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2005 Grand Cherokee Limited 5.7
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Discussion Starter · #1 · (Edited)
Looking for performance upgrades for a 2005 Grand Cherokee 5.7. The big problem is I live in a CARB state (Colorado) and I was going to either get a camshaft swap or aftermarket headers and every shop told me it would absolutely fail emissions. It's a daily driver so I can't have that. One shop did offer to put a supercharger on for 12,000. Not sure if that's a fair price but the ones I've found online that actually fit are 8000 after taxes etc. Either way still much more than I am willing to spend even if I was willing to do it myself. Speaking of which, my mechanical skills are very limited to easy dumb shit such as changing a headlight. I am willing to try and follow some instructions to save on labor.
I'm willing to spend about $1000.00 - $2000.00

Existing upgrades:
20 inch rims with low profile tires
"Performance" air filter
Dual rear exit axle back exhaust and accommodating bumper

Random things I've considered:
Ignition packs or coils: supposedly they increase horsepower
Bigger throttle body
Cold Air Intake
: I read a lot about this one. Some people say that CAI will make no difference because the stock air filter and box are just that good. Saved me 390 dollars.
Muffler delete: not sure if this would make a difference. Should still pass emissions since I wouldn't touch the cats. High flow cats if they're CARB legal also? Not sure if that exists.
Tune: The shops had mixed opinions on this too. One guy said said that you would have to flash tune it back to stock for it to pass emissions then retune it. I guess that's not a huge deal but gas prices being what they are and making 10.8mpg I'd like to avoid this one for now.
WEIGHT REDUCTION: I can't find any concrete numbers on the internet about weights of different body panels but you could definitely drop 50 lbs just replacing the front fenders. This one, obviously, has nothing to do with emissions so I'd really like to know more. I'd prefer not to gut the A/C as every summer this car makes me regret blacking it out.
Polishing cylinder heads: I read some posts saying that polishing the cylinder heads nice and smooth would improve horsepower. I mentioned it to the family mechanic and he laughed and said no way
Paying a friend tell me my car is fast: might work might not
 

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Jeep Grand Cherokee
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64 Posts
Hello, I did much of the same research you have. I purchased the American Racing long tube headers for my 07 WK 5.7 They were $1850. I ended up asking the shop who did my engine swap at 188k to install the aftermarket headers while they were doing the work. The consensus was that there was a possibility of not passing emissions. Others I saw who had installed them had no issues. I took the the chance. I thought if I was close to passing but couldn't; I could run some E85. I have done this many times with other modified vehicles. The higher temp burn and allows just enough particulate to be removed and pass. I did order the high flow cats. Unfortunately I have the Superlift with the additional cross member that prevented them from fitting. The shop attempted to make it work but no go. I have them - never installed sitting in the original box with paperwork if you are interested. Heavily discounted and I am in Fort Collins.
Wood Automotive exhaust Hardwood Gas Flooring
 

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2005 Grand Cherokee Limited 5.7
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4 Posts
Discussion Starter · #4 ·
Damn that's actually so sad. I think I was looking at those exact ones as one of my options but I was also wondering about the rest of the exhaust. Supposedly you do get like 25-35hp gains just installing headers alone. But then what about the stock cats and muffler? Doesn't that just undo all the work the headers do? Then again I think the long tube ones replace that whole section of pipe with the cats on it so some cats would probably have to be added if it doesn't pass. Just some of my thoughts on it.

The shops did tell me the exact same thing. Camshaft will for sure not pass emissions. Headers there's a chance it doesn't. My car passes really far under the limit but I'm not sure if that matters.
 

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Jeep Grand Cherokee
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64 Posts
Actually the long tube headers with the cats replace the stock. Everything downstream of the y pipe is just mid pipe and muffler. I have a Borla mid pipe and muffler. I haven't really made an effort to unload the headers yet. It is on my to do list. If in the end you decide you're interested hit me up. It would be nice to do that business locally. Maybe someone in Weld county without the same concerns will be interested.
 

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Welcome to the WK world. First advice, before spending $ modding, always make certain that ALL maintenence items are up to date. Performance loss is due to maintenance issues more than anything, and costly upgrades won't do anything to remedy those. First thing to get is a catch can, and clean your TB, as it will be totally gunked up. If you want a larger TB, get a CNC taper ported one to preserve low end torque. Modern muscle carries them.
Intake and exhaust do not improve performance on the 5.7, unless you put on headers or SRT exhaust manifolds. They are a waste of money, just make more noise, and lose low end torque, where you want it most. The stock intake is a CAI, and works better than aftermarket ones. I had an AFE II and it lost low end torque, was horribly loud.
If your suspension is original, it will be badly worn, spend the $ first to redo that before modding for mo' powa.
Useful power upgrades are seen in my sig. My 06 is much faster than when I bought it new, and has 170k.
 

