3.7L Performance

[2002KJLimited]

How to make your Powertech engine really scoot.

 

[2002KJLimited]

The first thing to do is basic maintenance. I highly recommend the use of K&N air and oil filters. The spark plugs that are the most basic also perform the best, these would be the NGK V=Power copper core plugs. Fancy iridium or platinum plugs are not necessary, this is after all a truck engine. The precious metal plugs are also harder to fire due to the higher resistance inherent to these metals. Quality oil is a must for longevity, use a 5w30 semi or full synthetic such as Castrol GTX. Synthetics are not a mystery, they flow better and don't degrade or sludge as much as conventional.

 

[2002KJLimited]

The next part is to increase airflow. The first thing to do is to get a later model intake tube. To make it work you'll have to do something with the valve cover vent tubes. The easiest option is to tee them together and top it with a small pod filter. Wrapping the intake tube with DEI cooltape will help to lower intake temps some. Next you'll want to port and polish the throttle body. This is cheap and can be done with a dremel and about 5 hours. All you want to do is just open the entrance to the edges and blend it, creating a smoother opening. Don't mess with the area near the blade or behind it, you could do more damage than good there. For the exhaust just replace the muffler with a higher flowing unit such as a Cherry Bomb glasspack, or just delete the muffler. Deleting the muffler will not make it too loud as the catalytic converter will still muffle out the high pitched sound. The exhaust will definitely sound and flow better with either option.

 

[jeepbeep]

When I was first shopping for a Liberty a local guy had a 2002 with a supercharger on it. I never asked what the vendor was.

You can get a bolt on cat-back for <$200 and magnaflow for $350. I like mandrel bent aluminium catback with a flowmaster 70 series personally.

There are HID projector headlights and altezza style tailights pretty cheap. I'd imagine you could get one up to 380HP or so low-RPM.

I would do a new set of heads from one of the newer engines first based on common block-level-failures I typically see.

Oh Yeah you can do the HD clutch fan and shroud setup for cooling for a couple hundred ordering from Hayes and a Mopar dealer.

 

[JeepinJarhead03]

You'll get no measurable gain by grinding on the tb without enlarging the butterfly, as for flow characteristics the composite intake is tuned to optimize flow patterns within the intake. If you intend to increase anything with the tb , fastman throttle body isn't terribly priced for the same tb, already ported and polished, with a larger butterfly

The stock tb does have a restriction, of about 0.9mm versus the size of the butterfly, but doing it with a dremel probably isn't going to be worth the potential mess vs the gain

And i cut engine blocks and cams on a regular basis for international strokers, so it's not that I'm anti diegrinder.

 

[HoosierJeeper]

Castrol GTX is a conventional. Group II. Castrol Magnatec is their semi synthetic, has the Dexos certification. Conventionals are just as clean as synthetics, just can't do extended intervals. At least that's my conclusion after being on Bob is the oil guy for a while.

 

[tommudd]

After testing, trying different things etc on my own 04 for over 221,000 miles most of the above will only make you wallet lighter
CAIs waste
Throttle body mods waste
Muffler makes more noise but figuring in price of it, not really going to give you much if any more power
Keeping up on maintenance and regearing is the only real bang for the buck
Thing is if you do replace the TB, add exhaust the computer is only going to do so much so unless you have a custom reflash done, you're not going to notice much if any difference.
YES I have ran a bored out TB, yes I have run aftermarket exhaust , tried different airfilters etc
K&N is ok on a race engine but not a DD, tests have shown a good Wix airfiler flows better and does a better job of keeping dirt out

Can not run a supercharger on these engines UNLESS you have deep pockets

 

[Boomhawr]

Thanks.

But also make sure to check state and local laws before removing the muffler. In Texas, you won't pass inspection. Some people used to hallow out mufflers and catalytic converters so the canisters were still there for visual inspection, but some counties here require it to be emissions tested too. Not sure if it (mufflers) will show any difference on the test, but since they started that, I haven't heard anymore about coring out mufflers and catalytic converters anymore.

