5.9 Jeep Grand Cherokee Performance Mods - JeepForum.com
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post #1 of 31 Old 09-04-2011, 12:25 PM Thread Starter
MattJGC59
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5.9 Jeep Grand Cherokee Performance Mods

Hi everyone, I have just bought my first truck, 1998 Jeep Grand Cherokee 5.9 limited yesterday. I have been reading up on what kind of performance mods i can do to it but i am just not fimiliar with some of the mods. I want to make my 5.9 Jeep faster and if possible help my MPG. What kind of Performance upgrades or mods should i start off with that will help me all around and that wouldnt cost too much for now. What should i start with off doing? Basically decent enough power for decent amount of money. For now. Thanks guys!

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post #2 of 31 Old 09-04-2011, 01:06 PM
zachjf
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Well, gas mileage and mods dont really go hand in hand so I cant help you there. Mod wise the first thing to go should be the stock exhaust, as much as humanly possible while staying in your budget because the stock system is too small and basically choking your engine. Follow that up with a good cold air intake and a full performance tune, i.e. good high performance ignition parts and you'll have a great base to build off of.

Instead of posting here you should check this site out, tons of info and great people into the speed side of Jeeps.

http://thespeedfreaks.net

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post #3 of 31 Old 09-04-2011, 01:22 PM Thread Starter
MattJGC59
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I see how that makes sense about getting better gas mileage. So about changing the exhaust, what would be the best bet for me. What kind of exhaust system because i am still new to this and dont know much about what kind to get. Also, what kind of good cold air intake would be beneficial for the 5.9 to get more power and a good v8 sound still. Thanks so much for your help
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post #4 of 31 Old 09-04-2011, 02:13 PM
zachjf
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well the best place to start would be a cat back exhaust, followed by a custom downpipe/collector assembly then a set of headers. Your going to want to try and go with 2.5" downpipe's into a 3" collector and 3" from there back since its going to offer the least restriction. Not really sure who makes the best "kit" since I usually have my stuff custom made and any competent exhaust shop should be able to fab you up a nice system for less than a pre made "kit". As for an intake you can either pick up a pre made kit like a K&N which includes everything you need or fab one up yourself from easily available parts.

check out this exhaust thread, lots of info with pics and video/audio clips etc.
Performance Exhaust Thread

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post #5 of 31 Old 09-04-2011, 02:19 PM Thread Starter
MattJGC59
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alright thanks for your help. I will check out where to get the exhaust system and the cold air intake. It might be easier for me to find some stuff cause i work at canadian tire automotive dept behind the counter. thanks again!
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post #6 of 31 Old 09-04-2011, 02:26 PM
Candymancan
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Changing to fully synthetic oil is supposedly suppose to give around 2-3% improved fuel econemy which isnt much... maybe around .4mpg. I dont think you can tell if your getting .4mpg better as driving can be so variable so im sticking with dino oil myself
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post #7 of 31 Old 09-04-2011, 04:11 PM Thread Starter
MattJGC59
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yea i have noticed when i would change my oil every time, i get a more responsive feel. I noticed a bit better gas mileage like you said aswell. I have always used synthetic oil on all of my cars, mercedes and jeeps. I am very soon going to be changing the oil on my jeep to synthetic. thanks!
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post #8 of 31 Old 09-04-2011, 06:38 PM
Kolak
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Congratulations on getting a 5.9! I own one as well and they are very responsive to proper modification.

You'll notice that a lot of Jeep owners have my Kolak Exhausts and I also offer all sorts of other power upgraded including cold air intakes, ignition upgrades, computer programmers, ported throttle bodies, etc.

Send me a PM with your email address and I'll email you some initial information about upgrades. JeepForum members get 10% off my exhausts and preferential pricing elsewhere as well.

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Member: Specialty Equipment Market Association
Telephone: 480 998-3661

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post #9 of 31 Old 09-24-2011, 02:26 AM
XJClassic
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Kolak is the man you want to talk to... he is the 5.9 guru. Always good to deal with!
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post #10 of 31 Old 09-24-2011, 06:40 AM
PolkaPower
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Quote:
Originally Posted by XJClassic View Post
Kolak is the man you want to talk to... he is the 5.9 guru. Always good to deal with!
What he said. I had the 3" Kolak on my last 5.2 with Mike Leach headers and it was a good improvement.

These things not in any order

Bored and polish Throttle Body
Mopar Performance computer
Headers and y pipe
hi flow catalytic converter
larger diameter exhaust
new airhat for stock intake(stock one is too restrictive)
re gear to 4:11's
IAT relocation
light weight pulley's
supercharger

I would stay away from any cold air oil and cotton cone filtration as they let in a lot of dust and dirt into the engine. I had one on my 5.2 and the tube was always dirty on the inside. The stock airbox flows just fine and filters the best if you modify the airhorn where it sucks in the air. The most restriction comes from the stock airhat on top of the TB. The Dakota or Durango's have a larger better flowing airhat that will fit.
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post #11 of 31 Old 09-24-2011, 12:59 PM
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Kolak ignition upgrade is a great bet... i took off my exhaust after the cat and it sounds great, a hair loud but deep and throughty and it didnt cost a dime
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post #12 of 31 Old 02-21-2020, 12:12 AM
5.9limited 92
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Hey guys, I am new to the site. I have beautiful 1998 5.9 limited with 220,000 1 owner, I’m looking at adding power. Any advice would be greatly appreciated.
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post #13 of 31 Old 02-21-2020, 01:20 AM
Timo_90xj
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Depending on what kind of power gains you want, but the main thing to remember is that the stock cylinder heads are restrictive if you're going for intake/ cam upgrades.
If you're looking for something more than just an upgraded tune from Flyin' Ryan (he is the ONLY one you want to use regarding tunes for these), get yourself a set of EQ large-valve (2.02"/ 1.60") or Edelbrock cylinder heads, new cam, better intake manifold & 2 x 52mm throttle body, spectre air hat or a stock one from a dodge (Jeep pancake- style airhat is restrictive).
Better exhaust, preferably Doug thorley headers & a full 3" setup from the Y- pipe back. Flyin' Ryan tune is a must.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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post #14 of 31 Old 02-22-2020, 01:00 AM
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There's impressive gains to be had with a good air intake, headers, my 3" Kolak Exhaust and a good tune.

After that, the next order of business is to upgrade the intake manifold and get a ported throttle body.

Don't forget a good ignition tuneup kit - my Kolak Ignition is nice

Then once you've become accustomed to those gains and want more, heads and cam are next in line.

Don't forget better tires, brakes, and suspension so you can put that power to good use.
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Telephone: 480 998-3661

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post #15 of 31 Old 02-22-2020, 05:51 AM
StPaul59
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A larger throttle body will hurt gas mileage just so you know.
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