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2006 WK Overland
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2,212 Posts
Welcome to the forum. Most of what dmsfun said is true, but you're wanting to get more power and still get past the smog nazi's in Colorado. I am in a "smog nazi" state and have fairly extensive mods. (about 125-140 hp. more than stock) and still pass the smog test. I will say that, if your nazis do a visual AND are looking for CARB approved performance goodies, you'd definitely not pass with most of the mods. that I have. California is one that is extremely strict in this regard. Most of these smog guys where I live don't even know what they're looking at. You'd have to make that decision based on what you know about the Colorado inspections.

That being said, there are some mods you can do that will increase performance without adversely affecting emissions. The problem is, you may not be able to do all of them in order to get their full benefit.....i.e., you can put a nice mild cam in it that would normally give you 50-75 more horsepower with a good header back exhaust system but, if you couldn't install a good header back exhaust system, the same cam may only give you 15-25 horsepower, because the stock early 5.7 Hemi Jeep's exhaust system is probably the biggest "choke point" that restricts power output of the early Jeep Hemi's.

If you read the following article, I have done most of the same stuff they did and, in some cases a little more. Some of the things you addressed work and some don't do much that is noticeable with a stock rotating assembly. Hemi Head Test - Mild & Wild Note, in that article they're pulling over 400 lb. ft. of torque from 3600 RPM on up.....the stock cam doesn't quite make 400 lb. ft. of torque with a stock or nearly stock setup. It will, however, have slightly better torque than a cammed 5.7 below 3600 RPM. On mine, above about 3000 RPM, it's like turning on another engine.

You can look at my mods in my signature and see most of what I've done over the years. Below I'll address the items you indicated in your first post:
--Ignition Coils will deliver a higher voltage and allow you to run a wider gap on the spark plugs, possibly giving you more complete burning of the fuel, but you'll probably not notice anything except maybe a slightly better idle quality.
--A bigger throttle body, for the most part won't do squat for you, as long you're running the stock 5.7 displacement. Even the stock 6.1's run the exact same throttle body that the 5.7 uses. I've run the stock 80 mm one, as well as 85 mm and 90 mm ones and, at best you'll get slightly better throttle response with the bigger ones. I currently run an 85 mm one on my Jeep and a 90 mm one on my 5.7 Magnum which is modded almost exactly like the Jeep.
--An aftermarket CAI is a giant waste of $$$$. The stock airbox is capable of flowing more air than the stock 5.7 engine is capable of processing. You can make it a little better though by adding a second air inlet that routes air from the back of the grill into the airbox, add a high flow filter element and ditch the giant silencer in favor of an SRT or Airaid intake tube from the airbox to the throttle body.
--A muffler delete will help somewhat but, as said, do you want all that additional noise? The stock 5.7 Hemi exhaust logs are the majority of the problem, but a good cat. back can help a little. Again, if you look at my signature, you can see that I run the ARH headers as shown above and a low restriction, custom cat. back.
--I have the TEA ported and polished heads on mine, just like the article above. I also had .030 in. milled off of mine to slightly increase the compression ratio. IMO, with the stock displacement, the gains (about 25-30 hp. from both) aren't worth the $$$$. Live and learn though.
--I have 20 inch SRT Reproduction wheels with the stock SRT size tires on mine and they look great. The only problem, if you want to go fast, is that they weigh more than twice of what the stock wheel and tire set up weighs. This adversely affects both performance and fuel economy. On mine, about 2 mpg on the highway and 3-4 tenths of a second in the quarter mile. As is though, I only lost to a 2021 Jeep SRT8 with a 6.4, 8 speed transmission and lauch control by about 4 car lengths. Stock wheels and tires "could have" made it almost even. See this thread: My mildly modded 06 5.7 Overland against a 2021 GC SRT8

Bottom line in a CARB state, know your inspection process and try to determine what will fly and what won't. Stuff like a mild performance cam, a tuner, a good cat. back, an underdrive crank pulley, and such will help you somewhat, and not likely cause you any problems. Also remember, most mods. won't yield much by themselves, but collectively they'll start adding up.


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