 

[K9JEEP]

I haven't had my KJ for very long but I have been modding my cars for a long time, 2 SRT4's, 05 WRX and a 13' GTI. I threw all sorts of parts at all of these cars and just about $15k at the GTI, intake, turboback exhaust, front mount intercooler, hard piping, full suspension,mounts, bracing, wheels and tires and the single thing that made all the difference was the custom tune. Performance parts usually won't yield much gains with out the ECU knowing these parts are on the car and how to work with them.
The SRT4's were plug and play ECU's, the WRX was protuned with a laptop and a road tune. The GTI is where I did the most and it's the newest of the pack so I went with a plug in reader that allows you to monitor over 60 live parameters of the car, I E-tuned so I would do a 3rd gear WOT pull and email it to the tuner, he would make adjustments based on the data log and send a new map back, I did this about 6 times back and forth and with the tune alone I gained 40hp with the parts bringing me up from stock 210hp/210tq to 266hp/307tq, and that's usuable power over the entire powerband. Most people only care about peak numbers, I care about what the power curve looks like and where is the power usable at. I would much rather have a torquey car than a high horsepower car. All of these cars are turbocharged so it's a different game when modding and tuning but from what I get from the 3.7 is most of it is maintanance and if you can keep it cooler and free up some flow it might like that a bit better but it's already a pretty basic system that doesn't seem to have much room to play with.
I also feel the engine is very underpowered for the size of this Jeep so I see why we might think about doing things to it, all my previous cars make more power out of 4 cylinders and weight 2k lbs less, so this feels sluggish to me but I also don't drive it like a tuned car.
I would also say that I tuned my GTI into the next price bracket, I could have been in a nicer Audi for the money I put into it, I am now parting it out and looking to get rid of it, so beware of modding because it can be a huge snowball. My 2 cents

Also save any OEM parts you take off, you never know when you might need them. I had to drive 800 miles from LA to New Mexico with the stock downpipe in my WRX, change it out, smog the car, put the catless exhaust back on and drive 800 miles back. CA has probably the strictest modding laws regarding exhaust and intakes, I have paid sometimes double for CARB legal parts but have never been pulled over in my GTI. I have been pulled over in the WRX which is full 3inch and catless, he made me pop the hood but I made sure to fit everything like stock so you could not tell it had been modified from that angle, he did ask if I had a cat and I just said yes. Being the car is registered in NM he let me go. I now have it registered in a county with no smog requirements.

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[tommudd]

IT'S A JEEP NOT A TUNER
:happy175::happy175:
Its good basic vehicle that has enough power to take us anywhere we need to go. I can cruise all day long at 75 MPH and get 20-21 MPG , get where I am going and drive off road over the rivers and through the woods.
But like K9JEEP stated start modding and there is no end to what you want and the cost climbs and climbs
Of course I grew up driving 302 powered Z-28 motors in 55 Chevrolets, AAR Cudas and 66 Vettes with 427s :happy175:

 

[K9JEEP]

Lol I agree it's not a tuner, but same concept.
I got this truck because I wanted something completely opposite of what I have, basic and gets the job done like you said, I don't have to worry about the shit roads here in LA

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[tommudd]

Lol I agree it's not a tuner, but same concept.
I got this truck because I wanted something completely opposite of what I have, basic and gets the job done like you said, I don't have to worry about the shit roads here in LA

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No potholes in LA ??
Seems I hit a few last time I was there or was it just my imagination?:happy175:
Of course had just driven straight through from North Carolina, so ........:emotions34:

 

[2002KJLimited]

I understand many peoples' doubts about what the mods I listed will actually do. What I'm mostly stating is engine performance theory that's used for everything from the SBC to the 2JZ. You won't notice huge improvements, but you will notice things like better acceleration and maybe better MPGs. To each his own on what you want to spend your money on.

 

[K9JEEP]

Oh no I am saying I love the Jeep because the roads are shit and I'm constantly avoiding potholes and uneven pavement with my VW. I still avoid them with the Jeep I just don't cringe if I do hit them

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[tommudd]

I understand many peoples' doubts about what the mods I listed will actually do. What I'm mostly stating is engine performance theory that's used for everything from the SBC to the 2JZ. You won't notice huge improvements, but you will notice things like better acceleration and maybe better MPGs. To each his own on what you want to spend your money on.

I totally understand the " theory " behind of what you are saying ( been doing this over 40 years )
BUT Like stated I tried many different ways / different filters/ filter setups, mufflers etc
BEST all around gas mileage and power
stock airbox with Wix filter and 3 inch hose to grill area
Now the 04 was at 4.5 inches of lift, 32 inch tires, 4.10 gears, front and rear steel bumpers, heavy roof rack, rock rails, skids etc
Taking off from dead start I could smoke the 32s, plenty of power for what it is, a Jeep
Also averaged 21-22 mpg on the highway and have gotten as high as 23 on a trip across Pa. ( from Ohio to Philly area ) at an average of 75 mph plus.
Now I've also made that trip ( well from Ohio to Boston, used to go every other weekend for over a year ) with a lot of different setups on mine and never quite got as much as with stock box etc.
I bought it new and put way over 221,000 miles and tracked everything I did . So I know the results. The 3.7s just don't go for any of that stuff that works on " some " others . Sorry............but thats my story and I'm sticking to it. :happy175:

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[K9JEEP]

After having multiple intakes on different cars I agree that the stock intake on my 07 is probably the best it's going to get. There isn't much restriction and an OEM filter will do the job. My opinion of any engine is flow and heat are your number one concerns, keep it flowing in and out the easiest way possible and the engine will stress less. Keep it cool and it will perform its best at all times. I've learned a lot from my turbocharged cars, they produce way more heat and need to flow properly but it's the same across the board with any engine. We are limited in what improvements can be made on these 3.7. As stated it's a truck engine and I'm starting to understand that more

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[tjkj2002]

I haven't had my KJ for very long but I have been modding my cars for a long time, 2 SRT4's, 05 WRX and a 13' GTI. I threw all sorts of parts at all of these cars and just about $15k at the GTI, intake, turboback exhaust, front mount intercooler, hard piping, full suspension,mounts, bracing, wheels and tires and the single thing that made all the difference was the custom tune. Performance parts usually won't yield much gains with out the ECU knowing these parts are on the car and how to work with them.
The SRT4's were plug and play ECU's, the WRX was protuned with a laptop and a road tune. The GTI is where I did the most and it's the newest of the pack so I went with a plug in reader that allows you to monitor over 60 live parameters of the car, I E-tuned so I would do a 3rd gear WOT pull and email it to the tuner, he would make adjustments based on the data log and send a new map back, I did this about 6 times back and forth and with the tune alone I gained 40hp with the parts bringing me up from stock 210hp/210tq to 266hp/307tq, and that's usuable power over the entire powerband. Most people only care about peak numbers, I care about what the power curve looks like and where is the power usable at. I would much rather have a torquey car than a high horsepower car. All of these cars are turbocharged so it's a different game when modding and tuning but from what I get from the 3.7 is most of it is maintanance and if you can keep it cooler and free up some flow it might like that a bit better but it's already a pretty basic system that doesn't seem to have much room to play with.
I also feel the engine is very underpowered for the size of this Jeep so I see why we might think about doing things to it, all my previous cars make more power out of 4 cylinders and weight 2k lbs less, so this feels sluggish to me but I also don't drive it like a tuned car.
I would also say that I tuned my GTI into the next price bracket, I could have been in a nicer Audi for the money I put into it, I am now parting it out and looking to get rid of it, so beware of modding because it can be a huge snowball. My 2 cents

Also save any OEM parts you take off, you never know when you might need them. I had to drive 800 miles from LA to New Mexico with the stock downpipe in my WRX, change it out, smog the car, put the catless exhaust back on and drive 800 miles back. CA has probably the strictest modding laws regarding exhaust and intakes, I have paid sometimes double for CARB legal parts but have never been pulled over in my GTI. I have been pulled over in the WRX which is full 3inch and catless, he made me pop the hood but I made sure to fit everything like stock so you could not tell it had been modified from that angle, he did ask if I had a cat and I just said yes. Being the car is registered in NM he let me go. I now have it registered in a county with no smog requirements.

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I'm agreeing with Tom on every point.

I've also gotten just shy of 22mpg's(21.9) in my KJ going from Colorado Springs to MOAB and it's not a flat route.That was when my KJ was still IFS but with 3.75" of lift,265/75R16's(D range),4.10's,and weighing 5500lbs.This was also at 78mph,the Jeep never liked slower speeds and would get up to 10mpg's less at 65mph then 78mph(around 3000 rpm's).

Now SFA's with 35" tires and 5.13 gears tipping the scales at over 6200lbs I can still pull 18mpg at 65mph(3000 rpm's,I'm gear limited now) on that same drive to MOAB.

And my KJ has a completely stock 3.7 and yes I do have a AFE intake and MagnaFlow race muffler but that is due to space,intake for ARB compressor and muffler for rear suspension.

It's a Jeep and shines in low range at 2-3mph.

6200+lbs......................

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5500lbs.......................

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[Boomhawr]

Tommud, you sure do like that laughing smiley, don't ya? Hahaha. You use it a LOT!!! :happy175:

 

[Boomhawr]

tjkj, what's that bumper/grill guard, and where'd ya get it?

 

[tjkj2002]

tjkj, what's that bumper/grill guard, and where'd ya get it?

ARB front bumper,got it 14 years ago from 4 wheel parts($600 back then).