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Unread 12-17-2008, 08:41 PM   #1
gakio12
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4.0 Engine upgrades

My sister recently purchased a 4.0L V6 Mustang (2006). It has way more get up and go than my Jeep. Both engines are 6 cylinder and 4.0L, so I figured there shouldn't be too much of a difference in power (sans the V vs. inline).

First I looked at the compression ratio of the two engines. The Mustang V6 is 9.7:1, while the Jeep engine is 8.8:1. This is probably the most important factor, so shaving the Jeep's cylinder head to 9.7:1 ratio will probably give you as much power. But I have found more.

I then looked at the exhaust aspect. The Mustang has cast iron headers (or really good manifolds) and all mandrel bent exhaust tubing, while the Jeep has a standard manifold and compression bent tubing. The exhaust tubing on the Mustang is noticeably bigger than the Jeep's, as well.

Of course, putting bigger piping and all mandrel bent on a stock Jeep engine, torque will be sadly sacrificed. Which is indeed why the Jeep would need the 9.7:1 compression ratio (more exhaust pressure). An added plus to the increased compression ratio is the Jeep would use the same amount of gas, instead of the stroked engine using more gas.

Has anyone increased the compression ratio of their 4.0L Jeep? Any ideas on the subject?

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Unread 12-17-2008, 08:50 PM   #2
halfmoonclip
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An article in JP magazine addressed most of this. They dynoed a 4.0 after various mods; less restrictive intake, headers, less restictive muffler. The results were surprising; there was very little power gain until they revised the engine management computer with a chip. This gave a not insignificant power gain (20-25 hp IIRC), at the expense of running on premium fuel.
I don't recall an effort to raise compression, but this might also require high test. Keep in mind that the I6 originally powered Roman chariots; it's been around a long time, and any effort for more power will likely cost you something.
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Unread 12-17-2008, 08:56 PM   #3
gakio12
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Well, it is rather cool to watch a Jeep beat a Mustang in a race (regardless of the Mustang's engine) I was more thinking of comparing the higher compression vs. stroking the engine in upgrades to the Jeep. With the stroker it needs more gas because of the increased displacement. In fact, the Jeep would probably be a 3.8L engine with 9.7:1 compression.
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Unread 12-17-2008, 08:58 PM   #4
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Oh My God!
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Unread 12-17-2008, 09:22 PM   #5
halfmoonclip
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Quote:
Originally Posted by gakio12 View Post
In fact, the Jeep would probably be a 3.8L engine with 9.7:1 compression.
Milling the head doesn't shorten the stroke, unless you're funning us.
While I'd applaud whupping a Mustang with a Wrangler, that makes as much sense as modding the 'stang so that it can navigate logging roads.
It can be done, but it is losing sight of the vehicle's purpose.
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'12 Ford Focus-the sure way to get good Jeep mileage
'07 Dodge Caliber R/T AWD-da kid's ride
Goodbye Old Blue XJ; 10+yrs, 100K+ miles; virtually trouble free; Long may you run!
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Unread 12-17-2008, 09:31 PM   #6
Greg_Volkman
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hook a tow rope onto her mustang and have a tug-of-war, then you'll see what your I-6 is good for....

her engine is obviously a much more advanced design - it has a better intake manifold design than any I-6 could dream of, and the cylinders are flow-through design. You' be hard pressed to match the performance with an I-6.

The 4.0L I-6 is good at what it does, and that is produce torque.
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Unread 12-17-2008, 09:34 PM   #7
gakio12
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Quote:
Originally Posted by halfmoonclip View Post
While I'd applaud whupping a Mustang with a Wrangler, that makes as much sense as modding the 'stang so that it can navigate logging roads.
It can be done, but it is losing sight of the vehicle's purpose.
Moon
I actually want to put a Geo Metro body on a CJ frame...
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Unread 12-17-2008, 09:50 PM   #8
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or get both for yourself . One for speed and one for everything else since it is as likely that the jeep will outrun the mustang as the mustang will ever see a trail.


don't know why they aren't showing up click free
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Unread 12-17-2008, 10:05 PM   #9
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^ Nice rides man

I agree unfortunately I have two rides the 08 GTI and a 99 Jeep. I wish I could get rid of the GTI so I would have more $$ for the Jeep.
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Unread 12-18-2008, 04:01 PM   #10
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Quote:
Originally Posted by gakio12 View Post
I actually want to put a Geo Metro body on a CJ frame...
I keep bringing that up to my friends. Probably wouldnt put it on a CJ. Maybe a sami...
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Unread 12-18-2008, 05:07 PM   #11
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Quote:
Originally Posted by gakio12 View Post
I actually want to put a Geo Metro body on a CJ frame...
Now THERE is a mind movie.....
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'12 Ford Focus-the sure way to get good Jeep mileage
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Unread 12-18-2008, 05:10 PM   #12
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I've taken mustang GTs with no problem to 60, between the gearing of 4th and drag, thats usually when any car will take me =/

do you remember what chip they used in that test?
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Unread 12-18-2008, 05:20 PM   #13
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Quote:
Originally Posted by keithrj View Post
I've taken mustang GTs with no problem to 60, between the gearing of 4th and drag, thats usually when any car will take me =/

do you remember what chip they used in that test?
I had a buddy in High School with a '48 Ford pickup; it was geared so short that he could beat about anything between the first two phonepoles; after that, the big stuff would come screaming past, indignation and shame all over the driver's face.
Sorry; don't remember the specific chip they used. Somebody here should be able to give you some direction.
Of course, there is always the JATO bottle trick.....
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'04 Rubi, manual, usual options, Hella H-4s, any range lockers, Randy's booster seats, Oly pushbar, 245/75R16 BFG
'09 Audi A4 Avant- my bride's schnellpuffenpanzer
'12 Ford Focus-the sure way to get good Jeep mileage
'07 Dodge Caliber R/T AWD-da kid's ride
Goodbye Old Blue XJ; 10+yrs, 100K+ miles; virtually trouble free; Long may you run!
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Unread 12-19-2008, 03:57 PM   #14
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Well you mustang is not made for torque like jeeps are!
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Unread 12-19-2008, 04:44 PM   #15
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Quote:
Originally Posted by halfmoonclip View Post
that makes as much sense as modding the 'stang so that it can navigate logging roads.
There is a beat up old 1st gen mustang body on a truck frame with some 4x4 running gear under it, it made me smile a little. Gotta love redneck Indiana
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