 on: October 21, 2006, 06:44:28 PM »
The 2.4 engine is supposed to actually be a longer lasting engine than its predecessor...............Time will tell. It works well for me as I use it to get to work. I drive on older state highways about 60 miles round trip & rarely get over 65MPH.When you think about it the Jeep isn't really a good car for interstate travel with it's soft top(mine anyway), solid front axle & VERY short wheel base. Also the peak HP comes long before 6000 RPM(this is where my tach is at extreme redline)more like 5000RPM. I would have to say the two engines are pretty much alike all things said. I have yet to get under 20MPG out of mine & get about 22MPG most of the time. Here is the specs straight from Chrysler..............Enjoy............ :D




The 2.4 L (2429 cc) EDZ engine is very similar to the 2.0, sharing the same bore and DOHC cylinder head, but it has a taller block and longer 101 mm stroke. It also uses balance shafts to smooth vibrations and is built in Saltillo, Mexico. Output was up to 140 hp when production started in 1994 for the 1995 model year. As of 2004, output is 147 hp SAE (110 kW) at 5200 rpm with 165 ft·lbf (224 N·m) of torque at 4000 rpm.

It has a cast iron engine block and an aluminum DOHC cylinder head. It uses SFI fuel injection, has 4 valves per cylinder with roller followers and features fracture-split forged powder metal connecting rods, a one-piece cast camshaft cast, and an aluminum intake manifold.

Applications:

Chrysler PT Cruiser
Dodge Stratus/Chrysler Cirrus/Chrysler Sebring/Plymouth Breeze
Dodge Caravan/Chrysler Voyager
Jeep Liberty
2003-2005 Jeep Wrangler

keithert

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2.5 vs 2.4 engine
« Reply #14 on: October 21, 2006, 06:55:25 PM »
Quote from: "YJmechanic"
but the 2.4 in the jeep is not a neon motor.  the 2.4 in the neons and the jeeps are totally different motors.  the 2.4 in the jeeps is actually from the stratus coupe and is actually a mitsubishi motor.


I don't think it is a Mitsu motor.  The Mitsu 2.4 is a SOHC engine and the Mitsu DOHC heads look a lot different than the one in the SE.